Impact of systemic immune-inflammation index in patients with limited-stage small cell lung cancer.

Abstract

e20626 Background: The systemic immune-inflammation index (SII) has been suggested as a prognostic marker in several solid malignant neoplasms. However, there are few studies on the prognostic value of SII in patients with limited-stage SCLC. This study explored the impact of SII on overall survival (OS) and progression-free survival (PFS) in patients with limited-stage small cell lung cancer, and compared the predictive ability of SII and platelet/lymphocyte ratio (PLR) to find a better prognostic marker. Methods: In total, 572 patients with new diagnosis of limited-stage SCLC were included in this study. The optimal threshold of SII and PLR were determined using the outcome(OS)-based method by maximizing the log-rank test statistic and the survival differences.The predictive ability of SII and PLR were compared by drawing the continuous time-dependent receiver operating characteristic curves (time-dependent ROC). Logistic multivariable analysis was performed to identify factors associated with high SII. Propensity score matching (PSM) was used to balance confounders between groups and adjust observed selection bias. Kaplan-Meier methods and Cox proportional hazards models were used to assess the impact of pre-treatment SII on OS and PFS. Results: The median age of the whole group was 60.0 (25.0-81.0) years, and the median follow-up time was 56.5 (2.5-95.4) months. The optimal cutoff value of SII and PLR were 760.6 and 137.3, respectively. The area under the time-dependent ROC curves of SII and PLR in 1-, 2- and 3-year were 0.727, 0.708, 0.680 and 0.680, 0.669, 0.649, respectively. The high SII group was correlated with pleural effusion (P = 0.001), T stage (P = 0.009), N stage (P = 0.048), and pretreatment serum sodium (P = 0.003). The median OS and PFS of the whole group was 26.0 months (95%CI 23.8-28.2) and 13.0 months (95%CI 11.3 -14.7), and the 1-, 3-, 5-year OS rates and the 1-, 3-, 5-year PFS rates were 81.1%, 35.5%, 27.1% and 52.8%, 24.8%, 19.9%, respectively.There were 414 patients after PSM. In multivariable survival analysis, SII remained an independent prognostic factor for OS (HR1.792; 95%CI 1.416-2.268; P < 0.001) and PFS (HR1.410; 95%CI 1.043-1.906; P = 0.025). Conclusions: Elevated SII is an independent adverse prognostic factor in patients with limited-stage SCLC and is superior to PLR in terms of prognostic ability.