Nine percent of all cancer patients had diabetes at diagnosis. The prevalence of diabetes was highest among patients with pancreatic or uterine cancer, 19% and 14%, respectively. The lowest prevalence was in older men with prostate cancer or non-Hodgkin's lymphoma.

Patients with diabetes were more often diagnosed with a higher tumor stage than non-diabetics. In addition, diabetics were treated less aggressively for cancer, including less chemotherapy and radiation therapy than those without diabetes.

Overall, 3902 of 5555 cancer patients with diabetes and 29,909 of 52,943 cancer patients without diabetes died during follow-up. "After adjusting for the confounding effects of different stage at diagnosis, age, gender, treatment and even cardiovascular disease, we found that patients with diabetes experienced a significant increase in overall mortality, ranging from 0 to 40% for different types of cancer, compared to those without diabetes," the investigators conclude.

"With the ageing of the population, the number of persons who suffer from more than one chronic disease is increasing," the researchers added.

"As a consequence, more and more patients require a multidisciplinary approach for their multiple diseases. One disease with its specific treatment can influence the treatment and prognoses of other comorbid conditions."