Cancer Chemotherapy & Biotherapy: Principles & Practices, 4th Edition

Infertility After Cancer Chemotherapy

Angela Bradbury

Richard L. Schilsky

During the past 30 years, major strides have been made in the treatment of neoplastic disease with cytotoxic chemo-therapy. Progress in understanding tumor cell biology and mechanisms of drug resistance, the introduction of new, effective antineoplastic drugs and technological advances that allow for more detailed and complete pharmacogenetic studies have all contributed to the successful application of cancer chemotherapy. Many patients with Hodgkin's disease, acute leukemia, non-Hodgkin's lymphoma, testicular cancer, and other tumors now regularly achieve sustained clinical remissions and cures. Moreover, adjuvant chemotherapy is now commonly employed for treatment of micrometastatic disease in clinically well patients with breast cancer, colorectal cancer, lung cancer, and soft tissue sarcoma and prolongs survival for many individuals. Thus, many more patients currently receive chemotherapy than ever before, and, of greater significance, many more individuals are cured of their tumors and survive to experience the potential late adverse effects of such treatment. Among these, infertility and mutagenesis are often of particular concern to cancer survivors who have new hopes and expectations for a return to normal lifestyle. This chapter will review the effects of cancer chemotherapy on the gonadal function, sexuality, and progeny of patients treated for malignant disease.

EFFECTS OF CANCER CHEMOTHERAPY ON GONADAL FUNCTION

Neoplastic disease and its treatment can potentially interfere with any of the cellular, anatomic, physiologic, or behavioral processes that comprise normal sexual function. The nature of the patient's illness, the extent of necessary surgery or radiation therapy, and the patient's relationship with spouse and family may all play an important role in reestablishing normal sexual interest and function following treatment for cancer. Further, many drugs used in the treatment of malignant disease have profound and often lasting effects on the testis and ovary. Germ cell production and endocrine function may both be altered, with the magnitude of the effect related to the age, pubertal status, and menstrual status of the patient as well as to the particular drug, dosage, or combination administered.

CHEMOTHERAPY EFFECTS IN MEN

The normal adult testis is an organ composed of diverse and highly specialized cell types, which may vary in their sensitivity to cytotoxic drugs. The exocrine function of the gland, spermatogenesis, proceeds in the seminiferous tubules, while the interstitial cells of Leydig carry out the primary endocrine function of the testis, testosterone production.1

The seminiferous tubules, which constitute 75% of the testicular mass, are lined by stratified epithelium composed of two cell types: spermatogenic cells and Sertoli cells. The spermatogenic cells are arranged in an orderly fashion: spermatogonia lie directly on the tubular basement membrane, and primary and secondary spermatocytes, spermatids, and maturing spermatozoa progress centrally toward the tubular lumen. Sertoli cells also lie on the basement membrane, and serve to regulate the release of mature spermatozoa from the germinal epithelium as well as to maintain the integrity of the blood-testis barrier.

Spermatogenesis is a dynamic and complex process that may be divided into three phases: (a) proliferation of spermatogonia to produce spermatocytes and to renew the germ cell pool, (b) meiotic division of spermatocytes to reduce the chromosome number in the germ cells by half, and (c) maturation of the spermatids to become spermatozoa.2 Cytotoxic drugs could potentially effect this process in a number of ways: (a) a specific cell type within the germinal epithelium might be selectively damaged or destroyed; (b) the proliferative and meiotic phases of spermatogenesis might proceed normally, but sperm maturation might be abnormal, leading to functionally incompetent mature spermatozoa; or (c) chemotherapy might damage Sertoli cells, Leydig cells, or other supportive or nutritive constituents of the testis in such a way as to alter the particular microenvironment necessary for normal germ cell production.

Clinical Assessment

Testicular function in patients receiving cancer chemotherapy can be adequately evaluated with a careful physical examination, semen analysis, and determination of serum gonadotropin and testosterone levels (Table 4.1). Occa-sionally, testicular biopsy is necessary to complete the evaluation. Since the seminiferous tubules comprise such a large portion of the testicular mass, damage to the germinal epithelium frequently results in testicular atrophy, which is readily detected on physical examination. Impaired spermatogenesis is also manifest as a decrease in the number and/or motility of sperm present in the ejaculate and, since pituitary gonadotropin secretion is under feedback control by the testis, an increase in serum follicle stimulating hormone (FSH) level.3, 4Leydig cell dysfunction may also occur and is detected by an increase in serum luteinizing hormone (LH) level, and if uncompensated, a fall in serum testosterone level. Subclinical abnormalities of Leydig cell function may occasionally be demonstrated by administration of LH-releasing hormone. An excessive rise in serum LH levels in this provocative test suggests the presence of abnormal Leydig cell function.5, 6, 7, 8

TABLE 4.1 EVALUATION OF THE PATIENT WITH GERMINAL APLASIA

 

Normal

Germinal Aplasia

Testicular size

Length × width (cm)

5.0 × 3.0

3.7 × 2.3

Volume (mL)

16–30

8–15

Sperm count (106/mL)

20–100

0

FSH (mIU/mL)

4–25

25–90

LH (mIU/mL)

4–20

8–25

LH response to LH–RH

Normal

Exaggerated

Testosterone (ng/dL)

250–1200

200–700

Drug Effects on Spermatogenesis

Following cytotoxic chemotherapy, there appear to be common histopathologic changes that occur in the testis, independent of the type of drug employed, but related to the total dose administered. The primary testicular lesion caused by all antitumor agents studied thus far is depletion of the germinal epithelium lining the seminiferous tubules.9, 10, 11, 12, 13 Testicular biopsy in most patients reveals complete germinal aplasia with only Sertoli cells left lining the tubular lumens. Occasionally, scattered spermatogonia, spermatocytes, or spermatids may be seen or there may be evidence for maturation arrest occurring at the spermatocyte stage. This latter finding appears most often in patients receiving short courses of chemotherapy with antimetabolites.14

Drugs Highly Toxic to Male Germ Cells

Chlorambucil

Among the anticancer drugs, alkylating agents most consistently cause male infertility. In particular, chlorambucil and cyclophosphamide deplete the testicular germinal epithelium in a dose-related fashion. Progressive oligospermia occurs in men with lymphoma who are treated with up to 400 mg of chlorambucil,13and those patients receiving cumulative doses in excess of 400 mg are uniformly azoospermic. Despite a high incidence of damage to the germinal epithelium, partial or full recovery of gonadal function may be possible for some individuals. Complete recovery of spermatogenesis has been reported in three of five previously azoospermic patients after therapy with chlorambucil at cumulative doses of 410 to 2600 mg.15 In these patients, sperm counts were found to be normal at 33, 34, and 42 months following completion of chemotherapy. Two additional patients, who received the highest cumulative drug doses, demonstrated a partial return of spermatogenesis at 38 and 58 months after discontinuing treatment.15

Cyclophosphamide

Decreased sperm counts may occur in men treated with 50 to 100 mg of cyclophosphamide daily for courses as brief as 2 months, although azoospermia and germinal aplasia are infrequent until higher doses have been administered. Rivkees and Crawford16 found that 80% of men treated with more than 300 mg/kg of single-agent cyclophosphamide developed gonadal dysfunction. As with chlorambucil, recovery of gonadal function is possible, although the probability of recovery appears to be related to the administered dose. In one study, all 26 men treated for 5 to 34 months with 50 to 100 mg of cyclophosphamide daily became azoospermic within 6 months of starting therapy.17 Serial sperm counts demonstrated a return of spermatogenesis in 12 patients after a mean period of 31 months following discontinuation of cyclosphosphamide. Those patients demonstrating a recovery of spermatogenesis tended to receive lower initial drug doses. Other investigators found that 40% of men treated with cyclophosphamide-based regimens for sarcoma had recovery of spermatogenesis at 5 years, but only 10% had recovery when cumulative doses exceeded 7.5 g/m2.18

Ifosfamide

Ifosfamide may be less toxic to the germinal epithelium than cyclophosphamide. One group reported recovery of spermatogenesis in 15 of 16 patients who received between 15 and 30 g/m2 of ifosfamide.19 Longhi et al20 evaluated the effect of ifosfamide-based regimens in men with osteosarcoma. Although cisplatin, another gonadotoxic agent, was included in the treatment program, the investigators found that the likelihood of infertility was associated with the ifosfamide dose. The median ifosfamide dose in this study was 42g/m2, with some men receiving up to 60 g/m2. This group found a higher rate of azoospermia with ifosfamide-based regimens when compared with combinations that did not include ifosfamide. These studies suggest that ifosfamide, like other alkylating agents, has a dose-dependent effect on gonadal function.

Procarbazine

Several studies have suggested that procarbazine is particularly damaging to the germinal epithelium.21, 22 Animal studies have shown that procarbazine is severely toxic to the germinal epithelium in adult male monkeys and rats.23, 24 Human studies evaluating germinal damage after combination chemotherapy also suggest that procarbazine plays an important role in the development of chemotherapy-related infertility. In a report of 32 patients receiving combination chemotherapy for lymphoma, 31 patients developed increased serum FSH levels during their initial therapy, and of 15 patients studied, all had azoospermia. Sixteen patients were later evaluated for recovery of testicular function. Ten patients received regimens without procarbazine, and 7 of the 10 had normal serum FSH levels at 34 months post-treatment. In contrast, only one of six patients treated with a procarbazine-containing regimen demonstrated a decrease of serum FSH, or an increase in sperm count, during 52 months of follow-up.21 In another study, patients treated with combination chemotherapy for non-Hodgkin's lymphoma appeared to have a lower incidence of gonadal dysfunction than those treated for Hodgkin's disease, despite receiving similar cumulative doses of cyclophosphamide and vincristine. Most of the patients with Hodgkin's disease also received procarbazine, whereas those treated for non-Hodgkin's lymphoma did not.22 Although the patient numbers are small, these data suggest that the use of procarbazine in combination chemotherapy regimens may be associated with longer-lasting testicular damage than occurs with the use of alkylating agents alone.

