Relationship between diabetes and cancer is complex, new research has found

by Barbara Hewitt on March 7, 2016

It is already known that diabetes is linked to an increased risk of some cancers but now new research shows that while the risk is there it is a much more complex relationship.

A new study that analysed data from national registries of people with type 1 diabetes in Australia, Denmark, Finland, Scotland and Sweden from 2008 to 2012 and linked them to cancer registries found the risk is not the same for all cancers.

People with type 1 diabetes are indeed more likely than the general population to develop cancers of gastric organs and the kidneys, as well as endometrium and ovaries for women.


But the researchers also found that other sex-specific cancers, including prostate and breast, were significantly less common among people with type 1 diabetes and concluded that the overall risk for people with type 1 diabetes is moderate.

They pointed out that while diabetes has been tied generally to increased cancer risk in the past, studies have relied mostly on data from people with type 2 diabetes, which develops slowly, usually in adults who are overweight or obese.

“People with diabetes and those with cancer have many common risk factors, including obesity, poor diet, physical inactivity and smoking,” said study co-author Jessica Harding of the Baker IDI Heart and Diabetes Institute in Melbourne, Australia.

“However, the overall excess cancer risk among type 1 diabetes is moderate. People with type 1 diabetes should not be alarmed about the results from this study but follow current guidelines for cancer prevention and participate in national screening programs as per the general population,” she added.

The study identified 9,149 first incidences of cancer in the diabetic patients, half of which happened before age 51. Compared to the general population for the same time period, men with type 1 diabetes had a similar rate of cancer diagnosis overall, and women with type 1 diabetes were about seven percent more likely to be diagnosed with cancer.

Cancers of the stomach, liver, pancreas, endometrium and kidney were about 25% to 50% more common among people with type 1 diabetes, though breast cancers were 10% less common and prostate cancers were 56% less common.

The researchers found that the biggest risk increase for liver cancer in men, which was twice as common in those with type 1 diabetes, and 78% more common in women with diabetes.

“The risk of some cancers is altered slightly among people with type 1 diabetes but not enough to cause serious concern,” said co-author Sarah Wild, who researches diabetes and cardiovascular disease at The University of Edinburgh in Scotland.

“One question that the work addresses is whether long-term insulin treatment increases the risk of cancer and the good news is that there does not appear to be a strong effect,” she explained.

But she added that the pattern of cancers is similar to that seen with people that are overweight or have type 2 diabetes, although the changes in risk are smaller, so weight may play a role.

She pointed out that the apparent reduction in breast cancer among women with type 1 diabetes needs confirming but may be related to different patterns of child bearing. The cancer risk was highest shortly after diabetes diagnosis.

“This could happen if the cancer caused symptoms that meant people received a test for diabetes before the cancer was diagnosed, because liver and pancreatic cancers can cause diabetes and also because people with newly diagnosed diabetes will be seeing doctors and nurses frequently and so may report symptoms and get cancers picked up earlier than people without diabetes,” Wild added.

The opinions expressed in this article do not necessarily reflect the views of the Community and should not be interpreted as medical advice. Please see your doctor before making any changes to your diabetes management plan.

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