Patients with coronary artery disease are at high risk for developing colorectal cancer and adenoma: an interim analysis of a prospective study

Abstract

BACKGROUND: Identifying high risks groups for developing colorectal neoplasia (cancer and adenoma) (CN) allows early detection and hence prevention. We observed in our retrospective study that there was a strong association between patients with CN and coronary artery disease (CAD), probably due to common risk factors. Aim: To investigate the prevalence of CN in patients with and without CAD in those aged ≥ 50 years in a prospective study and to identify the underlying risk factors. METHODS: Patients were recruited for screening colonoscopy after undergoing coronary angiogram, and was defined as CAD+ if there was greater than 50% stenosis of one of the main arteries, and CAD- if not. Advanced colonic lesion was defined as the presence of cancer, or adenomas with villous component, or with moderate to severe dysplasia, or ≥1cm, or >2 adenomas. Underlying risk factors were recorded. The calculated sample size was 200 in each arm. An interim analysis was carried out at a sample size of 150 at each arm. Pearson chi-square test was carried out to test for the association between CN and CAD. To adjust for the factors of age, sex and other risk factors, a random-effects bivariate logistic regression analysis was used. Bayesian analysis was carried out using the software WinBUGS. Intra-cluster correlation (ICC) is a side product of the model that gives an idea of the strength of the association after adjusting for the explanatory variables. RESULTS: There were 307 patients (68.7% male) recruited, 46.3% of them were CAD+. The prevalence of CN was 30.3% vs 19.4% (p=0.027), and advanced lesions was (16.9% vs 6.7%, P=0.005) in patients with and without CAD. There were 5 colorectal cancers (3.5%) detected in the CAD+ arm but none in CAD- (p=0.015). All the cancers were asymptomatic except anemia was found incidentally in one patient. Using logistic regression analysis, the variance of the random effects σ2 =1.7 (95% CI: 0.42, 4.59), and ICC = 0.32 (95% CI: 0.11, 0.58), both indicates a strong association between CN and CAD after adjusting for the risk factors. Male sex and smoking were risk factors for predicting the occurrence of the two diseases. Conclusion: Patients with CAD+ are at high risk for developing colorectal cancer and adenomas, screening by colonoscopy for these patients is mandatory.