Neoadjuvant Trastuzumab and Pyrotinib for Locally Advanced HER2-Positive Breast Cancer (NeoATP): Primary Analysis of a Phase II Study.

Purpose: Despite accumulating evidence on dual blockade of HER2 for locally advanced HER2-positive breast cancer, no robust evidence supports the addition of pyrotinib to trastuzumab in the neoadjuvant setting. The NeoATP trial aimed to evaluate the efficacy and safety of pyrotinib with neoadjuvant trastuzumab and chemotherapy.

Patients And Methods: The phase II NeoATP trial included female patients with histologically confirmed stage IIA to IIIC and HER2-positive primary invasive breast cancer. Eligible patients received pyrotinib and trastuzumab with weekly paclitaxel-cisplatin neoadjuvant chemotherapy for four cycles. The primary endpoint was pathologic complete response (pCR; ypT0 ypN0) rate. Key secondary endpoints included locoregional pCR (ypT0/is ypN0) rate, biomarker analysis, and safety.

Results: Among 53 enrolled patients (median age, 47 years; 73.58% stage III), 52 completed the study treatment and surgery. Overall, 37 patients (69.81%) achieved pCR. For women with hormone receptor-negative and -positive tumors, the pCR rates were 85.71% and 59.38% (P = 0.041), while the corresponding rates were 69.23% and 70.00%, respectively, for those with and without PIK3CA mutation (P = 0.958). The most frequently reported Grade 3 to 4 adverse events were diarrhea (45.28%), leukopenia (39.62%), and neutropenia (32.08%). No deaths occurred, and no left ventricular ejection fraction <50% or >10 points drop from baseline to before surgery was reported.

Conclusions: The addition of pyrotinib to trastuzumab plus chemotherapy is an efficacious and safe regimen for patients with HER2-positive locally advanced breast cancer in the neoadjuvant setting. The randomized controlled clinical trial is warranted to validate our results.