Abstract
BACKGROUND: In previous clinical trials, pyrotinib has shown good antitumor activity and manageable toxicity in human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). However, real-world data on pyrotinib remain limited. In this study, we reported the latest real-world data on the efficacy and safety of pyrotinib in HER2-positive MBC. METHODS: This multicenter retrospective study included 337 HER2-positive MBC patients treated with pyrotinib between October 2016 and October 2024. We reported the analysis of the efficacy and safety of pyrotinib in HER2-positive MBC. The primary endpoints were progression-free survival (PFS) and overall survival (OS). RESULTS: As of April 1, 2025, the median follow-up duration was 42.6 months (range, 2.0-92.7). The median line of treatment was two. The median PFS was 15.3 months (95% CI, 12.9-17.6). By treatment line, the median PFS was 21.4 months (95% CI, 10.1-32.6) for first-line treatment, 14.8 months (95% CI, 11.4-18.1), and 10.9 months (95% CI, 8.1-13.7) for second-line and third-line or above treatment. The 3-year OS rate was 54.6% overall, with 63.2%, 61.1%, and 37.7% for first-line, second-line, and third-line or above treatment. The ORR, DCR, and CBR were 41.5%, 91.2%, and 80.0%. We further analyzed 57 patients with brain metastases (BM). The result showed that the median duration of response (DoR) and time to response (IQR) of radiotherapy-naïve ones were 12.6 months (95% CI, 6.8-18.4) and 1.7 months (95% CI, 1.3-2.2), respectively. The most frequent grade 3 or 4 adverse event was diarrhea. No treatment-related deaths were reported. CONCLUSION: The updated analysis demonstrated that pyrotinib could be a promising treatment option in HER2-positive MBC with acceptable toxicity in the real world. Survival is still under assessment with longer follow-up.