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.