Relationship between BMI, CT-derived body composition and colorectal neoplasia in a bowel screening population.

INTRODUCTION: Obesity is associated with an increased risk of colorectal cancer (CRC). Unlike the indirect measures such as BMI, CT-Body composition (CT-BC) allows for the assessment of both volume and distribution of adipose tissue. Therefore, the aim of this study was to examine the relationship between host characteristics, BMI, CT-BC measurements and the incidence of colorectal neoplasia. METHODS: Patients undergoing CT Colonography (CTC) as part of the Scottish Bowel Screening Programme, between July 2009 and February 2016, were eligible for inclusion. Data were collected including demographic data, clinicopathological variables and CT-BC measurements including skeletal muscle index (SMI), subcutaneous fat index (SFI) and visceral fat area (VFA). CTC, colonoscopy, and pathology reports were used to identify CRC incidence. Associations between demographic data, clinicopathological variables, CT-BC measurements, colorectal neoplasia and advanced colorectal neoplasia were analysed using univariate and multivariate binary logistics regression. RESULTS: 286 patients met the inclusion criteria. Neoplasia was detected in 105 (37%) of the patients with advanced neoplasia being detected in 72 (69%) of patients. On multivariate analysis sex (p < 0.05) and high VFA (p < 0.001) remained independently associated with colorectal neoplasia. On multivariate analysis a high SFI (p < 0.01) remained independently associated with advanced colorectal neoplasia. BMI was not associated with either colorectal neoplasia or advanced colorectal neoplasia. CONCLUSION: When directly compared to BMI, CT derived fat measurements were more closely associated with the degree of neoplasia in patients undergoing colorectal cancer screening. In patients investigated with CT colonography, CT adipose measures may stratify the risk and grade of neoplasia.

The role of faecal calprotectin in the identification of colorectal neoplasia in patients attending for screening colonoscopy.

AIM: Although the relationship between colorectal neoplasia and inflammation is well described, the role of faecal calprotectin (FC) in clinical practice to diagnose or screen patients for colorectal neoplasia is less defined. This prospective study characterizes the relationship between FC and colorectal neoplasia in patients within the faecal occult blood testing (FOBT) positive patients in the Scottish Bowel Screening Programme. METHODS: All FOBT positive patients attending for colonoscopy between February 2016 and July 2017 were invited to participate. Patients provided a stool sample for FC before commencing bowel preparation. All demographics and endoscopic findings were collected prospectively. RESULTS: In all, 352 patients were included. 210 patients had FC > 50 µg. Colorectal cancer (CRC) patients had a higher median FC (138.5 µg/g, P < 0.05), in comparison to those without CRC, and 13/14 had an FC > 50 µg/g (93%). FC had a high sensitivity (92.8%) and negative predictive value (99.3%) for CRC, but with a low specificity (41.7%) and positive predictive value (6.2%). FC sensitivity increased sequentially as neoplasms progressed from non-advanced to malignant neoplasia (48.6% non-advanced adenoma vs. 92.9% CRC). However, no significant relationship was observed between FC and non-cancer neoplasia. CONCLUSION: In an FOBT positive screening population, FC was strongly associated with CRC (sensitivity 92.8%, specificity 41.7% for CRC, at 50 µg/g). However, although sensitive for the detection of CRC, FC failed to show sufficient sensitivity or specificity for the detection of non-cancer neoplasia. Based on these results we cannot recommend routine use of FC in a bowel screening population to detect cancer per se, but it is apparent that, with further optimization, faecal assessments including quantification of haemoglobin and inflammation could form part of a risk assessment tool aimed at refining the selection of patients for colonoscopy in both symptomatic and screening populations.