Pyrotinib and Trastuzumab Plus Chemotherapy Serve as an Acceptable Neoadjuvant Regimen Exhibiting Good Efficacy and Tolerance in HER2-Positive Breast Cancer Patients.

Objective: Pyrotinib, a new irreversible dual pan-human epidermal growth factor receptor 2 (HER2) receptor tyrosine kinase inhibitor blocking EGFR and HER2, has achieved a promising efficacy for advanced HER2-positive (HER2⁺) breast cancer. This study intended to further investigate the efficacy and safety of neoadjuvant pyrotinib and trastuzumab plus chemotherapy for HER2⁺ breast cancer treatment. Methods: Thirty-eight HER2⁺ breast cancer patients who received neoadjuvant pyrotinib and trastuzumab plus chemotherapy (docetaxel and carboplatin) were retrospectively reviewed. Clinical response by Response Evaluation Criteria in Solid Tumors (RECIST), pathological complete response (pCR), and adverse events data was retrieved. Results: According to the RECIST, the complete response rate was 0.0%, 10.5%, and 15.8% after second-cycle, fourth-cycle, and sixth-cycle therapy, respectively; whereas the objective response rate was 76.3%, 92.1%, and 100.0%, accordingly. The total pCR (tpCR) rate was 52.6%, the pCR rate of the breast was also 52.6%, and the pCR rate of lymph nodes was 86.8%. The tpCR rate was lower in patients with HER2 immunohistochemistry (IHC)++ and amplification by fluorescent in situ hybridization (FISH) than in those with HER2 IHC+++ (14.3% vs. 61.3%, p = 0.024), which was also lower in patients with Ki-67 expression ≥30% than in those with Ki-67 expression <30% (40.0% vs. 76.9%, p = 0.031). The common adverse events included diarrhea (84.2%), anemia (73.7%), nausea and vomiting (63.2%), fatigue (50.0%), hypomagnesemia (44.7%), leukopenia (42.1%), thrombocytopenia (39.5%), elevated transaminase (36.8%), and pruritus (31.6%). Conclusions: Pyrotinib and trastuzumab plus chemotherapy serve as an acceptable neoadjuvant regimen exhibiting good efficacy and tolerance in HER2⁺ breast cancer patients, while further large-scale validation is warranted.