Population-based determinants of radical prostatectomy surgical margin positivity

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.