Selective Estrogen Receptor Modulators. Antonio Cano

Chapter 13. Other Clinical Effects of SERMs

• P. Acién

• F. Quereda

• M.I. Acién

As shown in previous chapters, selective estrogen receptor modulators (SERMs) are drugs that bind to estrogen receptors (ERs); in some tissues they act like estrogen (agonists), while in other tissues they oppose the action of estrogen (antagonists). The SERM tamoxifen acts as an estrogen antagonist in the breast in that it prevents and treats breast cancer, but it acts as an estrogen agonist in the endometrium, where it can increase the risk of cancer. So the resulting estrogen agonistic or antagonistic activity of SERMs is tissue and organ dependent. The complexity of these interactions becomes even more confusing when one takes into consideration that different SERMs may act similarly in certain tissues, as in the case with tamoxifen and raloxifene in the breast, and dissimilarly in others, as seen with these same two in the endometrium. Therefore, each individual SERM may have, within itself, differing effects on different tissues and organs. This is what makes them so interesting. And since there are ERs in almost every tissue, SERMs are also likely to have some effect on nearly all the organs of the human body.

Descriptions exist of several SERMs: ethamoxytriphetol, cyclofenil, clomiphene, tamoxifen, raloxifene, arzoxifene, rolxifene, lasofoxifene, basodoxifene, levormeloxifene, ospemifene, tofupill/femarelle (DT56a) - a new phytoselective estrogen receptor modulatorlike substance - and fulvestrant, the first of a new class of drugs, an ER down regulator that may have advantages over tamoxifen in the treatment of estrogen-dependent diseases. But after several years of use of clomiphene citrate in the induction of ovulation, the first widely used SERM was tamoxifen in the treatment and prevention of breast cancer. Raloxifene is another SERM in clinical use, and it was developed to avoid some of the undesirable estrogen agonistic actions of other SERMs in order to improve the drug safety profile. It has been introduced for clinical use in the treatment and prevention of postmenopausal osteoporosis. All the other SERMs are still undergoing further research, a scrutiny that is even more necessary in those clinically introduced. This requirement is strengthened by the wide distribution of ERs in organs and systems distinct from the traditional targets, the genital apparatus and the breast. The actions of SERMs on those relevant systems, such as the cardiovascular tree, the bones, or the central nervous system, have been widely analyzed, together with several actions on the reproductive organs, in other chapters. Therefore, in this chapter we will review other clinical actions of SERMs that can be of clinical interest.

13.1

Urogenital Tract

13.1.1

Vaginal Trophism and Dyspareunia

In general, SERMs have an antiestrogenic or null estrogenic effect on the epithelium and on the vaginal trophism. Some, however, such as ospemifene have a significant estrogenic effect on the vaginal epithelium, as evidenced by an increase in intermediate and superficial cells in repeated Pap smears (Rutanen et al. 2003). Nevertheless, Morales et al. (2004) have recently studied the effects of tamoxifen and third-generation aromatase inhibitors on menopausal symptoms of breast cancer patients. Musculoskeletal pain and dyspareunia significantly increased with first-line nonsteroidal aromatase inhibitors, while patients using tamoxifen had a significant decrease in sexual interest. At a younger patient age, tamoxifen has been associated with hot flashes and vaginal dryness after 1 and 3 months of therapy. The relative incidence and correlation of subjective and psychosexual symptoms have also been studied during and after tamoxifen treatment by Mourits et al. (2002) in 98 breast cancer patients < 56 years of age in a randomized study comparing different doses of adjuvant chemotherapy, followed by radiotherapy and tamoxifen. During tamoxifen treatment there were complaints of vaginal dryness and/or dyspareunia in 47%, decreased sexual desire in 44%, and musculoskeletal symptoms in 43%. Decreased sexual interest correlated with vaginal dryness and/or dyspareunia. After discontinuation of tamoxifen, symptoms improved significantly. However, hot flashes, disturbed sleep, and vaginal dryness persisted more often in patients who remained postmenopausal after high doses of chemotherapy.

Likewise, raloxifene’s effect on the postmenopausal vagina has been neutral in some studies, unlike estrogen’s beneficial effect (Davies et al. 1999); in relation to placebo it does not increase the incidence of events related to vaginal atrophy. There are, however, few data on the effects of these drugs on urogenital atrophy (Robinson et al. 2003). In the paper by Modugno et al. (2003), raloxifene was not different from placebo with respect to comfort during sexual intercourse in postmenopausal women with osteoporosis, but the authors warn that no conclusion can be made about the effect of raloxifene on sexual function in premenopausal women, in younger postmenopausal women, or in women experiencing menopausal symptoms.

