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Increased Cancer Risk Associated with Type 1 and Type 2 Diabetes

Why is cancer risk higher among diabetes patients?…

Evidence indicates an increased risk of certain cancers among people with type 2 diabetes. Evidence for rarer cancers and for type 1 diabetes is limited. Australian researchers recently explored the excess risk of site-specific cancer incidence and mortality among people with type 1 and type 2 diabetes, compared with the general Australian population.

Registrants of a National Diabetes Registry (953,382) between 1997 and 2008 were linked to national death and cancer registries. Standardized incidence and mortality ratios (SIRs/SMRs) are reported.

For type 1 diabetes, significant elevated SIRs were observed for pancreas, liver, esophagus, colorectal (females only [F]), stomach (F), thyroid (F), brain (F), lung (F), endometrial, and ovarian, and melanoma and prostate (decreased risk). Significantly increased SMRs were observed for pancreas, liver, and kidney (males only), non-Hodgkin’s lymphoma, brain (F), and endometrium. For type 2 diabetes, significant SIRs were observed for almost all site-specific cancers, with highest SIRs observed for liver and pancreas, and decreased risks for prostate and melanoma. Significant SMRs were observed for liver, pancreas, kidney, Hodgkin’s lymphoma, gallbladder (F), stomach (F), and non-Hodgkin’s lymphoma (F). Cancer risk was significantly elevated throughout follow-up time but was higher in the first 3 months post-registration, suggesting the presence of detection bias and/or reverse causation.

The researchers concluded that, “Type 1 and type 2 diabetes are associated with an excess risk of incidence and mortality for overall and a number of site-specific cancers, and this is only partially explained by bias. We suggest that screening for cancers in diabetic patients is important.”

Practice Pearls:

  • This study has demonstrated that both type 1 and 2 diabetes are associated with increased risk of cancers but the reasons are unknown.
  • Due to limitations, the results may be detected by bias or reverse causation. Therefore, more studies are necessary to remove these limitations to provide strong evidence of this study.
  • Diabetes patients should be screened for cancer.

Harding, JL, Shaw JE, Peeters A, et al. Cancer Risk Among People With Type 1 and Type 2 Diabetes: Disentangling True Associations, Detection Bias, and Reverse Causation. Diabetes Care 2015;38:264-270