The association between tumour sub-site and local nodal and/or distant metastasis at the time of resection of colorectal cancer: a prospective study of 3,360 consecutive cases.

The concept that right and left sided colorectal cancer may be biologically different has led to a review of the pathology and molecular characteristics expressed by the two sides. The aim of this cross-sectional study was to examine the association between tumour sub-sites and the presence of any metastasis by multivariable modelling. Pathology data were drawn from a hospital series of 3360 consecutive patients who had their first cancer resected between 1995 and 2019 inclusive. A preliminary analysis of the distribution of sex, age and a range of routinely reported pathology features showed that the simple division of the bowel into right and left sides masks the considerable variation in pathology features which occurs between sub-sites within each side. Logistic regression adjusting for sex, age, a range of routinely reported pathology features and tumour sub-site showed that age ≤70, direct tumour spread (T3 and T4), high grade, venous invasion and perineural invasion all carried a significantly increased risk for the presence of metastatic spread. The only tumour sub-sites to show an increased risk were the sigmoid colon and rectum (adjusted odds ratio 1.72, P < 0.001 and 1.78, P < 0.001, respectively). These findings suggest that multivariable modelling could usefully be applied to identify associations between sub-sites and molecular characteristics.