Cancer Risk Higher With Type 1 Diabetes
Overall Increase Is Modest, but Study Shows Double the Stomach Cancer Risk
Nov. 2, 2003 -- 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 Surprise
Type 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
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
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
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
"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."
The 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