Cancer Risk Higher With Type 1 Diabetes

By Salynn Boyles People with type 1 diabetes are at increased risk for developing certain cancers, say Swedish researchers. Researchers from Stockholm’s Karolinska Institute found that people with type 1 diabetes had a modest overall increase in cancers compared with people without diabetes. But they had nearly double the risk for developing stomach and cervical cancer and almost three times the risk for developing cancer of the uterus.

People with type 1 diabetes are at increased risk for developing certain cancers, say Swedish researchers.Researchers from Stockholm’s Karolinska Institute found that people with type 1 diabetes had a modest overall increase in cancers compared with people without diabetes. But they had nearly double the risk for developing stomach and cervical cancer and almost three times the risk for developing cancer of the uterus.The population-based study is published in the Dec. 3 issue of the Journal of the National Cancer Institute.Difference Is No SurpriseType 2 diabetes has been linked to an increased risk for cancers of the liver, pancreas, kidney, and uterus, but until now little has been known about the cancer risks associated with type 1 diabetes. Previous studies examining the question have been small and had short follow-up times.In this study, lead researcher Kazem Zendehdel and colleagues used a Swedish national health registry to track cancer incidence over time among people with type 1 diabetes.Study investigator Weimin Ye, MD, PhD, tells WebMD that it is no surprise that, with the exception of uterine cancer, the malignancies linked to type 1 diabetes differed from those associated with type 2 disease.That is because the two diabetes types have different metabolic and hormonal characteristics. Type 2 diabetes is associated with increased circulating insulin levels, whereas type 1 patients tend to have very low or no circulating insulin levels. This increase in insulin is believed by many to play a role in certain cancers linked to type 2 diabetes, especially pancreatic cancer.Obesity Also Implicated”We thought we would see a difference in the cancer-risk profile in patients with type 1 diabetes, and that is what we found,” Ye says. “The fact that we did not find an increase in pancreatic cancers suggests that circulating insulin is involved in the promotion of this cancer.”National Cancer Institute director of cancer prevention Peter Greenwald, MD, says while circulating insulin may play a role in pancreatic cancers associated with type 2 diabetes, obesity is also a likely cause. Obesity is a major cause of type 2 diabetes, and a recent study showed that obesity plays a role in 20% of all cancers in women and 14% of cancers in men.”Obesity substantially increases the risk of (type 2) diabetes and many types of cancer,” he tells WebMD. “So it stands to reason that there would be a link between the two.”20% IncreaseThe study included slightly more than 29,000 Swedes under the age of 30 hospitalized for type 1 diabetes between 1965 and 1999. Patients were followed for an average of 14 years, and cancers diagnosed within one year of hospitalization were excluded from the total.The remaining 355 cancers identified in the type 1 diabetes patients corresponded to a 20% overall increase in cancers expected among the general, age-matched population. Ye says the biggest surprise was that people with diabetes had double the expected number of stomach cancers. One possible explanation for this is the high numbers of Helicobacter pylori infection among people with type 1 diabetes. Inflammation caused by H. pylori — the bacteria that causes stomach ulcers — is believed to play a role in stomach cancer.The Karolinska Institute researchers plan to continue following the patients as they age to learn more about their specific cancer risks.The research indicates that people with type 1 diabetes need to discuss their cancer risk with their doctors and be vigilant about following through with routine cancer screening, such as Pap smears to check for cervical cancer.