RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining hormone therapy with chemotherapy may kill more tumor cells.

PURPOSE: Randomized phase III trial to study the effectiveness of tamoxifen, octreotide, and chemotherapy in treating women who have stage I or stage II breast cancer.

OBJECTIVES: I. Determine whether the addition of octreotide pamoate to tamoxifen alone or to tamoxifen and chemotherapy improves the disease free survival of patients with primary invasive breast cancer with estrogen receptor (ER) positive tumors and histologically negative axillary lymph nodes or histologically negative sentinel lymph nodes if participating in NSABP B-32. II. Determine whether the rate of endometrial cancer associated with tamoxifen is altered by the concurrent administration of octreotide pamoate. III. Determine whether the addition of octreotide pamoate to tamoxifen decreases the rate of opposite breast cancer more than tamoxifen alone. IV. Evaluate the incidence of gallstone formation (including the development of symptoms and complications of biliary tract disease), hyper and hypoglycemia, hypothyroidism, and vitamin B12 deficiency in patients treated with octreotide pamoate in comparison with patients not treated with octreotide pamoate.

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.

PROJECTED ACCRUAL: Total accrual of 3,000 patients will be acrrued for this study over 5 years.

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

PATIENT CHARACTERISTICS: Age: Not specified Sex: Female Menopausal status: Not specified Life expectancy: At least 10 years (excluding diagnosis of cancer) Performance status: Not specified Hematopoietic: WBC at least 4,000/mm3 Platelet count postoperative at least 100,000/mm3 Hepatic: Bilirubin normal SGOT/SGPT normal Renal: Creatinine normal Cardiovascular: No cardiac disease that would preclude the use of doxorubicin (for patients who are to receive adjuvant chemotherapy in this study), including: Myocardial infarction Angina pectoris that requires antianginal medication History of congestive heart failure Arrhythmia associated with concurrent heart failure or cardiac dysfunction Valvular disease with cardiac compromise Cardiomegaly or ventricular hypertrophy unless left ventricular function is within normal limits Poorly controlled hypertension Other: No prior invasive breast cancer or ductal carcimoma in situ No systemic disease that would preclude patients from any part of study No history of symptomatic gallbladder or biliary tract disease unless patient has undergone cholecystectomy No ulceration, erythema, infiltration of the skin or underlying chest wall (complete fixation), peau d'orange, or skin edema of any magnitude No prior nonbreast malignancies in past 10 years except: Squamous or basal cell carcinoma of the skin that has been effectively treated Carcinoma in situ of the cervix that has been treated by operation only Lobular carcinoma in situ of the ipsilateral or contralateral breast treated by segmented resection only No psychiatric or addictive disorders Not pregnant or nursing Negative pregnancy test

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior biologic therapy for breast cancer Chemotherapy: No prior chemotherapy for breast cancer No prior anthracycline therapy for patients who are to receive adjuvant chemotherapy in this study Endocrine therapy: No prior endocrine therapy for breast cancer Must discontinue any sex hormonal therapy before prior to and during study Radiotherapy: No prior radiotherapy for breast cancer No breast radiation therapy before randomization for patients who receive lumpectomy Surgery: See Disease Characteristics At least 2 weeks since last surgical procedure Other: No concurrent cyclosporine therapy No concurrent heparin or warfarin anticoagulation therapy