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 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: 12146 cases were identified. 8593 cases were analysed after exclusion. 717 (8.6%) patients had CRM ≤1.0 mm and 7577 (91.4%) patients 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% CI 16.2-34.4) and 19.5% (95% CI 18.5-19.5) when CRM was 0.0 mm, 0.1-1.0 mm, 1.1-1.9 mm and CRM ≥2 mm respectively. Multivariable analysis revealed higher DM risk in CRM 0.0-1.0 mm versus >1.0 mm (HR 1.28, 95% c.i. 1.06 to 1.56; P=<0.011). No significant difference in DM risk in CRM 1.1 - 1.9 mm versus ≥2.0 mm (HR 0.66, 95% c.i. 0.34 to 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.