Type 2 diabetes and colorectal cancer survival: The multiethnic cohort

This analysis examined type 2 diabetes (T2D) as a predictor of colorectal cancer (CRC) survival within the Multiethnic Cohort Study. Registry linkages in Hawaii and California identified 5,284 incident CRC cases. After exclusion of cases with pre‐existing cancer diagnosis within 1 year and systemic disease, the analytic dataset had 3,913 cases with 1,800 all‐cause and 678 CRC‐specific deaths after a mean follow‐up of 9.3 ± 5.2 years. Among CRC cases, 707 were diagnosed with T2D 8.9 ± 5.3 years before CRC. Cox regression with age as time metric was applied to estimate hazard ratios (HR) and 95% confidence intervals (CI) for T2D status as predictor of CRC‐specific and all‐cause survival while adjusting for known confounders. Overall, CRC‐specific survival was not associated with pre‐existing T2D (HR = 0.84; 95% CI = 0.67–1.07). However, a significant interaction was seen for comorbidity (p_interaction = 0.03) with better survival among those without pre‐existing conditions (HR = 0.49; 95% CI = 0.25–0.96) while no association was seen in patients with comorbid conditions. All‐cause mortality was also not related to pre‐existing T2D (HR = 1.11; 95% CI = 0.98–1.27), but significantly elevated for individuals with T2D reporting comorbid conditions (HR = 1.36; 95% CI = 1.19–1.56). Stratification by T2D duration suggested higher CRC‐specific and all‐cause mortality among participants with a T2D history of ≥10 than <10 years. The findings were consistent across sex and ethnic subgroups. In contrast to previous reports, pre‐existing T2D had no influence on disease‐specific and all‐cause survival among CRC patients. Only participants with additional comorbidity and possibly those with long T2D duration experienced higher mortality related to T2D.