Differential long-term tamoxifen benefit by menopausal status in breast cancer patients: pooled secondary analysis of three randomized trials

Estrogen receptor-positive breast cancer patients have a long-term risk of distant metastatic disease, and this risk in higher in premenopausal patients than in postmenopausal patients. Randomized studies with long-term follow-up are required to understand treatment benefit. Pooled secondary analysis of three Stockholm tamoxifen trials found that benefit from adjuvant tamoxifen differed by menopausal status. In premenopausal patients, benefit from tamoxifen only lasted beyond 10 years for genomic low-risk tumors. Postmenopausal patients showed long-term benefit for all good-prognosis markers, including low-grade, lymph node-negative, progesterone receptor-positive, Ki-67 low, and genomic low-risk tumors; and regardless of tumor size. Premenopausal patients with no poor-prognosis tumor characteristics (clinical marker score = 0) showed early benefit and postmenopausal long-term benefit. The authors conclude that the analysis suggests differential benefit from adjuvant tamoxifen by menopausal status.