Researchers here note a correlation between cancer diagnosis and greater risk of later onset of type 2 diabetes. A reasonable guess is that this is mediated by the increased burden of cellular senescence produced by chemotherapy and radiotherapy, though, as the researchers point out, the widely different risks by cancer type may indicate that tumors are metabolically active in ways that specifically promote the metabolic dysfunction that leads to type 2 diabetes.
For patients with cancer, prevalent type 2 diabetes at the date of cancer diagnosis is associated with increased cancer-specific and all-cause mortality. Yet, despite potential health implications, there is limited knowledge on whether cancer is also a risk factor for type 2 diabetes. We investigated the incidence of type 2 diabetes following a cancer diagnosis and evaluated the influence of new-onset type 2 diabetes in patients with cancer on overall survival.
We included 51,353 incident cancer case subjects diagnosed from 2004 to 2015 living in the Greater Copenhagen area without type 2 diabetes. We sampled all 112 million tests from 1.3 million individuals, performed by the Copenhagen General Practitioners' Laboratory, contained in the Copenhagen Primary Care Laboratory Database (CopLab) (2015-57-0121) from 2000 to 2015, data for which were merged with data on incident cancer from the Danish Cancer Registry. The median follow-up time was 2.34 years for all case subjects and 4.41 years for cancer-free control subjects.
We found an increased hazard of new-onset type 2 diabetes for all cancers (hazard ratio [HR] 1.09). The hazard of new-onset type 2 diabetes for different cancer types in comparisons with control subjects was particularly strong for pancreatic cancer (HR 5.00), cancer of the brain and other parts of the nervous system (HR 1.54), and cancer of the corpus uteri (HR 1.41). Patients diagnosed with lung (HR 1.38), urinary tract (HR 1.32), and breast (HR 1.20) cancers also had a significantly increased hazard of type 2 diabetes.
Our results align with a smaller study of 15,130 incident cancer survivors where investigators observed an overall 35% increase in the hazard of diabetes following a cancer diagnosis. We included more than three times the number of incident cancer cases and observed similar effects; thus, our findings bolster the evidence for associations that was previously less strongly supported. The underlying mechanisms still remain to be defined but could include common risk factors, tumor-secreted factors, or effects of treatment.