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.