Associations between pretreatment composite inflammatory indices and pathological response to neoadjuvant therapy in breast cancer: a retrospective cohort study.

BACKGROUND: Pretreatment inflammatory indices may reflect the host immune-inflammatory status in breast cancer. Evidence comparing multiple composite indices across pathological response endpoints after neoadjuvant therapy remains limited. This study evaluated the associations between pretreatment composite inflammatory indices and pathological response in breast cancer. METHODS: This retrospective study included 280 patients with breast cancer who underwent neoadjuvant therapy followed by surgery. Baseline neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, systemic immune-inflammation index, systemic inflammation response index, and pan-immune-inflammation value were calculated from pretreatment blood tests. The primary endpoint was pathological complete response, defined as ypT0/is ypN0. Miller-Payne grades 4-5 were defined as favorable pathological response. Logistic regression and receiver operating characteristic analyses were performed. RESULTS: A total of 115 patients achieved pathological complete response. Patients with pathological complete response had lower neutrophil-to-lymphocyte ratio, systemic immune-inflammation index, and pan-immune-inflammation value than those without pathological complete response. These indices remained inversely associated with pathological complete response after multivariable adjustment. For favorable Miller-Payne response, lower systemic immune-inflammation index and pan-immune-inflammation value and higher lymphocyte-to-monocyte ratio were associated with better response. Systemic immune-inflammation index had the numerically highest area under the curve, with values of 0.673 for pathological complete response and 0.666 for favorable Miller-Payne response, although its discriminatory ability remained modest. CONCLUSION: Baseline composite inflammatory indices were associated with pathological response to neoadjuvant therapy in breast cancer, but their discriminatory ability was modest. These indices may be more suitable as supplementary markers than as standalone predictors.