Systemic immune-inflammation and inflammation response indices as biomarkers of lymph node metastasis and lymphovascular space invasion in vulvar squamous cell carcinoma

The objective of this study is to evaluate the systemic immune-inflammation index (SII) and systemic inflammation response index (SIRI) in relation to lymph node metastasis, lymphovascular space invasion (LVSI), tumor size, stromal invasion depth, and p16/p53 status in vulvar squamous cell carcinoma. This retrospective single-center cohort study included 92 patients treated between January 2017 and March 2026. SII and SIRI were calculated from routine complete blood counts. Associations were assessed using non-parametric tests and multivariable logistic regression. Receiver operating characteristic analysis evaluated discrimination, expressed as the area under the curve (AUC), with paired DeLong comparison of the two indices. Incremental predictive value was assessed by nested logistic regression, with internal validation using 2000 bootstrap resamples. Both indices were higher in patients with lymph node metastasis and LVSI and correlated positively with tumor size, but not with stromal invasion depth or p16/p53 status. Discrimination was moderate and similar for lymph node metastasis (AUC, 0.670 vs 0.653; paired DeLong, p = 0.679) and for LVSI (0.733 vs 0.732; p = 0.964). In the cutoff-based multivariable model, elevated SIRI remained independently associated with lymph node metastasis (adjusted odds ratio, 4.30; 95% confidence interval, 1.51–12.27; p = 0.006), whereas elevated SII did not. Adding continuous SIRI to a clinicopathological base model improved neither fit ( p = 0.159) nor discrimination (AUC difference, 0.013; p = 0.716). SII and SIRI were associated with adverse pathological features, but their discriminatory performance did not differ significantly, and SIRI provided no significant incremental predictive value beyond the clinicopathological base model. These indices should be considered exploratory adjunctive biomarkers requiring external validation.