Development of a Predictive Nomogram for Circumferential Resection Margin in Rectal Cancer Surgery

Introduction: Circumferential resection margin (CRM) is a key quality metric and predictor of oncologic outcomes and overall survival following surgery for rectal cancer. We aimed to develop a nomogram to identify patients at risk for a positive CRM in the preoperative setting. Methods: We performed a retrospective evaluation of the National Cancer Database from 2010 to 2014 for patients with clinical stage I-III rectal cancer who underwent total mesorectal excision. Patients were excluded for emergency operation, resection for cancer recurrence, palliative resection, transanal resection, and missing CRM status. The primary outcome was positive CRM. Secondary outcomes included overall survival. Results: There were 28,790 patients included. 2245 (7.8%) had a positive CRM. Higher tumor grade, lack of neoadjuvant chemotherapy, mucinous/signet tumor histology, open approach, abdominoperineal resection, higher T stage, lymphovascular invasion, and perineural invasion were all significantly associated with positive CRM (P < 0.05) and were included in the nomogram. The C-statistic was 0.703, suggesting a good predictive model. Conclusions: Positive CRM is associated with specific patient demographics and tumor characteristics. These factors can be used along with preoperative MRI to predict CRM positivity in the preoperative period and plan accordingly.