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.