Circumferential Resection Margin is Associated With Distant Metastasis After Rectal Cancer Surgery A Nation-wide Population-based Study Cohort

Objective:To evaluate circumferential resection margin (CRM) as a risk factor for distant metastasis (DM) in rectal cancer. Summary of Background Data: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. Methods: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. Results: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. Conclusions: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.