The long-term effects of hormone replacement therapy (HRT) significantly increase the risk of breast cancer, stroke and blood clot on the lung, according to a report published in the journal Lancet.

Scientists undertook a comprehensive review of the incidence of seven major, life threatening conditions from four major randomized trials of HRT following the recent results from the Women's Health Initiative.

The review, which included information on 20,000 postmenopausal women who had taken HRT for about five years, has established that there is a significant increase in the risks of breast cancer, stroke and blood clot on the lung.

Professor Valerie Beral of Cancer Research UK, who led the review, also found that overall there was a significant reduction in bowel cancer and hip fractures in the women taking HRT.

On balance, evidence from the trials shows that a woman is more likely to contract a life threatening disease than to be protected against one.

The review estimates that among healthy women using HRT over a five year period, there would be a total of six extra cases of either breast cancer, stroke or clot on the lung (pulmonary embolism) among every 1,000 HRT users aged between 50-59. The number doubles to 12 per 1,000 HRT users aged 60-69.

The corresponding reduction in the number of expected cases of bowel cancer or hip fracture is estimated at 1.7 per 1,000 HRT users aged 50-59 and 5.5 per 1,000 HRT users aged between 60-69.

The review also found there was no significant change in the risks of endometrial cancer or coronary heart disease.

Prof. Valerie Beral, of Cancer Research UK's Epidemiology Unit at the Radcliffe Infirmary in Oxford, says: "These estimates provide a rough guide to the likely overall change in incidence of these conditions over a five-year period for typically healthy women in western countries who use HRT. Each woman may, understandably, give different weight to the importance of each condition, as well as to the relief of menopausal symptoms with HRT. The issues are different for every woman."

Dr. Gillian Reeves, a researcher on the review, added: "Women need to be aware of the new information we are learning about long-term effects of HRT. There are a variety of reasons why women take HRT. Each individual should weigh up the pros and cons of HRT with regard to their own particular circumstances and after discussion with their doctor."

Three of the randomized controlled trials reviewed had studied the effects of combined estrogen and progestagen HRT and one had studied estrogen only. The findings for each of the seven conditions were similar in all trials and applied to women with varying background risks of the disease and personal characteristics, including different ages, ethnic groups, disease histories and users of various medications.

SOURCES:
The Lancet, September 21, 2002
Cancer Research UK (http://www.cancerresearchuk.org)