Researchers uncover link between breast cancer treatment and type 2 diabetes

Tamoxifen is one of the most widely prescribed drugs to prevent a recurrence of breast cancer in women who have been treated for the condition, but new research suggests that the drug may contribute to an increased risk of developing type 2 diabetes.

The University of Toronto researchers who conducted the study said that no one taking tamoxifen should discontinue their use of the medication, but they and their doctors should be aware of the association.

For the study, the researchers examined the medical records of more than 14,000 individuals being treated for breast cancer, some of whom were taking tamoxifen. The results, which were published in the journal Cancer, showed that tamoxifen patients are 25 percent more likely to develop type 2 diabetes.

"Current tamoxifen therapy is associated with an increased incidence of diabetes in older breast cancer survivors," the researchers wrote in their report. "These findings suggest that tamoxifen treatment may exacerbate an underlying risk of diabetes in susceptible women."

They added that it is unlikely that tamoxifen is directly responsible for new diabetes cases. Rather, many of the women who developed the condition after being treated with the drug likely had preexisting risk factors like obesity or a family history of diabetes. Tamoxifen may amplify the effects of these susceptibilities.

The findings could have important implications for many women. More than 500,000 individuals are currently taking the drug to prevent a recurrence of breast cancer. These women may benefit from taking proactive steps to prevent type 2 diabetes, such as eating a healthy diet that is low in fat and getting plenty of exercise.

Additionally, until the extent of the relationship between tamoxifen and type 2 diabetes is determined, doctors may want to consider whether or not their patients have metabolic risk factors before starting them on the medication. The researchers said more analysis is needed to fully understand the link between tamoxifen treatment and type 2 diabetes.