Breast cancer is one of the leading causes of cancer deaths in women worldwide. Neoadjuvant chemotherapy (NACT) has increased rates of breast-conserving procedures and enabled the identification of patients with a particularly poor prognosis. Achieving a pathological complete response (pCR), an indicator of NACT efficacy, contrasts with residual disease (RD), which identifies patients at higher risk of recurrence. This review provides an overview of current evidence on the clinical and prognostic significance of pCR and RD in patients receiving NACT for breast cancer. The analysis is based on data from randomized clinical trials, meta-analyses, and current clinical guidelines for contemporary systemic treatment. Pathological complete response varies according to tumor subtype, with the highest rates observed in triple-negative and non-luminal HER2-positive breast cancer. In HER2-positive disease, the combination of chemotherapy with HER2-targeted therapies increases pCR rates, while the presence of RD supports escalation of postoperative treatment with antibody–drug conjugates. In triple-negative breast cancer (TNBC), the inclusion of platinum agents and immune checkpoint inhibitors improves treatment efficacy. In HER2-negative breast cancer and germline BRCA1/2 mutations, adjuvant PARP inhibitors improve survival independently of pCR, highlighting the complex relationship between pathological response and prognosis. Immunotherapy and targeted therapies are used alongside standard chemotherapy and hormone therapy in perioperative treatment. Further research is required to refine response assessment, integrate new biomarkers such as circulating tumor DNA (ctDNA), and optimize treatment selection, while clarifying the significance of reassessing hormone receptor and HER2 status in residual disease and its impact on subsequent treatment decisions.
Gorzelak-Magiera et al. (2026) studied this question.