Optimal Cutoff for the Neutrophil-to-Lymphocyte Ratio as a Tool for Pre-chemotherapy Prognosis Stratification of Breast Cancer Patients

Introduction The neutrophil-to-lymphocyte ratio (NLR) is an established inflammatory marker in cancer patients. The optimal cut-off as an independent prognostic factor for breast cancer (BC) progression in patients undergoing chemotherapy remains debatable, hindering effective stratification. This study explored the optimal NLR cut-off by comparing various thresholds and assessing their effectiveness in stratifying BC patients according to prognosis. Methods This was a longitudinal quantitative study conducted at Queen's University in Kingston, Ontario, Canada, and the associated hospital is Kingston General Hospital. Demographic, clinical, and cancer-specific data on 42 BC patients were recorded, including complete blood counts before and after two cycles of chemotherapy. The receiver operating characteristic curve assessed discriminatory performance. Diagnostic metrics and Youden's J index were calculated, and McNemar's test was used to compare baseline NLR cutoffs of 2.5, 3.0, and 3.5. Kaplan-Meier curves assessed the relationship between various NLR cut-offs and other cancer prognostic markers. Results The three NLR cutoffs demonstrated distinct diagnostic metrics and Youden's J index values (p < 0.001), with the 3.0 cutoff providing the most balanced performance. Patients with pre-chemotherapy NLR > 3.0 were predicted to develop advanced stage BC more rapidly compared to those with pre-chemotherapy NLR < 3.0. Conclusion We believe that a more stringent NLR cutoff of 3.0 may be a suitable predictor of prognosis in BC patients based on the ranges evaluated in the literature. Findings of this paper could help clinicians in stratifying BC patients by risk, improving personalized treatment intensity while monitoring strategies accordingly.