Clinicopathological factors associated with positive circumferential margins in rectal cancers

Positive circumferential resections are associated with local disease recurrence and reduced survival in rectal cancer. We studied a cohort of consecutive rectal cancer resections to assess for clinicopathological differences and survival in patients with positive and negative circumferential margins.

Rectal cancers were identified from a retrospective histopathology database of colorectal resections performed at five western Sydney hospitals from 2010 to 2016. Univariate and multivariate analysis with binary logistic regression were performed on histopathology data matched with survival times from the New South Wales Registry of Births Deaths and Marriages.

A total of 502 rectal cancer patients were identified including 66 (13.1%) with involved circumferential margins. Patients with positive and negative circumferential margins had a similar distribution of age, gender and use of neoadjuvant radiotherapy. Tumours with involved circumferential margin comprised 98.5% T3 and T4 disease of which 51.5% received neoadjuvant radiotherapy. These were significantly associated with metastatic disease, increasing tumour size, circumferential and perforated tumours on univariate analysis. Multivariate analysis identified abdomino-perineal resection (odds ratio (OR) 3.35; P = 0.003), en-bloc multivisceral resection (OR 2.56; P = 0.032), T4 stage (OR 6.99; P < 0.001), perineural (OR 5.61; P < 0.001) and vascular invasion (OR 2.46; P = 0.022) as independent risk factors. Five-year survival was significantly worse for patients with involved circumferential margins (26% versus 69%; P < 0.001).

Circumferential margin status reflects not only technical success but also aggressive disease phenotypes which require adjuvant therapy. Further work is needed to determine whether omission of radiotherapy has had an effect on long-term outcomes in some of our at-risk patients.