Cisplatin

The effects of cisplatin alone on testicular function are difficult to discern, as the majority of men with testicular cancer have impaired spermatogenesis prior to therapy. Early studies reported that patients with testicular cancer treated with cisplatin-based combination chemotherapy uniformly became severely oligospermic or azoospermic soon after chemotherapy was initiated.25, 26, 27, 28, 29, 30 Subsequent studies have found that higher doses of cisplatin, or more cycles of chemotherapy, are associated with more profound and persistent decreases in sperm counts.31, 32 In a review of five published studies, DeSantis et al19 determined that cumulative cisplatin doses less than 400 mg/m2 were unlikely to cause azoospermia, whereas patients who received higher doses, or more than four cycles of chemotherapy, had a higher risk of impaired spermatogenesis when compared with controls. Likewise, other studies have found that almost all patients who receive cumulative cisplatin doses above 600 mg/m2 have severe oligospermia or azoospermia.33 As with other severely gonadotoxic agents, reversibility is possible even when there is severe azoospermia initially. Even after receiving a cumulative dose of 600 mg/m2, 50% of men recovered spermatogenesis at 2 years and 80% had recovery at 5 years.34

Several groups have recently evaluated the gonadal toxicity of carboplatin. Although animal studies suggested a dose-related effect on spermatogenesis similar to cisplatin,35 recent human studies suggest less germinal damage with carboplatin-based regimens. One group followed 22 patients with stage I seminoma who were treated with orchiectomy followed by single-agent carboplatin. After surgery, and prior to chemotherapy, 53% of the men had oligospermia and 35% were normospermic. At 2 years after therapy, 68% of men were normospermic, suggesting a significant recovery of spermatogenesis after therapy with single-agent carboplatin.36 A second group found that patients who received carboplatin-based chemotherapy were 4.4 times more likely to recover spermatogenesis when compared with patients who received cisplatin-based therapy for testicular cancer.37

Vincristine

Although single-agent vincristine was thought to cause temporary and reversible damage to the germinal epithelium and to have an additive effect when combined with other highly gonadotoxic agents, a recent multivariate analysis suggests that vincristine itself may have a significant effect on fertility.38Vincristine does not appear to have significant germinal cell toxicity in animals. Vincristine is rarely administered as a single agent, and is often administered with other highly gonadotoxic agents, such as procarbazine. For this reason, it is difficult to assess the germinal toxicity of vincristine in humans. A recent study evaluated sperm counts in 55 males who received various chemotherapeutic regimens for different malignancies during childhood. The investigators employed multivariate methods to assess the effect of individual agents on future sperm quality. In this analysis, only vincristine and cyclophosphamide were shown to independently affect spermatogenesis, suggesting that vincristine may be more toxic to the germinal epithelium than previously suspected.38

Drugs with Low Toxicity to Male Germ Cells

Antimetabolites in conventional doses seem to have relatively few effects on spermatogenesis, although one study suggested that high-dose methotrexate (MTX, 250 mg/kg) may produce transient oligospermia in some patients.39 This modest effect of MTX on spermatogenesis may result from the presence of a significant barrier to MTX passage from blood to seminiferous tubule.40 Several reports have suggested that doxorubicin may be less toxic to the human testis than expected, based on animal studies. In both the mouse41 and the rat,42, 43 doxorubicin produces severe germinal epithelial injury. Yet, clinical studies of the effects of doxorubicin-containing regimens on testicular function in men have revealed reversible testicular injury in the majority of patients under age 40.44, 45, 46, 47 Amsacrine, an acridine derivative with activity in acute leukemia, causes rapidly reversible azoospermia, suggesting that this drug produces little toxicity to stem cells in the human testis.48 Recombinant interferon-α-2b, an active agent in the treatment of some chronic leukemias and solid tumors, seems to have no adverse effects on testicular function in men treated chronically for hairy cell leukemia.49

In considering individual agents, these data suggest that chemotherapeutic agents vary in toxicity to the germinal epithelium (Table 4.2). In addition, there appears to be a threshold dose for the development of testicular germinal aplasia for each particular drug. However, prospective studies of testicular function in large numbers of men receiving a variety of antitumor agents are needed to provide more reliable information concerning the threshold drug dose above which severe or irreversible testicular injury occurs. As newer agents are incorporated into standard cancer treatment programs, additional studies need to be completed to assess their effects on fertility.

TABLE 4.2 TOXICITY OF SINGLE AGENTS TO MALE GERM CELLS

Single Agent Drug

References

Drugs highly toxic to male germ cells

   Chlorambucil

13, 15

   Cyclophosphamide

16,17,18

   Ifosfamide

19, 20

   Procarbazine

21,22,23,24

   Cisplatin

19, 25,26,27,28,29,30,31,32,33,34,35,36,37

   Vincristine

38

Drugs with low toxicity to male germ cells

   Methotrexate

40, 44

   Doxorubicin

39, 41,42,43, 45,46,47

   Interferon-α–2B

49

Combination Chemotherapy and Disease-Specific Considerations

Hodgkin's Disease

As might be expected, combination chemotherapy regimens that include alkylating agents produce germinal aplasia and infertility in the majority of patients. This is clear in Hodgkin's disease, where the effects of MOPP (nitrogen mustard, vincristine, procarbazine, and prednisone) and a related regimen, MVPP (in which vinblastine replaces vincristine), have been extensively investigated. Sherins and DeVita50 first reported the effects of combination chemotherapy on the fertility of 16 men with lymphoma in complete remission 2 months to 7 years after MOPP, CVP (cyclophosphamide, vincristine, and prednisone), or cyclophosphamide alone. All except three patients had azoospermia or severe oligospermia on semen analysis. Those patients with normal ejaculates and testis biopsies, of whom two received MOPP and one received CVP, had been off therapy for 2 to 7 years. Subsequent studies have confirmed that at least 80% of men receiving MOPP combination chemotherapy develop azoospermia, germinal aplasia, testicular atrophy, and elevated FSH levels.8, 51, 52, 53, 54 Patients who receive COPP (cyclophosphamide, vinblastine, procarbazine, and prednisone) have significant gonadal dysfunction as well. In 92 men who received COPP, all developed azoospermia, and of the 19 who underwent testicular biopsy, all had evidence of germinal epithelial damage.55 ChlVPP (chlorambucil, vincristine, procarbazine, and prednisolone) appears to be equally toxic as indicated in a study in which 11 of 13 patients remained azoospermic with no evidence of biochemical recovery 17 years after completing therapy.56 Chapman et al52 found that all 74 men who received cyclic combination chemotherapy for Hodgkin's disease were azoospermic after treatment, and only 4 of 74 recovered spermatogenesis after a median follow-up of 27 months. A decline in libido and decreased sexual activity also occurred during therapy and only partially recovered after treatment. Interpretation of this data is complicated by pretreatment azoospermia that occurs in at least 50% of men with advanced Hodgkin's disease.52, 57 In addition, a recent study found that 70% of men with Hodgkin's disease had dyspermia (defined as oligospermia, forward motility disturbances, or abnormal morphology) prior to treatment.

Although reversibility of gonadal dysfunction has been known to occur with single-agent therapy, patients who receive combination chemotherapy are likely to develop long-lasting and frequently permanent infertility. Sherins and DeVita53 noted azoospermia and testicular germinal aplasia in patients as long as 4 years after completion of MOPP chemotherapy. Another group observed a return of spermatogenesis in only 4 of 64 men followed for 15 to 51 months after completion of MVPP chemotherapy.5 Several other studies have confirmed these findings, and it seems reasonable to conclude that only about 10% of patients receiving MOPP or MVPP will ultimately have a return of spermatogenesis. In addition, recent evidence has shown that age is not protective because age at chemotherapy did not affect post-treatment sperm counts and recovery in patients who received combination chemotherapy for Hodgkin's disease and non-Hodgkin's lymphoma.58, 59

A number of alternative combination chemotherapy regimens to MOPP have now been developed for the treatment of advanced Hodgkin's disease. Among these ABVD (Adriamycin, bleomycin, vinblastine, and dacarbazine) has been shown to be more efficacious and less toxic than the MOPP regimen. A comparison of these regimens revealed that azoospermia occurs in 100% of patients treated with MOPP, but in only 35% of patients receiving ABVD. In addition, recovery of spermatogenesis occurs rarely in patients treated with MOPP but nearly always in those treated with ABVD.60, 61, 62 Hybrid regimens of MOPP or COPP and ABVD also produce persistent testicular dysfunction, with 60 to 80% of patients experiencing prolonged germinal damage.57, 61 Other regimens have been designed to reduce long-term toxicity and some may have less germinal toxicity. In a study evaluating patients with Hodgkin's disease treated with three cycles of mitoxantrone, vincristine, vinblastine, and prednisone, followed by radiation therapy, 90% developed severe oligospermia or azoospermia within 1 month of beginning chemotherapy, but sperm counts returned to normal in 63% of patients between 2.6 and 4.5 months after the completion of chemotherapy.63 Another vincristine-based therapy, VEEP (vincristine, epirubicin, etoposide, and prednisolone) was designed to reduce treatment-related cardiotoxicity and infertility. In a phase II trial, 92% of patients had normal post-treatment sperm counts 2 years after completion of therapy.64

Non-Hodgkin's Lymphoma

Unlike patients with Hodgkin's disease, those with non-Hodgkin's lymphoma often have normal pretreatment sperm counts and motility.65 Regimens containing modest doses of cyclophosphamide such as MACOP-B (MTX-leucovorin, Adriamycin, cyclophosphamide, vincristine, prednisone, and bleomycin) or VACOP-B (including vinblastine rather than MTX) have produced only transient azoospermia, with recovery of spermatogenesis in 100% of patients at a mean of 28 months after completion of chemotherapy.65 However, with the standard cyclophosphamide regimens, sperm counts recovered in only two-thirds of patients at 7 years. Pryzant et al66 found that 83% of men who received less than 9.5 g/m2 of cyclophosphamide recovered a normal sperm count, and only 47% had recovery after cumulative doses greater than 9.5 g/m2. Those who also received pelvic irradiation had more profound and longer-lasting gonadal damage. A small study evaluating 14 patients who received VAPEC-B (vincristine, doxorubicin, prednisolone, etoposide, cyclophosphamide, and bleomycin) for either Hodgkin's disease or non-Hodgkin's lymphoma reported only 1 case of azoospermia in a patient who also received pelvic radiation therapy.67

As new regimens are developed, they will need to be compared with standard regimens for efficacy. In addition, larger studies are necessary to confirm and compare the effects on spermatogenesis. This information may play an important role in treatment planning for young men with Hodgkin's disease and non-Hodgkin's lymphoma and who are concerned about preservation of fertility during and after treatment.

