OUTLINE: Randomized study. All patients are randomized on Arms I, II, and III. Lumpectomy patients must receive radiotherapy on Regimen A. At the discretion of the physician, mastectomy patients may receive radiotherapy on Regimen B for a tumor greater than 5 cm in diameter, 4 or more positive nodes, or extranodal extension of the tumor into the axillary fat. Patients randomized to Arm I who are to receive radiotherapy should begin as soon as feasible postoperatively; these patients may be irradiated while receiving tamoxifen. Patients on Arms II and III who are to receive radiotherapy are treated either postoperatively prior to registration or after completion of and recovery from 6 courses of CAF. Arm I: Antiestrogen Therapy. Tamoxifen, TMX, NSC-180973. Arm II: 3-Drug Combination Chemotherapy followed by Antiestrogen Therapy. CAF: Cyclophosphamide, CTX, NSC-26271; Doxorubicin, DOX, NSC-123127; Fluorouracil, 5-FU, NSC-19893; followed by TMX. Arm III: 3-Drug Combination Chemotherapy plus Concurrent Antiestrogen Therapy. CAF; plus concurrent TMX. Regimen A: Radiotherapy. Irradiation of the breast and underlying chest wall and (optionally) of the supraclavicular area and, if indicated, the axilla, using megavoltage equipment with photon energies of up to 6 MV followed, if indicated, by a tumor bed boost using either electrons or iridium-192 (192-Ir) implants. Regimen B: Radiotherapy. Irradiation of the chest wall using either megavoltage photons via a tangential field or electrons via a direct field plus (optional) photon irradiation of the supraclavicular area and, if indicated, the axilla.