Population―based determinants of radical prostatectomy surgical margin positivity

Study Type – Prognosis (cohort) Level of Evidence 2b What’s known on the subject? and What does the study add? Prior population and single-centre studies have assessed incidence of positive surgical margins. The current study derived population-based positive surgical margin cut-offs in order to help identify underperforming surgeons who may benefit from further courses and/or self study to improve outcomes. OBJECTIVE • To characterize factors associated with positive surgical margins (PSMs) and derive population-based PSM cutoffs to evaluate surgeon performance in radical prostatectomy (RP). PATIENTS AND METHODS • SEER-Medicare data were used to identify 4247 men diagnosed with prostate cancer during 2004–2005 who underwent RP up to 2006. • We performed logistic regression to assess the impact of tumour characteristics, surgeon volume and surgical approach on the likelihood of PSMs for pT2 and PT3a disease. • Moreover, we derived 25th and 10th percentile cutoffs from binomial distribution equations. RESULTS • Overall, 19.4% of men experienced PSMs with a pT2 vs pT3a PSM rate of 14.9% vs 42% (P < 0.001). Extrapolating from our population-based results, a surgeon incurring more than three PSMs in 10 cases of pT2 disease performed below the 25th percentile. • There was a trend for fewer PSMs with minimally invasive vs open RP (17.4% vs 20.1%, P= 0.086), and the PSM rate also decreased over the study period from 21.3% in 2004 to 16.6% in 2006 (P= 0.028) with significant geographic variation (P < 0.001). • In adjusted analyses, temporal and geographic variation in PSM persisted, and men with high (odds ratio 3.68, 95% CI 2.82–4.81) and intermediate (odds ratio 2.52, 95% CI 2.03–3.13) vs low-risk disease were at greater odds to experience PSMs. Notably, neither surgical approach nor surgeon volume was significantly associated with PSMs. CONCLUSION • Our population-based PSM benchmarks allow identification of under-performing outliers who may seek courses or video self-study to improve outcomes. There was significant temporal and geographic variation in PSMs but neither surgeon volume nor surgical approach was associated with PSMs.