Survival After Adjuvant Oophorectomy and Tamoxifen in Operable Breast Cancer in Premenopausal Women

Abstract

PurposeWorldwide, approximately 750,000 new cases of breast cancer are diagnosed annually in premenopausal women with limited economic resources. Longer-term survival benefits from adjuvant therapies in such women with operable breast cancer are unknown.Patients and MethodsFrom 1993 to 1999, we recruited 709 premenopausal women with operable breast cancer to a multisite randomized clinical trial of adjuvant oophorectomy and tamoxifen for 5 years or observation and this combined hormonal therapy on recurrence.ResultsWith a median follow-up of 7.0 years, disease-free and overall survival were significantly improved with the adjuvant treatment (log-rank P = .0003 and .0002, respectively). Five year disease-free survival (DFS) probabilities of 74% and 61% (95% CI for difference, 7% to 21%) and overall survival (OS) rates of 78% and 71% (95% CI for difference, 1% to 21%) were observed in the adjuvant and observation groups. Ten-year DFS probabilities of 62% and 51% (95% CI for difference, 4% to 22%) and OS probabilities of 70% and 52% (95% CI for difference, 6% to 34%) between adjuvant and observation groups, respectively, were observed. In the subset of estrogen receptor–positive patients, 5-year DFS probabilities were 83% and 61%, and 10-year DFS probabilities were 66% and 47%, while 5-year OS probabilities were 88% and 74%, and 10-year OS probabilities were 82% and 49% in the adjuvant and observation groups, respectively.ConclusionIn premenopausal women with operable breast cancer not selected for estrogen receptor status or with estrogen receptor–positive tumors, 5- and 10-year DFS and OS rates are significantly improved following adjuvant oophorectomy and tamoxifen.