To compare the short-term oncological and health-related quality of life (HRQOL) outcomes between open (ORP) and robot-assisted (RARP) radical prostatectomy in the population-based Victorian Prostate Cancer Registry.

This is a prospective cohort of patients with prostate cancer who had RP (1117 ORP and 885 RARP) between January 2009 and June 2012. The oncological outcomes of interest were: positive surgical margin (PSM) and biochemical recurrence (BCR), defined as postoperative PSA level of >0.2 ng/mL. The HRQOL outcomes were: sexual and urinary bother, assessed using the Expanded Prostate Cancer Index Composite at 1- and 2-years after diagnosis. For univariate comparison of continuous variables the Student's t-test or Mann-Whitney U-test were used, and the Pearson's chi-squared test was used for categorical variables. Bonferroni correction was applied to account for multiple testing, with a threshold for significance of P < 0.003 for univariate analyses. The inverse-probability-treatment-weighting (IPTW) approach was used to adjust for differences in baseline characteristics between ORP and RARP patients [including age, National Comprehensive Cancer Network (NCCN) risk categories, hospitals, and year of RP] in all multivariate analyses. Logistic regressions were used to analyse for PSM, Cox regressions for BCR, and ordinal logistic regressions for HRQOL outcomes. All multivariate analyses also adjusted for surgeons' average annual caseload, and employed the robust standard errors for clustering by surgeon.

ORP and RARP patients were followed for a median of 19 and 17 months, respectively. The proportion of patients with NCCN low-risk prostate cancer was significantly higher among RARP patients (21% vs 26%; P = 0.002). Most RPs was done in private hospitals (77% ORP, and 85% RARP, P < 0.001). A higher proportion of RARP patients were operated by surgeons with higher annual caseloads (65% RARP and 53% ORP operated by surgeons with >20 case/year; P < 0.001). In the IPTW-adjusted multivariate analyses, RARP patients had a lower risk of PSM (odds ratio [OR] 0.56, 95% confidence interval [CI] 0.38-0.81), and BCR (hazard ratio [HR] 0.73, 95% CI 0.55-0.99). In the sensitivity analyses (excluding public hospital patients), the lower PSM risk with RARP remained (OR 0.63, 95% CI 0.38-0.81), but the lower BCR risk with RARP was no longer statistically significant (HR 0.79, 95% CI 0.57-1.12). At 1-year follow-up, 61% of ORP and 59% of RARP patients reported 'moderate-big' sexual bother (P = 0.2), while 14% of ORP and 11% of RARP patients reported 'moderate-big' urinary bother (P = 0.08). The sexual and urinary bothers at 2 years were similar between ORP and RARP. In multivariate analyses, there were no statistically significant differences in the HRQOL outcomes between ORP and RARP.

We report on a large population-based comparative study of ORP and RARP with better short-term oncological outcomes favouring RARP, but no significant differences in HRQOL outcomes. The results have to be interpreted taking into account significant surgeon heterogeneity in a population-based study.