A new study from Public Health Sciences Division researchers found that breast cancer survivors with a history of diabetes have a two-fold increased risk of developing breast cancer in their opposite breasts. These findings—the first of their kind—showed the risk was most pronounced among women diagnosed with their first breast cancer before age 60. The study was published online July 13 in the journal Breast Cancer Research and Treatment.
Contralateral breast cancer is an outcome of considerable concern to breast cancer survivors, as they have a two to six times greater risk of developing a second primary contralateral breast cancer than women in the general population have of first developing breast cancer. Diabetes is only modestly related to breast cancer incidence and mortality, and the association seen here with contralateral breast cancer is much stronger than these relationships. No prior studies have assessed the relationship between diabetes and second breast cancers.
“While adjuvant hormonal therapy can reduce contralateral breast cancer risk by 47 percent, other risk factors for contralateral breast cancer are not completely understood,” said Dr. Christopher Li, primary author of the study.
Li, along with Drs. Janet Daling, Mei-Tzu Tang and Kathi Malone, evaluated data from nearly 1,000 survivors of invasive estrogen receptor positive breast cancer.
“Identification of risk factors for second contralateral tumors is of clinical and public health importance given the ever growing number of breast cancer survivors,” Li said. “If other studies confirm this relationship between diabetes and second breast cancers, efforts to insure that diabetic breast cancer survivors are carefully screened for cancer may be warranted.”
This research was supported by the National Cancer Institute.