Hormone Therapy for Breast Cancer May Cause Diabetes

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It was unknown whether breast cancer treatment plays a causal role in the onset of diabetes.
It was unknown whether breast cancer treatment plays a causal role in the onset of diabetes.

Hormone therapy may significantly increase a patient with breast cancer's risk of diabetes, according to research published in the Journal of Clinical Oncology.1

Previous research has suggested that diabetes may increase a patient's risk of developing breast cancer, though it was unknown whether breast cancer treatment plays a causal role in the onset of diabetes. For this case-cohort study, researchers enrolled 2246 patients diagnosed with non-metastatic breast cancer between 2002 and 2012 to determine whether survivors treated with hormone therapy have an increased risk of diabetes.

Three hundred and twenty-four patients developed diabetes over a mean 5.9 years. The prevalence of diabetes among breast cancer survivors increased from 6% in 2002 to 28% in 2015.

Hormone therapy was linked with a much higher risk of developing diabetes (hazard ratio [HR], 2.4). The risk was particularly high among those who received an aromatase inhibitor (HR, 4.27), though was still noted among those who received tamoxifen (HR, 2.25).

The characteristics of 259 of the patients with diabetes were compared with 311 non-cases. At baseline, patients with diabetes were more likely to be older and have less education. During follow-up, patients with diabetes had more outpatient visits, received more diabetes-promoting medication, and received hormone therapy for longer than those without diabetes.

The authors concluded that hormone therapy “is a significant risk factor of diabetes among breast cancer survivors. […] 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.”


  1. Hamood R, Hamood H, Merhasin I, Keinan-Boker L. Diabetes after hormone therapy in breast cancer survivors: a case-cohort studyJ Clin Oncol. 2018 Apr 4. doi: 10.1200/JCO.2017.76.3524 [Epub ahead of print]

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