Metformin is one of the oldest and most tried-and-true diabetes treatments around, but apparently it has a new talent. According to research from the M.D. Anderson Cancer Center at the University of Texas, good ol’ metformin reduces a type 2 person’s risk of pancreatic cancer by 62 percent.
This is great news for people with diabetes, whose risk of developing pancreatic cancer is higher than that of people without diabetes. Lowering that risk is definitely worthwhile, especially because pancreatic cancer is the most virulent form of cancer and has the lowest survival rate: Only 20 percent of people diagnosed with it live past the one-year mark, and only 5 percent reach the five-year mark.
Metformin was first marketed in France in 1979, but was not approved by the FDA for sale in the United States until 1994. The following year, Bristol-Meyers Squibb introduced it under the brand name Glucophage. Today metformin is available as a generic, and doctors write approximately 35 million prescriptions for it each year in this country.
Metformin is frequently described as a “first-line” drug because it is the drug most often prescribed for newly diagnosed type 2 patients, usually when they are overweight and demonstrate insulin resistance. It works by increasing cellular sensitivity to insulin while simultaneously decreasing the amount of insulin circulating in the body.
Those effects are crucial because some scientists believe that insulin may actually promote cancer cell growth. By lowering insulin levels, metformin reduces the risk that the hormone will abet the development of cancerous growths.
In their four-year study, conducted from 2004 to 2008, the researchers studied 1,838 participants, including 973 patients with pancreatic adenocarcinoma (a malignant gland tumor). People with diabetes were divided into four groups according to the type of anti-diabetes drug they were taking: insulin or insulin secretagogues; metformin; TZDs (thiazolidinediones); or “other” common diabetes drugs.
Type 2s who took metformin, either alone or in combination with other drugs, experienced a 62 percent reduction in their risk of developing pancreatic cancer compared to those who never used the drug. Interestingly, common diabetic risk factors, such as smoking, obesity, and poor glycemic control, did not significantly affect the overall risk reduction experienced by metformin users.
The study also found, however, that people with diabetes who had previously taken insulin or insulin secretagogues ran, respectively, a 4.99-fold and a 2.52-fold increased risk for pancreatic cancer compared to people who had never used insulin.
The Texas researchers’ interest in metformin’s cancer-preventive properties was inspired by an animal study showing that the drug prevented pancreatic tumors. The researchers were also encouraged by several epidemiological studies of people with diabetes showing that metformin reduced the risk of any kind of cancer. Their findings, which will have to be confirmed by a much larger research sample, could lead to the use of metformin as a “chemopreventive,” an agent employed to thwart the onset of cancer.
Results of the study, which was led by Prof. Donghui Li, PhD, of the Department of Gastrointestinal Medical Oncology at M.D. Anderson, were published in the August 1 issue of Gastroenterology.