13.1.2

Pelvic Floor Function and Urinary Disorders

It has traditionally been considered that exogenous estrogens could improve incontinence and urinary control in postmenopausal women. In 2001, however, a large randomized blinded study compared oral daily estrogen plus progestin therapy vs. placebo in postmenopausal women with incontinence (Grady et al. 2001). Among the women who were assigned to hormonal treatment, incontinence was more likely to worsen and less likely to improve when compared with women who received placebo. The number of incontinent episodes per week increased an average of 0.7 in the hormone group and decreased by 0.1 in the placebo group (p < 0.001). It must be pointed out that the urethra and trigone of the bladder are covered by nonkeratinizing squamous epithelium of similar origin to the vagina and that these tissues have estrogen receptors and respond to estrogen (Bergman et al. 1990). The evidence of this randomized study, however, contradicted the traditional clinical teaching, which held that the administration of exogenous estrogen improves urinary control in postmenopausal women.

More recently, Robinson and Cardozo (2003) reviewed the role of estrogens in female lower urinary tract dysfunction and conclude that, although the role of estrogen replacement therapy (ERT) in the management of postmenopausal urinary incontinence (UI) remains controversial, its use in the treatment of women with urogenital atrophy is now well established. Estrogen therapy alone has little effect on the management of urodynamic stress UI, although in combination with an alpha-adrenergic agonist it may improve urinary leakage. Additionally, estrogen therapy may be of benefit for the irritative symptoms of urinary urgency and frequency and urge UI, although this effect may result from reversal of urogenital atrophy rather than a direct action on the lower urinary tract. Moreover, there is now some evidence that vaginal administration may be effective.

Concerning genital prolapse, the gynecological literature has traditionally favored the notion that postmenopausal atrophy of fascial and muscular support elements seems to be the important precipitating factor in older patients. It is unclear whether this is simply an aging phenomenon or is related to estrogen deprivation. Connective tissues may be weakened during the aging process as a result of decreases in collagen content (Affinito et al. 1999). Estrogen deprivation, which is associated generally with the postmenopausal state, has been considered to result in pelvic floor atrophy and the subsequent increased incidence of pelvic floor relaxation in older women (Rekers et al. 1992). Again, traditional teaching holds that ERT has positive effects on pelvic floor relaxation (Casper et al. 1998), although there have been no randomized trials to validate this.

Several clinical trials, however, demonstrated a neutral or antiestrogenic effect of raloxifene on the endometrium and uterus (Goldstein et al. 2000; Cohen et al. 2000), and, as previously mentioned, unlike estrogen’s beneficial effect on the postmenopausal vagina, raloxifene’s effect seems neutral (Davies et al. 1999). Thus, it becomes even more intriguing that, in an analysis of safety data of 3 raloxifene trials that included 6926 postmenopausal women, the relative risk of undergoing a surgical procedure for pelvic floor relaxation was 0.5 (95% CI, 0.31,0.81) compared with the placebo control subjects (Goldstein et al. 2001). Therefore, raloxifene therapy was associated with a significantly reduced risk of pelvic floor surgery (1.51% vs. 0.75%) through 3 years of treatment (Fig. 13.1).

Hendrix and McNeely (2001) reviewed published and unplublished data on the effect of SERMs on reproductive tissues other than the endometrium. They identified the pharmaceutical companies developing or marketing SERMs, and the investigators at each company responsible for the conduct of investigational trials were contacted and queried about reports of adverse events in any ongoing or completed trials involving SERMs produced by their company. Levormeloxifene and idoxifene trials noted a higher proportion of surgery for pelvic organ prolapse in treated vs. untreated women. The development of these pharmaceutical agents was discontinued, primarily due to concerns over effects on the endometrium. Nevertheless, pelvic organ prolapse was reported to the FDA as an adverse event associated with both drugs. Study weaknesses preclude a definitive association between the agents and pelvic organ prolapse, since the treated groups were not necessarily similar due to confounding factors such as age, parity, obesity, cigarette smoking, and other risk factors for pelvic organ prolapse.

Fig. 13.1. A Incidence of surgery for pelvic floor relaxation in postmenopausal women followed for up to 3 years represented as a percentage of all randomized patients. Overall incidence and incidence in subgroups defined by age are shown. Statistical significance of the difference between placebo and raloxifene groups was assessed by a Cochran-Mantel- Haenszel test. B The cumulative probability of pelvic floor surgery for women in the placebo group as compared with those in the raloxifene group is represented as a percentage of women enrolled in the trial. Statistical significance of the difference between placebo and raloxifene groups was assessed by the log rank test (from Goldstein et al. 2001).

