OUTLINE: This is a randomized study. Patients are randomized into one of four treatment arms. Arm I: Patients receive oral tamoxifen (TMX) daily continously for 5 years. Lumpectomy patients receive breast radiotherapy following recovery from surgery. Arm II: Patients receive TMX as in Arm I and octreotide pamoate (SMS 201-995 pa LAR) intramuscularly (IM) every 21 days for 4 doses, followed by octreotide pamoate IM for 28 days for 23 additional doses. Lumpectomy patients receive breast radiotherapy following recovery from surgery. Arm III: Patients receive doxorubicin (DOX) IV and cyclophosphamide (CTX) IV every 3 weeks for 4 courses and TMX as in Arm I. Lumpectomy patients receive breast radiotherapy after recovery from chemotherapy. Arm IV: Patients receive DOX and CTX as in Arm III, TMX as in Arm I, and octreotide pamoate as in Arm II. Patients receive TMX and octreotide pamoate on day 1 of first course of chemotherapy. Lumpectomy patients receive breast radiotherapy after recovery from chemotherapy.