Circumferential margin involvement after total mesorectal excision for mid or low rectal cancer: are all R1 resections equal?

Abstract

Our aim was to assess the prognostic influence of the circumferential resection margin (CRM) exact value after total mesorectal excision for mid or low rectal cancer. All patients (n = 321) who underwent total mesorectal excision from 2005 to 2013 were identified from a prospective database, including 49 (15%) who presented with a CRM ≤ 1 mm. Four groups were defined: group 1, CRM = 0 mm (n = 21); group 2, 0 < CRM ≤ 0.4 mm (n = 13); group 3, 0.4 < CRM ≤ 1 mm (n = 15); group 4, CRM > 1 mm (n = 272). After a mean follow-up of 42 ± 26 months, locoregional recurrence rates were 8/21 (38%) in group 1, 3/13 (23%) in group 2, 0/12 (0%) in group 3 and 26/272 (10%) in group 4 (P < 0.001), leading to significantly impaired 3-year locoregional recurrence-free survival in group 1 (57% ± 13%) and group 2 (56% ± 15%) compared to group 3 (85% ± 10%, vs group 1, P = 0.021, vs group 2, P = 0.049) and to group 4 (89% ± 2%, vs group 1, P < 0.001, vs group 2, P < 0.001). In multivariate Cox analysis, a CRM ≤ 0.4 mm was identified as an independent factor impairing both locoregional recurrence-free survival (OR 3.14, 95% CI 1.53-6.46; P = 0.002) and disease-free survival (OR 2.15, 95% CI 1.28-3.63; P = 0.004). Our study suggests that the prognosis after mid or low rectal cancer surgery was worse with a CRM ≤ 0.4 mm. The prognosis was similar in patients with a CRM > 0.4 mm or ≤ 1 mm and patients with an R0 resection.