Type 1 diabetes is associated with increased risk of several cancersBMJ 2016; 352 doi: https://doi.org/10.1136/bmj.i1210 (Published 01 March 2016) Cite this as: BMJ 2016;352:i1210
People with type 1 diabetes have a higher incidence of cancer of the liver, pancreas, kidney, endometrium, and ovary and a lower incidence of prostate cancer than the general population, an analysis of diabetes registers across five countries has shown.1
Previous research has found that people with diabetes have a 20-25% higher incidence of cancer than people without diabetes, but most studies have looked at type 2 diabetes.
Researchers analysed data from nationwide diabetes registers in Australia (2000-08), Denmark (1995-2014), Finland (1972-2012), Scotland (1995-2012), and Sweden (1987-2012). They found 9149 cases of cancer from 3.9 million person years. The team then compared the incidence of cancer in people with type 1 diabetes with that of the general population.
Grouping together all types of cancer, the study found that women with type 1 diabetes had a 7% higher risk of cancer overall. Men with type 1 diabetes did not show this increase, having a 44% lower incidence of prostate cancer than the general population. But when sex specific cancer types were excluded the men showed a 15% higher risk of cancer and women a 17% higher risk.
Analysing the results for specific cancers showed that women with type 1 diabetes had a 78% higher risk of stomach cancer than women without diabetes (hazard ratio 1.78 (95% confidence interval 1.49 to 2.13)). In men this risk increased by 23% (1.23 (1.04 to 1.46)).
Men with type 1diabetes had a twofold risk of liver cancer, while women had a 55% increased risk (men 2.00 (1.67 to 2.40); women 1.55 (1.14 to 2.10)). With cancer of the pancreas, men with type 1diabetes showed a 53% increased risk and women a 25% increased risk. With kidney cancer the increased risk was 30% in men and 47% in women. And women with type 1 diabetes were 42% more likely to have cancer of the endometrium but 10% less likely to have breast cancer.
The incidence of cancer was highest shortly after a diagnosis of diabetes, the study found: the authors said that this may be due to the detection of pre-existing cancers because of increased medical attention at that time.
The excess in cancer incidence in people with type 1 diabetes was smaller than in previous studies that looked at people with type 2 diabetes. This does not support the theory that insulin treatment contributes to increased cancer risk, the authors said: if insulin was a cancer risk factor then the risk would be expected to be higher in people with type 1 diabetes, as a substantially higher proportion of them receive insulin treatment.
The study authors added that the increased cancer risk in people with diabetes may be due to a common mechanism such as elevated blood sugar levels in both type 1 and type 2 diabetes.