Efficacy and Side Effects in HER2-Positive Advanced Breast Cancer Patients Treated with Pyrrotinib: A Real-World Study in China

Abstract

Background: Pyrotinib is a molecular and irreversible tyrosine kinase inhibitor independently developed in China, and its efficacy against HER2- positive breast cancer in the real world is not clear. In this study, we evaluated the efficacy and safety of pyrotinib in the treatment of HER2-positive advanced breast cancer based on real-world evidence. Materials and Methods: We designed a prospective observational study. Thirty-six patients with HER2-positive advanced breast cancer from a single medical center were included in the study from December 2018 to February 2021. All patients received the oral HER2 receptor inhibitor pyrotinib and received concurrent chemotherapy or endocrinotherapy. The follow-up endpoint is set as April 1, 2021. The primary endpoint is Objective Response Rate (ORR) and Disease Control Rate (DCR), and the secondary endpoint is Progression- Free Survival (PFS) and related side effects. Results: By the end point of follow-up, a total of 17 patients had progressed (including 6 deaths), and the progression-free survival rate was 52.78%. The median PFS was 13months (PFS range: 3-22 months). As the best response, 4 patients achieved CR, 20 patients achieved PR, 9 patients achieved SD, and 3 patient developed PD. The ORR was 66.67% and DCR was 91.67%. In the analysis, first-line pyrotinib treatment appeared to have higher ORR (88.88% vs 59.26%), but there was no significant difference. In addition, pyrotinib showed significant efficacy in patients with brain metastases, with an ORR of 42.85%. In terms of safety, the incidence of diarrhea was 80.55%, but only 4 patients had grade 3 diarrhea, which was tolerable after the drug dose was reduced; 1 patient had grade 4 neutropenia and grade 3 and thrombocytopenia, which were considered to be related to the chemotherapy drugs. The incidence of other adverse reactions was low, and all were grade 1 to 2. Conclusion: Pyrotinib combined with chemotherapy has a significant effect on HER2-positive breast cancer, and there is still a high ORR in patients who fail multiple lines of treatment. Side effects are overall controllable and safe.