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What Comes First, Diabetes or Cancer?

Jul 28, 2018
 

Diabetes after cancer: new study shows that within the first two years of a diagnosis of cancer, the risk for type 2 diabetes increases.

Cancer is a global burden for clinical and public health systems, with 14 million newly diagnosed cases in 2012.  Early detection and improved treatment have increased survival in many types of cancer, making long-term quality of life a consideration in patient management. Chronic comorbidities, including diabetes, are key determinants of quality of life in cancer. Diabetes, a major risk factor of cardiovascular disease, is the main cause of noncancer mortality among cancer survivors and is associated with increased mortality in patients with cancer.

While multiple studies have established that diabetes is a risk factor for the development of several types of cancer and a prognostic factor for cancer-related mortality, a limited body of evidence suggests that cancer can increase the risk of developing new cases of diabetes, especially after pancreatic, colorectal, and breast cancer.  Current studies, however, are limited by small sample sizes or by restriction to specific cancer types. Furthermore, obesity, physical inactivity, and smoking are common causes of diabetes and cancer, but few studies have information on diabetes risk factors prior to the development of cancer and are unable to separate the specific contribution of cancer or cancer-related therapies to the development of diabetes.

So, this study was done and the researchers followed 524,089 individuals in South Korea with no history of diabetes or cancer for up to 10 years, and they found the strongest association between pancreatic cancer and diabetes, followed by kidney, liver, gall bladder, lung, blood, breast, stomach, and thyroid cancers. The highest diabetes risk was detected in the first two years after cancer diagnosis.

We know that diabetes increases the risk for cancer, but now we also know that cancer increase the risk for type 2 diabetes. Diabetes, a major risk factor of cardiovascular disease, is the main cause of noncancer mortality among cancer survivors and is associated with increased mortality in patients with cancer. Although multiple studies have established that diabetes is a risk factor for the development of several types of cancer and a prognostic factor for cancer-related mortality, a limited body of evidence suggests that cancer can increase the risk of developing new cases of diabetes, especially after pancreatic, colorectal, and breast cancer.

Over a median sweven years of follow-up for 494,189 individuals (mean age, 41.8 years; 50% women), 15,130 patients developed cancer and 26,610 developed diabetes.  Of those who developed diabetes, 834 patients had previously been diagnosed with cancer.

The study end-point was the development of diabetes. Participants were included in the study at the baseline screening examination and were observed until the development of diabetes, death, or the end of the study period (December 31, 2013). The study exposure was cancer development, considered as a time-varying variable (participants who developed cancer contributed unexposed person-time prior to the development of cancer). Cancer cases that occurred after the development of diabetes were not included in the study because follow-up ended when a participant developed diabetes. In addition, to reduce the potential impact of surveillance bias, they excluded from the analysis cases of diabetes that occurred in the first 31 days after cancer diagnosis (n = 72) by censoring observation time for these individuals at the time of cancer development.

Cancer appeared associated with an increased risk for subsequent diabetes after adjustment for age, sex, precancer diabetes risk factors, metabolic factors, and comorbidities. Diabetes risk appeared highest the first two years following cancer diagnosis. However, it remained elevated throughout the follow-up period.

From the results it was concluded that cancer development was associated with an increased risk of diabetes. This increase was evident after the development of pancreatic, kidney, liver, gallbladder, lung, blood, breast, stomach, and thyroid cancers.

Practice Pearls:

  • The excess risk for diabetes after cancer development was higher in the first two years after cancer diagnosis, although it persisted throughout the duration of follow-up.
  • As medical professionals, we need to remember that patients with cancer develop other clinical problems, such as diabetes, with higher frequency than individuals without cancer.
  • Consider routine diabetes screening in your cancer patients.

JAMA Oncol. Published online June 7, 2018. doi:10.1001/jamaoncol.2018.1684