Impact of neutrophil-to-lymphocyte ratio on pathological response in HER2-positive breast cancer patients: A retrospective analysis.

e12577 Background: Pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) combined with HER2-targeted therapy is a strong surrogate for survival in HER2-positive breast cancer. However, treatment response remains heterogeneous. Identification of simple and cost-effective biomarkers capable of predicting pathological response is therefore of clinical importance. The neutrophil-to-lymphocyte ratio (NLR), a marker of systemic inflammation and immune status, has shown prognostic and predictive value in multiple malignancies, though its role in HER2-positive breast cancer remains incompletely defined. Methods: This retrospective study included 186 patients with non-metastatic HER2-positive breast cancer treated with NAC and trastuzumab with or without pertuzumab at a single tertiary care center. Baseline NLR was calculated from absolute neutrophil and lymphocyte counts obtained prior to initiation of NAC. Patients were categorized into high and low NLR groups using predefined cut-off values from published literature. Pathological complete response was defined as the absence of residual invasive disease in the breast and axillary lymph nodes (ypT0N0). Associations between NLR, pCR, and clinicopathological variables were analyzed using appropriate statistical methods. Results: The cohort was predominantly female, with most patients presenting with stage II–III disease and invasive ductal carcinoma. High-grade tumors and elevated Ki-67 indices were common. Patients received anthracycline- and/or taxane-based chemotherapy regimens with single-agent or dual HER2-targeted therapy. A higher frequency of pCR was observed among patients with low baseline NLR compared with those with elevated NLR. Elevated NLR was associated with lower pCR rates across treatment subgroups. No consistent association was observed between common comorbidities and pathological response. Conclusions: Baseline neutrophil-to-lymphocyte ratio appears to be a useful predictive biomarker for pathological response in HER2-positive breast cancer treated with neoadjuvant HER2-targeted therapy. Incorporation of NLR into routine pretreatment assessment may aid in risk stratification and individualized treatment planning.