Key clinical point: Among patients with human epidermal growth factor receptor 2–positive (HER2+) breast cancer, adding trastuzumab to adjuvant chemotherapy reduces risk of recurrence for at least 10 years.

Major finding: Patients with hormone receptor–positive (HR+) HER2+ breast cancer who were treated with adjuvant trastuzumab-based chemotherapy had a significantly higher rate of recurrence-free survival within 5 years than that of patients with HR–HER2+ disease (hazard ratio, 0.60; P less than .001).

Study details: A post hoc analysis of 3,177 patients with HER2+ breast cancer from the phase 3 North Central Cancer Treatment Group N9831 and National Surgical Adjuvant Breast and Bowel Project B-31 trials.

Disclosures: The study was funded by the National Institutes of Health, the Breast Cancer Research Foundation, Bankhead-Coley Research Program, the DONNA Foundation, and Genentech. Dr. Chumsri disclosed a financial relationship with Merck. Coauthors disclosed ties with Merck, Novartis, Genentech, and NanoString Technologies.