Inflammatory bowel disease and risk of urinary cancers: a systematic review and pooled analysis of population-based studies

Background: The aim of this study is to elucidate the risk of urologic cancers in patients with Crohn's disease (CD) and ulcerative colitis (UC). Methods: Electronic databases including PubMed, the Cochrane Library, Embase and Web of Science, and manual retrieval were conducted from inception to June 2020. Two reviewers independently searched the above databases and selected the studies using prespecified standardized criteria. The Newcastle-Ottawa Scale was used to assess the risk of bias in the included studies, and this meta-analysis was completed by STATA version 14.2. Results: A total of 12 cohort studies and 4 case-control studies were included in this meta-analysis. Overall, patients with inflammatory bowel disease (IBD) were at significantly increased risk of renal cancer (RCa) [standardized incidence ratio (SIR): 1.53; 95% confidence interval (CI): 1.25-1.80; I-2=42.4%], but not at increased risk of prostate cancer (PCa), bladder cancer (BCa) and male genital cancer. In the subgroup analysis, CD patients had a significantly higher RCa risk (SIR: 1.95; 95% CI: 1.45-2.44; I-2=39.9%). Besides, CD patients seemed to be at borderline significantly increased risks of PCa (SIR: 1.07; 95% CI: 0.93-1.20; I(2=)15.1%) and BCa (SIR:1.19; 95% CI: 0.94-1.44; I-2=0%), and UC patients seemed to be at borderline significantly increased risks of RCa (SIR: 1.31; 95% CI: 0.94-1.67; I-2=48.0%) and PCa (SIR: 1.13; 95% CI: 0.93-1.33; I-2=73.5%). Notably, we observed that IBD patients in Eastern countries have significantly increased PCa risk (SIR: 2.66; 95% CI: 1.52-3.81; I-2=13.6%), especially for UC patients (SIR: 3.01; 95% CI: 1.75-4.27; I-2=0.0%). Conclusions: Our findings indicate that IBD patients with special reference to CD patients increase the risk of RCa. Besides, IBD patients in Asian countries have significantly increased risk of PCa, especially for UC patients. Further studies are warranted to elucidate the potential mechanism of RCa associated with IBD and the differences of the risk of urinary cancers between Eastern and Western countries.