Statistical analysis
Analyses were performed with the Statistical Package for the Social Sciences (SPSS) 28.01.1. Missing data analysis revealed missing data > 5% for ASA and WHO performance status. Therefore, imputation of missing data was done in SPSS using the median of nearby points for the variables ASA status and WHO performance status.23
Mann-Witney U testing was used to assess significant differences in median values. Pearson’s chi-squared testing was performed to assess the correlation between categorical dependent variables with ≥ 2 groups and the dichotomous independent variable (training case yes/no). Multivariable logistic regression analysis was performed to assess the correlation between continuous clinical variables and the dichotomous independent variable. Multivariable logistic regression analysis was performed to assess the correlation between clinical, operative, histopathological and treatment variables and post-operative outcomes. Cox-regression analysis was performed for 5-year disease-free and disease-specific survival. Statistical tests were two-sided with significance set at p < 0.05, with confidence intervals (CI) at the 95% level. Post-hoc testing was performed if Pearson’s chi-squared testing rendered group differences. Bonferroni-adjusted p-values reached significance when p < (0.05/number of analysed groups).24