Lymph Node Radiation Therapy in Patients With Stage I, Stage II, or Stage III Breast Cancer That Has Been Surgically Removed

DISEASE CHARACTERISTICS: * Histologically confirmed unilateral adenocarcinoma of the breast * Stage I/II/III (Tx, T0-3, N0-2) disease in one of the following categories or multifocal tumors if one of the foci is in agreement with the following: * Centrally or medially located with any lymph node status * Central location defined as underlying the areola * Medial location defined as at least partial involvement of upper or lower medial quadrant of breast * Externally located with axillary node involvement * Prior mastectomy or breast-conserving surgery and axillary dissection required * Sentinel node procedure as axillary intervention without further axillary surgery is allowed * No prior internal mammary chain dissection * No upper inner lesion treated with breast-conserving surgery that precludes sparing of internal mammary lymph node chain from radiotherapy volume * Decision at radiation oncologist's discretion * Hormone receptor status: * Not specified PATIENT CHARACTERISTICS: Age: * 75 and under Sex: * Female Menopausal status: * Not specified Performance status: * Not specified Hematopoietic: * Not specified Hepatic: * Not specified Renal: * Not specified Cardiovascular: * No prior cardiac disease Other: * No prior malignancy except adequately treated nonmelanomatous skin cancer or carcinoma in situ of the cervix PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * Not specified Endocrine therapy: * Not specified Radiotherapy: * Not specified Surgery: * See Disease Characteristics Other: * Concurrent enrollment in other randomized trials allowed