Predictors of Positive Circumferential Resection Margin in Rectal Cancer: A Current Audit of the National Cancer Database

BACKGROUND: Positive circumferential resection margin is a predictor of local recurrence and worse survival in rectal cancer. National programs aimed to improve rectal cancer outcomes were first created in 2011 and continue to evolve. The impact on circumferential resection margin during this time frame has not been fully evaluated in the United States. OBJECTIVE: The purpose of this study was to determine the incidence and predictors of positive circumferential resection margin after rectal cancer resection, across patient, provider, and tumor characteristics. DESIGN: This was a retrospective cohort study. SETTINGS: The study was conducted using the National Cancer Database, 2011-2016. PATIENTS: Adults who underwent proctectomy for pathologic stage I to III rectal adenocarcinoma were included. MAIN OUTCOME MEASURES: Rate and predictors of positive circumferential resection margin, defined as resection margin <= 1 mm, were measured. RESULTS: Of 52,620 cases, circumferential resection margin status was reported in 90% (n = 47,331) and positive in 18.4% (n = 8719). Unadjusted analysis showed that patients with positive circumferential resection margin were more often men, had public insurance and shorter travel, underwent total proctectomy via open and robotic approaches, and were treated in Southern and Western regions at integrated cancer networks (all p < 0.001). Multivariate analysis noted that positive proximal and/or distal margin on resected specimen had the strongest association with positive circumferential resection margin (OR = 15.6 (95% CI, 13.6-18.1); p < 0.001). Perineural invasion, total proctectomy, robotic approach, neoadjuvant chemoradiation, integrated cancer network, advanced tumor size and grade, and Black race had increased risk of positive circumferential resection margin (all p < 0.050). Laparoscopic approach, surgery in North, South, and Midwest regions, greater hospital volume and travel distance, lower T-stage, and higher income were associated with decreased risk (all p < 0.028). LIMITATIONS: This was a retrospective cohort study with limited variables available for analysis. CONCLUSIONS: Despite creation of national initiatives, positive circumferential resection margin rate remains an alarming 18.4%. The persistently high rate with predictors of positive circumferential resection margin identified calls for additional education, targeted quality improvement assessments, and publicized auditing to improve rectal cancer care in the United States.