Testicular Cancer

As with patients with Hodgkin's disease, patients with testicular cancer have a high rate of oligospermia prior to treatment. Studies have shown that up to 50% of men with testicular cancer have oligospermia at diagnosis.37, 68, 69 In addition, many patients undergo orchiectomy and retroperitoneal lymph node dissection, potentially contributing to future infertility. Studies have shown that patients who receive chemotherapy in addition to orchiectomy have a higher likelihood of azoospermia, oligospermia, and loss of testicular volume when compared with patients who receive orchiectomy alone.26, 28 Patients with testicular cancer treated with cisplatin-based combination chemotherapy uniformly become severely oligospermic or azoospermic soon after chemotherapy is initiated.25, 26, 27, 28, 29, 30, 70 Despite this immediate gonadal injury, there appears to be a high degree of reversibility of testicular dysfunction, with as many as 50% of patients demonstrating resumption of spermatogensis within 2 years of completing chemotherapy. Among 98 patients with testicular germ cell tumors, 28 were treated with cisplatin-based chemotherapy and had profound decreases in sperm counts 1 year later, but a return to pretreatment levels 3 years after completion of chemotherapy, accompanied by a normalization of FSH values.71 In a study with a median follow-up of 5 years, 27% of men who received PVB (cisplatin, vincristine, and bleomycin) were azoospermic. While some studies suggest that recovery of spermatogenesis is rare after 2 years,28, 72there have been reports of recovery of spermatogenesis and fertility long after treatment. For example, a patient with malignant teratoma who underwent orchiectomy, chemotherapy, and pelvic irradiation was found to be azoospermic 8 years after completing treatment, but recovered fertility 6 years later, which was 14 years after completing treatment.73 A recent study evaluated 22 men with testicular cancer who were followed between 6 and 13 years after receiving six cycles of PVB. Although the majority of patients had no recovery in sperm counts, three patients had a significant recovery, despite early azoospermia.74 Therefore, even though recovery beyond 2 years is rare, it does occur in isolated cases. Higher doses of chemotherapy generally induce longer-lasting oligospermia.31 As previously described, patients who receive carboplatin-based therapy are more likely to recover spermatogenesis when compared with those who receive cisplatin-based therapy. Other predictors of recovery include normospermia prior to therapy and less than five cycles of chemotherapy.37

High-Dose Chemotherapy and Bone Marrow Transplantation

Recently, more information has become available regarding the impact of bone marrow transplantation-conditioning regimens on fertility. In general, conditioning regimens involving total body irradiation appear to severely affect fertility, and gonadal recovery occurs in a portion of patients receiving chemotherapy-only conditioning regimens. In men receiving a preparative regimen of high-dose cyclophosphamide alone, potential for recovery of spermatogenesis is reasonably high. In 72 men who received this treatment in Seattle, 65% had a normal FSH and normal sperm counts, and 94% had normal serum LH and testosterone levels.75 Recovery of spermatogenesis was not age-related in this population. Recent studies evaluating different conditioning regimens found that 61 to 90% of men regain spermatogenesis within 3 years after single-agent cyclophosphamide.76, 77 Recovery of spermatogenesis was significantly lower in two studies that employed a busulfan-cyclophosphamide (Bu-Cy) conditioning regimen. Although early studies using 200 mg/kg of cyclophosphamide reported a dismal recovery rate of 17%,76 more recent studies using a lower dose of cyclophosphamide (120 mg/kg + 16mg/kg busulfan) have reported higher rates of recovery, ranging from 50 to 84%.77, 78 Conditioning regimens combining cyclophosphamide with total body irradiation appear to severely affect gonadal function, with only 17% of patients recovering spermatogenesis and never earlier than 4 years post-treatment.77

Leukemia

There have been relatively few studies evaluating the gonadal effects of combination chemotherapy for acute lymphoblastic leukemia (ALL). An early study of 44 boys with ALL reported impaired spermatogenesis in 40% of patients and found that combinations including cyclophosphamide and cytosine arabinoside were associated with a higher likelihood of gonadal damage.79 Quigley et al80 also found severe germinal damage in 13 of 25 boys with ALL who received the modified LSA2L2 protocol, a regimen including both cyclophosphamide and cytosine arabinoside. Despite these discouraging results, other ALL regimens have been associated with lower rates of gonadal damage. An aggressive eight-drug regimen that did not contain procarbazine was used in the treatment of adult ALL and was associated with preservation of fertility in the majority of patients.81 More recently, Wallace et al82 evaluated 37 men who received combination chemotherapy for ALL in childhood. Only six men had evidence of severe germinal damage at a median follow-up of 10 years. In addition, all six had received either cyclophosphamide or cyclophosphamide and cytosine arabinoside, supporting the hypothesis that ALL regimens excluding cyclophosphamide and cytosine arabinoside are less likely to cause permanent germinal aplasia.

Leydig Cell Dysfunction

Although the effect on spermatogenesis appears to be the most clinically relevant effect of cytotoxic chemotherapy, Leydig cell dysfunction may occur as well. Leydig cells remain morphologically intact after chemotherapy and basal serum LH levels generally remain normal, yet many patients have been found to have hypersecretion of LH in response to LH-releasing hormone, an indication of Leydig cell dysfunction.5, 8, 55, 83, 84 In addition, the incidence of Leydig cell dysfunction appears to be associated with increasing age and more severe germinal damage.84, 85 As with germinal epithelial damage, there is evidence of partial recovery of Leydig cell function following treatment, although a recent study suggests that recovery beyond 5 years is unlikely.85 The mechanism of Leydig cell failure is unclear. Even though it is possible that chemotherapy is directly toxic to the Leydig cells, germinal cell damage may indirectly affect Leydig cell function by decreasing testicular blood flow, disrupting paracrine control, or decreasing testicular volume, leading to structural changes in the testes.84

Despite recognition of these biochemical abnormalities, the clinical significance of these changes is unclear. Complete androgen deficiency has been associated with altered body composition, decreased sexual function, hot flushes, excessive sweating, fatigue, anxiety, depression, and reduced bone mineral density (BMD).86, 87, 88, 89, 90 Mild-to-moderate testosterone deficiency has been less well studied, but may be associated with sexual dysfunction,91, 92 increased serum cholesterol,93 and decreased BMD.94 Howell et al 95 compared 36 men with mild Leydig cell dysfunction to similarly treated men without evidence of Leydig cell dysfunction. They found a significantly lower BMD, increased incidence of truncal fat distribution, but no change in lipid profiles in the group with mild androgen deficiency. Testosterone replacement in men with complete androgen deficiency has been shown to increase BMD, increase muscle mass, and decrease body fat.96, 97, 98, 99 These recent studies suggest that testosterone replacement may also be beneficial to the subset of men with moderate Leydig cell dysfunction. Further investigation is warranted to determine the incidence and clinical significance of mild androgen deficiency, as well as the role of replacement therapy.

Mutagenic Potential of Cancer Chemotherapy

In addition to the effects on fertility and Leydig cell function, cytotoxic treatment may be associated with chromosomal abnormalities in germ cells. These alterations may contribute to post-treatment infertility and may place subsequent generations at risk for carcinogenesis or developmental disorders. A study employing multicolor fluorescence in situ hybridization (FISH) suggests that up to 19% of sperm from healthy men may have chromosomal alterations.100 The frequency of structural abnormalities of sperm in cancer patients receiving chemotherapy or radiation has been estimated at 9 to 40%, with more damage seen in patients who received multiple chemotherapeutic agents and longer durations of therapy.101, 102 Although many feel the rate of structural abnormalities is increased after exposure to chemotherapy, others have suggested that patients with cancer have a higher rate of sperm DNA abnormalities at baseline.103, 104,105 Until this controversy is resolved, there remains a concern that even men who have minimal germinal damage or recover germinal function may have underlying chromosomal changes that can be passed on to their progeny, resulting in genetic diseases including developmental abnormalities, metabolic abnormalities, or cancer.106

These concerns originate from animal studies, which have established the transgenerational effects of cytotoxic therapies. For example, dominant lethal mutations have been detected in zygotes after animals were treated with doxorubicin, melphalan, and chlorambucil.107, 108 The effects on the progeny of animals treated with cyclophosphamide, chlorambucil, doxorubicin, cisplatin, and procarbazine have included intrauterine death and developmental and morphologic abnormalities.109, 110, 111 Despite the concerns generated from these studies, human studies to date have been inconclusive, and the significance to future generations remains unclear. Human epidemiologic studies have failed to show increased developmental abnormalities or carcinogenesis in the offspring of men who received chemotherapy.112, 113, 114, 115, 116, 117 Human studies evaluate men treated with chemotherapy who have conceived children after recovery of spermatogenesis, often well after treatment was completed, but animal studies appear to reflect the consequences of progeny conceived either during or shortly after exposure to cytotoxic therapy.110 For this reason, many clinicians interpret the transgenerational human studies cautiously. Despite eight documented normal births to men who were receiving chemotherapy at the time of conception, it is reasonable to counsel men about the potential hazards to their future offspring. In addition, it is reasonable to recommend contraception for 6 months to 1 year after completion of treatment to allow for clearance of potentially affected germ cells from the reproductive tract.106, 111, 118

The absence of transgenerational effects may not apply to offspring conceived by specialized infertility techniques that utilize sperm collected during or soon after chemotherapy. It is likely that some natural selection occurs at the time of fertilization in vivo, decreasing the likelihood of fertilization by sperm with abnormal chromosomal material.109 Sperm collected by advanced reproductive technology (ART) during chemotherapy or after completion of chemotherapy may not be subject to this natural selection.106 The transgenerational animal studies support this potential, and Meistrich111 discourages the use of sperm collection and cyropreservation during cancer treatment.

