Statistics.
Statistical analysis was performed using Stata software version 15.1
(College Station, TX: StataCorp LLC.) and Excel (Windows Excel 2016,
Microsoft, Redmond, Washington). Continuous variables were tested for
normality distribution with the Kolmogorov-Smirnov test and were
expressed as a mean with standard deviation (SD). Independent t-tests
were performed for normally distributed variables, or Mann-Whitney U
tests otherwise. Categorical variables were presented as frequencies
with percentages, and analyzed by Chi-square test or Fisher’s exact
test, as appropriate. Analysis of adverse events was performed and
tabulated. Kaplan-Meier curves were used to display the survival for
stage- I and II ET procedures.