Study of one million patients shows link between type 2 diabetes and many types of cancer
A million-patient study from the Institute for Clinical Evaluative Sciences (ICES) and Women’s College Research Institute published this week in the journal Cancer provides more detail on the association between type 2 diabetes and cancer, suggesting that prevention of the two diseases should go hand-in-hand.
Diabetes has been known for some time to be associated with an increased risk of multiple cancers. However, the nature of that relationship is a complex blend of genetic, metabolic, behavioural and environmental factors. The researchers set out to shed some light on these associations by looking for patterns in timing between when patients develop type 2 diabetes, and their cancer diagnosis. They also looked for patterns in the types of cancers diagnosed in people with diabetes.
The study was published today in the journal Cancer.
Using secure health data housed at ICES, researchers examined health records for one million Ontario patients spanning 10 years between 1997 and 2007. They looked at data for over 500,000 patients who had been diagnosed with type 2 diabetes between 2003 and 2007, and compared them with a control group made up of an equal number of age- and sex-matched non-diabetic individuals.
There were 9,090 cancers diagnosed in the diabetic individuals in the 10-year period prior to their diabetes diagnosis and 7,466 cancers among patients who did not have diabetes, a 23 per cent difference. Examining the three months immediately following a diabetes diagnosis, 2,434 of these patients were diagnosed with cancer, compared to 1,342 for the non-diabetic patients in the control group.
“We found that the adjusted rate of any cancer diagnosis was 62 per cent higher among individuals who had been diagnosed with diabetes in the previous three months,” says Iliana Lega, the lead author on the paper who is a scientist at Women’s College Research Institute. “This spike could be partly due to the increased health screening and health interactions that are triggered by a diabetes diagnosis. But it also points to a higher risk of cancer that likely predates the diabetes diagnosis, meaning there may be opportunities to catch or prevent those cancers earlier.”
Patients with diabetes were more likely to have been diagnosed with cancer in the 10 years prior to their diabetes diagnoses for nine of the 11 cancers examined (pancreas, colorectal, lung, liver, breast, endometrial, prostate, thyroid, bladder). The rate was highest for pancreas or liver cancers, which were approximately tripled in the diabetic group. Only ovarian or cervical cancers did not have higher rates.
“We’ve seen strong evidence previously that there are shared risk factors that make people who develop diabetes more likely to also develop cancer,” notes Lega. “Our study provides more detail about how those risks manifest in a large population over time, and suggests a role for enhanced cancer screening not only for all patients diagnosed with diabetes, but also for people who are at higher risk of developing diabetes.”
“Given the growing prevalence of diabetes in Canada and throughout the world, these projections have implications not only for the future burden of diabetes, but may also predict higher rates of cancer in the future,” comments Lorraine Lipscombe, the senior author on the paper who is a senior adjunct scientist at ICES. “We know that diabetes can be reversed with physical activity and lifestyle interventions in high-risk individuals, and it is possible that such interventions may not only reduce the risk of diabetes and vascular complications, but may also potentially reduce the burden of cancer population-wide.”
“The temporal relationship between diabetes and cancer: a population- based study” was published today in the journal Cancer.
Author block: Iliana C. Lega, Andrew S. Wilton, Peter C. Austin, Hadas D. Fischer, Jeffrey A. Johnson, Lorraine L. Lipscombe.
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