Later, Goldstein and Nanavati (2002) reported the adverse events associated with the SERM levormeloxifene in the aborted phase III osteoporosis treatment study. This study was stopped abruptly after 10 months because of the magnitude of adverse events compared to placebo. Thus, no bone mineral efficiency data were evaluated, nor was the comparability of the treatment groups at baseline analyzed statistically, though because it was a randomized study of > 2900 women, it is likely that the groups would be similar. Among the 2924 women who were studied, those who were treated with levormeloxifene had a marked increase compared with placebo in leukorrhea (30% vs. 3%), increased endometrial thickness on ultrasound scan (19% vs 1%), enlarged uterus (17% vs. 3%), uterovaginal prolapse (7% vs. 2%), urinary incontinence (17% vs. 4%), increased micturition frequency (9% vs. 4%), lower abdominal pain (17% vs. 6%), hot flashes (10% vs. 3%), and leg cramps (6% vs. 0.8%). All of these differences were highly statistically significant (Table 13.1). Therefore, the treatment group (with the SERM levormeloxifene 0.5 mg or 1.25 mg daily) had a > 3-fold increase in the risk of developing uterovaginal prolapse and an almost 5-fold increased risk of developing UI compared with placebo.

Subsequently, Goldstein (2002), in an update on nonuterine gynecological effects of raloxifene, insisted on the results formerly shown and that, unlike levormeloxifene, in the raloxifene-treated patients there was a decrease of 50% in surgery for pelvic organ prolapse and/or UI. It should be noted, however, that these trials were not designed to assess the effect of raloxifene on the pelvic floor and that there was no systematic evaluation for pelvic organ relaxation.

Table 13.1. Comparison of selected adverse event risk ratios during treatment (all patients who received levormeloxifene are combined vs. placebo) (from Goldstein and Nanavati 2002)

Robinson and Cardozo (2003) concluded saying that the long-term effects of SERMs on the urogenital tract remain to be determined, and there are few data on the effects of these drugs on UI and urogenital atrophy.

13.2

Central nervous system

Animal studies have suggested that raloxifene may affect brain function, although the effects of SERMs on the human brain remain to be established (Nickelsen et al. 1999). Before mentioning them, it is worthwhile to review the actions of estrogens.

Evidence from randomized, controlled trials and from cross-sectional and longitudinal studies show that ERT preferentially protects against a decline in verbal memory in healthy postmenopausal women and decreases the risk of Alzheimer’s disease (AD) (Sherwin 2002). Although results are not consistent across studies, they indicate that treatment with estrogen during the postmenopausal years might protect against cognitive aging in women during the latter part of their life. Experimental studies demonstrate a consistent beneficial effect on verbal memory, but these are short-term studies of the more acute effects of ERT. The observational studies suggest that there may be a long-lasting effect of continued ERT on cognitive functioning, and that with respect to the effects of ERT on AD, such therapy is associated with a decreased risk for dementia; however, there is little evidence for a positive effect on cognition in women with AD. Consequently, it is pointed out that definitive answers to questions about the long-term effects of ERT on cognitive aging and risk of developing AD should be provided by ongoing clinical trials (Zec et al. 2002).

The CNS is one of the main target tissues for sex steroid hormones, which act both through genomic mechanisms, modulating synthesis, release, and metabolism of many neuropeptides and neurotransmitters and through nongenomic mechanisms, influencing electrical excitability, synaptic function, and morphological features. The identification of the brain as a de novo source of neurosteroids modulating cerebral function suggests that the modifications in mood and cognitive performance occurring in postmenopausal women could also be related to a modification in the levels of neurosteroids, particularly allopregnanolone and DHEA, GABA-A agonist, and antagonist (Bernardi et al. 2003). Likewise, Shively and Bethea (2004) state that ovarian steroids have multiple effects on serotonin synthesis, reup take, and degradation, on neural activity that drives serotonin release, and on receptor activation in primates. Moreover, as already mentioned, several studies have suggested that estrogen may improve cognitive function or prevent the development of dementia, but other studies have not shown benefits.

