Study: High Insulin Doses May Increase Cancer Risk in Patients With Type 1 Diabetes

For patients with type 1 diabetes, higher insulin doses may be associated with increased cancer incidence, according to a new study in the Journal of the American Medical Association (JAMA) Oncology led by Dr. Yuanjie Mao. Working with epidemiologist at Merck Research Labs, Wenjun Zhong, PhD, the researchers analyzed 28 years of data on 1303 patients with type 1 diabetes.

The researchers studied the association of 50 common risk factors, including smoking, exercise, metabolic risk factors, medication use, and family history of cancer in patients with type 1 diabetes.

“In patients with type 1 diabetes, our results show that traditional metabolic factors such as obesity (represented by body mass index), sugar control (represented by hemoglobin A1c), and blood pressure control do not associate with cancer incidence,” Mao said in a press release. “However, cancer incidence was higher for those who took larger dose of insulin. Our results implied that clinicians might need to balance the potential cancer risk when treating patients with type 1 diabetes on a high daily insulin dose or that improving insulin sensitivity may be preferred than simply increasing the insulin dose.”

The investigators used data from The Diabetes Control and Complications Trial (DCCT), along with its follow-up, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, conducted by the National Institute of Diabetes and Digestive and Kidney Diseases Central Repository.

In the DCCT, 1441 patients with type 1 diabetes were randomized into conventional diabetes therapy or intensive therapy. Researchers tested whether reducing hyperglycemia lowered complication risks in type 1 diabetes.

The researchers classified daily insulin dose as low (less than 0.5 units/kg per day), medium (between 0.5 units/kg per day and 0.8 units/kg per day), or high (greater than or equal to 0.8 units/kg per day). Within the low, medium, and high groups, cancer incidence was 2.11, 2.87, and 2.91, respectively, per 1000 people, showing that high insulin dose was directly associated with a greater risk of cancer.

Daily insulin doses were found to pose a greater risk of cancer in participants than factors of age. However, the study found that women in the analyzed cohort had a greater risk of developing cancer than men, but not all the risk factors are known.

“We know that people with type 1 diabetes have a higher incidence of cancer compared to people without diabetes,” said Liz Beverly, PhD, co-director of the Diabetes Institute and professor at Heritage College, in a press release. “Dr. Mao’s research identifies a potential mechanism to explain this association. His findings will lead to continued research in this area and potential policy changes in cancer screening and insulin dosing recommendations.”

This is the first study to look at cancer incidence factors for type 1 diabetics, according to the authors. Although previous research found that patients with diabetes face higher cancer risks, Mao said further investigation needs to be done exploring insulin dose and cancer.

“Type 1 diabetes accounts for an estimated five to 10 percent of all diabetes cases, and recent studies in type 1 diabetes also found a higher incidence of certain cancers such as stomach, liver, pancreas, endometrium and kidney cancers in the population compared with the general population,” Mao said.

Reference

JAMA study, led by Heritage College faculty, finds association between high insulin dosage and cancer. EurekAlert! July 29, 2022. Accessed Aug. 1, 2022. https://www.eurekalert.org/news-releases/960395