The authors said the incidence rates in type 1 diabetes compared with type 2 show that insulin treatment is not to blame for increased cancer rates.
Certain organ cancers—those in the pancreas, ovary, kidney, and liver—as well as stomach and endometrial cancer, are more strongly associated with having type 1 diabetes, according to a study just published in Diabetetologia, the journal of the European Association for the Study of Diabetes.
Researchers examined more than 9000 cancer cases in T1D patients from 5 counties, using data from national registries in Australia, Denmark, Finland, Scotland, and Sweden. While the years used from each registry varied, researchers had data form at least 8 years per country.
Earlier work had found that persons with diabetes had 20-25% increased incidence of cancer compared those without the disease; however, most studies involved patients with type 2 diabetes, which affects many more people than T1D.
The analysis found increased risks of cancer of the stomach (23% for men, 78% for women); liver (50% for men, 55% for women); pancreas (53% for men, 25% for women), endometrium (42%), and kidney (30% for men, 47% for women). While women with T1D had higher risks than men for many cancers, the study showed they had a 10% lower risk of breast cancer than the general population, although the study could not find why.
Curiously, the study found patients faced their greatest risk of a cancer diagnosis shortly after their diagnosis with T1D. Incidence was more than twice as high as the general population among men and women with T1D compared with the general population right after diagnosis, and fell to the same level at 20 years after diagnosis. There was some speculation that these may actually be the discovery of existing cancers that are discovered due to increased medical attention after diagnosis with T1D.
The authors state their findings point against blaming insulin for the rise in cancer incidence. If Insulin was to blame, they say, excess cancers among people with T1D would be much higher than among those with T2D, most of whom are not treated with insulin. The more common thread among the 2 groups is elevated blood sugar levels.