MONDAY, Dec. 3 (HealthDay News) -- Ovarian cancer may join a growing list of malignancies that seem to be slowed by a commonly prescribed diabetes drug.

Ovarian cancer patients who were taking metformin at the time of their diagnosis survived longer than patients who weren't on the drug, a new study by Mayo Clinic researchers shows.

Metformin goes by the brand name Glucophage and is derived from French lilacs. It's typically prescribed to lower blood sugar levels in people with type 2 diabetes but has shown promise as a potential anticancer agent in recent prostate, colon, pancreas, brain and breast cancer studies, as well as in lab experiments with ovarian cancer cells.

The new research, published online Dec. 3 in the journal Cancer, was a retrospective study where the scientists evaluated the medical records of ovarian cancer patients who had received their cancer diagnosis between 1995 and 2010. Sixty-one patients were taking metformin at the time of their cancer diagnosis while 178 patients -- the control group -- weren't on the medication.

The scientists reported that 67 percent of the women using metformin had not died within five years of their diagnosis, while only 47 percent of the control group had survived that long.

Overall, patients taking metformin were 3.7 times more likely to survive throughout the study than those who did not take it, the researchers said.

"Our study demonstrated improved survival in women with ovarian cancer that were taking metformin," said Dr. Sanjeev Kumar, a Mayo Clinic gynecologic oncology fellow, who also noted that the scientists took into account each patient's body mass index, cancer severity, type of chemotherapy they were taking and surgery quality.

Dr. Pamela Soliman, an associate professor in the department of gynecologic oncology at the University of Texas M.D. Anderson Cancer Center in Houston, said, "Even after controlling for all of those factors, there still showed a benefit for metformin."

Soliman was not involved with the study, but has conducted similar research in endometrial cancer cells. "This is good first evidence that maybe metformin will have a benefit to patients with ovarian cancer," she said. "There's information to gain, but I think more studies need to be done."

Scientists are still trying to better understand why metformin improves cancer outcomes. Kumar and colleagues said in the lab they have shown that if you feed ovarian cancer cells metformin, they stop dividing. In patients with diabetes, it lowers blood sugar levels and increases insulin sensitivity, two factors associated with cancer growth. Still, more research is needed to understand the biological mechanism at play, Kumar said.

According to the American Cancer Society, about 22,280 women are newly diagnosed with ovarian cancer each year, and about 15,500 die from the disease annually.

Many patients may wonder if the drug could help curb their cancer, Kumar said, but he advised that it's too early for doctors to start prescribing metformin as an ovarian cancer treatment.

"We don't have sufficient evidence that patients with ovarian cancer should be on metformin. This is a study that forms a hypothesis, but patients should wait until large-scale randomized trials are conducted," Kumar said.

Study co-author Dr. William Cliby, a professor of obstetrics and gynecology at the Mayo Clinic, said if a cancer patient develops prediabetes or diabetes after diagnosis, using metformin is an option, though. "If you have patients who are borderline diabetic and they could use a diabetic agent, in that case, this study indicates there might be a benefit."

More information

For more on ovarian cancer, go to the American Cancer Society.