Statistical analysis
Data are presented as mean (SD) when normally distributed or as median
with 25th and 75th percentiles (interquartile range [IQR]) when
normality assumptions (the Shapiro-Wilk test) were not met. Categorical
data are expressed as a number and percentage. Kaplan–Meier
time-to-event curves were generated for the entire cohort and
the subgroups were compared with the log-rank (Mantel–Cox) test. The
five year survival with standard error was estimated for both groups.
GraphPad Prism 8.2.0 (GraphPad Software, San Diego, California, United
States) was used for all statistical analysis, except the Cox analysis
which was done with IBM SPSS Statistics for Windows, version 22 (IBM
Corp. Armonk, New York, United States).