HealthDay News — Daily insulin dose is associated with cancer risk among individuals with type 1 diabetes, according to a research letter published online in JAMA Oncology.

Wenjun Zhong, PhD, from Merck Research Labs in West Point, Pennsylvania, and Yuanjie Mao, MD, PhD, from the Diabetes Institute at Ohio University in Athens, examined the incidence of cancer among individuals with type 1 diabetes during a 28-year follow-up period. The researchers used data for 1441 patients in North America who were enrolled in the Diabetes Control and Complications Trial and the Epidemiology of Diabetes Interventions and Complications study. By year 18, 1304 patients had completed the annual cancer history update. One patient was excluded due to a previous cancer diagnosis.

The researchers found that 7% of the patients in the cohort had cancer diagnoses after a total of 33,813 person-years of follow-up, with an incidence rate of 2.8 per 1000 person-years. Of the 93 patients with cancer, 61% and 39% were female and male, respectively. Overall, 9%, 33%, and 58% developed cancer within 10 years, between 11 and 20 years, and between 21 and 28 years, respectively. In the multivariable model, daily insulin dose remained associated with cancer incidence (hazard ratio, 5.93). In the low-, medium-, and high-dose groups, cancer incidence was 2.11, 2.87, and 2.91 per 1000 person-years, respectively.

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“The association found may be subject to residual confounding and was not necessarily causal,” the authors write. “Larger studies in type 1 diabetes are needed to validate this association.”

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