Predictors of Positive Radial Margin Status in a Population-Based Cohort of Patients with Rectal Cancer

Background: Surgical margin status is an important predictor of risk of relapse among patients with rectal cancer. Methods: Patients referred to the British Columbia Cancer Agency for consideration of adjuvant therapy for rectal adenocarcinoma were included. Predictors of margin positivity were determined from uni- and multivariate analysis. Results: Among 340 patients, 83% had negative resection margins. In 268 patients with resectable tumours, a significantly higher rate of margin positivity was observed in low rectal tumours (32.2%) as compared with midrectal (3.9%) and high rectal (14.3%) tumours. Among 59 patients with locally advanced rectal cancer treated with preoperative radiation (with or without chemotherapy), 32% with low tumours had margin positivity. Of patients with T4 tumours, 50% (11/22) had a positive resection margin. Conclusions: In a population cohort, distal-third rectal location, locally advanced presentation, and T4 cancer represent subgroups for whom further improvement in therapy is required.