RATIONALE: Radiation therapy uses high-energy x-rays to damage cancer cells. It is not yet known whether radiation therapy is more effective than observation only after sugery in treating endometrial cancer.

PURPOSE: This randomized phase III trial is studying radiation therapy to see how well it works compared to observation only in treating patients with stage I or stage II endometrial cancer who have undergone hysterectomy and oophorectomy.

OBJECTIVES:

• Compare the overall survival in patients with intermediate-risk endometrial cancer treated with pelvic radiotherapy vs observation after laparoscopically-assisted vaginal hysterectomy or total abdominal hysterectomy and bilateral salpingo-oophorectomy.
• Compare the time to locoregional recurrence (i.e., in the vaginal mucosa or elsewhere in the central pelvic area or lateral pelvic walls) in patients treated with these regimens.
• Compare the duration of ultimate pelvic control and event-free survival in patients treated with these regimens.
• Compare the toxic effects of these regimens in these patients.
• Compare the quality of life of patients treated with these regimens.
• Compare sexual health issues in patients treated with these regimens.

OUTLINE: This is a randomized, multicenter study. Patients are stratified by center, tumor grade (1 vs 2 vs 3), surgical staging (yes vs no), and sexual health assessment (yes vs no).

Patients undergo laparoscopic-assisted vaginal hysterectomy or total abdominal hysterectomy and bilateral salpingo-oophorectomy. After surgery, patients are randomized to 1 of 2 treatment arms.

• Arm I: Patients undergo observation alone.
• Arm II: Beginning within 12 weeks (preferably within 6-8 weeks) after surgery, patients undergo radiotherapy 5 days a week for 5 weeks in the absence of disease progression or unacceptable toxicity. Protocol-defined brachytherapy is allowed.

Quality of life is assessed at baseline; at 16-18 weeks after surgery (arm I) or 5 and 9 weeks after initiating radiotherapy (arm II); and then at 6, 12, 18, 24, 36, 48, and 60 months.

Patients are followed every 3 months for 2 years, every 4 months for 1 year, every 6 months for 2 years, and then annually thereafter.

PROJECTED ACCRUAL: A total of 400 patients will be accrued for this study.

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