The Pharmaceutical Journal
Vol 269 No 7217 p431
28 September 2002

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The Lancet (www.thelancet.com)

Long-term HRT use can increase breast cancer and stroke risk

Women who take hormone replacement therapy (HRT) for five years are more likely to contract a life-threatening disease then be protected against one, a British study has concluded.

Researchers at the Cancer Research UK epidemiology unit in Oxford calculated there would be six extra cases of breast cancer, stroke or pulmonary embolism per 1,000 HRT users aged 50–59 years. And there would be twice as many cases among the 60–69 age group.

In contrast, there would only be 1.7 fewer cases of bowel cancer or hip fracture per 1,000 women aged 50–59 taking HRT for five years, and 5.5 fewer cases among those aged 60–69 years. The researchers found no change in the risks of developing endometrial cancer or coronary heart disease after five years of HRT therapy.

The study reviewed the incidence of seven life-threatening conditions from four major clinical trials, involving 20,000 post-menopausal women who had taken HRT for about five years. Three of the trials had used combined HRT, and one involved estrogen alone.

The researchers found that the relative risks for each of the seven conditions were similar in all four trials and applied to all women, regardless of their background, risk of disease and personal characteristics. The researchers calculated that the increased incidence of any one of the seven conditions studied was greater than any reduction, with the estimated net excess over five years being one per 230 users aged 50–59 and one per 150 aged 60–69.

Lead author of the study, Professor Valerie Beral, said the estimates provided healthy women using HRT with "a rough guide to the likely overall change in incidence of these conditions over a five-year period".

She added: "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."

However, the research team also says that existing trials are too small to provide reliable information on conditions such as ovarian cancer, or on cause-specific mortality. In addition, these trials are not looking at specific types of estrogen and progestogen used in HRT formulations. They conclude: "Observational studies will thus be needed to answer many outstanding questions about the effects of HRT."

The research was published in The Lancet (2002;360:942).