What is the role for the circumferential margin in the modern treatment of rectal cancer?

Purpose Treatment of rectal cancer has changed dramatically over the last decade. The worldwide introduction of total mesorectal excision in combination with the increasing use of radio(chemo) therapy has led to an improved prognosis. One of the main prognostic factors in rectal cancer is the circumferential resection margin (CRM). Since the initial description of its clinical importance in 1986, the involvement of this margin (also called lateral or radial resection margin) has been associated with a poor prognosis. Methods In the current review, the evidence for the importance of the CRM in more than 17,500 patients is reviewed, and the relevance of this assessment to modern treatment is assessed. Results We demonstrate that, after neoadjuvant therapy (both radiotherapy and radiochemotherapy), the predictive value of the CRM for local recurrence is significantly higher than when no preoperative therapy has been applied (hazard ratio [HR] = 6.3 v 2.0, respectively; P < .05). Furthermore, involvement of the CRM is a powerful predictor of both development of distant metastases (HR = 2.8; 95% CI, 1.9 to 4.3) and survival (HR = 1.7; 95% CI, 1.3 to 2.3). In addition to the prognostic data, this review describes different modes of margin involvement, exact definitions, and factors influencing its presence. Conclusion CRM involvement is one of the key factors in rectal cancer treatment.