The Risk of Colorectal Cancer Is Not Increased after a Diagnosis of Urothelial Cancer: A Population-Based Study

Background The data about whether patients with a prior urothelial cancer (UCa) are at increased risk of colorectal cancer (CRC) are conflicting. We used a competing risks analysis to determine the risk of CRC after UCa. Methods Historical cohorts were assembled by record linkage of Manitoba Cancer Registry and Manitoba Health databases. The incidence of CRC for individuals with UCa as their first cancer between 1987 and 2009 was compared with the incidence for randomly selected age- and sex-matched individuals without a cancer diagnosis at the index date (UCa diagnosis date). Three competing outcomes (CRC, another primary cancer, and death) were evaluated by competing risks proportional hazards models with adjustment for relevant confounders. Results The cohorts of 4591 patients with UCa and 22,312 without UCa were followed for a total of 179,287 person– years (py). After UCa, the rate of subsequent colon cancer in UCa patients was 4.5 per 1000 py compared with 3.6 per 1000 py in the non-cancer cohort. In the multivariable analysis, no overall increase in CRC risk was observed for patients first diagnosed with UCa (hazard ratio: 0.88; 95% confidence interval: 0.70 to 1.1; p = 0.26). Conclusions Because of similar CRC risk, a similar CRC screening strategy should be applied for individuals with and without UCa.