Pyrotinib Treatment in Patients With HER2-positive Metastatic Breast Cancer and Brain Metastasis: Exploratory Final Analysis of Real-World, Multicenter Data

Patients with HER2-positive (HER2+) metastatic breast cancer (MBC) have poor prognoses. Pyrotinib has shown promising antitumor activity in MBC to improve progression-free survival (PFS). However, findings based on real-world data to analyze whether pyrotinib affects overall survival (OS) remain scarce.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.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).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.