Predictors of long-term durable response in de novo HER2-positive metastatic breast cancer and the real-world treatment experience at two institutions.

Nearly a third of patients with de novo HER2 + MBC achieved DR. Factors that correlate with DR include single metastatic site, initial trastuzumab, pertuzumab and taxane therapy, and surgical resection of primary tumor. Among patients with DR, indefinite trastuzumab administration is the norm.