Real-World Outcome and Prognostic Factors Among HER2-Positive Metastatic Breast Cancer Patients Receiving Pyrotinib-Based Therapy: A Multicenter Retrospective Analysis

PURPOSE: To explore the efficacy, safety, and potential factors influencing efficacy and outcome of pyrotinib-based therapy in human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) in complex clinical practice. METHODS: Real-world data for HER2-positive MBC patients treated with pyrotinib-based regimens from 6 hospitals in Northern Anhui, China, from September 2018 to February 2022, were retrospectively collected, and clinicopathological features, efficacy, prognosis, and safety were analyzed. Potential influencing factors including baseline serum vascular endothelial growth factor-A (VEGF-A) for evaluating pyrotinib’s treatment response and outcome were also explored. RESULTS: A total of 169 patients with HER2-positive MBC were enrolled. The objective response rate (ORR), disease control rate (DCR), and median progression-free survival (mPFS) of the overall cohort were 65.1%, 87.6%, and 12.4 months, respectively. Pyrotinib is highly beneficial as different treatment lines and appears to be a feasible strategy both in combination with chemotherapeutic drugs and alone. The mPFS values were 16.5 months, 12.4 months, and 9.3 months in the first, second, and third-or-higher lines of anti-HER2 therapy, respectively (P=0.027). The most common adverse event (AE) was diarrhea (88.2%), and patients with < grade 3 diarrhea achieved a longer mPFS than patients with ≥ grade 3 diarrhea (13.3 months vs 6.9 months, P=0.007). Among the patients with available baseline VEGF-A data, the ORR was 43.5% in patients with a high level of VEGF-A, compared to 81.5% in patients with a low level of VEGF-A (P=0.005). Moreover, patients in the VEGF-A-high group exhibited a shorter mPFS time than those in the VEGF-A-low group (7.8 months vs 19.1 months, P=0.004). Further analysis demonstrated AE of diarrhea and VEGF-A at baseline to be independent prognostic factors for PFS. CONCLUSION: Pyrotinib-based regimens showed promising efficacy, with manageable tolerance, and AE occurrence of severe diarrhea and baseline level of serum VEGF-A are helpful in predicting the treatment outcome of pyrotinib in HER2-positive MBC.