RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. It is not yet known whether receiving radiation therapy or no further therapy after surgery is more effective for cancer of the uterus.

PURPOSE: Randomized phase III trial to compare the effectiveness of radiation therapy with that of no further therapy in treating patients who have stage I or stage II cancer of the uterus that has been surgically removed.

OBJECTIVES: I. Compare the rates of pelvic recurrence and development of distant metastases in patients with completely resected, stage I or II, high-grade uterine sarcoma treated with adjuvant pelvic radiotherapy vs observation alone.

OUTLINE: This is a randomized, multicenter study. Patients are stratified according to center, tumor histology (leiomyosarcoma vs mixed mesodermal sarcoma vs endometrial stromal sarcoma), and surgical procedure (total abdominal hysterectomy (TAH) with or without bilateral salpingo-oophorectomy (BSO) vs TAH and BSO with pelvic and para-aortic node sampling and random biopsies). Patients are randomized to 1 of 2 treatment arms. Arm I: Beginning within 6 weeks after surgery, patients undergo pelvic radiotherapy 5 days a week for 5.6 weeks. Arm II: Patients undergo observation alone. Patients are followed every 2 months for 1 year, every 3 months for 2 years, and then every 6 months thereafter.

PROJECTED ACCRUAL: A total of 200 patients (100 per arm) will be accrued for this study within 3 years.

DISEASE CHARACTERISTICS: Histologically proven high-grade uterine sarcoma Eligible subtypes: Leiomyosarcoma Mixed mesodermal (mullerian) sarcoma Endometrial sarcoma Surgically proven stage I or II (T1-2, N0, M0) disease No leiomyoma with a high mitotic activity index after hormonal therapy (especially estrogen) Mixoid leiomyosarcoma with a low mitotic activity index allowed Completely resected disease Prior abdominal hysterectomy as minimal surgical procedure required

PATIENT CHARACTERISTICS: Age: Any age Performance status: WHO 0-2 Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: No other prior malignancy except basal cell skin cancer or carcinoma in situ of the cervix No serious mental disorder

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: See Disease Characteristics Radiotherapy: No prior radiotherapy Surgery: See Disease Characteristics