What is the Prognostic Significance of Positive Lymph Nodes at the Circumferential Resection Margin in Rectal Cancer: A Systematic Review.

INTRODUCTION: Circumferential resection margin (CRM) positivity is an established predictor of local recurrence and survival in rectal cancer. The prognostic impact of CRM positivity specifically attributable to tumour within lymph nodes at the CRM (node-positive CRM) is unclear. We performed a systematic review to determine whether CRM positivity caused by lymph node metastases confers similar oncological risk to CRM positivity from direct tumour extension. METHODS: A systematic search of MEDLINE, EMBASE, CINAHL and Cochrane Library was conducted in March 2026 for studies reporting outcomes for patients with CRM positivity specifically due to lymph node involvement. Search strings combined terms for "rectal cancer", "circumferential resection margin" and "lymph node". Two reviewers screened records and extracted data. Study quality was assessed with the Newcastle-Ottawa Scale. Outcomes of interest were overall survival, disease-free survival, local recurrence and distant recurrence. Due to heterogenous outcome reporting and small numbers no meta-analysis was performed and a structured narrative synthesis was conducted. RESULTS: From 138 records screened, 5 studies (published between 2002-2024) including 5,303 patients met inclusion criteria; 162 patients were CRM-positive due to lymph nodes. Across all studies, node-positive CRM patients generally demonstrated more favourable outcomes than patients with CRM positivity due to direct tumour extension: 5-year overall survival ranged 49-51% for node-positive CRM versus 20-29% for tumour-extension CRM. Local recurrence in node-positive CRM ranged from 5-12% versus 22-52% for tumour-extension CRM. CONCLUSION: CRM positivity due solely to metastatic lymph nodes may be associated with more favourable oncological outcomes than CRM positivity resulting from direct tumour extension. Prospective multicentre studies with standardised pathological classification and reporting are required to determine whether the mechanism of CRM involvement represents an independent prognostic factor before these findings can inform clinical practice.