Radiation Therapy in Treating Women Who Have Undergone Surgery for Early-Stage Invasive Breast Cancer

DISEASE CHARACTERISTICS: * Histologically proven invasive carcinoma of the breast * No evidence of T4, N2-3, or M1 disease prior to surgery * Node positive or high-risk node negative * Prior breast-conserving therapy (BCT) (e.g., lumpectomy, partial mastectomy, or segmental mastectomy) and axillary node dissection or sentinel node biopsy required and must be a candidate for breast radiotherapy after BCT * Normally patients should have microscopically clear resection margins and those with positive margins should undergo reexcision * Patients with microscopically focally positive margins (defined as no greater than 3 times high power fields) are candidates for breast radiotherapy plus a boost to the lumpectomy site * Patients with prior sentinel node dissection eligible if node negative, but still meet high-risk criteria * If node positive, then a level I and II axillary dissection must be performed * No evidence of residual disease in axilla after dissection * Must be treated with currently accepted adjuvant systemic chemotherapy and/or hormonal therapy * High risk of regional and systemic recurrence due to one of the following: * Pathologically positive axillary lymph nodes * Pathologically negative axillary lymph nodes with one of the following: * Primary tumor greater than 5 cm * Primary tumor greater than 2 cm and less than 10 axillary lymph nodes excised and one of the following: * Estrogen receptor negative * Skarf-Bloom-Richardson grade 3 * Lymphovascular invasion * Hormone receptor status: * Estrogen and progesterone receptor status known PATIENT CHARACTERISTICS: Age: * 16 and over Sex: * Female Menopausal status: * Premenopausal or postmenopausal Performance status: * ECOG 0-2 Life expectancy: * At least 5 years Hematopoietic: * Not specified Hepatic: * SGOT and/or SGPT no greater than 3 times upper limit of normal (ULN)\* * Alkaline phosphatase no greater than 3 times ULN\* NOTE: \* Patients with laboratory values greater than 3 times ULN may still be eligible if no metastatic disease by imaging examinations Renal: * No serious nonmalignant renal disease Cardiovascular: * No serious nonmalignant cardiovascular disease Pulmonary: * No serious nonmalignant pulmonary disease Other: * Not pregnant or nursing * Fertile patients must use effective contraception * No other serious nonmalignant disease (e.g., systemic lupus erythematosus or scleroderma) that would preclude definitive surgery or radiotherapy * No other malignancy except: * Nonmelanomatous skin cancer * Carcinoma in situ of the cervix or endometrium * Contralateral noninvasive breast cancer (unless prior radiotherapy to the contralateral breast) * Invasive carcinoma of the cervix, endometrium, colon, thyroid, or melanoma that was curatively treated at least 5 years prior to study participation * No psychiatric or addictive disorder that would preclude informed consent or study compliance PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * See Disease Characteristics * Concurrent standard adjuvant chemotherapy allowed Endocrine therapy: * See Disease Characteristics * Concurrent standard adjuvant hormonal therapy allowed Radiotherapy: * See Disease Characteristics Surgery: * See Disease Characteristics