Hormone therapy for breast cancer more than doubles a woman’s risk for developing type 2 diabetes, results of a case-cohort study suggest.
Hormone therapy with tamoxifen was associated with a more than twofold increase in risk of diabetes, and aromatase inhibitors were associated with a more than fourfold increase, reported Hatem Hamood, MD, of Leumit Health Services in Karmiel, Israel, and colleagues.
Among 2,246 women with breast cancer and no diabetes at baseline, followed for a mean of 5.9 years (longest follow-up 13 years), the crude cumulative lifetime incidence rate of diabetes was 20.9%, the investigators wrote. The report was published in the.
“[Hormone therapy] is a significant risk factor of diabetes among breast cancer survivors. The underlying mechanism is unclear, and additional research is warranted. Although cessation of treatment is not recommended and progression of breast cancer often is inevitable, devised strategies aimed at lifestyle modifications in patients at high risk of diabetes could at least preserve the natural history of breast cancer,” they wrote.
Diabetes has previously been identified as a possible risk factor for breast cancer, but the potential for breast cancer therapy as a precipitating factor for diabetes is uncertain, the authors said.
“Given the detrimental impact of diabetes on breast cancer survival, additional exploration of the role of breast cancer treatment in the development of diabetes is important not only because it would add valuable information on the etiology of diabetes but also because it would help to identify high-risk patients in need of accentuated clinical care,” they wrote.
To explore the possible association between hormone therapy and diabetes risk, the investigators performed a retrospective case-cohort study of 2,246 women who had been diagnosed with primary nonmetastatic breast cancer treated with hormone therapy from 2002 through 2012.