Ovarian cancer is one of the deadliest types of the illness and half of women diagnosed do not survive beyond five years.
Often it is only detected once it has spread to other organs, at which point there are very few effective treatments available.
But U.S. researchers claim metformin taken by thousands of Britons for diabetes-could more than double survival odds. Their study, published in journal cancer, followed 239 women with ovarian cancer.
This included 73 with diabetes who were taking daily doses of metformin and 178 women not on the drug.
The researchers found that 67% of women on the drug were still alive five years after diagnosis, against 44% of other group. But when they took into account the stage at which each women was diagnosed, they calculated it was even more effective. They estimate women taking the drug are 2.2 times more likely to be alived after five years.
Dr. Viji Shridhar, who led the study at the Mayo clinic in Rochester, Minnesota said that in future the drug could be routinely used for ovarian cancer.
He added, This study opens the door for using metformin in large –scale randomized trials in ovarian cancer which can ultimately lead to metformin being one option for treatment of patient with the disease. Earlier this year the same drug was found to lower the chance of developing breast cancer.
Scientist from University of California in Los Angeles, found middle-aged woman who had taken metformin were 25% less at risk.
A study is now under way to work out how effective the drug is at treating breast cancer.
Researches behind these latest finding want to carry out a similar trial for ovarian cancer. The illness is the fifth commonest cancer in women and there are 6,500 new cases in Britain year, leading to 4,400 deaths.