BACKGROUND: The prognostic value of the present definition of microradicality in colon cancer is poorly understood, especially considering the vast influence it has in rectal cancer prognosis.

OBJECTIVE: This study aims to investigate whether the risk of recurrence after complete mesocolic excision (CME) for stage III colon cancer is associated with the distance from tumor tissue to resection margin, and whether the location of involved margin is of any significance.

DESIGN: A prospective cohort of patients was stratified into two groups to distinguish between direct margin invasion (0 mm resection margin) and a <= 1 mm resection margin without direct invasion, or three groups to distinguish between the location of margin involvement (lateral tumor resection margin, central vascular ligation margin, and non-peritonealized mesocolic resection margin). Patients with microradical resections were used as control group.

SETTINGS: We included all patients undergoing elective CME for UICC stage III colon cancer at Nordsjaellands Hospital, Denmark, between Jan. 1, 2008 and Dec. 31, 2016.

PATIENTS: A total of 276 patients met all inclusion criteria and none of the exclusion criteria.

MAIN OUTCOME MEASURES: Primary outcome was risk of recurrence after 3[middle dot]2 years.

RESULTS: A total of 41 (15%) patients had a non-microradical resection. The 3[middle dot]2-year cumulative incidence of recurrence for 0 mm margin was 43%, and 24% for <= 1 mm margin without direct invasion, corresponding to a hazard ratio of 4[middle dot]3 (p=0[middle dot]0146) and 1[middle dot]3 (p=0[middle dot]474) respectively. The location of the involved margin showed no significant differences.

LIMITATIONS: Single-center study with limited number of patients with a non-microradical resection with a risk of type II error.

CONCLUSIONS: We found of no increased risk of recurrence for <= 1 mm margin without direct invasion, indicate that the present classification of microradicality might not be justified, if an intact posterior mesocolic fascia without invasion of tumor tissue is present See Video Abstract at http://links.lww.com/DCR/B625.