Desmoid Tumors
BACKGROUND
What are desmoid tumors (DT)?
DTs are rare, benign, slow-growing fibroblastic neoplasms that arise from musculoaponeurotic stromal elements with high recurrence even after complete resection.
What is another commonly used name for DT?
DT is also known as aggressive fibromatosis (previously called fibrosarcoma grade I of desmoids type).
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.?
~900 cases/yr of DT in the U.S.
Is there a sex or racial/ethnic predilection for DT?
Yes, with regard to gender. Women are slightly more commonly affected than men. 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 decades 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). Wnt/beta-catenin pathway may play a key role in both FAP and sporadic DT.
What is the clinical syndrome associated with DT?
Gardner syndrome is associated with DT, and 10%–20% of pts with this syndrome will develop DT.
Sebaceous cysts
Osteomas
Desmoid tumors
(Mnemonic: Gardner 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. Intra-abdominal DTs are often a source of significant morbidity and mortality.
What 2 environmental conditions are associated with DT?
Retrospective and anecdotal data suggest 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, obstruction, or complications with ileoanal anastomosis after colectomy for FAP.
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.
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?
A core needle or open incisional Bx is the preferred method for any tumor that may be a malignant soft tissue sarcoma.
TREATMENT/PROGNOSIS
What is considered the primary modality for Tx of DT?
Surgical resection is considered the primary modality for Tx of DT. Resection does not appear to affect survival.
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?
For pts with intra-abdominal DTs that are large, slow growing, involve the mesentery, or encase vessels and/or organs, initial treatment with a nonsurgical approach is recommended.
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 factors should be considered when determining whether or not to offer adj RT for DT?
Factors to be considered when considering adj RT for DT:
1. Margin status. Margin– pts are unlikely to benefit
2. Tumor size. Large tumors may be considered for PORT even if margin–
3. Location. Adj RT for resected retroperitoneal/intra-abdominal DTs is associated with significant treatment risks
4. Salvage options. Lesions that may undergo repeat resections may be appropriately observed
5. Pt age. There should be a high threshold for using adj RT in children
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 clinical target volume for RT in the management of DT.
The clinical 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 and 2 cm in all other directions.
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)
Name 1 prognostic classification system for FAP-associated DT.
The Cleveland Clinic devised a prognostic stratification system for FAP-associated DT:
Stage I: asymptomatic, ≤10 cm in max diameter, not growing
Stage II: mildly symptomatic, ≤10 cm, not growing
Stage III: moderately symptomatic or bowel/ureteric obstruction of 10–20 cm in max diameter, slowly growing
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)
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)
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