A drug that costs only 8p a day could be a major breakthrough in the prevention of ovarian cancer.
Metformin comes in tablet form and is widely used on the NHS to treat patients with type two diabetes.
Now a study of more than 1,600 British women reveals taking metformin for long periods could slash their risk of ovarian cancer by around 40 per cent.
Researchers found that women who had been prescribed metformin at least ten times for their diabetes were less likely to develop a tumour than women who never took the drug, or had been prescribed it fewer than ten times.
The findings, published in the journal Gynaecologic Oncology, come at a time when several research groups are investigating the anti-cancer properties of the cheap drug.
American scientists at Duke University in North Carolina are carrying out trials to see if giving metformin to obese women with high cholesterol and blood pressure can help to keep breast cancer at bay. German researchers are looking at whether it can help protect against breast tumours by boosting the immune system so it can destroy malignant cells before they take a hold.
The drug is also being tested against prostate and lung cancers.
But the latest investigation is the first to suggest it could have a protective effect against ovarian cancer, which kills 4,000 women a year in the UK.
Researchers at the University of Basel in Switzerland looked at ovarian cancer rates among metformin users because of mounting evidence it can fight off tumours.
The drug belongs to a class of medicines known as biguanides, which have been used for decades to treat type two diabetes – the form of the disease that normally affects the middle-aged or elderly.
Metformin works by reducing the glucose produced by the liver and helping cells mop up sugar that is circulating in the bloodstream. This prevents damage from excessive blood sugar levels. It can also decrease appetite and lower dangerous blood fat levels.
The Swiss team – using the UK’s General Practice Research Database – identified 1,611 ovarian cancer cases and matched each one to at least six other women of similar age, in order to compare their use of the diabetes drugs.
The results showed women who had used metformin for long periods were 39 per cent less likely to have developed a tumour on their ovaries.
It is thought the tablet combats cancer by restricting the growth of tumour cells, or by lowering levels of insulin, which can encourage cancer-like behaviour in healthy cells when too high.
However, the drug can have side-effects, ranging from nausea to a rare but potentially fatal condition called lactic acidosis, where the body’s cells become starved of oxygen.
Research leader Professor Christoph Meier said: ‘If these results can be confirmed, the drug may play a role in the prevention of various cancers.
‘It will be very interesting to see what role metformin could play in the future, but it’s too early to tell.’