19 Apr 07

Women who take hormone replacement therapy are more likely to be diagnosed with ovarian cancer and to die of the disease, according to a study led from Oxford University and published online by The Lancet today. The study suggests, however, that a woman's risk of ovarian cancer returns to a normal level within a few years of stopping HRT.

Results from the Million Women Study, which is the biggest study of its kind in the world, show that over five years there is one extra case of ovarian cancer in every 2,500 women who take HRT, and one extra death in every 3,300 women who take HRT.

The researchers, who are largely funded by Cancer Research UK, estimate that use of HRT between 1991 and 2005 has resulted in an extra 1,300 cases and 1,000 deaths from ovarian cancer.

Ovarian cancer is the fourth most common cancer in women in the UK, with almost 7,000 new cases each year. The five-year survival rate for the disease is less than 30 per cent, which reflects the fact that ovarian cancer is often diagnosed at a late stage.

Professor Valerie Beral, Director of Cancer Research UK's Epidemiology Unit at Oxford University, is lead researcher for the Million Women Study and for the Lancet paper. She said: 'The results of this study are worrying because they show that not only does HRT increase the risk of getting ovarian cancer, it also increases a woman's risk of dying of ovarian cancer.

'This study, along with our previous research, clearly demonstrates the cancer risks of taking HRT.'

The researchers assessed data from 950,000 post-menopausal women who were followed for an average of seven years. Around 30 per cent were current HRT users and 20 per cent had taken it in the past. For every 1,000 women using HRT, 2.6 developed ovarian cancer over five years, compared to 2.2 in every 1,000 women not using HRT. The type of HRT made no significant difference.

Previous results from the Million Women Study have linked the use of HRT with breast and endometrial cancer (cancer of the womb lining). Combined with ovarian cancer, these three diseases account for almost 40 per cent of all cancers in women in the UK and 25 per cent of cancer deaths. The overall incidence of these three cancers in women who take HRT is 31 cases for every 1,000 women over five years. This compares with 19 cases per 1,000 in women who have never taken HRT.