Obtaining data on comorbid diabetes among patients in a U.S. population-based tumor registry.

Comorbid diabetes mellitus has been shown to be associated with outcomes among cancer patients, but population-based data have been limited to elderly patients through linkages between the US National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program database and Medicare databases. Reporting of comorbidity to the population-based Connecticut SEER registry is not required, but the extent of voluntary reporting of comorbid diabetes was assessed in this preliminary study. Of 15,145 Connecticut residents diagnosed at age 20+ years with invasive cancer in 2006, who were ascertained from 33 registry sources, 8688 (57.4%) from 21 sources were included in the analysis of comorbid diabetes. The prevalence of comorbid diabetes was 12.5%, and was lowest for patients with prostate cancer (8.5%) and highest for with liver-pancreas cancer (25.9%), consistent with the literature. Diabetes prevalence was substantial (9.5%) within the non-elderly subgroup aged 20-64 years at cancer diagnosis who comprised 45% of the 8688 patients. These results indicate an opportunity for future large-scale studies of the impact of diabetes on outcomes among all newly diagnosed cancer patients (both non-elderly and elderly) in the Connecticut SEER registry and other US central cancer registries.