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

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 6 weeks 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 39 months 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 1 mm for local recurrence and 2 mm for distant metastasis. Factors independently associated with local recurrence included CRM a parts per thousand currency sign1 mm, and high-grade tumor (p = 0.012 and 0.007, respectively). CRM a parts per thousand currency sign2 mm, 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 a parts per thousand currency sign1 mm is an independent risk factor for local recurrence and is considered a positive margin. CRM a parts per thousand currency sign2 mm was associated with distant recurrence, independent of pathological tumor and nodal stage.