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Real-World Outcomes of Pertuzumab and T-DM1 for Metastatic Breast Cancer
Study findings suggest survival among patients with ERBB2-positive metastatic breast cancer receiving pertuzumab and trastuzumab emtansine (T-DM1) in the real-world setting appears inferior to results from pivotal clinical trials (JAMA Oncol. 2021;e212140. doi:10.1001/jamaoncol.2021.2140).
“Clinical trials have shown that the addition of pertuzumab to trastuzumab-based chemotherapy for first-line treatment of ERBB2-positive metastatic breast cancer is associated with considerable improvement in overall survival (OS),” wrote Josee-Lyne Ethier, MD, MSc, Department of Oncology, School of Medicine, Queen’s University, Kingston, Ontario, Canada, and colleagues.
“In the second-line setting, [T-DM1] improves OS compared with capecitabine/lapatinib in patients previously treated with trastuzumab-based chemotherapy,” they added.
This study aimed to describe practice patterns and outcomes associated with pertuzumab and T-DM1 in the real-world setting.
The Ontario Cancer Registry linked to electronic treatment databases was used to identify patients with stage IV ERBB2-positive metastatic breast cancer treated with pertuzumab and T-DM1. Pertuzumab and T-DM1 cohorts were analyzed separately.
A total of 795 women received pertuzumab and 506 women received T-DM1. Among the entire population, median OS was 43 months and median time on treatment was 14 months.
In the T-DM1 cohort, the proportion of pertuzumab-naïve patients decreased over time from 68 (74.7%) of 91 patients in 2014 to 16 (18%) of 89 patients in 2017 (P <.001). Median OS was 15 months and median time on treatment was 4 months.
Patients that had prior pertuzumab treatment had a median OS of 12 months compared to 19 months in those who were pertuzumab-naïve (HR: .70; 95% CI, .55-.89; P = .004).
“In this population-based cohort study, the survival of patients treated with pertuzumab and T-DM1 in routine practice appeared inferior to results from pivotal clinical trials,” wrote Dr Ethier and colleagues.
“Differences in outcome likely reflect differences in patient population and previous lines of therapy in routine practice. Further work is needed to understand the effectiveness of T-DM1 after pertuzumab exposure,” they concluded.—Janelle Bradley