Assisted Reproductive Techniques for Men

Semen Cryopreservation

Pretreatment sperm banking is presently the only proven means of preserving fertility for men who are to receive combination chemotherapy for cancer. Although pretreatment sperm banking does not guarantee a successful conception in future years, advances in management of male factor infertility have made conception possible for many men who are not azoospermic.119

One of the significant challenges for preserving fertility in male patients with cancer has been poor quality semen, even prior to treatment. Studies have shown that approximately 50 % of male cancer patients have reduced sperm quality prior to chemotherapy.52, 57, 120, 121, 122, 123, 124 Men with testicular cancer and Hodgkin's disease have significantly lower sperm motility and a higher incidence of azoospermia than men with other malignancies.124, 125 A review of patients from a single cryopreservation center found that 9.6% of men with testicular cancer and 18% of men with Hodgkin's disease were azoospermic prior to chemotherapy.124 The cause of impaired spermatogenesis in male cancer patients prior to therapy is unknown. Hypotheses in testicular cancer include testicular fibrosis, orchidectomy, retroperitoneal lymph node dissection (RPLND), sperm antibodies, and elevated β-HCG and α-fetoprotein.124 Postulated causes in Hodgkin's disease include elevated cytokines (IL-1, IL-6, TNF-α) or tumor-associated fever.126 Although the majority of studies in untreated patients with Hodgkin's disease and testicular cancer have suggested that oligospermia does not correlate with age, stage, presence of symptoms or fever,28, 57, 68, 127,128, 129 a recent study suggests that infertility is more frequent in patients with advanced Hodgkin's disease when compared with those with early stage disease.130

Despite a high rate of abnormal sperm quality, the majority of male cancer patients have adequate parameters for sperm storage.131 The German Hodgkin Lymphoma Study Group found that 70% of their male patients had semen abnormalities prior to treatment, but only 8% had azoospermia and 13% had severe sperm abnormalities.125 Other recent studies have found that only 12 to 17% of referred male cancer patients are unable to donate sperm for cryopreservation because of severe azoospermia prior to therapy.124, 132 In the past, minimal standards of sperm quality for crypreservation were used to maximize the chances of successful insemination. These included sperm concentration of at least 20 × 106 per milliliter, post-thaw motility greater than 40%, and post-thaw progression greater than 2+. It was thought that lower values were associated with a low probability of successful semen preservation, and ultimately of conception. Based on these critieria, many male cancer patients would be denied cryopreservation. In addition, cryopreservation itself has been known to decrease sperm motility.68 More recent data suggest that despite poor semen quality at the time of cryopreservation, many cancer patients are able to have been able to conceive using advanced reproductive techniques.133, 134, 135, 136, 137 Poor prefreeze semen quality has been associated with poor post-thaw outcome, but the association does not appear to be disease-related and the decline in semen quality does not appear to be different than in men without cancer.128, 138, 139 Therefore, many groups recommend that suboptimal prefreeze sperm analysis should not be used to deny sperm banking, and cryopreservation should be offered to all male patients who have some motile spermatozoa in their sperm sample, even if the quality is below the required minimum standard for in vitro fertilization (IVF) (2 × 106).131, 133, 138, 139

Although the technology of freezing, preserving, and thawing human semen has advanced considerably, ultimate conception rates using preserved semen have been limited by artificial insemination techniques. In the past, classic artificial insemination by husband (AIH) of the female partner using thawed spermatozoa was the only insemination technique available. AIH requires high numbers of spermatozoa and high-quality semen. Most early studies suggest that it is not very effective in subfertility secondary to sperm abnormalities.140, 141 More recent studies have reported better cumulative pregnancy rates with this technique in male cancer patients, ranging from 20 to 45%.133 Despite success for some patients, the majority of male cancer patients have inadequate sperm quantity or quality for this procedure. IVF can be used with low spermatozoa quantity or when female factors prevent successful AIH. The fertilization rate with IVF for male factor infertility, and specifically male cancer patients, has been reported at 57 to 60 %.135, 142, 143, 144 The newest advance in fertilization technique is intracytoplasmic sperm injection (ICSI), a type of gamete micromanipulation. This procedure has revolutionized the treatment of male factor infertility and holds particular promise for azoospermic and oligospermic cancer survivors. ICSI involves the direct injection of a single spermatozoa into the cytoplasm of an oocyte in the context of in vitro fertilization. In the setting of male factor infertility, pregnancy rates of 52% have been reported with ICSI. The take-home-baby rate has been estimated at 22 to 37% per cycle, comparable with the 30% rate of successful pregnancy per cycle with natural conception.145, 146, 147 Lass et al124 described their experience at a tertiary-assisted conception center and reported successful pregnancies in all six cancer patients that returned for use of their cryopreserved sperm. Two were accomplished with AIH cycles, two with in vitro fertilization cycles, and two with ICSI.

Despite the increased success of semen cryopreservation with ICSI, the utility of sperm banking has been questioned by several authors because of the low percentage of later use to achieve pregnancy.131, 148, 149 A survey of male cancer survivors found that only 24% of men completed sperm banking prior to cancer treatment.150 In addition, of those who completed sperm collection, less than 10% returned to use their collected sperm for fertilization.131, 132, 151Regardless, many believe that sperm collection prior to therapy should still be pursued as the number of patients referred for cryopreservation has been increasing over the last several years, and the studies to date may be biased by a short period of follow-up.132 In addition, a recent survey suggests that the low rate of referral may be related to a lack of discussion on the part of treating physicians. Of 201 men with a diagnosis of cancer in the preceding 2 years, 51% of men were interested in having children in the future, including 77% of childless men. On the other hand, only 51% recalled being given the option of semen cryopreservation and only 35% of respondents were not interested in having children in the future.150 A companion study found that fewer than 50 % of practitioners were consistently discussing sperm banking with their male cancer patients.150 The authors also found that men who were informed of fertility options by their oncologist, rather than by other means, were more likely to undergo sperm banking.152 If lack of information is the primary reason for not pursuing sperm banking, increased attention to, and education regarding sperm cryopreservation may increase the number of referrals and later use of cryopreserved sperm.

Testicular Sperm Extraction

Although the majority of patients are able to have sperm collected prior to therapy, there are a proportion of male cancer patients who are azoospermic prior to therapy and therefore unable to undergo standard semen collection. In addition, many men fail to have sperm collected prior to therapy and find themselves azoospermic after treatment. For these patients, sperm may be obtained through newer technologies such as epididymal aspiration, testicular sperm extraction (TESE), or transrectal electroejaculation (TE). With TESE, testicular biopsy tissue is macerated, centrifuged, and examined for the presence of sperm. TESE is an important method of sperm recovery for patients who have undergone cytotoxic chemotherapy and have apparent germinal aplasia. Recovery rates with TESE in patients with either complete germinal aplasia or maturation arrest on biopsy have ranged from 45 to 76%, presumably because of adjacent areas of intact spermatogenesis.153, 154 The reported pregnancy rates with TESE and ICSI range from 30 to 40%, do not appear to be significantly altered by the source of sperm or the testicular history,153, 154 and are comparable with rates in men with nonobstructive azoospermia caused by non-neoplastic disorders.154 As this technology is becoming more available, even men with long-standing azoospermia and absent sperm production may be able to father children. In addition, one group has suggested incorporating TESE prior to therapy in azoospermic men. Although a proportion of men who are azoospermic prior to therapy will regain spermatogenesis following therapy, many will remain azoospermic because of the therapy. Schrader et al155 successfully collected spermatozoa in 14 of 31 azoospermic patients prior to therapy, 14 with a germ cell tumor and 17 with malignant lymphoma. These authors advocate pretreatment TESE in azoospermic men as it is difficult to predict who will regain fertility after therapy, there is a theoretical teratogenic risk to offspring, and pretreatment banking can reduce fertility-related concerns for the future. In addition, in men with tumor-associated azoospermia who were unable to undergo cryopreservation, TESE post-treatment was unsuccessful in over half of patients, likely because of cytotoxic germinal damage.154, 155, 156

Testicular Germ Cell Transplantation

Testicular germ cell transplantation is an additional experimental technique that may be available to male cancer patients in the future. This procedure was first developed in male mice, in which spermatogonial stem cells were transferred into the seminiferous tubules of busulfan-sterilized recipient animals.157Several animal studies have shown that spermatogonial stem cells can repopulate the seminiferous tubules with resumption of spermatogenesis and production of functional spermatozoa, leading to natural live births in the recipient animals.157, 158, 159 Human application has just begun and remains experimental. One group has cryopreserved testicular cells in 12 patients with lymphoma prior to therapy. To date, seven of these patients have completed therapy and have undergone transplantation of their cryopreserved stem cells into the intratesticular rete testes. The outcomes of these transplants have not yet been published, but there is great hope that this will be feasible in humans.157, 160 Despite the great interest in testicular germ cell transplantation, there is a theoretical risk of disease transmission, especially in the setting of hematologic malignancies. This concern has been validated in an animal model in which all rats that received testicular germ cells from leukemic donors developed leukemia after testicular germ cell transplantation.161 Tumor cell depletion techniques are currently being developed to address this limitation. If successful, testicular germ cell transplantation may be a viable option for male cancer patients hoping to preserve their reproductive potential.

Hormonal Manipulation To Prevent Male Infertility

The recognition that some chemotherapy regimens produce irreversible gonadal injury has prompted a search for means to protect the testis from the toxic effects of these drugs. Reducing the rate of spermatogenesis by interrupting the pituitary-gonadal axis has been proposed as a means of rendering the germinal epithelium relatively resistant to cytotoxic agents. Gonadotropin-releasing hormone (GnRH) analogs, both agonists and antagonists, have been shown to inhibit spermatogenesis in animals162, 163, 164 and man.165 In 1981, Glode et al166 reported that treatment of mice with a GnRH analog resulted in protection of the testis from the damaging effects of cyclophosphamide.These findings stimulated the initiation of clinical trials to evaluate this approach in patients receiving cancer chemotherapy, but human trials to date have been largely unsuccessful.167, 168, 169, 170

These failures in human studies have prompted new hypotheses, and recent studies suggest that the mechanism of hormonal therapy is stimulation of the surviving type A spermatogonia to differentiate, rather than to-protection of the germ cells through inhibition of spermatogenesis.171, 172, 173 The animals studied had elevated FSH, LH, and intratesticular testosterone, but serum testosterone levels remained normal. These findings have led to the recent hypothesis that testosterone and FSH may inhibit spermatogonial differentiation in surviving germ cells. Further animal studies have shown that GnRH agonists and antagonists can prevent this block in differentiation through suppression of testosterone and FSH.173, 174, 175 GnRH-treated rats had increased sperm counts and a significant increase in fertility.176 The role of testosterone as a key inhibitor of differentiation has been shown in GnRH-treated animals. After treatment with GnRH, rats had the expected increase in spermatogenic differentiation. Animals were then administered exogenous androgens and spermatogonial differentiation declined in a dose-dependent fashion.177, 178

Although these animal studies are very encouraging and much has been learned about the hormonal mechanisms controlling spermatogenesis, the relevance to humans remains unclear. The optimal timing and duration of hormonal therapy remains unclear and may be drug-dependent.179 Meistrich suggests that future studies in humans should include frequent sperm samples and cryopreservation of sperm because the recovery of spermatogenesis was transient in some of the animal studies.171 It appears that hormonal manipulation is likely to be most successful in a setting in which there is some survival of type A spermatogonia.180 Therefore, human studies will need to start with cytotoxic agents and doses that do not completely deplete the germinal stem cell population.

