2.5 Statistical analysis
Differences between groups were tested with the Kruskal–Wallis or Mann–Whitney U test for quantitative variables and with Fisher’s exact test for qualitative variables. Spearman’s correlation test was used to determine the relationships. Receiver operating characteristic (ROC) curves were plotted to assess the efficacy of significant parameters and performed to determine the optimal cutoff value using maximum Youden’s index. A Bayesian formula was used to analyze the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the cutoff value. Progression-free survival (PFS) was estimated from the date of initial treatment until the date of one of the following events: progression, relapse, or death, whichever came first. The patients without event were censored at the date of the last contact. Univariate analysis for survival was performed by Cox regression. All risk factors with P < 0.05 in the univariate analysis were used as covariates and selected in the Cox regression of the multivariate analysis. A significant difference was defined as P < 0.05. All data were analyzed using the Statistical Package for Social Sciences (SPSS) software, version 26.0 (IBM Corp, NY, USA). The cut-off date for follow-up was December 31, 2023.