One of the largest trials for screening of ovarian cancer is being set up to establish whether such a programme can save lives, doctors said yesterday.

The £8m study of the fourth most common cancer in women will take 10 years. There are 6,000 cases of ovarian cancer a year and it causes more than 4,000 deaths, three times as many as cervical cancer. Most women have few symptoms until the disease has spread beyond the ovaries when it is difficult to treat, which causes the high mortality.

Like most cancers, the ovarian type is commoner in older women, although one in 10 cases affects women under 45. The trial will involve 200,000 post-menopausal women who will be invited for monitoring at 12 regional centres. Half of them will be given an annual blood test or ultrasound scan of their ovaries with a probe inserted into the vagina. The remaining half - the control group - will be offered ordinary care.

To eliminate bias and ensure random selection, women will not be allowed to volunteer for the study. The researchers want to establish not only whether screening saves lives but also its impact on those screened.

Professor Ian Jacobs of Queen Mary and Westfield College, University of London, who will head the trial from St Bartholomew's hospital in London, said: "At the end of this study we will have information about how many lives ovarian cancer screening could save, how much this will cost, how women feel about screening and the associated complications of screening."

The two screening tests have been refined over a decade. Women who appear abnormal on either test will be offered a detailed scan plus a repeat blood test and if necessary, will be referred to a a specialist for investigation and treatment.

The trial is being funded by £5.7m from the Medical Research Council and £1.5m each from the Cancer Research Campaign and the Imperial Cancer Research Fund. The Department of Health will also contribute.