Certainly, to evaluate the effect of estrogen plus progestin on the incidence of dementia and mild cognitive impairment compared with placebo, the Women’s Health Initiative Memory Study (WHIMS), a randomized, doubleblind, placebo-controlled clinical trial, was designed, and it began enrolling participants from the Women’s Health Initiative (WHI) estrogen plus progestin trial in May 1996. Of the 4894 eligible participants of the WHI study, 4532 (92.6%) postmenopausal women aged 65 years or older were free of probable dementia. Participants received either 1 daily tablet of 0.625 mg of conjugated equine estrogen plus 2.5 mg of medroxyprogesterone acetate (n = 2229) or a matching placebo (n = 2303). The incidence of probable dementia (primary outcome) and mild cognitive impairment (secondary outcome) were identified through a structured clinical assessment. The mean time between the date of randomization into WHI and the last Modified Mini-Mental State Examination for all WHIMS participants was 4.05 (1.19) years. Overall, 61 women were diagnosed with probable dementia, 40 (66%) in the estrogen plus progestin group and 21 (34%) in the placebo group. Therefore, the hazard ratio (HR) for probable dementia was 2.05 (95% CI, 1.21-3.48; 45 vs. 22 per 10,000 person-years; p = 0.01), and this increased risk would result in 23 additional cases of dementia per 10,000 women per year. Treatment effects on mild cognitive impairment did not differ between groups. So the conclusion of the authors (Shumaker et al. 2003) was that the estrogen plus progestin therapy increased the risk for probable dementia in postmenopausal women aged 65 years or older. In addition, estrogen plus progestin therapy did not prevent mild cognitive impairment in these women.

These results are not congruent, however, with all the previously published studiesonthe valueofestrogens as neuroprotectiveagentswithpotentialeffects on the pathogenesis of AD. Conflicting findings may be due to differences in the types of hormone therapy given, specifically the addition of progestin. Moreover, some posterior studies, to be commented on later (Eberling et al. 2004), provide both physiological as well as anatomical evidence for the neuroprotective effects of estrogen.

With the recognition that SERMs have differential tissue-dependent effects on ER function, there has been recent interest in the effects of raloxifene, tamoxifen, and other SERMs on mood, sleep, cognitive function, and AD severity. What follows is an analysis of the effects of SERMs on several conditions.

13.2.1

Hot Flashes and Beta Endorphins

The most commonly observed side effect in patients taking raloxifene or tamoxifen was hot flashes (Agnusdei 1999; Muchmore 2000; Miller 2002). In the study by Mourits et al. (2002) in breast cancer patients < 56 years of age, the most frequent complaints during tamoxifen treatment were hot flashes (85%) and disturbed sleep (55%), whereas in the CORE study (Martino et al. 2004) hot flashes were observed in 12.5% of the raloxifene group vs. 6.9% in the placebo group.

Recently, Aldrighi et al. (2004) analyzed the predictors of hot flashes in postmenopausal women who received raloxifene therapy to assess the clinical usefulness of various therapeutic strategies for their reduction. In this randomized, double-blind, placebo-controlled study, 487 unselected postmenopausal women were assigned randomly to receive treatment for 8 months with raloxifene, which was administered either at a dose of 60 mg/d every other day for 2 months followed by 60 mg/d (slow-dose escalation) or 60 mg/d throughout (raloxifene), or placebo. Data on the number, duration, intensity, and severity of hot flashes and awakenings due to night sweats were collected, and logistic regression models were used to examine the predictive value of various demographic and menopausal factors on the development or worsening of hot flashes. At baseline, 40.4% of all randomly assigned patients did not have flashes, but the mean number of hot flashes (3-5 per week) was low. Fewer years postmenopause, surgical menopause, and previous estrogen or estrogen/progestin therapy were significant predictors of hot flashes at baseline but were not predictive of incident hot flashesduring treatment with raloxifene. Of the women who received raloxifene therapy who had preexisting hot flashes/during apart at baseline, 36% had none at the end point. Early postmenopause and surgical menopause were significant predictors of a biologically relevant increase in hot flashes (> 14 flashes/week). Early postmenopause, previous estrogen/progestin therapy, high body mass index, and greater duration of hot flashes at baseline were significant predictors of the need for symptomatic treatment. After 2 months of treatment, women in early postmenopause had significantly more hot flashes with raloxifene therapy than with slow-dose escalation (p = 0.042), whereas there was no significant difference between raloxifene therapy and slow-dose escalation among women in later postmenopause. In the 50 patients who requested symptomatic treatment during the study, phytohormones or veralipride did not reduce the number of hot flashes markedly.

In conclusion, a shorter time since menopause and surgical menopause are important predictors of hot flashes not only before but also during treatment with raloxifene. Previous estrogen/progestin therapy also increases the risk of hot flashes at baseline. For women in early postmenopause, slow-dose escalation of raloxifene therapy may be a suitable therapeutic strategy for the reduction of the risk of hot flashes.

