Inflammatory Indices Related to the Postoperative Prognosis of Thymic Epithelial Neoplasms: A Propensity Score Matching Evaluation

Background: Thymic epithelial tumors presented a variable 5-year survival rate, histological subtype dependent. Efforts have been made to identify new prognostic markers. Neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and Systemic Inflammatory Index (SII) proved effective in predicting survival in other solid tumors. We evaluated the prognostic significance of NLR, PLR, and SII on disease-free, overall, and tumor-related survivals in patients undergoing surgery with radical intent for thymic epithelial neoplasms. Methods: We conducted a retrospective analysis in patients operated in four high-volume Italian thoracic surgery centers, followed for a minimum period of 6 months. Immediate preoperative values of NLR, PLR, and SII were recorded. Patients were categorized for each factor based on cutoff values determined statistically by using the Youden index. Survival outcomes were analyzed using Kaplan-Meier curves, log-rank tests, and multivariable Cox regression after propensity score matching (1:1) performed for each inflammatory index. Results: A total of 376 patients were enrolled. The mean values for NLR, PLR, and SII were 3.0 (3.2), 131.4 (84.1), and 754.6 (28.8), respectively. The calculated cutoff values were 2.9 for NLR, 123.8 for PLR, and 489.0 for SII. After propensity score matching, we obtained 212 cases for NLR, 256 for PLR, and 280 for SII. Multivariable Cox regression analysis revealed a significant association between tumor-related survival and NLR (p = 0.030) and SII (p = 0.033). Conclusions: Higher NLR and SII cutoff values can be considered predictors of worse thymic epithelial tumors-related survival after surgery, suggesting their potential role in long-term risk stratification.