Irritable Bowel Syndrome Is Not Associated with an Increased Risk of Polyps and Colorectal Cancer: A Systematic Review and Meta-Analysis

Colorectal cancer (CRC) is the third most common malignancy in the US. Several factors are associated with increased/decreased CRC risk and often linked to adenomatous colorectal polyps (CRP). Recent studies suggest a lower risk of neoplastic lesions among irritable bowel syndrome (IBS) patients. We aimed to systematically assess the occurrence of CRC and CRP in IBS patients.Searches of the Medline, Cochrane, and EMBASE databases were performed, blindly and independently, by two investigators. Studies of CRC or CRP incidence in IBS patients (diagnosed by Rome or other symptom-based criteria) were eligible for inclusion. CRC and CRP effect estimates were pooled in meta-analyses using random models.Of 4941 non-duplicate studies, 14 were included, comprising 654,764 IBS patients and 2,277,195 controls in 8 cohort studies, and 26,641 IBS patients and 87,803 controls in 6 cross-sectional studies. Pooled analysis revealed a significantly decreased prevalence of CRP in IBS subjects vs. controls, with a pooled odds ratio (OR) of 0.29 (95% CI (0.15, 0.54)). There was significant heterogeneity between studies (I2 = 96%, p < 0.01). This finding persisted when studies which did not report pre-cancerous polyps separately were excluded (OR 0.23, 95% CI (0.15, 0.35), I2 = 85%, p < 0.01). CRC prevalence was lower in IBS subjects, but this did not reach statistical significance (OR 0.40, 95% CI (0.09, 1.77]).Our analyses reveal a decreased incidence of colorectal polyps in IBS, although CRC did not reach significance. Mechanistic studies with detailed genotypic analysis and clinical phenotyping are needed to better elucidate the potentially protective effect of IBS on CRC development.