Finally, it should be noted that Neele et al. (2002) have observed that raloxifene treatment significantly increases plasma levels of beta endorphin in postmenopausal women but does not significantly affect climateric symptoms with the exception of worsening vasomotor symptoms, so that the increase of hot flashes with raloxifene could be related to the changes in the beta endorphins.

13.2.2

Mood, Sleep, Waking Episodes

Nickelsen et al. (1999) studied raloxifene effects on cognition and mood in postmenopausal women participating in a randomized, double-blind osteoporosis treatment trial. After 12 months of treatment there were no significant differences between the raloxifene groups and the placebo one, suggesting that raloxifene does not affect mood in postmenopausal women treated for 1 year. Natale et al. (2004) have also studied its effect on psychological functions in 49 women. This SERM does not appear to affect adversely any psychological function such as libido, mood, or memory. And though it may worsen attention, it reduces waking episodes, so it may improve sleep.

As for tamoxifen, in the aforementioned studies by Mourits et al. (2002) on breast cancer patients analyzing the effects on subjective and psychosexual well-being, disturbed sleep (55% of patients) correlated with hot flashes and concentration problems.

13.2.3

Cognitive Function, Alzheimer’s Disease (AD)

As previously mentioned, Nickelsen et al. (1999) analyzed the safety assessment of raloxifene effects on cognitive function and mood in postmenopausal women participating in a randomized, double-blind osteoporosis treatment trial. The results did not suggest that raloxifene impaired cognition or affected mood in postmenopausal women treated for 1 year. Additionally, Lacreuse et al. (2002) examined the effects of ERT and raloxifene on cognitive function in a rhesus monkey model ovariectomized long term (10-16years). Estradiol was able to enhance some aspects of spatial working memory in aged monkeys despite many years of estrogen deprivation, while raloxifene did not affect cognitive function after long-term ovarian hormone deprivation. Bernardi et al. (2003), however, state that raloxifene administration in postmenopausal women has an estrogenlike effect on circulating beta endorphin and allopregnanolone levels, and it restores the response of beta endorphin and allopregnanolone to neuroendocrine tests encouraging the positive effects of estrogens with fewer side effects. In one study by Yaffe et al. (2001) as well as in a more recent one by Natale et al. (2004), raloxifene treatment did not affect overall cognitive scores. Finally, the randomized clinical trial by Haskell and Richardson (2004) on 50 postmenopausal women receiving raloxifene 60 mg or placebo, for 8 weeks, drew identical conclusions, stating that the results showed no significant effect attributable to treatment with raloxifene on cognitive, psychological, or health variables.

As for tamoxifen, several studies have shown cognitive decline in women receiving it for the treatment of breast cancer, but the focus of those studies was on the effects of chemotherapy. For this reason Shilling et al. (2001) designed a pilot study to examine whether hormone therapy for breast cancer (with anatrozole, tamoxifen alone, or combined) affects cognition. The authors included not only the 94 patients but also another group of women without breast cancer (n = 35) who completed the battery of neuropsychological measures (Jenkins et al. 2004). The results showed specific impairments in processing speed and verbal memory in women receiving hormone therapy. The authors point out that verbal memory may be especially sensitive to changes in estrogen levels and that in view of the increased use of hormone therapies in an adjuvant and preventative setting, their impact on cognitive functioning should be investigated more thoroughly.

In this sense, then, the most recent and interesting material is the study by Eberling et al. (2004) on the estrogen- and tamoxifen-associated effects on brain structure and function. The researchers evaluated the effects of estrogen and tamoxifen on positron emission tomography (PET) measures of brain glucose metabolism and magnetic resonance imaging (MRI) measures of hippocampal atrophy. Three groups of postmenopausal women were studied, women taking estrogen (ERT+), women with breast cancer taking tamoxifen, and women not taking estrogen or tamoxifen (ERT-). All subjects received a PET scan, an MRI scan, and cognitive testing. The tamoxifen group showed widespread areas of hypometabolism in the inferior and dorsal lateral frontal lobes relative to the other two groups. The ERT- group showed lower metabolism in the inferior frontal cortex and temporal cortex with respect to the ERT+ group. The tamoxifen group also showed significantly lower semantic memory scores than the other two groups. Finally, the tamoxifen group had smaller right hippocampal volumes than the ERT+ group, an effect that was of borderline significance. Both right and left hippocampal volumes were significantly smaller than the ERT+ group when a single outlier was removed. The ERT- group had hippocampal volumes that were intermediate to the other two groups (Fig. 13.2). These findings provide physiological and anatomical evidence for the neuroprotective effects of estrogen and support the notion of an antagonistic role of tamoxifen in both the frontal lobes and hippocampus.

