DISEASE CHARACTERISTICS: Histologically proven stage T1-3, pN1, M0 carcinoma of the breast considered suitable for adjuvant treatment with endocrine therapy alone Estrogen receptor at least 10 fmol/mg cytosol protein or positive on immunohistochemical assay Potentially curative resection within 6 weeks of entry by one of the following: Total mastectomy with negative margins Breast-conserving procedure (lumpectomy or quadrantectomy) for tumors less than 5 cm Adequate re-resection or mastectomy within 4 weeks of initial surgery required if margins are positive after initial surgery Axillary clearance (not sampling) required at surgery, with at least 1 node positive upon histopathologic examination of at least 8 nodes Suspicious manifestations of metastatic disease (e.g., hot spots on bone scan, skeletal pain of unknown cause) must be proven benign No bilateral breast cancer Any mass in contralateral breast must be proven benign by biopsy