Kristina Ranc, of the University of Copenhagen in Denmark, and colleagues examined data from a national registry of all patients diagnosed with cancer from 1995–2009. The authors sought to compare mortality rates among cancer patients with and without diabetes.
The researchers found that mortality rates were higher for cancer patients with diabetes than for cancer patients without diabetes. The highest mortality rates were observed among patients with diabetes who were treated with insulin. For insulin-treated patients with diabetes for two years at the time of diagnosis of any type of cancer, mortality rate ratios were 3.7 (95% confidence interval [CI], 2.7–5.1) for men and 4.4 for women (95% CI, 3.1–6.5) at one year after cancer diagnosis, and increased to 5 (95% CI, 3.5–7.0) for men and 6.5 (95% CI, 4.2–9.3) for women at nine years after cancer diagnosis. Mortality rates also were higher among patients receiving oral hypoglycemic agents for diabetes.
“In conclusion, our study provides strong support for the notion that pre-existing diabetes increases mortality among cancer patients, and that the excess mortality is larger among patients with diabetes treated with oral hypoglycemic agents or, particularly, insulin,” the authors write.