Pamela Goodwin has received hundreds of emails from patients asking if they should take a cheap, readily available drug, metformin, to treat their cancer.
It’s a fair question: Metformin, commonly used to treat diabetes, has been investigated for treating a range of cancer types in thousands of studies on laboratory cells, animals, and people. But Goodwin, an epidemiologist and medical oncologist treating breast cancer at the University of Toronto’s Mount Sinai Hospital, advises against it. No gold-standard trials have proved that metformin helps treat breast cancer—and her recent research suggests it doesn’t.
Metformin’s development was inspired by centuries of use of French lilac, or goat’s rue (Galega officinalis), for diabetes-like symptoms. In 1918, researchers discovered that a compound from the herb lowers blood sugar. Metformin, a chemical relative of that compound, has been a top type 2 diabetes treatment in the United States since it was approved in 1994. It’s cheap—less than a dollar per dose—and readily available, with few side effects. Today, more than 150 million people worldwide take the stuff.