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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.
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.
Showing the technology this term belongs to: MRI.
Shares TNM staging, Histopathology & immunohistochemistry, Colon cancer (adenocarcinoma of the colon), Rectal cancer and the tags gi, colorectal.
Shares Resection margins (R0 / R1 / R2), Colon cancer (adenocarcinoma of the colon), Rectal cancer, Colorectal cancer and the tags gi, colorectal.
Shares Histopathology & immunohistochemistry, Colon cancer (adenocarcinoma of the colon), Rectal cancer, Colorectal cancer and the tags gi, colorectal.
Shares TNM staging, Colon cancer (adenocarcinoma of the colon), Rectal cancer, Colorectal cancer and the tags gi, colorectal.
Shares TNM staging, Colon cancer (adenocarcinoma of the colon), Rectal cancer, Colorectal cancer and the tags gi, colorectal.
Shares MRI, Colon cancer (adenocarcinoma of the colon), Rectal cancer, Colorectal cancer and the tags gi, colorectal.
Shares Total mesorectal excision (TME), Colorectal cancer and the tags gi, colorectal.
Shares Histopathology & immunohistochemistry, Colon cancer (adenocarcinoma of the colon), Rectal cancer, Colorectal cancer and the tags gi, colorectal.