Purpose: Worldwide, 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 methods: From 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.
Results: With 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.
Conclusion: In 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.