RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Estrogen can stimulate the growth of breast cancer cells. Hormone therapy using tamoxifen may fight breast cancer by blocking the uptake of estrogen by the tumor cells. It is not yet known if radiation therapy is more effective than observation, with or without tamoxifen, in treating ductal carcinoma in situ.

PURPOSE: Randomized phase III trial to compare the effectiveness of radiation therapy with that of observation, with or without tamoxifen, in treating women who have ductal carcinoma in situ.

OBJECTIVES:

• Compare the efficacy of whole breast radiotherapy vs observation with or without optional tamoxifen in decreasing or delaying the appearance of local failure (both invasive and in situ) and preventing the need for mastectomy in women with good-risk ductal carcinoma in situ (DCIS) of the breast.
• Compare distant disease-free survival of patients treated with these regimens.

OUTLINE: This is a randomized, multicenter study. Patients are stratified according to age (under 50 vs 50 and over), final path margins (negative vs 3-9 mm vs at least 10 mm), mammographic size of primary (no greater than 1 cm vs greater than 1 cm to 2.5 cm), nuclei grade (low vs intermediate), and tamoxifen use (yes vs no). Patients are randomized to 1 of 2 treatment arms.

• Arm I: Patients undergo observation and may receive optional oral tamoxifen once daily (at the discretion of the physician) for 5 years.
• Arm II: Beginning within 12 weeks after final surgery, patients receive radiotherapy to the whole breast once daily, 5 days a week, for 3.5-5.5 weeks. Patients may receive optional tamoxifen as in arm I.

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

PROJECTED ACCRUAL: A total of 1,790 patients will be accrued for this study within 6 years.

DISEASE CHARACTERISTICS:

• Ductal carcinoma in situ (DCIS) of the breast detected by mammogram at the time of diagnosis

  • Unicentric
  • Lesions ≤ 2.5 cm
  • Low nuclei grade (NG1) or intermediate nuclei grade (NG2) with necrosis in < one third of the involved ducts
  • Inked margins ≥ 3 mm
  • Clinically node negative
  • Non-palpable

• No suspicious areas on post-operative mammogram taken within 12 weeks after final surgery

• No bloody nipple discharge

• No more than 12 weeks since prior final surgery (arm II only)

• Hormone receptor status:

  • Not specified

PATIENT CHARACTERISTICS:

Age:

• 26 and over

Sex:

• Female

Menopausal status:

• Not specified

Performance status:

• Not specified

Life expectancy:

• Not specified

Hematopoietic:

• Not specified

Hepatic:

• Not specified

Renal:

• Not specified

Other:

• Not pregnant or nursing
• No active connective tissue disorders (e.g., lupus or scleroderma)
• No prior malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• Not specified

Chemotherapy:

• No prior chemotherapy

Endocrine therapy:

• No other concurrent hormonal therapy (e.g., raloxifene, hormone replacement therapy, or birth control pills)

Radiotherapy:

• No prior radiotherapy

Surgery:

• See Disease Characteristics