Fig. 13.2. A Neuropsychological test results. Mean scores for each group on the Center for Epidemiological Studies-Depression Scale (CES-D), verbal episodic memory (VEM), semantic memory (SM), verbal attention span (VAS), and pattern recognition (PR). B PET scan, region of interest (ROI) analysis. Regional cerebral glucose metabolism ratios for women taking estrogen, women not taking estrogen, and women taking tamoxifen. Regions are right and left dorsal lateral frontal cortex (DLF) and right and left orbital frontal cortex (ORBF). P < 0.05 between ERT+ and ERT- plus TAM in rORBF and lORBF. C Normalized hippocampal volumes (NHV). Mean NHV for women taking estrogen for each group. Error bars indicate standard deviations. ERT+, women taking estrogen; ERT-, women not taking estrogen; TAM, women taking tamoxifen. * TAM < ERT-,p = 0.05 (from Eberlingetal.2004)

Nevertheless, the authors point out that additional, well-controlled studies are warranted to further explore the association between tamoxifen and these measures.

13.2.4

Libido, Sexual Function

As previously mentioned, Morales et al. (2004) recently studied the effects of tamoxifen and third-generation aromatase inhibitors on menopausal symptoms of breast cancer patients. Patients taking tamoxifen had a significant decrease in sexual interest, and at a younger, premenopausal age tamoxifen was associated with hot flashes and vaginal dryness. Likewise, Modugno et al. (2003) studied the effects of raloxifene compared with placebo on sexual function in older postmenopausal women undergoing therapy for the treatment of osteoporosis in a subset of 943 women of the MORE trial (624 women with raloxifene and 319 with placebo). Subjects were administered the sexual function questionnaire (a modification of McCoy’s Sex Scale Questionnaire) at baseline and again after 36 months of treatment, and they were informed that for this study, sexual activity was defined as “any activity that is sexually arousing to you - masturbation, oral sex, intercourse, etc.” All women were asked to report their frequency of sexual activity and desire during the last 6 months. For sexually inactive women, the reason for inactivity was reported. For sexually active women, additional questions evaluated feelings during sexual activity, intensity of orgasms, and sexual problems. Overall, sexual function and changes in sexual function from baseline to study and between the raloxifene and placebo groups did not differ. In particular, there were no differences in sexual desire or frequency of sexual activity between the groups. Among sexually active women, there were no differences in enjoyment, satisfaction, orgasm, or reported sexual problems. Therefore, sexuality does not seem to be affected by treatment with raloxifene.

The results of the pilot study by Natale et al. (2004) in which mood, sleep, libido, and cognitive function were studied in 49 postmenopausal healthy women were similar. No significant differences were found in mood, wellbeing, libido, and indices of sexual activity.

13.3

Gallbladder and Hepatobiliar System

Several studies have shown that estrogens and their receptors play a role in the modulation of cholangiocyte proliferation. Alvaro et al. (2000) observed that cholangiocytes expressed both ER-alpha and ER-beta subtypes, whereas hepatocytes expressed only ER-alpha, and that the treatment with tamoxifen or ICI 182.780 of 3-week BDL rats inhibited cholangiocyte proliferation and induced overexpression of Fas antigen and apoptosis in cholangiocytes. Vickers et al. (2002) also evaluated the response of human cholangiocarcinoma cells to tamoxifen treatment through the Fas pathway by pretreatment with interferon-gamma. Tamoxifen exposure to human cholangiocarcinoma after pretreatment with INF-gamma allows for induction of apoptosis in vitro and significant inhibition tumor xenograft growth. The combination of these two compounds may provide a novel treatment regimen for cholangiocarcinoma. Likewise, Reddy et al. (2004) suggest tamoxifen as a novel treatment for primary biliary cirrhosis.

It is not, however, efficient in the treatment of hepatocarcinoma. Nowak et al. (2004), in a review by Cochrane, pointed out that the available data do not support the use of tamoxifen for patients with hepatocellular carcinoma. This same conclusion was reached by Gerard and Bleiberg (2004), who stated that hormonal therapy with tamoxifen or antiandrogens had shown no efficacy and might even be detrimental in patients with hepatocarcinoma.

Finally, and with respect to raloxifene, Grady et al. (2004), when analyzing the safety and adverse effects associated with raloxifene in the MORE study, noticed that this did not increase the risk for gallbladder disease.

