Surgery With or Without Radiation Therapy in Treating Patients With Primary Soft Tissue Sarcoma of the Retroperitoneum or Pelvis

DISEASE CHARACTERISTICS: Histologically confirmed primary soft tissue sarcoma of the retroperitoneum or pelvis (e.g., iliac fossa) The following histologies are eligible: Alveolar soft part sarcoma Anaplastic sarcoma Angiosarcoma Atypical lipomatous tumor (low-grade liposarcoma) Clear cell sarcoma Epithelioid sarcoma Fibrosarcoma Leiomyosarcoma Liposarcoma (all subtypes) Malignant fibrous histiocytoma Malignant peripheral nerve sheath tumor Myxofibrosarcoma Neurofibrosarcoma Spindle cell sarcoma Synovial sarcoma Unclassified sarcoma The following histologies are not eligible: Rhabdomyosarcoma Extraosseous Ewing's sarcoma Primitive neuroectodermal tumor Osteosarcoma Chondrosarcoma Aggressive fibromatosis (desmoid tumor) Gastrointestinal stromal tumor Sarcomatoid carcinoma Hemangiopericytoma Retroperitoneal sarcomas located predominantly in the retroperitoneum extending across the inguinal ligament into the abdominal wall are allowed provided that ≥ 90% of the tumor volume is located within the retroperitoneal space No bowel obstruction OR history of previous bowel obstruction attributed to retroperitoneal tumor Primary non-visceral retroperitoneal masses consistent with sarcoma allowed provided diagnoses of carcinoma, melanoma, and lymphoma are excluded by immunohistochemistry Measurable gross disease by abdominopelvic CT scan (with IV and oral contrast) or MRI (with IV contrast) Patients must have undergone radiotherapy consultation within the past 30 days to confirm the feasibility of preoperative external-beam radiotherapy Patients must have undergone surgical consultation within the past 30 days to confirm and document the feasibility of macroscopically complete resection No prior macroscopically incomplete (R2) resection (i.e., partial debulking or subtotal tumor resection with gross residual disease) No pelvic sarcoma extending through the sciatic notch No clinical or radiographic evidence of probable metastatic disease Equivocal pulmonary or liver lesion allowed provided the likelihood of metastatic disease is small No sarcoma arising from bone or any retroperitoneal viscus (except the kidney) No sarcoma extending across the diaphragm into the thorax No recurrent retroperitoneal tumor No multifocal disease PATIENT CHARACTERISTICS: Age 18 and over Performance status ECOG 0-1 OR Zubrod 0-1 Life expectancy Not specified Hematopoietic WBC ≥ 2,500/mm^3 Platelet count ≥ 80,000/mm^3 Hepatic Bilirubin ≤ 1.5 times upper limit of normal (ULN) AST ≤ 2.5 times ULN Albumin normal* NOTE: *Higher levels allowed Renal Creatinine normal BUN normal Functional kidney confirmed by intravenous pyelogram and/or differential renal isotope scan Other Not pregnant Negative pregnancy test Fertile patients must use effective contraception during and for 3 months after study participation No other malignancy within the past 5 years (except effectively treated basal cell or squamous cell skin cancer) unless patient was curatively treated AND is at low risk for recurrence PRIOR CONCURRENT THERAPY: Chemotherapy No concurrent chemotherapy for primary tumor Radiotherapy No prior abdominal or pelvic irradiation No concurrent intraoperative or postoperative radiotherapy for primary tumor Surgery See Disease Characteristics