Diabetic patients with ovarian cancer who took the drug metformin for their diabetes had a better survival rate than patients who did not take it, a study headed by Mayo Clinic shows.

The findings, published early online in the journal Cancer, may play an important role for researchers as they study the use of existing medications to treat different or new diseases.

Metformin is a widely prescribed drug to treat diabetes, and previous research by others has shown its promise for other cancers. The Mayo-led study adds ovarian cancer to the list.

Researchers compared the survival of 61 patients with ovarian cancer taking metformin and 178 patients who were not taking metformin.

Sixty-seven percent of the patients who took metformin were surviving after five years, compared with 47 percent of those who did not take the medication.

When the researchers analyzed factors such as the patients’ body mass index, the severity of the cancer, type of chemotherapy and quality of surgery, they found that patients taking metformin were nearly four times likelier to survive, compared with those not taking the medication.

“Our study demonstrated improved survival in women with ovarian cancer that were taking metformin,” says co-author Sanjeev Kumar, M.B.B.S., a Mayo Clinic gynecologic oncology fellow. “The results are encouraging, but as with any retrospective study, many factors cannot be controlled for us to say if there is a direct cause and effect. Rather, this is further human evidence for a potential beneficial effect of a commonly used drug which is relatively safe in humans. These findings should provide impetus for prospective clinical trials in ovarian cancer.”

The results may pave the way for using metformin in large-scale randomized trials in ovarian cancer, researchers say.

Given the high mortality rate of ovarian cancer, researchers say there is a great need to develop new therapies for ovarian cancer. Metformin may potentially be one of these options.