Real-World Data of Pyrotinib-Based Therapy in Metastatic HER2-Positive Breast Cancer: Promising Efficacy in Lapatinib-Treated Patients and in Brain Metastasis.

Purpose: Pyrotinib is a newly-developed irreversible pan-ErbB receptor tyrosine kinase inhibitor. This study reported the first real-world data of pyrotinib-based therapy in metastatic human epidermal growth factor receptor 2 (HER2)-positive (BC), focusing on efficacy in lapatinib-treated patients and in brain metastasis. Methods One hundred thirteen patients with metastatic HER2-positive BC treated with pyrotinib-based therapy in Fudan University Shanghai Cancer Center under non-clinical trial settings from September 1, 2018 to March 1, 2019 were included. Results: Over half patients have received more than two lines of systematic therapy and exposed to two or more kinds of anti-HER2 agents. Most patients received a combined therapy, commonly of pyrotinib plus capecitabine, or vinorelbine or trastuzumab. Median progression-free survival (PFS) was 6.3 months (range, 5.54 to 7.06 months) and objective response rate (ORR) was 29.5%, with two patients (1.9%) achieving complete response. Lapatinib-naive patients had significantly longer PFS than lapatinib-treated patients (9.0 months vs. 5.4 months, p=0.001). ORR for lapatinib-treated patients was 23.2%. Thirty-one of 113 patients have brain metastasis. Median PFS was 6.7 months and intracranial ORR was 28%. For patients without concurrent radiotherapy and/or brain surgery, the ORR was very low (6.3%). But for patients receiving concurrent radiotherapy and/or brain surgery, the ORR was 66.7%, and three patients achieved complete response. Most common adverse event was diarrhea. Conclusion: Pyrotinib-based therapy demonstrated promising effects in metastatic HER2-positive BC and showed activity in lapatinib-treated patients. For patients with brain metastasis, pyrotinib-based regimen without radiotherapy showed limited efficacy, but when combined with radiotherapy it showed promising intracranial control.