Aetiology of positive surgical margins in robotic assisted radical prostatectomy: a pathway approach.

PURPOSE: Positive surgical margin (PSM) rates in robot-assisted radical prostatectomy (RARP) remain high and understanding their cause remains key to their elimination. We examined the prostate cancer pathway as a whole to systematically identify and quantify sourcescontributing to PSMs. METHODS: Using a prospectively maintained database at a high-volume centre, we retrospectively analysed 100 consecutive patients with positive surgical margins (PSMs) following robot-assisted radical prostatectomy between January and December 2022. For each patient, a pre-operative imaging-based surgical plan was available. Potential sources contributing to PSMs were identified by reviewing diagnostic and staging information, the recommended surgical plan, the executed surgical template, and final pathology. Sources were categorised into three pathway phases: Diagnostic and Staging, Surgical Planning, and Surgical Execution. Proportions were reported with 95% confidence intervals calculated using the exact binomial (Clopper-Pearson) method. RESULTS: A total of 112 positive surgical margins (PSMs) were identified in 100 patients. One hundred and twenty-five contributing sources were identified, with a single source attributed to 102 PSMs, two sources to 7 PSMs, and three sources to 3 PSMs. Surgical execution accounted for the majority of identified sources (98/125, 78.4%; 95% CI 70.2-85.3%), followed by surgical planning (14/125, 11.2%; 95% CI 6.3-18.1%) and diagnostic and staging factors (13/125, 10.4%; 95% CI 5.7-17.1%). Within the surgical execution category, nerve-sparing was the most frequently implicated surgical step, being associated with 57/112 PSMs (50.9%; 95% CI 41.3-60.5%), followed by apical dissection (34/112, 30.4%; 95% CI 22.0-39.8%). CONCLUSION: Despite high volume, the most common sourceis surgical execution. This represents an opportunity for intra-operative margin assessment to reduce PSM rates. Diagnostic and planning steps still contributed to one- fifth of PSMs and can also be improved. We emphasise how this novel systematic approach can be used as a framework in quality assurance and improvement processes.