Radiation or Observation Only in Endometrial Cancer Who Have Undergone Surgery

DISEASE CHARACTERISTICS: Histologically proven adenocarcinoma or adenosquamous cell carcinoma of the endometrium Intermediate-risk of recurrence after laparoscopically-assisted vaginal hysterectomy (with or without laparoscopic staging) or total abdominal hysterectomy and bilateral salpingo-oophorectomy Postoperative pathologic stage IA/IB (grade 3), stage IC (grade 1-3), or stage IIA (all grades) Patients with more than 50% myometrial invasion (grade 1 or 2) or less than 50% myometrial invasion (grade 3) but with positive peritoneal cytology also eligible Patients whose sole criterion for increased risk is positive peritoneal cytology are not eligible No pathologically involved lymph nodes if staging procedure performed Stage I papillary serous or clear cell endometrial cancer allowed PATIENT CHARACTERISTICS: Age: Not specified Performance status: ECOG 0-3 Life expectancy: At least 3 years Hematopoietic: WBC at least 2,000/mm^3 Platelet count at least 100,000/mm^3 Hemoglobin at least 10 g/dL Hepatic: Not specified Renal: Creatinine less than 2 times upper limit of normal No serious renal disease that would preclude radiotherapy Cardiovascular: No serious cardiovascular disease that would preclude radiotherapy Other: No history of inflammatory bowel disease such as ulcerative colitis No other malignancy within past 5 years except curatively treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, colon cancer, or thyroid cancer No psychiatric or addictive disorder that would preclude study participation PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: No prior anticancer hormonal therapy No concurrent progestogens Radiotherapy: No prior pelvic irradiation No prior or other concurrent vaginal intracavitary radiotherapy Surgery: See Disease Characteristics Other: No prior anticancer therapy No other concurrent anticancer therapy