CHEMOTHERAPY EFFECTS IN WOMEN

Oogenesis is the process of maturation of the primitive female germ cell to the mature ovum. This process occurs primarily during intrauterine life and involves multiple mitotic divisions to increase the number of germ cells, followed by the beginning of the first meiotic division, which will eventually reduce the diploid chromosome number to half before fertilization. At the time of birth, the oocytes are in the long prophase of their first meiotic division, and they remain in that state until the formation of a mature follicle before ovulation.181

In the postnatal ovary, most of the ongoing cellular growth and replication is related to the growth and development of follicles. Primordial follicles develop during gestation and consist of a primary oocyte covered by a layer of mesenchymal cells called granulosa cells. At the time of birth, the ovary may contain 150,000 to 500,000 primordial follicles, many of which subsequently become atretic. From childhood to menopause, follicular growth occurs as a continuous process, with ovulation occurring in a cyclic fashion.182 The granulosa cells surrounding the primary oocyte proliferate, follicular fluid accumulates, and the ovum completes its first meiotic division to become a secondary oocyte. At this time, the follicle is known as a secondary or graafian follicle. The follicle continues to enlarge until the time of ovulation. Those follicles not undergoing ovulation become atretic and regress. During the reproductive life of a woman, only 300 to 400 oocytes mature and are extruded in the process of ovulation; the remainder undergo some form of atresia.

Assessment of Ovarian Function

The evaluation of chemotherapy effects on ovarian function is hampered by the relative inaccessibility of the ovary to biopsy. There is no readily available direct measurement of the female germ cell population analogous to semen analysis in men. Animal models to assess the effects of cytotoxic drugs on ovarian function have been developed only recently. Thus, one must rely primarily on menstrual and reproductive history and on determinations of serum hormone levels to assess the functional status of the ovary.

Follicular growth and maturation and estradiol production are under regulatory control of the pituitary and hypothalamus. Pituitary FSH stimulates granulosa cells to replicate and produce estradiol. The midcycle LH surge promotes ovulation and the ruptured follicle becomes the corpus luteum, which produces progesterone, thereby suppressing further LH secretion.183 Drug-induced ovarian failure interrupts this delicate hormonal balance and results in abnormally low serum levels of estradiol and progesterone, markedly elevated levels of FSH and LH, amenorrhea, and symptoms of estrogen deficiency.

The primary histologic lesion noted in the ovaries of women receiving antineoplastic chemotherapy is ovarian fibrosis and follicle destruction.184, 185 Clinically, amenorrhea ensues and is accompanied by elevation of serum FSH and LH levels and a fall in serum estradiol. Vaginal epithelial atrophy and endometrial hypoplasia occur, and patients may complain of menopausal symptoms such as vaginal dryness and dyspareunia.

Drug Effects on Ovarian Function

The onset and duration of amenorrhea varies with the cytotoxic agent (Table 4.3) and appears to be both dose-related and age-related. Generally, younger patients are able to tolerate larger cumulative drug doses before amenorrhea occurs and have a greater likelihood of resumption of menses when therapy is discontinued.

Drugs Highly Toxic to Germ Cells

Alkylating Agents

Alkylating agents are the most frequent cause of ovarian dysfunction among the anticancer drugs. During the early clinical trials of busulfan, amenorrhea was a common side effect. Several investigators noted the onset of permanent amenorrhea among patients receiving busulfan in doses varying from 0.5 to 14.0 mg/day for at least 3 months.186, 187 The effects of cyclophosphamide on ovarian function in humans were first noted in the rheumatology literature as noted in a study showing that early cessation of menses and menopausal symptoms developed in 6 of 33 patients treated for rheumatoid arthritis with daily cyclophosphamide for 6 to 40 months.188 One of these patients had elevated FSH levels consistent with primary ovarian failure.


Subsequently, several investigators documented the occurrence of amenorrhea, decreased urinary estrogens, and increased urinary gonadotropins in at least 50% of premenopausal women receiving 40 to 120 mg of cyclophosphamide daily for an average of 18 months.189, 190 Ovarian biopsy in some patients demonstrated arrest of follicular maturation and absence of ova.

TABLE 4.3 TOXICITY OF SINGLE AGENTS TO FEMALE GERM CELLS

Single Agent Drug

References

Drugs highly toxic to female germ cells

   Busulfan

186, 187

   Cyclophosphamide

188,189,190,191

   Melphalan

192

Drugs with moderate-to-low toxicity to female germ cells

   Methotrexate

39

   5–FU

191, 192

   Etoposide/vinca alkaloids

193, 194

   Doxorubicin

195

   Cisplatin

194, 196,197,198

   Taxanes

199

Studies of the use of adjuvant chemotherapy for the prevention of recurrence of breast cancer suggest that the onset of amenorrhea and the resumption of menses are related to the age of the patient during chemotherapy and to the total dose administered.191, 192, 193 Amenorrhea developed in 17 of 18 women treated with adjuvant cyclophosphamide for 13 to 14 months postoperatively.194 Permanent cessation of menses occurred after a mean total dose of 5.2 g in all patients 40 years of age and older. Amenorrhea also developed in four of five women younger than age 40, but only after a mean cyclophosphamide dose of 9.3 g had been administered. Menses subsequently returned in two of these patients within 6 months of discontinuing therapy. Furthermore, a prospective study of ovarian function in premenopausal women receiving melphalan alone or in combination with 5-fluorouracil (5-FU) demonstrated the occurrence of amenorrhea in 22% of patients younger than age 39 but in 73% of patients older than age 40.195 Time to the development of amenorrhea also appears to be age-related after adjuvant treatment with cyclophosphamide, MTX, and 5-FU (CMF).196 In women younger than age 35, mean time to the onset of amenorrhea is 5.54 months; for women aged 35 to 45 years, the mean time is 2.31 months, and in women older than age 45, amenorrhea develops very quickly, with a mean onset of 1.01 months. It seems, then, that alkylating agent chemotherapy accelerates the onset of menopause, particularly in older patients, whereas younger patients may tolerate higher total doses before amenorrhea becomes irreversible. Other large studies examining the effects of CMF also have documented this age-related effect.197, 198, 199, 200 In addition, recent studies evaluating pulse intravenous cyclophosphamide in inflammatory diseases have confirmed the associations of age at treatment and cumulative dose with therapy-related ovarian failure. Women who receive intravenous cyclophosphamide before the age of 25 rarely experience permanent amenorrhea. Yet, rates of amenorrhea after age 31 range from 45 to 62% and have been reported as high as 83% after age 40.201, 202 Similar to the findings in adjuvant breast cancer therapy, there was an increased risk of amenorrhea associated with greater cumulative dose, although the difference was not statistically significant.201

Drugs with Moderate to Low Toxicity to Germ Cells

Although many other chemotherapeutic agents have been evaluated for long-term ovarian toxicity, most evidence comes from studying the effects of combination chemotherapy regimens. Therefore, it is often difficult to determine the contribution of individual agents.

In general, chemotherapeutic agents that are cell cycle-specific appear to have low gonadotoxicity in women. Many of these agents are toxic to reproductive germ cells in men, but they do not have the same toxicity in women. This is likely because there is constant cell division during spermatogenesis, and in women, there is intermittent cell division involving only a small number of primary oocytes with each menstrual cycle.

Antimetabolites

Among the antimetabolites, high-dose methotrexate and 5-FU have been evaluated and appear to have no immediate ovarian toxicity.39 A study of single-agent 5-FU in nine patients with breast cancer found no evidence of ovarian failure.194 In addition, Fisher et al195 found no difference in the incidence of post-therapy amenorrhea in women who received 5-FU and melphalan compared with those who received melphalan alone.

Etoposide

The effects of oral etoposide on ovarian function were evaluated in one study of 22 patients receiving this agent. Age-related oligomenorrhea or amenorrhea occurred in 41% of patients after a mean cumulative etoposide dose of 5 g204 In addition, Meirow205 evaluated 168 women who received various combination regimens for lymphoma, leukemia, and breast cancer and found no association between vinca alkaloid administration and occurrence of amenorrhea.

Doxorubicin

Doxorubicin administration does not appear to have profound ovarian ablative effects. In women younger than age 35 who received adjuvant cyclophosphamide, doxorubicin, and 5-FU, 32% had temporary amenorrhea during treatment, and only 9% had permanent amenorrhea.206

Cisplatin

Although platinum chemotherapeutic agents have notable gonadal toxicity in men, the data in women are limited and contradictory. Many studies suggest that most women who receive platinum-based chemotherapy have temporary amenorrhea, but resume normal menstrual function. Low et al207 evaluated 44 females, aged 10 to 35 years old, who received cisplatin-based therapy for malignant germ cell tumors of the ovary. While two-thirds of the patients experienced amenorrhea during therapy, 43 of 47 (91%) resumed normal menstrual patterns and 95% of those who attempted conception were successful.As described previously, Meirow205 evaluated 168 patients who received combination chemotherapy for lymphoma, leukemia, or breast cancer for future risk of treatment-related ovarian failure. The author reported an odds ratio of 1.77 for cisplatin-containing therapy, although the results were not statistically significant. Other groups have reported persistent menstrual dysfunction in women after the administration of cisplatin-based therapies.203, 208, 209 The inconsistencies in the literature may be explained by differences in defining treatment-related ovarian failure, the duration of follow-up, dose received, and age at administration. It is clear that further studies are needed to determine the true impact of platinum-based therapy on future fertility.

