Question

In patients with early breast cancer, does 5 years of adjuvant tamox-ifen therapy reduce long-term recurrence and mortality? Review scope Included studies compared adjuvant tamoxifen therapy for approxi-mately 5 years with no tamoxifen in women with early breast cancer and provided individual patient data. Trials of women with ductal carcinoma in situ were excluded. Outcomes were breast cancer recurrence, death, and other second primary cancer over 15 years of follow-up. Review methods Individual patient data meta-analysis of 20 randomized controlled trials (n = 21 457) that met the selection criteria. 10 645 women had estrogen receptor (ER)–positive disease. Main results Tamoxifen reduced recurrence in patients with ER-positive breast cancer (Table) but not in those with ER-negative cancer (relative risk reduction 3%, CI −7 to 12). Among patients with ER-positive cancer, tamoxifen reduced overall and breast cancer mortality (Table) but did not affect non–breast cancer mortality (relative risk increase [RRI] 2%, P = 0.79). In ER-positive cancer, tamoxifen increased risk for cancer of the uterus (excluding the cervix) (RR