DISEASE CHARACTERISTICS: Histologically confirmed Stage I, IIA or IIB invasive adenocarcinoma of the breast with T1-3, pN0 and M0 classification Must have undergone total mastectomy or lumpectomy followed by an axillary dissection or sentinel node resection if participating in NSABP B-32 Histologically negative axillary lymph nodes OR Histologically negative sentinel lymph nodes if participating in NSABP B-32 Lumpectomy and axillary dissection acceptable only if margins of resected specimen are histologically free of invasive tumor or ductal carcinoma in situ and other dominant masses within the ipsilateral breast remnant are histologically confirmed to be benign Additional operation after resection is allowed in order to obtain clear margins No bilateral malignancy of the breast ER positive tumors as defined by at least one of the following: At least 10 fmol/mg cytosol protein by either dextran-coated charcoal or sucrose density gradient methods Positive or not definitely negative results by the enzyme immunoassay method (EIA) or by immunocytochemical assay No more than 63 days from time of initial cytologic or histologic diagnosis of breast cancer till randomization No bone metastases (confirmation must be made for those with skeletal pain) Tumor must be no greater than 5 cm in its greatest dimension for patients who are treated by lumpectomy and axillary dissection Hormone receptor status: Estrogen receptor positive