Metformin could improve health outcomes of diabetes patients with breast cancer

People with diabetes who also have breast cancer could live for longer following treatment with metformin, research suggests.
This international study also reported that metformin could improve the prognosis for breast cancer patients with diabetes who are treated with insulin.
Metformin, a commonly prescribed type 2 diabetes drug, has been shown in previous studies to improve health outcomes in people with cancers, and may even block the growth of cancer.
Scientists wanted to determine if metformin could improve outcomes of patients with diabetes who had human epidermal growth factor receptor 2 (HER2)-positive primary breast cancer.
They performed an analysis of the ALTTO breast cancer trial, in which 8,381 patients who tested positive for breast cancer received different combinations of drugs.
In this particular substudy, 260 people with diabetes were treated with metformin; 186 were not.
These participants were all measured for disease-free survival and overall survival compared to breast cancer patients who did not have diabetes.
Diabetes patients treated with metformin had better health outcomes relating to their cancer than those not treated with the drug.
Additionally, metformin had a positive effect on insulin-treated patients with breast cancer.
The researchers explained: “Whereas insulin treatment was associated with a detrimental effect, metformin had a [beneficial] effect in patients with diabetes who had HER2-positive and hormone receptor-positive breast cancer.”
The researchers conclude that patients with diabetes and HER2-positive early breast cancer may be able to reduce the likelihood of the worst-case scenario by taking metformin.
The study has been published online in the Journal of Clinical Oncology.