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Type 1 diabetes increases risk for nonsex-specific cancers
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Men and women with type 1 diabetes have a 15% increased risk for developing nonsex-specific cancers over 20 years, including stomach, liver, pancreas and kidney cancers; however, the risk decreases with diabetes duration, according to study findings.
In a multi-country analysis of diabetes and cancer databases, researchers also found that adults with type 1 diabetes have a lower risk for breast and prostate cancer than the general population.
Sarah Wild
“Fortunately, cancer among people with type 1 diabetes is rare, which is why this study needed an international collaboration to study the association,” Sarah Wild, MSc, PhD, professor of epidemiology at the University of Edinburgh, Scotland, told Endocrine Today. “People with type 1 diabetes are at slightly higher risk of some relatively common cancers compared to the general population, and the increased risk is most marked soon after diagnosis of diabetes.”
Wild, along with Bendix Carstensen, MSc, senior statistician in clinical epidemiology at the Steno Diabetes Center, and colleagues identified adults with type 1 diabetes from five nationwide diabetes registries: Australia (2000-2008), Denmark (1995-2014), Finland (1972-2012), Scotland (1995-2012) and Sweden (1987-2012). Researchers linked the data to national cancer registries and used Poisson models, adjusted for age and date of follow-up, to estimate HRs for total and site-specific cancers. Follow-up time and number of cancers in people with type 1 diabetes were classified by country, age, sex, calendar time and diabetes duration.
Bendix Carstensen
In 3.9 million person-years of follow-up, there were 9,149 first incident cancers; the majority of cases occurred when aged 40 to 60 years (mean age at cancer diagnosis, 51.1 years).
Researchers found that the rate for overall cancer was low among adults with type 1 diabetes, with an HR of 1.01 (95% CI, 0.98-1.04) in men and 1.07 (95% CI, 1.04-1.1) in women vs. the general population. However, when analysis was restricted to nonsex-specific cancers, HRs rose to 1.15 (95% CI, 1.11-1.19) for men and 1.17 (95% CI, 1.13-1.22) for women.
Researchers found significantly elevated HRs among both sexes for cancers of the stomach (HR for men = 1.23; 95% CI, 1.04-1.46; HR for women = 1.78; 95% CI, 1.49-2.13), liver, (HR for men = 2; 95% CI, 1.67-2.4; HR for women = 1.55; 95% CI, 1.14-2.1), pancreas (HR for men = 1.53; 95% CI, 1.3-1.79; HR for women = 1.25; 95% CI, 1.02-1.53), endometrium (HR = 1.42; 95% CI, 1.27-1.58) and kidney (HR for men = 1.3; 95% CI, 1.12-1.49; HR for women = 1.47; 95% CI, 1.23-1.77).
Women with type 1 diabetes exhibited a significantly reduced risk for melanoma, breast cancer and Hodgkin’s lymphoma; men with type 1 diabetes had a 44% lower rate of prostate cancer than the general population. The risk for overall cancer occurrence rose during the first year after diabetes diagnosis, according to researchers, with the rate for most cancers decreasing with diabetes duration.
“The cancer incidence subsequently decreased to that of the general population after approximately 20 years of follow-up for men and after 5 years of follow-up for women,” the researchers wrote.
Carstensen noted that the findings do not support the notion that insulin therapies contribute to an observed elevated cancer incidence.
“If insulin played a major role in cancer occurrence, we would expect a larger effect in [type 1] patients, and we would expect the excess to increase by duration of [type 1 diabetes],” Carstensen told Endocrine Today. “We see neither in this study.”
“Longer follow-up is required given the relatively young age of the participants and the importance of age as a risk factor for cancer,” Wild said. “The role of overweight and obesity in influencing cancer risk among people with type 1 diabetes should be explored further, as should patterns of risk factors for breast cancer, such as reproductive history.” – by Regina Schaffer
For more information: Sarah Wild, MSc, PhD, can be reached at the Center for Population Health Sciences at the University of Edinburgh, Old College, South Bridge, Edinburgh EH8 9YL, United Kingdom; email: sarah.wild@ed.ac.uk. Bendix Carstensen, MSc, can be reached at the Steno Diabetes Center, Niels Steensens Vej 2, 2820 Gentofte, Denmark; email: bxc@steno.uk.
Disclosure: Carstensen reports owning stock in Novo Nordisk and is an employee of the Steno Diabetes Center, a diabetes clinic and research institution owned by Novo Nordisk. Wild reports receiving honoraria from Global MedEd/AstraZeneca for contributing a lecture to a series of educational videos in 2014.
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