We first reported that the diabetes drug metformin may reduce the risk of breast cancer in a blog post last year. Since then, additional studies continue to excite researchers about the drug’s cancer-fighting potential. And more new studies are in the works with the hope of one day putting the drug into clinical practice.

One recent study looked at the relationship between diabetes, metformin use and breast cancer among over 68,000 postmenopausal women between 50 and 79 years old. At the start of the study 3,401 women had diabetes. During the study, 3,273 invasive breast cancers were diagnosed.

Women with diabetes using medications other than metformin had a slightly higher incidence of breast cancer compared to women without diabetes. However, women with diabetes who were taking metformin were less likely to have breast cancer.

Moreover, lower rates of cancer with metformin use was seen for both estrogen receptor (ER-positive) and progesterone receptor (PR-positive), and for those that were negative for human epidermal growth factor receptor 2 (HER2-negative).

Ongoing Research

The goal for new research is to understand the biological pathway that metformin may act on. Early findings from a five-year study launched last year have researchers thinking that the key may be in metformin’s ability to lower insulin levels. They believe that lower insulin levels in turn acts on breast cancer cells by decreasing an enzyme in the cell that slows or stops the growth and proliferation of the cancer cells.

This thinking is backed by a large body of evidence linking high sugar intake, insulin resistance, obesity and metabolic syndrome to a variety of cancers including colon, pancreatic, kidney and breast cancer.

Sources:

Chicago Tribune

Journal of Clinical Oncology

American Institute for Cancer Research

Cancer Prevention