Anthracycline-Free Neoadjuvant Pertuzumab-Trastuzumab-Taxane in Patients with HER2-Positive Early Breast Cancer: Hormone Receptor Status as a Key Determinant of Pathological Complete Response.

Background: Neoadjuvant chemotherapy plus dual HER2 blockade is standard for HER2-positive early breast cancer (EBC), but the impact of hormone receptor (HR) status and PIK3CA mutations with anthracycline-free regimens remains unclear. Methods: We retrospectively analyzed 56 patients with stage II-III HER2-positive EBC treated with neoadjuvant pertuzumab-trastuzumab-taxane (THP) at a single institution. Pathological complete response (pCR, ypT0/is ypN0) was the primary endpoint; secondary endpoints were safety and early disease-free/overall survival (DFS/OS), while associations of HR status and PIK3CA mutations with pCR were explored. Results: The overall pCR rate was 60.7%, in line with major dual-HER2 neoadjuvant trials. HR-negative patients achieved higher pCR rates than HR-positive patients (85.7% vs. 45.7%; p = 0.007; odds ratio 7.125), identifying HR status as the main clinical factor associated with response. Among 36 patients with PIK3CA testing, pCR rates appeared similar in mutated and wild-type tumors (62.5% vs. 60.7%), but the small number of mutated cases precludes firm conclusions. At a median follow-up of 42 months, only five DFS and one OS event had occurred, so survival analyses are exploratory and should be interpreted cautiously. THP demonstrated an excellent safety profile, with minimal grade 3-4 toxicity, and no clinically relevant hematological, cardiac, or pulmonary events. Conclusions: Anthracycline-free THP is a highly active, well-tolerated neoadjuvant option for HER2-positive EBC, with particularly high pCR rates in HR-negative disease. HR status emerged as a key determinant of pCR, whereas the role of PIK3CA mutations remains inconclusive and requires confirmation in larger prospective studies.