Taxanes

Although taxanes have become widely used in the treatment of breast cancer, there are little data regarding the ovarian toxicity of this class of chemotherapeutics. Early results of the BCIRG 001 trial reported that 51% of patients receiving TAC (docetaxel, Adriamycin, and cyclophosphamide) developed amenorrhea.210 These results are preliminary, with short-term follow-up and an unclear definition of amenorrhea. Therefore, further studies are needed to draw definitive conclusions regarding the incidence of treatment-related ovarian failure following taxane therapy.

Combination Chemotherapy and Disease-Specific Considerations

Breast Cancer

Studies of adjuvant chemotherapy for breast cancer have yielded other important information regarding the effects of dose and treatment duration on menstrual cycles (Table 4.4). Evaluation of 95 premenopausal women who received cyclophosphamide, MTX, 5-FU, vincristine, and prednisone documented permanent amenorrhea in 70.5% of patients.211 Women receiving chemotherapy for 12 weeks had a 55% incidence of amenorrhea, whereas 83% of women receiving a 36-week regimen were rendered amenorrheic. Breast cancer recurrence and mortality rates in women who experienced amenorrhea were lower than in those who continued to menstruate, even within each treatment group, suggesting a potential therapeutic benefit of ovarian ablation. However, the contribution of treatment-induced amenorrhea to the beneficial effects of adjuvant chemotherapy remains uncertain and controversial.

In counseling women with newly diagnosed breast cancer regarding the risk of chemotherapy-related amenorrhea or ovarian failure, age and risk of recurrence must be considered. Age at treatment is the primary factor in predicting chemotherapy-induced amenorrhea and is the most relevant consideration when counseling women with premenopausal breast cancer. Several studies have shown that younger women have a higher likelihood of resuming their menses and maintaining future fertility. For example, CMF has been associated with persistent amenorrhea in 21 to 71% of women under 40 years old, compared with 49 to 100% in those over 40 years old.199 Other groups have found low rates of persistent amenorrhea (0 to 4%) in women under the age of 30 who received CMF or doxorubicin-based therapy, rates of 50% in women between 30 and 40 years old, and rates of 86% and higher in women over 40 years old.212, 213

Although the choice of adjuvant therapy primarily depends on disease characteristics, it may be useful to consider the likelihood of amenorrhea with different adjuvant regimens in which subsequent fertility is of great importance to the patient. In general, studies suggest that the combination of cyclophosphamide, methotrexate and 5-FU (CMF) is the regimen with the highest likelihood of causing premature ovarian failure because up to two-thirds of premenopausal women who receive CMF will experience persistent amenorrhea.199 An early study of doxorubicin-based adjuvant therapy reported persistent amenorrhea in 59% of women,212 but more recent studies have found lower rates of persistent amenorrhea, ranging from 34 to 51% of premenopausal women treated with doxorubicin or epirubicin-based regimens.199, 210, 214 As described previously, ovarian failure with taxane-containing regimens is not well studied, although the early results of the BCIRG 001 trial reported that 51% of patients receiving TAC developed amenorrhea.210 Although the treatment is rarely used today, low rates of persistent amenorrhea (9%) have been reported with melphalan-based regimens.199 These rates ignore the wide variability secondary to age at the onset of treatment, so the probability on basis of the age of the patient must also be carefully considered.

TABLE 4.4 RATES OF AMENORRHEA AFTER ADJUVANT REGIMENS FOR BREAST CANCER

Regimen

<40 Years Old

≥40 Years Old

References

CMF

40–61%

76–95%

198, 204

 

30 Years Old

31–39 Years Old

40 Years Old

Doxorubin–based regimens

None

33%

96%

212

All Ages

CAF/CEF

32.8–51%

199, 206, 214

AC

34%

206

AC/Taxol

51%

199

Melphalan/5-FU

9%

206

Hodgkin's Disease

The risk of ovarian failure after other combination chemotherapy for hematologic malignancies is also clearly related to the age of the patient at the time of treatment. Overall, at least 50% of women treated with MOPP or related regimens become amenorrheic.215, 216, 217, 218, 219, 220, 221, 222 The cessation of menses is accompanied by elevations of serum FSH and LH consistent with primary ovarian failure. Apart from age, no clear differences have been noted between those women who become amenorrheic during therapy and those who do not. In one study, follow-up of MOPP-treated patients for a median of 9 years after the completion of chemotherapy revealed that 46% had developed permanent amenorrhea.217 Of these women, 89% were older than 25 years at the time of treatment. Moreover, the time of onset of amenorrhea seemed to be age-related; ovarian failure occurred within 1 year of discontinuing therapy in all patients 39 years of age or older, whereas in younger patients there was a gradual decrease in frequency of menses occurring more than several years after therapy. Another group found similar results with 76% of women who received MOPP or a related hybrid combination of chlorambucil, vinblastine, prednisolone, procarbazine, doxorubicin, vincristine, and etoposide developed amenorrhea during or immediately after treatment. Despite this, 10 women later regained normal menstrual periods and 16 had permanent amenorrhea. The mean age at treatment among the 10 with recovery was 25 years, and the mean age in the latter group was 36 years old, suggesting the importance of age at the time of therapy.222 Another group reported persistent ovarian failure in 86% of women over 24 years old who received COPP (cyclophosphamide, vincristine, procarbazine, and prednisone), but a much lower rate of 28% in those who were under 24 years old at the time of treatment.223 At present, it seems unlikely that those patients treated when younger than age 25 will experience any significant therapy-related ovarian dysfunction during the initial 5 to 10 years after the completion of therapy. As in men, ABVD chemotherapy may be less likely to produce premature ovarian failure, although longer follow-up is required to be certain. In a study comparing MOPP with ABVD, 50% of the patients who received MOPP and were over 30 years old developed prolonged amenorrhea. All the women who received MOPP under the age of 30 and all the women who received ABVD, regardless of age, had resumption of normal menstrual cycles.60

Non-Hodgkin's Lymphoma

Combination chemotherapy regimens for aggressive non-Hodgkin's lymphoma do not consistently cause premature ovarian failure, perhaps because procarbazine is rarely included in such regimens.22 Of 10 women who received various combined modality regimens for non-Hodgkin's lymphoma, only 1 developed gonadal dysfunction. Similarly, among seven women aged 35 to 43 treated with MACOP-B or VACOP-B for aggressive non-Hodgkin's lymphoma, only one developed amenorrhea.65

Ovarian Germ Cell Tumors

Although malignant germ cell tumors of the ovary are rare, they principally occur during adolescence and early adulthood. With the advent of cisplatin-based chemotherapy regimens, high cure rates have been obtained, even in the setting of metastatic disease.207 Fertility-sparing surgery has become the standard of care because evidence has shown that removal of the uninvolved ovary does not improve survival.224 Many patients receive combination chemotherapy, and the regimens used appear to cause relatively little ovarian toxicity. In one study, 70% of women maintained regular menses after treatment with a variety of regimens containing drugs such as actinomycin D, vincristine, and cyclophosphamide.225 Low et al207 evaluated 47 females between the ages of 10 and 35 years old who received conservative surgery followed by chemotherapy for malignant germ cell tumors of the ovary. Forty-four of the patients received cisplatin-based regimens. Although two-thirds experienced amenorrhea during therapy, 43 of 47 (91%) resumed normal menstrual periods after completion of therapy. In addition, 95% of those who attempted to conceive children were successful. Tangir et al203 found no difference in fertility outcomes between patients who received cyclophosphamide-based therapy versus cisplatin-based therapy. Other groups have reported similar results, and it appears that the majority of women who receive chemotherapy for germ cell tumors of the ovary will resume menstrual function.226, 227

High-Dose Chemotherapy and Bone Marrow Transplantation

The risk of treatment-related ovarian failure after high-dose chemotherapy and bone marrow transplant appears to be largely related to age at the time of treatment. From the Seattle experience, cyclophosphamide-containing preparative regimens for allogeneic bone marrow transplantation induced reversible amenorrhea in women younger than 26 years of age, but permanent amenorrhea in 67% of women older than age 26.228 Likewise, Schimmer et al229evaluated 17 premenopausal patients treated with a variety of conditioning regimens followed by autologous bone marrow transplant for predictors of ovarian failure. Of the 17 patients, only 5 (29%) had a return of normal menstrual cycles. The mean age of those with recovery of ovarian function was 19 years, and mean age of those with persistent amenorrhea was 30 years. In their analysis, younger age at treatment was a statistically significant predictor of future ovarian function. Univariate analysis suggested a trend toward total-body irradiation (TBI) as a predictor of permanent amenorrhea. In addition, the number of prior chemotherapy salvage regimens, or the number of regimens containing alkylating agents, did not predict for permanent amenorrhea. Other studies have suggested that regimens using TBI cause premature menopause in nearly all patients.228 Chatterjee and Goldstone230 found that 20 of 30 women who received conditioning regimens with chemotherapy only recovered normal menstrual patterns, and none of the 10 who received TBI recovered ovarian function. Others have found similar results, and it appears that most younger women, who receive chemotherapy-containing conditioning regimens will regain menstrual function, and the majority over age 26 years old will have treatment-related infertility.65, 205, 231, 232 Although most studies have found that the specific chemotherapy-conditioning regimen did not appear to affect future fertility, Singhal et al 233 reported a higher pregnancy rate among women who were conditioned with melphalan alone when compared with those who received other conditioning regimens. These authors suggested that this regimen is adequate for engraftment and may be less likely to cause treatment-related ovarian failure. Further studies are needed to confirm these results because variations in permanent ovarian failure among chemotherapy-conditioning regimens could be important to young women undergoing high-dose chemotherapy and bone marrow transplantation.

