Real-World Treatment Patterns and Outcomes Following First-Line Pertuzumab and Trastuzumab Among Patients with HER2+ Metastatic Breast Cancer

Introduction Many patients with human epidermal growth factor receptor-2-positive metastatic breast cancer (HER2+ mBC) require subsequent lines of therapy (LOTs) after being treated with pertuzumab and trastuzumab-based regimens in the first line (1L). Although the efficacy of the second-line (2L) therapies has been demonstrated in clinical trials, the real-world effectiveness of these treatments is understudied. This retrospective cohort study assessed the real-world treatment patterns and outcomes for patients with HER2+ mBC following 1L therapy with pertuzumab and trastuzumab-based regimens in the United States (US) during 2015–2019. Methods Adults with HER2+ mBC in the US who initiated 1L pertuzumab and trastuzumab-based regimens between 01/01/2015 and 09/30/2019 and had ≥ 60 days of follow-up after 1L initiation were identified from the IQVIA Oncology Electronic Medical Records database. The regimens utilized in 2L following 1L pertuzumab and trastuzumab-based regimens were described. Median treatment duration and time to treatment failure were reported for 2L based on Kaplan–Meier analyses. Results Of the 710 eligible patients who received pertuzumab and trastuzumab-based regimens in 1L (median age: 57.0 years [interquartile range: 48.0–65.0]; median follow-up: 20.3 months; median 1L duration: 15.3 months), 222 (31.3%) initiated 2L. The most common regimens in 2L were ado-trastuzumab emtansine (T-DM1)-based regimens ( n = 159 [71.6%]), followed by lapatinib-based ( n = 21 [9.5%]) and neratinib-based ( n = 18 [8.1%]) regimens. The median treatment duration and time to treatment failure were 5.9 (95% CI: 5.0, 8.7) and 8.6 (7.3, 11.5) months, respectively, among patients initiating 2L, and 5.7 (4.7, 7.8) and 7.9 (6.5, 10.0) months among those receiving 2L T-DM1. Conclusions Most patients with HER2+ mBC requiring additional treatments after 1L pertuzumab and trastuzumab-based regimens utilized T-DM1 in 2L during 2015–2019. The short median treatment duration and time to treatment failure highlight an unmet need that can potentially be fulfilled by recently approved treatment options.