Real-world retrospective cohort study of treatment patterns and outcomes in HER2-low metastatic breast cancer patients after chemotherapy

Real-world outcomes are poorly understood for patients with HER2-low metastatic breast cancer (mBC). Retrospective analysis of a US nationwide electronic health record database assessed demographics, treatment patterns, and outcomes of patients with HER2-low mBC who previously received one line of chemotherapy in the metastatic setting.The post-chemotherapy was termed the index line of therapy (LOT). In the database from 2011 through April, 2023, the authors identified 3765 patients (78.8% HR-positive; 21.0% HR-negative) who met the inclusion criteria. 61.7% of HR-positive patients received endocrine therapy prior to the index LOT. Most patients received single-agent chemotherapy at the index and subsequent two LOTs. The median time to treatment discontinuation or death was 4.1 months (95% CI 3.9-4.2) and the median time to next treatment or death was 5.1 months (4.8-5.3) from the index LOT. Median overall survival was 15.8 months (95% CI 15.2-16.5) from the index LOT. The authors conclude that these data highlight the unmet clinical needs of patients with HER2-low mBC.