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 mid-rectal (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.