Neoadjuvant pyrotinib for HER2 (IHC 2+/FISH+)/HR+ breast cancer with early non-response: a case report and literature review.

Neoadjuvant therapy (NAT) has been widely adopted in the multimodal management of HER2-positive breast cancer. Trastuzumab and pertuzumab (HP) combined with chemotherapy is the recommended neoadjuvant regimen for patients with HER2-positive locally advanced breast cancer. Achieving total pathological complete response (tpCR) after NAT is a strong predictor of long-term survival in patients with early-stage or locally advanced breast cancer. Nevertheless, approximately 40% of patients fail to achieve tpCR with this standard approach. Early identification of limited or non-responders and switching to a pyrotinib-containing regimen to improve tpCR currently lack a unified clinical standard. Here, we report a case of HER2 (IHC 2+/FISH+)/hormone receptor (HR)+ breast cancer that was assessed as limited early response after two cycles of standard therapy. The regimen was modified to trastuzumab plus pyrotinib plus nab-paclitaxel, resulting in total pathological complete response (tpCR) with good tolerability; only mild, controllable diarrhea occurred. This response-adapted strategy, based on early response assessment by chest CT, warrants further validation.