THURSDAY, Jan. 20 (HealthDay News) -- Having both breast cancer and diabetes greatly increases the chances of dying, new research shows.
Researchers conducted a meta-analysis, or pooled analysis, of previously published studies that looked at how breast cancer patients with diabetes fared.
Six of seven studies found pre-existing diabetes was associated with significantly higher long-term, all-cause mortality. Specifically, the studies showed breast cancer patients with diabetes were nearly 50 percent more likely to die than those who didn't have diabetes.
But much remains unknown, the study authors said, noting that it was premature to conclude that diabetes prevention or improved blood glucose control would lead to a better prognosis. The data didn't look at the specific causes of death, nor does the research establish whether having diabetes actually caused more breast cancer deaths.
"It's basically a signal that there may be a stronger association between diabetes and breast cancer mortality than we have appreciated," said lead study author Dr. Kimberly Peairs, an assistant professor of medicine at Johns Hopkins University School of Medicine in Baltimore. "The next step is to determine if there is causality between diabetes and breast cancer mortality."
The study, supported by grants from the U.S. National Institutes of Health, the American Cancer Society and the National Institute of Diabetes and Digestive and Kidney Diseases, is published in the January issue of the Journal of Clinical Oncology.
The reason why breast cancer patients with diabetes are more likely to do poorly isn't known, but several studies in the meta-analysis offer some clues.
One study, for example, found that women with type 2 diabetes tended to have their breast cancer diagnosed later than those without diabetes.
Women with pre-existing diabetes may also be sick
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