- Patients treated by lumpectomy and axillary node dissection to be followed by breast radiation therapy must meet all the eligibility criteria in addition to the following: Generally, lumpectomy should be reserved for tumors <5 cm. However, at the investigator's discretion, patients treated with lumpectomy for tumors ≥ 5 cm are eligible. The margins of the resected specimen must be histologically free of invasive tumor and DCIS as determined by the local pathologist. In patients in whom pathologic examination demonstrates tumor present at the line of resection, additional operative procedures may be performed to obtain clear margins. This is permissible even if axillary dissection has been performed. Patients in whom tumor is still present at the resected margin after re-excision(s) must undergo total mastectomy to be eligible. Whole breast irradiation is required. Irradiation of regional lymph nodes is optional, but partial breast irradiation and irradiation of any internal mammary nodes are prohibited in this trial. Intent to irradiate the axilla or other regional node groups must be declared by the investigator prior to randomization for stratification purposes.