2.4. Statistical analysis

All statistical analyses were performed using SPSS (Statistical Package for Social Sciences) version 26.0 (SPSS Inc., Chicago, IL). For descriptive purposes, continuous variables were summarized as arithmetic means, and standard deviations (SD), categorical and ordinal parameters such as sex (male vs. female), clinical stage (III vs. IV), histological subtype (epithelioid vs. non-epithelioid), and dichotomized PD-L1 expression (<15% vs. ≥15%) were analyzed using the χ2 test or Fisher’s exact test. For survival curve analysis, all variables were dichotomized. Overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method, and comparisons among subgroups were analyzed using the log-rank test. Finally, we performed a multivariate analysis with a Cox proportional model to estimate the hazard ratios (HRs) with 95% CI adjusting for those variables, which were statistically significantly associated with survival in the univariate analysis. Statistical significance was set at p <0.05 based on a two-sided test.