A higher risk of colorectal cancer (CRC) in patients with diabetes has been well documented. However, little is known regarding diabetes incidence in CRC survivors. This may have substantial impact on CRC survivorship care as well as enhancing the understanding of the interplay between the two diseases. We explored whether the incidence of diabetes was higher among patients with CRC than matched control subjects.
Using population-based data from Ontario, Canada, we generated a dataset comprising 39 707 incident CRC cases and 198 535 age- and sex-matched control subjects (1:5) dating from April 2002 to March 2010. We used cause-specific hazard models to estimate the hazard ratios (HRs) for diabetes overall and in subgroups stratified by receipt of systemic chemotherapy, diagnosis of metastatic disease, and site of cancer.
During a mean follow-up of 4.81 years, the association between CRC and diabetes varied: The rate of developing diabetes was 53% higher among CRC patients compared with control subjects in the first year postdiagnosis (HR = 1.53, 95% confidence interval [CI] = 1.42 to 1.64) and remained increased by 19% in the fifth year postdiagnosis (HR = 1.19, 95% CI = 1.05 to 1.35). Findings were similar in subgroups of patients who had colon cancer, received systemic chemotherapy, or had no evidence of metastasis.
We found that CRC patients were statistically significantly more likely to develop subsequent diabetes than persons without CRC for up to five years after the diagnosis. Our study suggests that active screening and counseling regarding modifiable risk factors may be warranted in this high-risk group.