The macroscopic circumferential resection margin (CRM) assessed on post-operative MRI (mrCRM) is a critical quality indicator in rectal cancer surgery. What CRM distance predicts significantly increased local recurrence?
- A CRM >5 mm
- B CRM >2 mm
- C CRM ≤1 mm (involved or threatened margin) ✓
- D CRM ≤3 mm
Correct answer: C. CRM ≤1 mm (involved or threatened margin)
Explanation
A circumferential resection margin of ≤1 mm (tumour at or within 1 mm of the mesorectal fascial margin on MRI or histology) is associated with a significantly higher local recurrence rate (>20-30%) compared to clear margins (>1 mm). Pre-operative MRI predicting mrCRM involvement dictates neoadjuvant therapy and surgical planning. R1 resection (positive CRM on histology) carries the highest recurrence risk. This threshold of ≤1 mm is standardised by the Royal College of Pathologists and is a key quality measure for TME surgery.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.