Radiation Oncology: A Question-Based Review

Desmoid Tumors

Russell K. Hales and Deborah A. Frassica

image Background

What are desmoid tumors (DT)?

DTs are deep-seated, benign, slow-growing −fibroblastic neoplasms that arise from musculoaponeurotic stromal elements.

What is another commonly used name for DT?

DT is also known as aggressive fibromatosis.

Do DTs have metastatic potential?

No. DTs do not have metastatic potential but are locally aggressive with a predilection for LR.

Approximately how many cases of DT are diagnosed annually in the U.S.?

~9,000 cases/yr of DT in the U.S.

Is there a gender or racial/ethnic predilection for DT?

Yes, with regard to gender. Women are more −commonly affected than men (2:1). There is no −significant racial or ethnic predilection in DT.

What is the avg decade of life in which pts present with DT?

On avg, DT pts present in the 3rd–4th decade of life.

What genetic abnormality is associated with DT?

2% of DTs are associated with mutations to the APC gene, resulting in familial adenomatous polyposis (FAP).

What is the clinical syndrome associated with DT?

Gardner syndrome is associated with DT, and 4%–20% of pts with this syndrome will develop DT.

1.     Sebaceous cysts

2.     Osteomas

3.     Desmoid tumors

(Mnemonic: gardener SOD)

What % of DTs are intra-abdominal, and with what clinical syndrome are intra-abdominal DTs associated?

10%–30% of DTs are intra-abdominal, and they are associated with Gardner syndrome.

DTs are a significant source of morbidity and mortality in what group of pts?

Pts with Gardner syndrome experience significant morbidity and mortality from their intra-abdominal tumors.

What 2 environmental conditions are associated with DT?

Retrospective data suggests an association between DT and (1) antecedent trauma and (2) high estrogen states (such as pregnancy).

DT appears histologically similar to what tumor?

DT appears histologically similar to well-differentiated (grade 1) fibrosarcoma.

Name 3 general anatomic sites in which DT develops.

DT develops in the (1) trunk/extremity, (2) abdominal wall, and (3) intra-abdominal compartment.

What is the typical presentation of an extremity DT?

Most DTs of the extremity present as a deep-seated painless mass with a Hx of slow growth.

What is the typical presentation of an intra-abdominal DT?

An intra-abdominal DT can present with bowel −ischemia or obstruction.

What is the natural Hx of untreated DTs?

Although DTs can regress spontaneously, they usually continue with slow growth and local Sx associated with tumor invasion into surrounding structures.

image Workup/Staging

After a careful H&P, what imaging should be done to evaluate for a DT?

An MRI of the extremity is recommended to evaluate the extent of a DT preoperatively. A CT or MRI of the abdomen may be helpful to evaluate an intra-abdominal or abdominal wall mass.

Full systemic staging of DTs includes what type of imaging?

DTs are benign and do not have metastatic potential. Consequently, no systemic imaging is needed outside of the primary tumor.

Can DT be distinguished from malignant soft tissue tumors on the basis of imaging?

No. DT cannot be distinguished from malignant soft tissue tumors on the basis of imaging.

Define the staging system for DT.

There is no defined staging system for DT. Important features to guide management include location, size, and the ability to resect with a wide margin.

What type of Bx should be done to evaluate a mass suspected of being a DT?

An incisional (needle or open) Bx is the preferred method for any tumor that may be a malignant soft tissue sarcoma.

image Treatment/Prognosis

What is considered the primary modality for Tx of DT?

Surgical resection is considered the primary modality for Tx of DT.

What type of primary surgery is recommended for pts with DT?

In pts with DT, function-preserving surgery with a goal of wide (2-cm) margin negative resection is preferred.

For what type of pts is nonoperative initial management of DT recommended?

Pts with intra-abdominal DTs that are large, slow growing, involve the mesentery, or encase vessels and/or organs should be treated upfront with nonsurgical approaches according to the American Society of Colon and Rectal Surgeons. (DeLaney T et al., Up to date 2009)

What is the recurrence rate after margin− surgery vs. margin+ surgery for DT in pts who do not get adj therapy?

