Progesterone Receptor Positive Tumor clinical trials at University of California Health

RATIONALE: Estrogen can stimulate the growth of breast tumor cells. Ovarian function suppression combined with hormone therapy using tamoxifen or exemestane may fight breast cancer by reducing the production of estrogen. It is not yet known whether suppression of ovarian function plus either tamoxifen or exemestane is more effective than tamoxifen alone in preventing the recurrence of hormone-responsive breast cancer. PURPOSE: This randomized phase III trial studies ovarian suppression with either tamoxifen or exemestane to see how well they work compared to tamoxifen alone in treating premenopausal women who have undergone surgery for hormone-responsive breast cancer.