A 60-year-old man with a T1 N0 rectal adenocarcinoma at 4 cm from the anal verge undergoes transanal endoscopic microsurgery (TME). Histopathology shows positive deep margin (R1) and lymphovascular invasion. What is the next best step in management?

• A Adjuvant chemoradiotherapy alone
• B Repeat transanal excision to achieve clear margins
• C Completion radical surgery (low anterior resection or APR) ✓
• D Observation with 3-monthly MRI and sigmoidoscopy

Explanation

After R1 local excision of rectal cancer with adverse features (positive margins, lymphovascular invasion), completion radical surgery (low anterior resection or APR) is indicated because residual disease and nodal metastasis risk are significant. Repeat local excision does not address potential nodal disease. Adjuvant CRT alone is inadequate for R1 resection with LVI. Observation risks progression.

Reference: NCCN Guidelines for Rectal Cancer, 2023 ed.

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Written and medically reviewed by the StethoPrep medical team.