Is the 1-cm Rule of Distal Bowel Resection Margin in Rectal Cancer Based on Clinical Evidence? A Systematic Review

BACKGROUND: Distal intramural spread is present within 1 cm from visible tumor in a substantial proportion of patients. Therefore, ≥1 cm of distal bowel clearance is recommended as minimally acceptable. However, clinical results are contradictory in answering the question of whether this rule is valid. The aim of this review was to evaluate whether in patients undergoing anterior resection, a distal bowel gross margin of <1 cm jeopardizes oncologic safety. METHODS: A systematic review of the literature identified 17 studies showing results in relation to margins of approximately <1 cm (948 patients) versus >1 cm (4626 patients); five studies in relation to a margin of ≤5 mm (173 patients) versus >5 mm (1277 patients), and five studies showing results in a margin of ≤2 mm (73 patients). In most studies, pre- or postoperative radiation was provided. RESULTS: A multifactorial process was identified resulting in selection of favorable tumors for anterior resection with the short bowel margin and unfavorable tumors for abdominoperineal resection or for anterior resection with the long margin. In total, the local recurrence rate was 1.0% higher in the <1-cm margin group compared to the >1-cm margin group (95% confidence interval [CI] −0.6 to 2.7; P = 0.175). The corresponding figures for ≤5 mm cutoff point were 1.7% (95% CI −1.9 to 5.3; P = 0.375). The pooled local recurrence rate in patients having ≤2 mm margin was 2.7% (95% CI 0 to 6.4). CONCLUSIONS: In the selected group of patients, <1 cm margin did not jeopardize oncologic safety.