Diabetes and cancer risk

"diabetes" in coloured text

Type 1 diabetes may be associated with increased risk of some cancer types, say researchers.

Type 1 diabetes may be associated with an increased risk of various cancer types including cancers of the stomach, liver, pancreas, endometrium, ovary and kidney, but a reduced risk of other cancer types, including prostate and breast cancer, say researchers. The results derive from a multicentre study of data from five countries, published in Diabetologia.

Previous studies have shown a 20-25% increased cancer incidence compared to people without diabetes; however, most of these findings have been based on people with type 2 diabetes, since they make up most (around 90%) of all people with diabetes. In this study, the authors explored the increased risk of various cancers associated specifically with type 1 diabetes.

The study analysed more than 9,000 cancer cases in type 1 diabetes patients in five countries: Australia (2000-2008), Denmark (1995-2014), Finland (1972-2012), Scotland (1995-2012) and Sweden (1987-2012).

The analyses across all cancers combined revealed no increased overall cancer risk among men with type 1 diabetes, whereas women with type 1 diabetes experienced a 7% increased overall cancer risk. The neutral overall cancer risk among men with type 1 diabetes was largely due to a 44% decreased incidence of prostate cancer – the most common non-skin cancer among men.

For specific cancer sites among people with type 1 diabetes, the study revealed increased risks of cancers of the stomach (23% for men, 78% for women); liver (two-fold among men, 55% for women); pancreas (53% for men, 25% for women), endometrium (42%) and kidney (30% for men, 47% for women). Conversely, women with type 1 diabetes were 10% less likely to have a diagnosis of breast cancer, although the reasons for this are unclear.

The study also reported that cancer incidence was highest shortly after diagnosis of diabetes. The authors emphasise that the highly elevated cancer incidence soon after diagnosis is plausibly due to the detection of pre-existing cancers when patients are receiving increased medical attention, rather than any association with the disease.

The authors state if insulin treatment was a major cancer risk factor, the excess cancer incidence would be expected to be higher than among people with type 2 diabetes, since all people with type 1 are treated with insulin, whereas a substantially smaller proportion of people with type 2 diabetes receive insulin.

“Our findings do not support changes in policy for cancer screening for persons with type 1 diabetes. Recommendations for lifestyle approaches to reducing cancer risk such as avoiding smoking, weight management and physical activity apply to persons with type 1 diabetes as for the general population.”

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