Does surgical approach impact on the risk of positive surgical margin at radical prostatectomy in patients with clinically localized prostate cancer? A single institution analysis

INTRODUCTION & OBJECTIVES: Recent studies showed that robotic-assisted radical prostatectomy (RARP) improves the rate of positive surgical margins (PSM) as compared to the open approach (ORP). However, these are based on multi-institutional series with great variability in terms of both surgical approaches and pathological examinations. We evaluated the rate of PSM at RARP and ORP performed at a single tertiary care center using standardized surgical technique and pathological examination. MATERIAL & METHODS: The study included 6,932 consecutive patients submitted to ORP (n=4995;72.1%) and RARP (n=1936;27.9%) between 1999 and 2014. Patients were stratified according to the D'Amico risk grouping. A PSM was defined as the presence of tumour cells on the inked margin. We addressed the rate of PSM according to the surgical approach in the overall population, as well as in each risk group category. Moreover, PSM rate was assessed among patients operated on by two expert surgeons (>200 cases performed) who routinely perform both RARP and ORP. Chi-square test was used to quantify the differences in the rate of PSM between RARP and ORP in the overall population and in each patient category, respectively. Uni-variable and multi-variable logistic regression analyses were used to predict the presence of PSM according to the surgical technique (RARP vs. ORP). Covariates consisted of risk group characteristics, nervesparing procedure, tumour and prostate volume. RESULTS: Overall, 1494 patients had one or more PSM with a PSM rate of 21%. PSM were detected in 1144 (22.9%) and 309 (16.0%) of ORP and RARP, respectively (p<0.001). PSM rate was 13.8, 22 and 27.5% in low, intermediate and high risk patients, respectively. When patients were stratified according to pre-operative risk groups, RARP showed statistically significant lower rate of PSM in low (11.5 vs. 15.2%,p=0.01) as well as in intermediate risk patients (18.9 vs. 23.3%,p=0.01). Interestingly, the greatest benefit of RARP was seen in highrisk patients, where the rate of PSM in patients treated with RARP was 19.5% vs. 29.6% in patients treated with ORP (p<0.001). When the analyses were repeated in the population of patients operated on by two expert surgeons performing both RARP and ORP, RARP showed a significantly lower rate of PSM only in high-risk patients (19.3 vs. 26.7%,p=0.04), while in low and intermediate risk patients no benefit was observed (p=0.14 and p=0.17, respectively). At MVA, RARP represented an independent predictor of lower PSM rate vs. ORP (OR=0.79; p<0.001) after adjusting for confounding variables. CONCLUSIONS: RARP leads to a significant reduction of PSM across all risk-groups patients. However, the benefit of RARP in achieving negative surgical margins reaches its highest in patients with high-risk disease.