Background: Pyrotinib, an irreversible pan-ERBB inhibitor, has shown promising antitumour activity, and acceptable tolerability. This research was conducted to evaluate the actual use and effectiveness of pyrotinib in China, therefore, contributed to solve the problem of real-world data scarcity. Methods: In this retrospective study, 168 patients who received pyrotinib treatment for HER2-positive metastatic breast cancer (MBC) in Hunan Province from June Chen et al.

Purpose: Patients with HER2-positive (HER2+) metastatic breast cancer (MBC) have poor prognoses. Pyrotinib has shown promising antitumor activity in MBC patients to improve progression-free survival (PFS). However, findings based on real-world data to analyze whether pyrotinib affects overall survival (OS) remain scarce. Experimental design:This real-world study is an exploratory analysis of brain metastasis (BM) and the final update of our preceding study of 168 patients with HER2+ MBC. PFS, OS, tumor mutation burden (TMB), clinical benefit rate (CBR) and overall response rate (ORR) were analyzed.Results: Pyrotinib treatment led to a median PFS time of 8.00 months and a median OS of 19.07 months in the 168 participants. High TMB was associated with poor OS (P = 0.0072) and PFS (P = 0.0028). In the 39 patients with BM, the median PFS and OS were 8.67 and 13.93 months, respectively. The surgery/radiation (S/R) group of patients with BM had prolonged survival (PFS: 9.97 vs. 7.73 months P = 0.19; OS: 20.67 vs. 12.43 months P = 0.021) compared with the no surgery/no radiation group (NS/NR). The CBR was 58.6% (S/R) vs. 41.4% (NS/NR), while the ORR was 24.1% (S/R) vs. 31.0% (NS/NR). Conclusion:Pyrotinib shows promise as a novel pan-HER2 tyrosine kinase inhibitor (TKI) for the treatment of BM and should be evaluated further. Surgical or radiotherapy in combination with pyrotinib was found to statistically improve OS in our cohort. TMB could be an exploratory biomarker for predicting PFS and OS, but its clinical application still needs further verification.

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