Estrogen Deficiency

Although infertility is a primary concern of many young women who receive cytotoxic therapy, women who develop premature ovarian failure may also be subject to the physical and emotional disorders that accompany estrogen deficiency. Depressed libido, irritability, sleep disturbances, and poor self-image all occur commonly in women with treatment-related amenorrhea.216, 234 Hormone replacement therapy may be of considerable benefit to patients with chemotherapy-induced amenorrhea, frequently producing dramatic relief of hot flashes, dyspareunia, and irritability. Another potential benefit of estrogen replacement therapy may be prevention of postmenopausal osteoporosis and diminished risk of premature atherosclerosis.

Mutagenic Potential of Cancer Chemotherapy in Women

As previously described, the mutagenic potential of cancer chemotherapy remains largely undefined. Some anecdotal reports suggest that there is no increased incidence of spontaneous abortion or fetal abnormalities in women treated with chemotherapy in comparison with the general population.206, 235, 236,237, 238 Several larger series and reviews have generally confirmed this observation.239, 240, 241, 242 However, there are other reports suggesting an increase in structural congenital cardiac defects, spontaneous abortions, and other congenital anomalies in women previously treated with chemotherapy when compared with controls.239, 243 At present, it is impossible to define the risk of fetal wastage or abnormality in patients previously treated with cytotoxic drugs. Whether a specific fetal abnormality may occur more commonly than others, or whether a specific drug class, dose, or combination is more mutagenic than others remains unknown. Additional studies carried out over many years are required before the true risks to subsequent generations are known.

The mutagenic effects of chemotherapy on the offspring from oocytes obtained by advanced reproductive techniques soon after chemotherapy administration are unknown. Women considering ooctye retrieval soon after the completion of chemotherapy should be counseled regarding the theoretical risk of congenital malformation and early pregnancy loss. Based on the timing of cyclophosphamide-induced follicular injury in rats, Meirow205 suggests that oocytes obtained in the 6 to 12 months following therapy may be compromised, and recommends that further studies are needed to better define the time period of greatest susceptibility.

Assisted Reproductive Techniques for Women

Embryo Cryopreservation

Prior to the development of embryo cryopreservation, no reliable techniques existed for women who wished to retain the ability to bear children following ovarian ablative chemotherapy. Embryo cryopreservation with later intrafallopian or intrauterine embryo transfer is the only successful clinical approach to postchemotherapy ovarian failure.244 Before initiation of chemotherapy, women may have oocytes harvested and fertilized in vitro with husband or donor sperm. The embryos can be stored in liquid nitrogen and thawed for implantation at a later date when the patient's endometrium has been hormonally prepared. This option has been associated with pregnancy and take-home baby rates of 30 to 35% and 29%, respectively.245 In women who did not have frozen zygotes or embryos stored before chemotherapy, donor ova are available for fertilization and implantation at specialized fertility centers.

Unfortunately, although successful, this procedure is not available for many women. First, embryo cryopreservation requires a partner at the time of harvest. Even though an anonymous sperm donor is an alternative, this is an unacceptable option for many women. In addition, embryo cryopreservation is not an option for prepubertal or pubertal girls. Secondly, the time involved in ovarian stimulation, monitoring, and oocyte retrieval requires a delay in beginning cancer treatment that many oncologists discourage. For this reason, some centers offer IVF only during breaks in treatment or after remission is achieved.246, 247 Lastly, ovarian stimulation increases levels of estradiol,248, 249 and studies have suggested that breast cancer cell proliferation and dissemination can be induced by estrogen.250, 251 For this reason, many oncologists believe that conventional stimulation programs are contraindicated in women with hormone-responsive malignancies such as breast cancer.

For women with breast cancer, an alternative to standard IVF is natural IVF, or oocyte retrieval without hyperstimulation. Unfortunately, unstimulated cycles generally only yield one or two metaphase II eggs. Hyperstimulation significantly increases the chance of a successful pregnancy and allows storage of multiple embryos for future transfer attempts. For this reason, alternative stimulation programs have recently been evaluated and may be available in the future. For example, tamoxifen has been used as an ovulation induction agent in Europe, similar to clomiphene in the United States. Oktay et al249 recently developed and evaluated tamoxifen for ovarian stimulation in patients with breast cancer. This group compared their tamoxifen stimulation protocol with natural cycle IVF and reported a greater number of embryos available for cryopreservation in the tamoxifen-stimulation group. Only 3 of 5 women in the natural IVF program had embryo formation, while all 12 in the tamoxifen group had at least one embryo recovered. To date, only two women in the tamoxifen-stimulation group have attempted embryo transfer. Although one of these attempts resulted in a miscarriage at 8 weeks, the other woman had a successful twin birth. Aromatase inhibitors are now being investigated as an alternative to ovulation induction, as they are associated with lower midcycle estradiol levels.249

Cryopreservation of Oocytes

Embryo cryopreservation is the standard option, but oocyte cryopreservation would benefit prepubertal girls and women without a partner at the time of oocyte retrieval. Embryo cryopreservation became the procedure of choice because embryos survive cryopreservation better than oocytes. Animal studies have shown that freezing and thawing of unfertilized oocytes results in changes in the zona pellucida, leading to decreased rates of fertilization.252 With advances and manipulation of cryopreservation media and conditions, oocyte freezing and storage have been partially successful in animals.252, 253, 254 These techniques have been attempted in humans, and there are 26 pregnancies derived from cryopreserved oocytes reported in the literature.255 Despite these successes, the overall pregnancy and delivery rates (4.7 and 3.1%, respectively) are too low for widespread clinical application. With continued advances, oocyte cryopreservation may become a valid reproductive option in the future.

Ovarian Tissue Cryopreservation and Transplantation

A technique that holds great promise for women anticipating treatment with potentially sterilizing chemotherapy is ovarian autografting. Already in clinical trials, the technique relies on the removal of oocyte-rich ovarian cortical tissue that is then slowly cooled and stored in a cryopreservative. At a later date, the tissue may be thawed and reimplanted near the fallopian tubes for potentially natural ovulation and fertilization. Ovarian tissue cryopreservation and transplantation offer several advantages over oocyte and embryo cryopreservation, including a greater number of immature oocytes, elimination of the need for hormonal stimulation and delays in therapy, and easier cryopreservation because follicles are small, lack a zona pellucida, and are metabolically inactive and undifferentiated. In addition, ovarian cryopreservation can be offered to prepubertal and pubertal girls.256 In addition, this technique could provide an alternative to hormone replacement therapy for patients who develop premature ovarian failure. Gosden et al,257 who pioneered this technique, reported successful pregnancies in sheep, and other groups have had similar success in various animals.258 Although still investigational, applications with cryopreserved ovarian implants have begun in humans.259, 260, 261 Cortical ovarian biopsies have been easily obtained in women via laparascopy without significant complications.205 In addition, case reports and small series of successful ovarian autotransplants have been described. Ovarian tissue transplantation has restored ovarian hormonal function in a single patient, resulted in a normal ovulatory cycle in another, and shown evidence of follicular development after transplantation in a small series.262, 263 In addition, retrieval of a single oocyte has been described after hetertopic autologous ovarian transplant in one patient.264 Despite these successes, this procedure is still in its infancy and pregnancies have not yet been reported. There are concerns with poor tissue survival as a result of ischemic-reperfusion injury, the longevity of ovarian tissue grafts, the ability to achieve follicular development within the graft, and malignant disease transmission via the autologous tissue graft. In addition, the optimal application for cryopreserved ovarian grafts is unclear. Although orthotopic autologous transplantation is the most obvious application, there are concerns for poor graft survival and follicular reserve. Heterotopic transplantation, involving grafting to a distant tissue site such as the arm or abdominal wall, may be an alternative, allowing for oocyte recovery prior to graft failure. Xenotransplantation, involving transplantation into an animal followed by later oocyte retrieval after adequate follicular development, could be an option to avoid malignant disease transmission.265 Lastly, in vitro maturation followed by IVF has been demonstrated in a mouse model.266 Although ovarian tissue transplantation remains investigational, it may become a management option for women with premature ovarian failure secondary to cytotoxic therapy.

Hormonal Manipulation in Women

Efforts to protect the ovary from the toxic effects of chemotherapy have focused on the use of oral contraceptives and GnRH agonists to induce ovarian suppression. Preliminary data reported by Chapman and Sutcliffe267 suggested that ovarian follicles could be protected and normal menses could be preserved by the administration of oral contraceptives during chemotherapy. Only a small number of young women were studied, and follow-up was brief. More recent studies with longer follow-up have failed to demonstrate a protective effect of oral contraceptives.220, 221, 268 Thus, the incomplete gonadal suppression induced by oral contraceptives may not be sufficient to protect ovarian follicles during cytotoxic therapy.269

Although GnRH analogs have not been proven to be protective of male germ cells, the studies in women have been more encouraging. The goal of this approach is to induce a dormant state in germ cells, suppressing cellular replication, and rendering the cells resistant to the cytotoxic effects of chemotherapy. GnRH analogs appear to partially protect ovarian follicles and fertility in rats and Rhesus monkeys from the damaging effects of cyclophosphamide,270, 271, 272,273 with variable protective effects from x-irradiation.274, 275 However, preliminary clinical observations have failed to demonstrate a protective effect of the LHRH analog buserelin on ovarian function in women undergoing chemotherapy for Hodgkin's disease.169 In contrast, GnRH agonists may have a protective effect in young women receiving chemotherapy for lymphoma.269 Similarly, Blumenfeld et al276 administered a GnRH agonist to 60 premenopausal women with lymphoma prior to chemotherapy and for 6 months during and after chemo-therapy. Six months after the start of chemotherapy, only 3 of the 60 (5%) developed ovarian failure compared with 32 of 58 (55%) age-matched and disease-matched controls. Continued long-term, prospective follow-up of women maintaining normal menses during chemotherapy is necessary to determine the degree of risk of premature ovarian failure and early menopause in these individuals.

CHEMOTHERAPY EFFECTS IN CHILDREN

Over 70% of children now survive cancer that is diagnosed and treated in childhood.277 Because discussion of remission rates, survival rates, and immediate toxicities tend to dominate initial dicussions regarding treatment options, consideration of future fertility is a quality of life aspect that is often neglected. Many regimens used as treatment for childhood cancer have significant gonadal toxicity. As a result, many survivors experience infertility as adults. Any study of the effects of cytotoxic chemotherapy on gonadal function in children is particularly complex because of the variables introduced by the continuum of sexual development in this patient population. Thus, the effects of chemotherapy can be expected to vary according to when drugs are given and when their effects are evaluated relative to puberty.

