Retroperitoneal Sarcoma (RS)

1. Retroperitoneal Sarcoma (RS) Hashmi

2. approximately 15% of all sarcomas • approximately 33% to 55% of all retroperitoneal tumors • malignant tumors arising from mesenchymal cells • located in adipose, muscle, connective tissue, or soft tissue • contrast to carcinomas • epithelial origin (breast, colon, pancreas, etc) • metastasize via hematogenous route • typically to the liver or lung • most common variants of RS • liposarcoma (40%) • leiomyosarcoma (30%) • malignant fibrous histiocytoma (<10%)

3. most common clinical presentation is an abdominal mass • non-specific, vague abdominal discomfort or pain, weight loss, and early satiety, intestinal obstruction or bleeding, lower extremity swelling or pain • computed tomography (CT) is the initial test of choice, then MRI • tumor location and size • relationship to surrounding anatomic structures • identification of metastatic lesions • differential diagnosis • germ cell tumor, teratoma, cyst, hematoma and abscess, functioning and non-functioning adrenal tumor, renal tumor, pancreatic tumor, advanced gastrointestinal carcinoma, soft tissue sarcoma, lymphoma, and other neoplasms

4. surgery is the standard treatment • surgical failures • large tumor size on presentation • inability to achieve wide surgical margins • limitations of existing adjuvant radiation and chemotherapy regimens • failure can be seen even 5 to 10 years in nearly 90% of patients • long-term recurrence rate is thought to be over 70% • prognosis is worse for RS than for other trunk or extremity sarcomas • >30% incidence of vascular involvement • >60% of cases of these lesions require multi-visceral resections • colon, kidney, small bowel, pancreas, bladder

5. Low grade sarcomas • treated surgically • adjuvant radiation therapy or chemotherapy • High grade sarcomas • neoadjuvant chemotherapy • these tumors are more likely to undergo metastasis • tumors are treated more aggressively

6. neo-adjuvant chemotherapy may be used in an attempt to ‘shrink’ the tumor • postoperative radiotherapy may be of benefit • adjuvant chemotherapy + surgical therapy may produce a modest improvement in the recurrence-free survival rate • recurrences can be treated with resection in the absence of metastasis • adjuvant treatment following re-resection should be considered for all patients who did not previously undergo chemotherapy • pulmonary metastasis have median survival of 6 to 12 months • pulmonary metastasis resection may associated with prolonged survival • hepatic metastasis survival rates have been lesser • unresectable metastatic disease • chemotherapy may provide some clinical efficacy

7. surveillance is based on low vs high grade tumor • low-grade disease • physical examination • ct scan of chest, abdomen, and pelvis • every 3 to 6 months for 2 to 3 years, then annually • high-grade disease • physical examination • ct scan of chest, abdomen, and pelvis • every 3 to 4 months for 3 years, then every 6 months for 2 years, then annually

8. gastrointestinal stromal tumors (GIST) • 1-3% of all gastrointestinal malignancies • GIST is a form of connective tissue cancer/sarcoma - a non-epithelial tumor • 70% occur in the stomach • 20% in the small intestine • <10% in the esophagus • characteristics of GISTs • spindle cells in 70-80%, epitheloid aspect in 20-30% • immunohistochemistry • antibodies that stain the molecule CD117 (also known as c-kit) • GISTs are thought to arise from interstitial cells of Cajal (ICC) • normally part of the autonomic nervous system of the intestine • pacemaker function in controlling motility • Most small GISTs (<5 and especially <2 cm) with a low rate of mitosis (<5 dividing cells per 50 HPF) are benign • surgery • do not require adjuvant therapy • Larger GISTs (>5 cm), and especially when the cell division rate is high (>6 mitoses/50 HPF) may be more malignant • neoadjuvant + surgery +/- adjuvant • c-kit tyrosine kinase inhibitor  imatinib (Glivec/Gleevec)