13.4

Desmoids and Mesenteric Fibromatosis

Tonelli et al. (2003) studied the effects of 120 mg/d raloxifene on progressive desmoid tumors and mesenteric fibromatosis in 13 patients with familiar adenomatous polyposis, selected on the basis of intra-abdominal localization of the lesion, refractoriness to other medical treatments, and ER-alpha expression. The patients had a significant response to raloxifene therapy, with complete remission in 8 cases and partial response in 5 cases, evaluated by regression of symptoms and tumor size. Serum biochemical parameters did not show any significant changes, and side effects were never observed. These results support the efficacy of raloxifene on desmoid tumors and mesenteric fibromatosis contributing to a novel option in the pharmacological treatment of these neoplastic lesions.

13.5

Endocrine Functions

Most endocrine functions have already been commented on in previous chapters, so only the following will be mentioned here:

13.5.1

Insulin Sensitivity and Diabetes

Andersson et al. (2002) have shown in a randomized clinical trial that raloxifene does not affect insulin sensitivity or glycemic control in postmenopausal women with type-2 diabetes mellitus. It has favorable or neutral effects on selected surrogate markers of cardiovascular risk while decreasing hyperan- drogenicity in these patients.

13.5.2

Thyroid Function

Estrogen may increase hepatic production of thyroxine-binding globulin (TBG) and decrease TBG clearance, thus increasing serum total thyroxine (tT4) and, to a lesser extent, total triiodothyronine (tT3). As a result, increased tT4 and tT3 are seen in states of excessive estrogen and/or progestin, such as pregnancy, HRT, and oral contraceptive usage. This phenomenon may cause problems in clinical diagnoses when tT4 or tT3 is used for these patients. Nevertheless, estrogen has been shown to increase thyroid-stimulating hormone (TSH) and to decrease free thyroxine (fT4) through a mild inhibitory effect on the thyroid gland (Hsu et al. 2001). Compounds such as tamoxifen increase TSH without decreasing fT4 (Zidan et al. 1999), but the effect of long-term raloxifene usage on TBG, T3 uptake, tT3, tT4, fT4, and TSH had not been well documented.

Therefore, Hsu et al. (2001) investigated whether raloxifene caused changes in serum concentrations of these markers comparing the effects of 1 year of treatment with either raloxifene or combined continuous estrogen and progesterone (CCEP) on the thyroid function test profiles, E2, and FSH. They studied 60 euthyroid postmenopausal women (age range 40-75 years) with relatively low bone mineral density. Fifty women received raloxifene (60 mg/d) before breakfast, and 10 women received combined conjugated equine estrogen (Premarin; 0.625 mg) and medroxyprogesterone acetate (Provera; 5 mg) daily. Fasting serum samples were collected for all participants at baseline and after 1 year of treatment. This study showed that the usual dosage of raloxifene administered for 1 year increased serum TBG. This increase in TBG is similar to the effects of CCEP and may then be associated with an increase in tT4 and tT3, whereas TSH and fT4 were not significantly changed. The slight but insignificant decreases in fT4 in both groups after 1 year of treatment were compatible with the findings that showed a mild suppression of thyroid function by tamoxifen and estrogen. The authors conclude that in patients treated with raloxifene, the results of tT3 and tT4 tests should be interpreted with caution because they could be falsely increased. Duntas et al. (2001), in another study on raloxifene and thyroid function, observed, however, that TBG levels and, consequently, thyroid function are not substantially affected by treatment with raloxifene.

13.6

Eye, Cataracts

Visual impairment and cataracts have been reported in patients undergoing long-term tamoxifen treatment (Gerner 1989). Similarly, it has been observed that tamoxifen and its derivatives are high-affinity blockers of specific chloride channels; this blockade appears to be independent of the interaction oftamox- ifen with ERs and therefore reflects an alternative cellular target. But, since chloride channels in the lens of the eye were shown to be essential for maintaining normal lens hydration and transmittance, Zhang et al. (1994) studied organ culture and observed that these channels were blocked by tamoxifen, leading to lens opacity associated with cataracts at clinically relevant concen trations. The study suggested a molecular mechanism by which tamoxifen could cause cataract formation and, consequently, have implications for its clinical use. In a later paper, Zhang et al. (1995) suggested that ocular toxic side effects of antiestrogens would be minimized by use of the steroidal (ICI 182780) rather than nonsteroidal antiestrogens (tamoxifen).

