Purpose: Diabetes is associated with increased risk of developing colorectal cancer (CRC), but its effect on overall and cancer-specific mortality in CRC patients has been little investigated. The aim of this study was to assess the influence of diabetes on overall and cancer-specific mortality in Italian CRC patients.
Methods: Cases of adult (≥15 years) CRC, diagnosed in 2003-2005, most followed-up to the end of 2008, were randomly selected from the Italian Cancer Registries database. Diabetic status, sex, age, tumor stage, subsite, treatment, morphology, and grade were obtained by consultation of patient clinical records. Poisson multivariable regression models, adjusted for potential confounding variables, were used to estimate hazard ratios (HRs) for all-cause and CRC-specific mortality, according to diabetic status.
Results: A total of 1,039 CRC cases with known fasting glucose or diabetic status, archived in 7 cancer registries, was analyzed. Compared to non-diabetics, diabetics (specific diagnosis or glucose ≥126 mg/dl) were older and less likely to receive adjuvant therapy. Diabetics were at higher risk of all-cause death [HR 1.41; 95 % confidence interval (CI) 1.18-1.70] and CRC death (HR 1.36; 95 % CI 1.11-1.67), with no differences by sex or subsite.
Conclusions: Diabetes was significantly associated with increased overall and CRC-specific mortality. Our findings indicate that diabetes is a negative prognostic factor for CRC and suggest that in patients with CRC, diabetes prevention and treatments that stabilize the condition and control its complications might reduce mortality. Further studies are required to ascertain the mechanisms linking diabetes to greater mortality in CRC patients.