Circumferential Resection Margin is Associated With Distant Metastasis After Rectal Cancer Surgery

To evaluate circumferential resection margin (CRM) as a risk factor for distant metastasis (DM) in rectal cancer.The treatment of rectal cancer has evolved over the last decades. Surgical radicality is considered the most important factor in preventing recurrences including local and distant. CRM ≤1.0 mm is considered to increase recurrence risk. This study explores the risk of DM in relation to exact CRM.All patients treated with abdominal resection surgery for rectal cancer between 2005 and 2013 in Sweden were eligible for inclusion in this retrospective study. Primary endpoint was DM.Twelve thousand one hundred forty-six cases were identified. Eight thousand five hundred ninety-three cases were analyzed after exclusion. Seven hundred seventeen (8.6%) patients had CRM ≤1.0mm and 7577 (91.4%) patients had CRM >1.0 mm. DM recurrence rate at 5 years was 42.1% (95% CI 32.5-50.3), 31.5% (95% CI 27.3-35.5), 25.8% (95% Confidence Interval (CI) 16.2-34.4), and 19.5% (95% CI 18.5-19.5) when CRM was 0.0 mm, 0.1 to 1.0 mm, 1.1 to 1.9 mm, and CRM ≥2mm, respectively. Multivariable analysis revealed higher DM risk in CRM 0.0-1.0 mm versus >1.0 mm (hazard ratio 1.30, 95% CI 1.05-1.60; P = 0.015). No significant difference in DM risk in CRM 1.1-1.9 mm versus ≥2.0 mm (hazard ratio 0.66, 95% CI 0.34-1.28; P = 0.224) could be detected.The risk of DM decreases with increasing CRM. Moreover, CRM ≤1.0 mm is a significant risk factor for DM. Thus, CRM is a dominant factor when discussing risk of DM after rectal cancer surgery.