Later, Gorin et al. (1998) estimated the prevalence of abnormalities in visual function and ocular structures associated with the long-term use of tamoxifen citrate in a sample of 303 women with breast cancer currently taking part in a randomized clinical trial to determine the efficacy of tamoxifen (20 mg/day) in preventing recurrences. There were no cases of vision-threatening ocular toxicity among the tamoxifen-treated participants, and, compared with non- treated participants, the tamoxifen-treated women had no differences in the activities of daily vision, visual acuity measurements, or other tests of visual function except for color screening. Nevertheless, intraretinal crystals and posterior subcapsular opacities were more frequent in the tamoxifen-treated group, leading the authors to conclude that women should have a thorough baseline ophthalmic evaluation within the first year of initiating tamoxifen therapy and receive appropriate followup evaluations.

Likewise, Paganini-Hill and Clark (2000) also studied 2653 women (but only information from 1297 women aged 57-75 years of age was analyzed) with primary breast cancer to evaluate the association of tamoxifen with cataracts and other eye problems. Women reporting treatment with tamoxifen were categorized as standard-term users (4-5years), short-term users (< 4years), or long-term users (6+ years) and compared to nonusers. The authors observed that standard-term and long-term users of tamoxifen reported developing cataracts more frequently than nonusers (18.2%, 21.4% vs. 14.8%). The relative risk was 1.40 (95% CI 0.94-2.10) for standard-term users and 1.70 (1.11-2.59) for long-term users. Yet tamoxifen was unrelated to frequency of glaucoma or macular degeneration or to Amsler grid test results. Thus this study suggested that five or more years of tamoxifen use increases risk of cataracts and that women choosingsuch therapy should be diligent about receivingregular ocular exams.

Bradbury et al. (2004), however, recently reanalyzed the relation between tamoxifen and cataracts and described it as “a null association,” They used a nested, matched, case-control study design and data collected in the General Practice Research Database. They identified all women 30-79 years old who were diagnosed with breast cancer and treated with tamoxifen within 6 months, or with bladder cancer, colorectal cancer, or nonmelanoma skin cancer between January 1991 and December 1999. From this population they identified all newly diagnosed cases of cataract and matched four female controls to each case on age, index date, and study entry data. They assessed the risk of cataracts for current, past, and sometime users of tamoxifen and according to cumulative use of tamoxifen. The findings showed no increased risk for cataracts among breast cancer patients treated with tamoxifen (OR = 1, 0.7-1.4) compared to women with other cancers who were not prescribed tamoxifen, and there was no evidence of an increased risk with increasing cumulative dose. Consequently, the tamoxifen-cataract relationship is controversial, and the latest findings show an absence of evident relation.

In respect to other SERMs, Bishai et al. (1999) have communicated a case of intrauterine exposure to clomiphene (100 mg/d for approximately 4 weeks) and neonatal persistent hyperplastic primary vitreous. These same authors mention another described case in humans with congenital retinal aplasia. Regarding raloxifene, no relation to ocular problems has been reported.

13.7

Other Effects

13.7.1

Arthritis

Creamer et al. (1994) reported cases of breast cancer where the use of tamoxifen was temporally related to the development of an inflammatory polyarthritis resembling rheumatoid arthritis. Cases of cyclical psoriatic arthritis, however, have positively responded to antiestrogen therapy (Stevens et al. 1993). Tsai and Liu (1992) have shown that tamoxifen concurrently injected with estradiol benzoate antagonizes the condrodestructive effects of estradiol at the early stage of knee osteoarthritis in rabbits.

13.7.2

Hemorheological Effects

Shand et al. (2002) have shown that, compared with placebo-treated subjects, long-term raloxifene treatment in postmenopausal women, at a dose of either 60 or 120 mg/d, was not associated with adverse changes in hemorheological factors (determinants of blood viscosity) that may contribute to venous thromboembolism.

13.7.3

Quality of Life (QoL)

The effect of raloxifene on QoL was investigated by Utian et al. (2004) in a prospective study using the Utian Quality of Life (UQoL) Scale in 74 women.

Although there were no treatment group differences, raloxifene was associated with an improvement from baseline in the occupational and health domains and in the overall score of the UQoL. The authors recommended more studies.

Palomba et al. (2004) have also studied the effects on cognigtion, mood, and QoL in 100 premenopausal women with symptomatic uterine leiomyomas treated with gonadotropin-releasing hormone agonist with or without raloxifene. The findings demonstrate that raloxifene is not able to prevent decreases in cognitive function and does not reduce the depresion and anxiety symptoms in women treated with GnRHa.

Finally, Fallowfield et al. (2004) analyzed the QoL of postmenopausal women in the Arimidex, Tamoxifen, Alone or in Combination (ATAC) Adjuvant Breast Cancer Trial. There were no differences among groups. Two years of treatment with these products had a similar overall QoL impact, showing gradual improvement over time.

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