In DT Tx with surgery alone, LR is 13% for − −margin resection, and LR is 52% for + margin resection. (Ballo MT et al., IJROBP 1998)

Estimate the LR rate by margin status for DT pts who are treated with surgery and then adj RT.

The LR rate for DT treated with surgery and then adj RT is 7% in margin − pts and 26% in margin + pts. (Ballo MT et al., IJROBP 1998)

What group of pts with DT should not be offered routine adj RT?

Pts with DT who have a margin − resection should not be offered routine adj RT; however, according to NCCN guidelines, PORT can be considered for large lesions.

What 2 factors should be considered when determining whether or not a pt with a margin+ DT needs adj RT?

Factors to consider whether a margin+ DT pt needs adj RT:

1.     Salvage options should be identified for a subsequent recurrence.

2.     The risk of significant morbidity if the tumor recurs should be considered in determining whether a margin+ resection of DT needs adj RT.

Note: If the lesion is amenable to salvage repeat −resection at the time of recurrence and is not likely to produce significant morbidity if the tumor recurs, then observation may be appropriate.

According to NCCN guidelines, what type of DT is usually not treated with RT?

According to NCCN guidelines, RT is not generally recommended for a DT that is retroperitoneal/intra-abdominal.

What is the LR rate for DT treated with RT alone?

The LR rate for DT treated with RT alone is 22%. (Nuyttens JJ et al., Cancer 2000)

What dose of RT is needed to control DT with RT alone?

A dose >50 Gy is needed to treat DT with RT alone. The recommended dose for gross Dz is 50–56 Gy. The LR for pts treated with RT alone is 60% with doses <50 Gy and ~15% with doses >50 Gy. (Nuyttens JJ et al., Cancer 2000)

What dose of RT is recommended after an R1 resection of DT in a pt who cannot be salvaged with repeat resection?

A pt treated with adj RT after an R1 resection should be treated to a dose of 50 Gy in 1.8–2 Gy/fx.

Define the target volume for RT in the management of DT.

The target volume to include when treating DT with RT includes the tumor bed (and/or gross tumor), a portion of the muscle compartment to cover fascial planes, or neurovascular structures along which tumor may track with a 3–5-cm margin longitudinally.

Define 4 nonsurgical, non-RT approaches to DT Tx.

Nonsurgical, non-RT approaches to DT Tx:

1.     Hormone ablation (tamoxifen)

2.     NSAIDs (sulindac)

3.     Low-dose cytotoxic chemo (methotrexate or doxorubicin based)

4.     Targeted therapy (imatinib)

Define 2 pt populations in which radiotherapy for DT should be avoided.

RT should be avoided in intra-abdominal DT or in children with DT. RT is avoided in skeletally immature pts to prevent RT effects associated with growth delay. However, in refractory cases, RT may be used in both cases.

Name 1 prognostic classification system for FAP-associated DT.

The Cleveland Clinic devised a prognostic stratification system for FAP-associated DT:

1.     Stage I: asymptomatic, ≤10 cm in max diameter, not growing

2.     Stage II: mildly symptomatic, ≤10 cm, not growing

3.     Stage III: moderately symptomatic or bowel/ureteric obstruction of 10–20 cm in max diameter, slowly growing

4.     Stage IV: severely symptomatic or >20 cm, rapidly growing

In a series by Church et al., there were no deaths for stages I–II, but there was a death rate of 15% for stage III and 44% for stage IV. (Dis Colon Rectum 2008)

image Toxicity

Define 6 late complications associated with RT Tx to the extremity.

Late complications associated with RT to the extremities:

1.     Fibrosis

2.     Edema

3.     Fracture

4.     2nd malignancy

5.     Joint stiffness

6.     Neuropathy

Define the dose of RT associated with premature closure of the epiphysis.

The dose of RT associated with premature closure of the epiphysis is >20 Gy.

What dose of RT is associated with an increased risk of late complications in Tx of DT of the extremity?

The risk of late complications for pts with DT of the extremity treated with RT is 30% with doses >56 Gy vs. 5% with doses <56 Gy. (Ballo MT et al., IJROBP 1998)