Is There a Link Between High Insulin Dosage and Cancer?

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A study looking at the correlation between daily insulin dose and cancer incidence among patients with type 1 diabetes found that higher insulin dose is positively associated with cancer incidence and that the association is stronger among those with insulin resistance. The results were published by Zhong and Mao as a research letter in JAMA Oncology.

Study Details

“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,” said coauthor Yuanjie Mao, MD, PhD, of the Diabetes Institute, Ohio University, Athens, who led the study. “However, cancer incidence was higher for those who took larger doses 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 to simply increasing the insulin dose.”

Dr. Mao collaborated with Wenjun Zhong, PhD, an epidemiologist at Merck Research Labs in West Point, Pennsylvania, to explore the associations of more than 50 common risk factors (eg, smoking, alcohol use, exercise, metabolic risk factors, medication use, and family history) with cancer incidence in 1,303 patients with type 1 diabetes whose data were collected over 28 years. They performed a statistical analysis of data acquired from the Diabetes Control and Complications Trial (DCCT) and its follow-up, the Epidemiology of Diabetes Interventions and Complications study, conducted by the National Institute of Diabetes and Digestive and Kidney Diseases Central Repository. The DCCT was a controlled clinical trial that included 1,441 patients with type 1 diabetes who were randomly assigned to receive conventional diabetes therapy or intensive therapy, to assess whether reducing hyperglycemia would decrease the risk of complications of type 1 diabetes.

Additional Findings

The investigators also found that age and sex are associated with cancer incidence when evaluated separately and that a daily insulin dose posed a higher risk of cancer than age, especially a higher insulin dose. According to the paper, when the daily insulin dose is classified into three groups: low (< 0.5 units/kg), medium (≥ 0.5 units/kg or < 0.8 units/kg), and high (≥ 0.8 units/kg), the hazard ratios were significantly higher in the high-dose vs the low-dose group. Cancer incidence was 2.11, 2.87, and 2.91 per 1,000 persons in the low, medium, and high insulin dose groups, respectively.

Dr. Mao went on to explain that specifically, women carry a higher risk than men. However, it was unclear what risk factors may contribute to the higher cancer incidence in type 1 diabetes.

Although previous studies have concluded that patients with diabetes have a higher risk of cancer in general, this is the first study to explore the associated cancer incidence factors in type 1 diabetes. 

“Type 1 diabetes accounts for an estimated 5% to 10% 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,” Dr. Mao noted. “In type 2 diabetes, increased risk is attributed to metabolic factors such as obesity, chronic inflammation status, and insulin resistance.”

Although the results of the study suggest that the higher the dose of insulin, the higher the cancer incidence, Dr. Mao says further investigation is still necessary.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.