the drug and breast cancer.
Women who take hormone replacement therapy have a slightly increased risk of developing breast cancer which rises the longer they are on the drug, researchers have found. When taken for five years starting around the age of 50, the drug is estimated to lead to two extra cases of cancer in every thousand women before the age of 70.
Professor Sir Richard Doll, the leading cancer epidemiologist said the "extremely important study" had established the precise size of the breast cancer risk but it remained to be determined what other benefits and disadvantages HRT had.
"It may well be that the benefits of reduced heart disease more than compensates for the increase in breast cancer. It could reduce the risk of heart disease by as much as 30 per cent."
The two extra cases in every thousand are on top of the 45 cases that would anyway be expected among women in the same age group not taking HRT, raising the total to 47. Longer use, over 10 years, is associated with six extra cases (a total of 51 compared with 45 in the non-HRT group) and over 15 years with 12 extra cases (57 compared with 45). The findings are based on the most comprehensive review of existing research on HRT. Fifty-one studies from 21 countries involving more than 52,000 women with breast cancer and 108,000 women without it were examined by a team at the Imperial Cancer Research Fund's epidemiology unit in Oxford. Professor Valerie Beral, co-ordinator of the study published in The Lancet, said that HRT delayed menopause and it was known that women with a late natural menopause had an increased risk of breast cancer.
"The issue is how big are the risks and how do they compare with the beneficial effects. There is nothing so bad in these results that women should stop HRT and nothing so clear that they can take it for ever. If they use HRT for a few years the effects on breast cancer are quite small."
When HRT is stopped the excess risk returns to normal and "virtually disappears" in five years, Professor Beral said. Although the study examined only the incidence of the disease and not survival, the cancers that occur in women on HRT appear to be smaller than in other women, possibly because those on the drug are alert to the risks and detect them sooner.
Cancer charities were yesterday bracing themselves for a flood of calls from worried women and were bringing in extra staff to run helplines. Family doctors were being informed of the results. Professor Michael Rawlins, chairman of the Committee on Safety of Medicines, said in a statement that women taking HRT did not need to stop the treatment. "If you are concerned and want to know more, you should make a routine non-urgent appointment with your doctor," he said. All women should be aware of any changes in their breasts and report them to their doctor.Reuse content