Chemotherapy Effects in Boys

Early reports suggested differences in the sensitivity of the prepubertal, pubertal, and adult testis to alkylating-agent chemotherapy, concluding that the prepubertal testis is relatively unaffected by chemotherapy. For example, one group found serum FSH, LH, and testosterone levels normal for their age in 15 boys treated with cyclophosphamide during the prepubertal years or early puberty.278 Another study evaluating gonadal function in boys undergoing combination chemotherapy (prednisone, vincristine, MTX, and 6-mercaptopurine) for ALL reported normal semen analyses in five of six patients after a median follow-up of 5.5 years.279 Other investigators found an initial decrease in spermatogonia among patients undergoing chemotherapy for acute lymphoblastic leukemia, but reported improvement to normal levels over many years,280, 281 concluding that leukemia therapy has definite, although at least partially reversible, effects on the germinal epithelium of the prepubertal and intrapubertal boy. More recent data have contradicted the hypothesis that the prepubertal state offers protection against the gonadotoxic effects of chemotherapy. As early as 1976, Etteldorf et al282 suggested that, even for the prepubertal patient, a dose-toxicity relationship may exist. These investigators evaluated eight boys, aged 7.5 to 13.0 years old, who received varying cumulative doses of cyclophosphamide. Those patients receiving 11.8 to 39.3 g of the drug were uniformly azoospermic with germinal aplasia as a finding on biopsy results, and those who received lower cumulative doses had normal sperm counts. More recently, Mustieles et al283 evaluated 15 men who received polychemotherapy between ages 6 and 10 years old (12 were prepubertal) and reported only 1 patient with normal sperm counts after a mean follow-up of 6 years. Similarly, among 19 prepubertal boys receiving MOPP or more than 9 g/m2 of cyclophosphamide, 12 were sterile at a mean follow-up of 9 years.284 Other studies have confirmed that MOPP is uniformly toxic, even when administered during the prepubertal state, as almost all patients have evidence of azoospermia or oligospermia as adults.285, 286, 287, 288 These findings suggest that the prepubertal testis may be more tolerant of moderate doses of alkylating agents than is the adult testis, yet a threshold dose does seem to exist, above which germinal epithelial injury will result.289, 290

Chemotherapy delivered to male patients during puberty appears to have profound effects on both germ cell production and endocrine function, similar to the effects seen in adult male cancer patients. Among 12 prepubertal and pubertal boys who received at least six cycles of MOPP for Hodgkin's disease at Stanford, all patients who provided semen for analysis had complete azoospermia as long as 11 years after treatment.287 Two of these boys (aged 8 and 12 at diagnosis) had recovery of fertility and subsequently fathered children 12 and 15 years after therapy, but none of the boys treated during puberty recovered spermatogenesis. However, all boys attained normal sexual maturation, and androgen replacement was not necessary in any patient. In a review of childhood cancer patients, alkylating agents were the most likely drugs to cause azoospermia, with 68% of 93 male childhood cancer survivors azoospermic after therapy. Of the 57 patients who received cisplatin or cisplatin-based regimens, only 37% had long-term azoospermia. An even lower rate of gonadal toxicity was reported in the 31 patients who received nonalkylating agents (adriamycin, vincristine, methotrexate, and 6-mercaptopurine) as only 16% had future azoospermia.291 Leydig cell dysfunction can also occur in some patients and may manifest as gynecomastia.

Although future fertility is not the most immediate concern when treating children or adolescent male cancer patients, improved survival rates have led to an increased appreciation for the long-term quality of life effects of chemotherapeutic treatment. For this reason, many authors suggest that clinicians address future infertility prior to instituting therapy. In addition, many authors advocate sperm collection and cryopreservation for peripubertal or postpubertal sexually mature adolescents. Although not routinely offered because of a presumption of inadequate collection in adolescent males, recent studies suggest there may be a role for sperm cryopreservation in adolescent cancer patients. Kleish et al291 compared sperm concentrations, motility, and morphology in male cancer patients and found no significant differences in semen parameters from adolescent boys (14 to 17 years old), young adult males (17 to 20 years old), and adult males, suggesting feasibility of cryopreservation in adolescent male cancer patients. Postovsky et al292 reported poor sperm collection in 27 male cancer patients aged 14 to 19 years old, with only 30% of attempts yielding a normal volume ejaculate and only 6.5 % of attempts producing semen with normal parameters. Similar inadequacies have been reported in male cancer patients in which 50 % of male cancer patients have reduced sperm quality prior to chemotherapy.52, 57, 120, 121, 122, 123, 124 Despite this high rate of abnormal sperm quality, most male cancer patients have adequate parameters for sperm storage.131 Successful sperm cryopreservation has been reported in more than 80% of male adolescent cancer patients.293 Lastly, other mechanisms such as epididymal aspiration or testicular biopsy can be employed if adolescent ejaculates are suboptimal. In light of these findings and alternative collection procedures, Bahadur et al293 suggest that all patients over 12 years old should be offered sperm cryopreservation prior to cytotoxic chemotherapy.

Although a feasible option for mature pubertal boys, semen cryopreservation is not an option for prepubertal male cancer patients because the prepubertal testes do not complete spermatogenesis and therefore do not have mature haploid spermatozoa. Prepubertal male cancer patients could potentially benefit from the development of gonadal tissue storage techniques, followed by autotransplant or in vitro maturation, sperm extraction, and ICSI. These techniques are still investigational but they may provide prepubertal boys receiving chemotherapy with an opportunity to remain fertile in adulthood.

Chemotherapy Effects in Girls

Early reports suggested no delay in menarche and no interruption of menses in girls treated with single-agent cyclophosphamide278, 290, 294, 295; Arneil288reported normal ovarian histology at postmortem examination in six girls treated with cyclophosphamide for malignancy. However, the drug doses in these early studies were not clearly specified. More recent evidence suggests that damage to the germ cell pool does occur, although clinical manifestations may vary. Ovarian biopsy in girls treated for ALL showed a reduction in the number of follicles and cortical stromal fibrosis, with more severe changes noted in postmenarchal girls.296 Others have noted absence or inhibition of follicle development after cytotoxic chemotherapy in girls dying from leukemia297 and solid tumors.298 As in adult female cancer patients, it is likely that the degree of gonadal damage depends on the specific cytotoxic agent, the cumulative dose, and the age of the patient at exposure.

Most studies that evaluated ovarian function in girls after exposure to chemotherapy have examined combination regimens. For this reason, it is difficult to make definitive conclusions regarding the contribution of individual agents. Nonetheless, the available information is useful to inform patients of the risk of ovarian failure when undergoing treatment for common childhood cancers. For example, studies evaluating combination chemotherapy for acute leukemia have generally found minimal ovarian damage. Siris et al299 reported normal ovarian function in 80% of prepubertal to postmenarchal girls with acute leukemia who received intermittent cycles of prednisone, vincristine, MTX, and 6-mercaptopurine, and in some cases, cyclophosphamide. Although three patients developed secondary amenorrhea and elevated gonadotropins consistent with ovarian failure, menses subsequently returned in two other patients. In another study, premenarchal female patients with ALL had a high incidence of elevated sex-steroid levels after treatment, but most had normal pubertal development and no delay in the onset of menses.80 Evaluation of 40 female survivors with ALL treated between ages 5 and 15 years old reported normal ovarian function in 90% of patients as only 4 patients had conclusive ovarian damage.300 These results suggest that the majority of young girls who receive therapy for ALL maintain ovarian function and have normal pubertal development. However, with long-term follow-up, some patients may later experience premature menopause.301 The effects of combination chemotherapy, including alkylating agents, on the prepubertal and pubertal ovary have also been studied in girls receiving treatment for Hodgkin's disease. Preliminary data suggested that ovarian function is likely to be preserved in most patients,286, 302 but more recent data from 32 female patients (aged 9 to 15) who received chemotherapy (chlorambucil, vinblastine, procarbazine, and prednisolone) for treatment of Hodgkin's disease found a higher rate of ovarian failure. Ten patients (31%) had evidence of symptomatic ovarian failure and six required hormone replacement therapy.303 Preservation of fertility has been noted in a high proportion of long-term survivors of patients with childhood non-Hodgkin's lymphoma treated with regimens containing cyclophosphamide, vincristine, doxorubicin, and high-dose MTX.304However, in one study of 13 prepubertal girls receiving nitrosoureas or procarbazine, or both, for brain tumors, 9 showed biochemical evidence of primary ovarian failure (elevated basal FSH level or abnormal peak FSH response to GnRH stimulation), and only 3 had normal pubertal development and menarche.305Likewise, female children who receive high doses of busulfan as part of bone marrow transplant conditioning regimens appear to have high rates of ovarian failure.306 Similar to adult women exposed to cytotoxic therapy, the age at administration may play a role in the risk of ovarian failure. Premenarchal girls appear to experience fewer menstrual irregularities and fewer elevations in gonadotropins than postmenarchal girls, consistent with the theory that younger females have a greater oocyte reserve than older girls.307 Despite these data, counseling young female cancer patients and their parents regarding the likelihood of future infertility remains difficult as there is limited published experience, and long-term follow-up is necessary. Even though many girls will have normal pubertal development and continue to menstruate, it is likely that many will experience early menopause, potentially limiting their ability to have children by narrowing their window of fertility.301

As previously discussed, future fertility is usually not the most immediate concern when treating children or adolescent cancer patients. Nevertheless, improved survival rates have increased the need to consider the long-term quality of life effects of chemotherapy treatment, including fertility. In addition, advanced reproductive techniques have improved and are continuing to evolve. Although girls may not be candidates for embryo storage, postmenarchal mature adolescents could consider oocyte storage for future use with an established partner or a sperm donor. There are no traditional options for prepubertal girls, but there is great hope that ovarian tissue storage and transplantation will continue to develop and become a feasible option for the youngest female cancer patient.308 Lastly, as discussed, many centers have ongoing trials evaluating the effectiveness of GnRH analogs for ovarian protection, providing an additional investigative option for young female cancer patients.309

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