A drug widely used to treat patients with type two diabetes and that costs only 8p a day could be a major breakthrough in the prevention of ovarian cancer, according to a new study. The 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, the Daily Mail reported. The researchers at the University of Basel in Switzerland found that women who had been prescribed metformin, which comes in tablet form, at least ten times for their diabetes were less likely to develop a tumour than women who nevertook the drug, or had been prescribed it fewer than ten times. Metformin 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. It 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. "If these results can be confirmed, the drug may play a role in the prevention of various cancers," said research leader Professor Christoph Meier. "It will be very interesting to see what role metformin could play in the future, but it's too early to tell," he added. The study has been published in the journal Gynaecologic Oncology. .