Association of systemic immune-inflammation index and neutrophil-to-lymphocyte ratio with all-cause mortality in patients with ovarian malignancies: a large retrospective cohort study

This study aims to evaluate the correlation between the Systemic Immune-Inflammation Index (SII) and the Neutrophil-to-Lymphocyte Ratio (NLR) with all-cause mortality in patients with ovarian malignant tumors. This single-center retrospective cohort study included 948 patients with ovarian malignant tumors between December 2019 and June 2025. Multivariate Cox regression analysis, subgroup analysis, receiver operating characteristic (ROC) curves, Kaplan–Meier survival curves, and restricted cubic spline (RCS) plots were used to assess the correlation between SII, NLR, and the risk of all-cause mortality. During a median follow-up of 30.63 months, 84 of 948 patients died. In the primary adjusted model, each one-standard-deviation increase in SII and NLR was associated with a 20.6% (HR = 1.206, 95% CI: 1.088–1.338, P < 0.001) and 22.5% (HR = 1.225, 95% CI: 1.073–1.397, P = 0.003) increase in the risk of all-cause mortality, respectively. Time-dependent ROC analyses showed that the AUCs for SII were 0.748, 0.655, and 0.652 at 12, 24, and 36 months, respectively, while the corresponding AUCs for NLR were 0.772, 0.651, and 0.645 ( P < 0.001). Secondary analyses based on categorical classifications generally supported the primary continuous-variable findings, although the strength of the associations varied according to the classification strategy. Kaplan–Meier analyses showed poorer overall survival among patients with higher SII and NLR levels, and RCS analyses indicated significant, approximately linear associations of SII and NLR with all-cause mortality (P for non-linearity = 0.777 and 0.193, respectively). Exploratory subgroup analyses showed that the associations of elevated SII and NLR with increased all-cause mortality were observed across multiple clinically relevant strata ( P < 0.05). Higher levels of SII and NLR are significantly associated with an increased risk of all-cause mortality in patients with ovarian malignant tumors.