Radiation Therapy in Treating Women With Stage I or Stage II Breast Cancer

DISEASE CHARACTERISTICS: Histologically confirmed nonlobular invasive breast cancer of one of the following histologies: Ductal Papillary Medullary Colloid (mucinous) Tubular Stage I/II (T1-2 N0-1 M0) tumor no greater than 3 cm Prior tylectomy and axillary lymph node dissection required No more than 3 positive axillary lymph nodes and no extracapsular extension At least 6 lymph nodes sampled OR Negative sentinal node Surgical clips in place delineating margins of tylectomy cavity Negative, or close but negative, inked histologic margins of tylectomy or re-excision specimen Negative margins defined as no tumor at least 2 mm away from the inked margins Close but negative margins defined as tumor within 2 mm of inked margin Positive margins defined as invasive or noninvasive tumor at inked resection margins Negative post-tylectomy or post-reexcision mammogram required if disease presented with malignancy-associated microcalcifications No remaining suspicious microcalcifications If catheters are placed at time of reexcision, the crieria may not be feasible but a post brachytherapy mammogram should be obtained as soon as possible No extensive intraductal carcinoma by the Harvard definition, i.e.: More than 25% of tumor is ductal carcinoma in situ (DCIS) and there is DCIS in adjacent breast tissue OR Intraductal carcinoma with microinvasion No proven multicentric carcinoma, i.e.: Tumor in different quadrants of the breast OR Tumor separated by at least 4 cm The following exclude: S…