Why carry out the study?

The real-world effectiveness of treatments after first-line (1L) pertuzumab and trastuzumab for patients with human epidermal growth factor receptor-2-positive metastatic breast cancer (HER2+ mBC) is understudied.

What was learned from the study?

This retrospective cohort study assessed the real-world treatment patterns, treatment duration, and time to treatment failure of second-line (2L) therapies for patients with HER2+ mBC following 1L pertuzumab and trastuzumab-based regimens in the United States during 2015–2019. Among patients on 1L trastuzumab and pertuzumab based regimen, about 31% progressed and moved to 2L and about 5% died on 1L.

The most common therapies used in 2L were ado-trastuzumab emtansine (T-DM1)-based regimens, irrespective of a brain metastasis diagnosis prior to the initiation of 2L, while 2L T-DM1 was associated with a short treatment duration (around 6 months) and a short time to treatment failure (8 months).

The short median treatment duration and time to treatment failure highlight an unmet need that can potentially be fulfilled by recently approved treatment options. More recent 2L treatments with better efficacy results will offer the opportunity to improve the outcomes of patients with HER2+ mBC who failed 1L trastuzumab and pertuzumab-based regimen.