Cancer Increases Risk of Developing Type 2 Diabetes, Study Finds

Having cancer boosts a person’s chances of later developing type 2 diabetes (T2D), even when risk factors that existed before cancer are taken into account, according to a study appearing today in JAMA Oncology.

Authors of the study, which examined health records of 494,189 people in South Korea for an average of 7 years, said the findings should alert primary care physicians to routinely screen cancer survivors for T2D. The authors speculate that some cancer-fighting drugs raise the risk of developing T2D, including corticosteroids, which are used in many regimens but raise the risk of hyperglycemia. Some chemotherapy agents also elevate blood glucose, they said.

Researchers used data from the National Health Insurance Service-National Sample Cohort, a 2.2% representative sample of the population. Under the country’s single-payer healthcare system, Koreans receive a free health screening every 1 to 2 years, when cardiovascular and diabetes risks are assessed.

By tracking diagnostic codes for patients who had been treated for cancer, researchers found a link between having the disease and being at increased risk for T2D, even after controlling for pre-existing conditions. During the study period, 15,130 participants developed cancer. Those who did were more likely to be female, to drink alcohol every day, to have a higher body mass index, and to have additional comorbidities. Of this group, the number of incident cases of diabetes seen at follow-up was 834, compared with 25,776 who developed diabetes but did not develop cancer. The overall sex- and age-adjusted hazard ratio (HR) for diabetes associated with cancer was 1.36 (95% CI, 1.26-1.45).

Cancer survivors were most at risk of developing T2D within the first 2 years after diagnosis, but their risk level remained elevated throughout the follow-up period. Risk levels varied by cancer type:

• Patients with pancreatic cancer had 5 times the risk of developing T2D (HR, 5.15; 95% CI, 3.32-7.99).
• Those with kidney cancer had twice the risk (HR, 2.06; 95% CI, 1.34-3.16), and those with liver cancer had close to twice the risk level (HR, 1.95; 95% CI, 1.50-2.54).
• Elevated risk was also seen among patients with some of the most common forms of cancer, such as lung (HR, 1.74; 95% CI, 1.34-2.24) and breast cancer (HR, 1.60, 95% CI, 1.27-2.01).
• Those with blood cancers had a significantly elevated risk (HR, 1.61; 95% CI, 1.07-2.43). Elevated risk was also seen among those who had gallbladder, thyroid, or stomach cancer.

Besides the risk of T2D posed by some of the cancer treatments, the authors noted that patients often lose weight and muscle, and many experience a loss of appetite, a condition called cancer cachexia that is associated with increased insulin resistance. Being hospitalized can trigger bouts of stress-hyperglycemia.

“Clinical studies in cancer traditionally focus on cancer progression, cancer-related mortality, and treatment-related complications but often neglect long-term consequences of cancer and its treatment,” the authors wrote. “Increased survival due to advances in cancer diagnosis and treatment, however, is driving the emphasis toward chronic disease and long-term outcomes.”

Reference

Hwangbo Y, Kang D, Kang M, et al. Incidence of diabetes after cancer development: a Korean National Cohort Study [published online June 7, 2018]. JAMA Oncol. doi: 10.1001/jamaoncol.2018.1684.