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Population-Based Determinants of Radical Prostatectomy Surgical Margin Positivity and Identifying Underperforming Surgeons
Stephen B. Williams, M.D., Xiangmei Gu, M.S., Stuart Lipsitz, PhD., Anthony D'Amico, M.D., Ph.D., Jim Hu, M.D., MPH.
Brigham and Women's Hospital, Boston, MA, USA.

BACKGROUND: Radical prostatectomy (RP) positive surgical margins (PSMs) increase the risk of recurrence. We characterized factors associated with PSMs and derived population-based PSM cutoffs to evaluate surgeon performance.
METHODS: We used SEER-Medicare data to identify 4,247 men diagnosed with prostate cancer during 2004-2005 who underwent RP through 2006. We performed logistic regression to assess the impact of tumor 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 3 PSMs in 10 cases of pT2 disease performed below the 25th percentile. Additionally, 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% to 16.6% in 2004 vs. 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 (OR3.68, 95%CI 2.82-4.81) and intermediate (OR 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. While there was significant temporal and geographic variation in PSMs, neither surgeon volume nor surgical approach was associated with PSMs.


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