Clinical

Preexisting diabetes raises mortality risk after cancer diagnosis

Last Updated: 2008-12-17 18:05:35 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Patients with diabetes are at increased risk of all-cause mortality during long-term follow-up after a diagnosis of cancer, according to a meta-analysis published in the Journal of the American Medical Association for December 17.

"Diabetes mellitus appears to be a risk factor for some cancers," reports the research team at Johns Hopkins Medical Institutes in Baltimore, "but the effect of preexisting diabetes on all-cause mortality in newly diagnosed cancer patients is less clear."

In their review of the literature, senior author Dr. Frederick L. Brancati and colleagues identified 48 studies that compared survival in cancer patients with and those without preexisting diabetes that included at least 3 months of follow-up. Most studies reported decreased survival associated with diabetes, and none "reported that diabetes was associated with significantly better survival."

Their meta-analysis involved 23 studies of various types of cancer analyzed by regression models that included estimates of risk and precision. Pooled data showed that diabetes was associated with a hazard ratio of 1.41 for the risk of all-cause mortality compared with patients without diabetes.

Risk was elevated for all types of cancers analyzed - endometrium, breast, prostate, gastric, colorectal, hepatocellular, lung and pancreas. The association was statistically significant for cancers of the endometrium (HR 1.76), breast (HR 1.61), and colorectum (HR 1.32).

Dr. Brancati's team speculates that "cancer patients with diabetes may have increased tumor cell proliferation and metastases in a physiologic environment of hyperinsulinemia and hyperglycemia." Another potential contributor to worse outcomes could be worse response to treatments, such as increased infection risk and intraoperative mortality.

On the other hand, the possibility exists that diabetics may be treated less aggressively for their cancer, the authors suggest, or else appropriate management of glycemia, blood pressure, and lipids may be neglected when cancer treatment is top priority.

"If a clinical or biological interaction between diabetes and cancer care is confirmed," the research team concludes, "subsequent trials should test whether improvements in diabetes care for patients with newly diagnosed cancer might reduce long-term mortality."

JAMA 2008;300:2754-2764.