Background: Trastuzumab and pertuzumab with taxane-based chemotherapy are considered the first-line standard therapy for human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (mBC). Pertuzumab is also a later-line therapy for mBC in Switzerland, although limited safety and efficacy data are available. This study assesses the therapeutic regimens, toxicities, and clinical outcomes after second- or later-line pertuzumab therapy in patients with mBC who did not receive pertuzumab as a first-line therapy.
Materials and Methods: Physicians from major Swiss oncology centers retrospectively completed a questionnaire for each pertuzumab-naive patient who was treated with pertuzumab as a second- or later-line therapy.
Results: Of 35 patients with HER2-positive mBC (median age: 49 years; range: 35-87 years), 14 received pertuzumab as a second-line therapy, six as a third-line therapy, and 15 as a fourth- or later-line therapy. Twenty patients (57%) died during the study period. The median overall survival was 74.2 months (95% confidence interval: 47.6-139.8 months). Grade (G) 3/4 adverse events (AEs) were reported in 14% of patients, with only one patient discontinuing therapy due to pertuzumab-related toxicities. The most common AE was fatigue (overall: 46%; G3: 11%). Overall, congestive heart disease occurred in 14% of patients (G3: 6%), nausea in 14% (all G1), and myelosuppression in 12% (G3: 6%).
Conclusion: The median overall survival of second- or later-line pertuzumab is similar to that reported for first-line pertuzumab, and the safety profile was acceptable. These data support using pertuzumab for second- or later-line therapy when it was not administered as first-line therapy.