More studies are needed to better understand whether there is a cause and effect link between metformin and cancer, or whether the increased risk is due to a lack of protection from metformin, Sandler said.
The results were published in the Annals of Oncology on January 29th.
Metformin has been hailed as a miracle for many diseases other than diabetes. Some research has linked it to longer lifespan, reduced risk of vision loss, and improved fertility in both men and women.
The new study doesn’t suggest that women without diabetes should take metformin to lower their risk of breast cancer, said Dr. Pamela Goodwin, co-author of an editorial that accompanied the study. She is Professor of Medicine at the University of Toronto and former Director of the Marvelle Koffler Breast Center at Mount Sinai Hospital in Toronto.
More research is needed to fully understand the link between diabetes and breast cancer and what role metformin might play, Goodwin said.
Losing weight and regular physical activity can help lower your risk of diabetes, she said, adding that it could also have benefits for breast cancer risk.
“If you have type 2 diabetes, you are being treated properly, and in many cases it means taking metformin. Make sure you also get regular mammograms,” Goodwin said.
Dr. Sarah Cate, director of the Special Monitoring and Breast Program at Blavatnik Family-Chelsea Medical Center on Mount Sinai in New York City, reviewed the results.
“Of course, metformin helps you lose weight, which is related to estrogen-related breast cancers. This could explain why fewer patients on metformin have this type of breast cancer,” she said.
Both Cate and Goodwin stated that the finding on triple negative breast cancer needs to be substantiated.
“The number of patients with triple negative breast cancer has been low, so we cannot draw any practice-changing conclusions,” said Cate.
More information
Breastcancer.org has more information on risk factors for breast cancer.
SOURCES: Dale Sandler, PhD, Head of Epidemiology, US National Institute for Environmental Health Sciences, Research Triangle Park, NC; Pamela Goodwin, MD, MSc, Professor of Medicine at the University of Toronto and former Director of the Marvelle Koffler Breast Center at Mount Sinai Hospital in Toronto; Sarah Cate, MD, Assistant Professor, Surgery, Icahn School of Medicine, Mount Sinai, New York City, and Director, Special Monitoring and Breast Program, Blavatnik Family-Chelsea Medical Center, Mount Sinai, New York City; Annals of Oncology, January 29, 2021
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