What is the Significance of the Circumferential Margin in Locally Advanced Rectal Cancer After Neoadjuvant Chemoradiotherapy?

Abstract

The circumferential resection margin (CRM) is highly prognostic for local recurrence in rectal cancer surgery without neoadjuvant treatment. However, its significance in the setting of long-course neoadjuvant chemoradiotherapy (nCRT) is not well defined. Review of a single institution's prospectively maintained database from 1998 to 2007 identified 563 patients with locally advanced rectal cancer (T3/T4 and/or N1) receiving nCRT, followed after 6weeks by total mesorectal excision (TME). Kaplan-Meier, Cox regression, and competing risk analysis were performed. The authors noted that 75% of all patients had stage III disease as determined by endorectal ultrasound (ERUS) and/or magnetic resonance imaging (MRI). With median follow-up of 39months after resection, local and distant relapse were noted in 12 (2.1%) and 98 (17.4%) patients, respectively. On competing risk analysis, the optimal cutoff point of CRM was 1mm for local recurrence and 2mm for distant metastasis. Factors independently associated with local recurrence included CRM ≤1mm, and high-grade tumor (p=0.012 and 0.007, respectively). CRM ≤2mm, as well as pathological, nodal, and overall tumor stage are also significant independent risk factors for distant metastasis (p=0.025, 0.010, and <0.001, respectively). In this dataset of locally advanced rectal cancer treated with nCRT followed by TME, CRM ≤1mm is an independent risk factor for local recurrence and is considered a positive margin. CRM ≤2mm was associated with distant recurrence, independent of pathological tumor and nodal stage.