Metastatic brain tumors respond favorably to pyrotinib in a HER2-positive breast cancer following failure using trastuzumab.

Treatment of breast cancer (BC) with overexpression of human epidermal growth factor receptor 2 (HER2) has undergone a prosperous development with the advent of emerging small molecule tyrosine kinase inhibitors (TKIs). However, their efficacy in brain metastases (BMs) requires further investigation in both clinical trials and practice by specifically targeting this population. We herein reported a HER2-positive metastatic bilateral BC case with symptomatic diffusion of parenchymal BM after first-line treatment with trastuzumab-based regimen. She then received pyrotinib (with a disease-free survival of 5.7 months) followed by whole brain radiotherapy. Unexpectedly, under satisfactory control of intracranial parenchymal lesions, the patient based on clinical manifestations, auxiliary examinations and exclusive diagnosis was diagnosed with meningeal progression, and soon died of tumor progression. Thus, pyrotinib response differed from meningeal to parenchymal BM in BC patients, and the need of comprehensive and systematic evaluation of TKIs in some particular clinical scenarios has become a critical issue.