Abstract PS3-11-26: A real-world study of pyrotinib as neoadjuvant therapy for HER2-positive breast cancer

Abstract Background: A double-blind, randomized Phase 3 clinical study, PHEDRA, met its primary endpoint with a significantly higher tpCR rate than placebo in patients treated with pyrotinib, trastuzumab, and docetaxel in HER2-positive early or locally advanced breast cancer (41.0% vs. 22.0%, unilateral P< 0.0001). At present, trastuzumab combined with pyrotinib and docetaxel has become the standard neoadjuvant treatment strategy for HER2-positive early or locally breast cancer.We aim to evaluate the efficacy and safety of pyrotinib-containing regimen as neoadjuvant therapy for HER2-positive early or locally advanced breast cancer in a real-world setting. Methods: This is a prospective, real-world, one-arm study. Patients with untreated HER2-positive operable early or locally advanced breast cancer were enrolled. Eligible patients received pyrotinib-containing regimen. Surgery was performed after the completion of the last cycle of study treatment. The primary endpoint was tpCR (ypT0/Tis ypN0) and secondary endpoints included objective response rate (ORR), bpCR and safety. Results: Between Feb 13, 2022, and May 29, 2025, a total of 104 patients with a median age of 51 years (range:26-66) were enrolled. 45% patients received AC/EC-THPy, 38% patients received TCbHPy and 15% patients received THPy regimens. As of the data cutoff date on Jun12, 2025, 66 patients underwent surgery, tpCR rate was 58%. The tpCR rates of HR- and HR+ patients were 68% and 42% respectively .Out of the 84 patients with evaluable response, 2 achieved complete and 66 achieved partial response, resulting in an ORR of 81%. The grade 3 or 4 adverse events were 24.03%. The most common treatment-related adverse events (AEs) were diarrhea (50%), Vomiting (26.9%), and decreased appetite (11.5%). Most AEs were tolerable. Conclusions: In this real-world study, neoadjuvant pyrotinib- containing regimens showed promising efficacy and safety in patients with HER2-positive breast cancer, further verify its effectiveness and safety in the real world. Citation Format: H. Zheng, Y. Tan, Q. Zhang, J. Li, H. Shen, G. Wang, Y. Tu, Y. Yang, J. Liu, J. Wang, R. Tian, X. Fu, X. Wu. A real-world study of pyrotinib as neoadjuvant therapy for HER2-positive breast cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-11-26.