Breast Cancer Risk Increased in Early Diabetes

 A case-control study drawing on data from Sweden's extensive birth-to-death population registry and a national prescription registry showed that diabetes was associated with a nearly 40% increase in risk for breast cancer, reported Hakan Olsson, MD, a professor in the departments of oncology and cancer epidemiology at Lund University in Lund, Sweden.

Dr. Olsson stated that, "There is a link between diabetes and breast cancer even after adjusting for obesity and abnormal blood lipids, especially seen within 4 years of a cancer diagnosis."

The authors also found a significant association between overall cancer risk among patients with diabetes who used the long-acting insulin analogue insulin glargine.

The oral antidiabetic agent metformin, in contrast, was associated with a trend toward lower cancer risk among people with diabetes, but this finding was not statistically significant.

The insulin findings, however, seem to contradict those of a meta-analysis also presented December 7 at the International Diabetes Federation (IDF) World Diabetes Congress 2011. That study, which included data from observational studies and randomized, controlled trials, found no additional cancer associated with the use of long-acting insulin, according to a Sanofi spokesperson.

The evidence for a link between diabetes and breast cancer risk, on the other hand, appears to be strong, commented Jennifer A. Ligibel, from the Division of Breast Oncology at the Dana Farber Cancer Institute in Boston, Massachusetts. "I think this work is very important as we try to better understand the relationship between obesity, which is unfortunately a growing health problem here in the US and around the world, and its link to cancer," Dr. Ligibel said.

Dr. Olsson and colleagues looked at data on 2724 case-patients with cancer and 20,542 controls (matched for age, sex, and residence) from outpatient and inpatient population-based registries to explore the relationship between cancer, diabetes, obesity, and/or abnormal blood lipids.

34th Annual San Antonio Breast Cancer Symposium (SABCS): Abstract P1-08-06. Presented December 8, 2011