Type I Diabetes Raises Risk For Certain Cancers
According to new research published in the journal Diabetologia, Type I diabetes may increase the risk for some forms of cancer but lower the risk for others.
Type I diabetes occurs when the pancreas is unable to produce the hormone insulin, resulting in high blood glucose levels, or hyperglycemia, and accounts for around 5% of all diabetes cases.
Type I Diabetes is most commonly diagnosed in children and young adults.
The condition is primarily managed through multiple daily injections with insulin pens, syringes or an insulin pump.
According to study co-author, Dr. Stephanie Read, of the Usher Institute of Population Health Sciences & Informatics at the University of Edinburgh in the UK, and colleagues, previous studies suggested that individuals with diabetes have a 20-25% greater risk of getting cancer than those without diabetes.
They also point out, however, that those studies primarily consisted of individuals who had Type II Diabetes, as that it is the most common form of diabetes, accounting for 90-95% of all cases. The association between Type I Diabetes and cancer is therefore less clear.
The authors noted that “It is possible that the relationship between Type I Diabetes and cancer is different from that observed between Type II Diabetes and cancer as a result of differences in the underlying disease characteristics, drug therapies and patterns of risk factors, such as obesity.”
For this reason, Dr. Read and colleagues compared cancer incidence among individuals with Type I Diabetes across 5 countries, with the aim of gaining a better understanding of the link between the two conditions.
Increased Risk of Site-Specific Cancers
Researchers identified individuals under the age of 40 with Type I Diabetes via nationwide diabetes registers from 5 countries; Australia, Denmark, Finland, Scotland and Sweden. These individuals were monitored for cancer incidence, and 9,149 cancers across 3.9 million person-years were identified.
This data was linked with information from national cancer registries in each of the countries, allowing for comparisons between the cancer incidence of people with Type I Diabetes with that of the general public.
Looking at the overall cancer risk, researchers found that men with Type I Diabetes were not at higher risk than those without the condition. Women with Type I Diabetes however, were found to have a 7% greater overall cancer risk than those without Type I Diabetes.
As far as specific cancers go, researchers found that men with Type I Diabetes were 23% more likely to develop stomach cancer, while women with Type I Diabetes were at 78% greater risk for the disease, compared with the general public.
Both men and women with Type I Diabetes were also at greater risk for cancers of the liver (two-fold for men, 55% for women), pancreas (53% for men, 25% for women) and kidney (30% for men, 47% for women), while women also had a 42% increased risk for endometrial cancer.
Lower Risk of Prostate, Breast Cancers
Some possibly good news though is that according to the research, women with Type I Diabetes had a 10% reduced risk of breast cancer, while men with Type I Diabetes had a 44% reduced risk of prostate cancer.
According to the team, this may explain why no increased overall cancer risk was identified among men with Type I Diabetes.
While the authors cannot explain exactly why Type I Diabetes was associated with a lower risk of breast and prostate cancers, they do have some theories:
- The reduced risk of breast cancer among women with Type I Diabetes in the study could be down to the younger cohort, which consisted of fewer post-menopausal women among whom breast cancer is most common.
- The lower risk of prostate cancer identified, the researchers speculate, could be down to lower testosterone levels often found among men with Type I Diabetes.
“Higher testosterone levels were previously shown to lead to an increased risk of prostate cancer, while hyperglycemia has also been shown to inhibit testosterone production,” the authors explain.
According to the researchers, the risk of cancer was highest in the first year after a diabetes diagnosis; cancer incidence was 2.3 times higher for both men and women in the 12 months after being diagnosed with Type I Diabetes.
The team suggests that this finding is likely down to identification of pre-existing cancers soon after a diabetes diagnosis rather than a result of diabetes itself, noting that cancers are more likely to be detected when a patient is receiving more medical attention.
Previous studies have suggested that insulin therapy may be to blame for increased cancer risk for diabetes patients, but Dr. Read and colleagues say their findings indicate this is not the case.
They explain that if insulin treatment was a key risk factor for cancer, their results would have shown a higher cancer incidence for people with Type I Diabetes than those with Type II, given that a significantly smaller number of people with Type II Diabetes are treated with insulin.
“Furthermore, the absence of an association between overall or site-specific cancer risk and increasing duration of diabetes in our study does not support a dose-response relationship between exogenous insulin use and cancer incidence,” they add.