Statistical analyses

Descriptive statistics of categorical variables focused on frequencies and proportions. Means, medians, and Interquartile ranges (IQR) were reported for continuously coded variables. Chi-square and Mann- Whitney tests were used to compare the statistical significance of differences in proportions and medians, respectively. Univariable and multivariable logistic regression analyses were built to assess the impact of preoperative parameters on the prediction of prostatic involvement. Specifically, two models were presented: one with all the available confounders and one with only preoperative variables. Kaplan-Meier curve to estimate overall mortality-free rates was built stratifying according to the level of prostatic involvement. Univariable and multivariable Cox regression analyses tested the impact of UPI on overall mortality after accounting for all available confounders. Statistical analyses were performed using the R statistical package (R Foundation for Statistical Computing, Vienna, Austria) and SPSS v. 20.0 (IBM Corp., Armonk, NY, USA). All tests are two-sided and p < 0.05 was considered as significant.