Discussion
toxicities, HR-positive
TUMOR PROGRESSION, HER2-POSITIVE BREAST CANCER
The current standard first-line treatment for patients with HER2-positive MBC is HER2-targeted therapy plus chemotherapy, regardless of the HR status [The HER2 and ER signaling pathways cross-talk extensively. As a result of ER signaling, HER2 blockade downstream signaling may be bypassed to facilitate tumor progression [Anti-HER2 TKIs also play an important role in HER2-positive breast cancer, and multiple drugs have been approved [In this study, 22% of patients had previously received trastuzumab, and the percentage is 11% in the CLEOPATRA study [In our study, no new or unexpected AE was identified, and all AEs were manageable. Previous studies also suggested that patients with MBC are more likely to experience toxicities after receiving chemotherapy than after receiving endocrine therapy [This study has some limitations. First, since this is a single-arm study with a small sample size and no control group, the results might be biased. Second, the OS data is immature now, and long-term follow-up is ongoing. Third, the current standard treatment is a dual-HER2 blockade, and our results can only provide preliminary evidence of pyrotinib in the first-line treatment of HR-positive and HER2-positive MBC patients. Of note, a phase III randomized trial on the pyrotinib, trastuzumab, and an AI for HR-positive and HER2-positive MBC patients is ongoing [