# Circumferential resection margin (rectal cancer)

Source: https://onco.cc/terms/circumferential-resection-margin/  
OnCo record `circumferential-resection-margin` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The circumferential resection margin is the side surface of the removed rectum, the plane the surgeon cut along. If cancer cells lie within a millimetre of it, the cancer is much more likely to come back in the pelvis. It is measured on the scan before surgery and on the specimen afterwards, and it is the single reading that most shapes rectal cancer treatment.

## Summary

Where it came from. In 1986 Quirke sliced 52 whole rectal specimens transversely rather than sampling them: 14 of 52 (27 percent) had tumour spread to the lateral resection margin and 12 of those 14 went on to local pelvic recurrence, with a specificity of 92 percent, sensitivity of 95 percent and positive predictive value of 85 percent. A stage- and grade-matched control series had the same recurrence rate but no lateral spread recorded, because routine sampling had missed it. Local recurrence was reinterpreted as the consequence of lateral spread left behind, not of inherent aggressiveness (Quirke 1986). The surgical answer had already been described: total mesorectal excision, removing the whole mesorectal envelope rather than cutting into it (Heald 1982).

What involvement predicts. A review of more than 17,500 patients found that an involved margin predicts local recurrence, distant metastases (hazard ratio 2.8) and shorter survival (hazard ratio 1.7), and that its predictive value for local recurrence is significantly greater after preoperative radiotherapy or chemoradiotherapy than without it (hazard ratio 6.3 against 2.0) (Nagtegaal and Quirke 2008). The conventional definition of involvement is tumour within 1 mm of the margin.

Reading it before surgery. High-resolution pelvic magnetic resonance imaging measures the distance from tumour to the mesorectal fascia, the plane that becomes the margin. In the MERCURY study of 408 consecutive patients across 11 European units, 87 percent had a clear margin at pathology; magnetic resonance imaging predicted a clear margin with 92 percent specificity, and of the 349 patients it predicted clear, 327 (94 percent) were clear at surgery (BMJ 2006). MERCURY II extended the approach to low rectal cancers within 6 cm of the anal verge, classifying the relationship of tumour to the surgical plane as safe or unsafe in 279 patients with an overall pathological margin involvement rate of 9.0 percent. A threatened margin on the scan is the usual reason to give radiotherapy or chemoradiotherapy before surgery rather than operating first.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: CRM; circumferential margin; radial resection margin; lateral resection margin; mesorectal fascia; threatened margin
- Tags: gi; colorectal

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Total_mesorectal_excision
- Quirke, Lancet 1986: local recurrence of rectal adenocarcinoma due to inadequate surgical resection (52 specimens sliced transversely): https://doi.org/10.1016/s0140-6736(86)92612-7
- Heald, Br J Surg 1982: the mesorectum in rectal cancer surgery, the clue to pelvic recurrence?: https://doi.org/10.1002/bjs.1800691019
- Nagtegaal and Quirke, J Clin Oncol 2008: what is the role for the circumferential margin in the modern treatment of rectal cancer? (more than 17,500 patients): https://doi.org/10.1200/jco.2007.12.7027
- MERCURY Study Group, BMJ 2006: diagnostic accuracy of preoperative magnetic resonance imaging in predicting curative resection of rectal cancer (408 patients): https://doi.org/10.1136/bmj.38937.646400.55
- Battersby, Ann Surg 2016: MERCURY II, prospective validation of a low rectal cancer magnetic resonance imaging staging system (279 patients): https://doi.org/10.1097/sla.0000000000001193
- NICE NG151: colorectal cancer, recommendations (Lynch 1.1, local disease 1.3, biomarkers 1.4, metastatic disease 1.5, ongoing care and support including follow-up 1.6): https://www.nice.org.uk/guidance/ng151/chapter/Recommendations

## Connected records

- cancers: [Colon cancer (adenocarcinoma of the colon)](https://onco.cc/cancers/colon-cancer/), [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Micropapillary adenocarcinoma of the colon and rectum](https://onco.cc/cancers/colorectal-micropapillary-carcinoma/), [Rectal cancer](https://onco.cc/cancers/rectal-cancer/)
- technologies: [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [MRI](https://onco.cc/technologies/mri/)
- terms: [Resection margins (R0 / R1 / R2)](https://onco.cc/terms/resection-margins/), [TNM staging](https://onco.cc/terms/tnm-staging/), [Total mesorectal excision (TME)](https://onco.cc/terms/total-mesorectal-excision/), [Total neoadjuvant therapy (TNT, rectal cancer)](https://onco.cc/terms/total-neoadjuvant-therapy/), [Watch and wait after chemoradiotherapy for rectal cancer](https://onco.cc/terms/watch-and-wait-rectal-cancer/)

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