SAN FRANCISCO – Among diabetes patients, the risk of cancer was significantly increased before diagnosis and 3 months after diabetes diagnosis, but not beyond that time point, results from a population-based study showed.
"Previous studies have focused on the risk of cancer following diabetes diagnosis or else compared risk of cancer between the pre- and postdiabetes period without taking into account the time period immediately following the diagnosis of diabetes," lead investigator Dr. Iliana C. Lega said in an interview prior to the annual scientific sessions of the American Diabetes Association, where the research was presented.
"We found that risk of cancer was highest in the prediabetes period and in the first 3 months following diabetes diagnosis, suggesting a role for hyperinsulinemia in the pathogenesis of cancer in the diabetes population. Furthermore, increased detection of preexisting cancers in the period following diabetes diagnosis may also contribute to the observed elevated risk of cancer," she said.
Dr. Lega, a clinician scientist with the division of endocrinology and metabolism at the University of Toronto, and her associates used population-based data from Ontario during 1997-2009 to identify incident diabetic cohorts that were matched 1:1 by age and gender to patients without diabetes. The researchers used time-varying Cox regression models to compare the relative risk of any invasive cancer between patients with and without diabetes in three separate time frames: 10 years prior to diagnosis, 3 months after diagnosis, and more than 3 months after diabetes diagnosis.
Dr. Lega and her associates evaluated cancer risk before diabetes diagnosis in 186,441 diabetes patients and matched controls and after diabetes in 51,463 diabetes patients and matched controls. Among diabetes patients, the risk of cancer was significantly increased before diabetes diagnosis (hazard ratio, 1.23) and 3 months after diabetes diagnosis (HR, 1.69), but the association abated beyond 3 months after diabetes diagnosis.
The findings "support a role for hyperinsulinemia in the relationship between diabetes and cancer, over surveillance bias," the researchers concluded in their abstract. "While further research is needed, these results support enhanced cancer screening in patients with diagnoses of prediabetes or diabetes."
Dr. Lega acknowledged certain limitations of the study, including the fact that other risk factors for cancer such as clinical features, smoking history, chronic alcoholism, and family history could not be taken into account.
Dr. Lega said that she had no relevant financial conflicts to disclose.
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