Statistical Analysis
All statistical analyses were performed using R software (version 3.6.3;
The R Foundation for Statistical Computing), SPSS (version 23, Chicago)
and STATA/MP(version 14, USA). Patients’ continuous characteristics were
summarized as median±quartile for non-normally distributed variables and
mean standard± deviations (SDs) for normally distributed variables.
Categorical variables were presented as numbers and percentages.
Differences between VD groups were analyzed using wilcox and chi-square
tests, where appropriate. We conducted Kaplan-Meier method, univariable
Cox proportional hazards models and multivariable Cox model (variables
with P <0.05) to estimate hazard ratios (HRs) and 95%
confidence interval to discover independent prognostic variables on OS.
All subgroup analyses were presented with a COX test for interaction. A
two-sided P < 0.05 was considered statistically
significant.