LONDON (Reuters) - A British study backed US findings on the side-effects of hormone replacement therapy (HRT) on Friday, saying the treatment taken by women to relieve menopause symptoms increases the risk of breast cancer and stroke.

A review of four major studies into the effects of HRT found that women who took the treatment for five years had a higher risk of breast cancer, stroke and blood clots in the lung but were less likely to suffer from bowel cancer or hip fractures.

Overall, the analysis showed that a woman is more likely to contract a life-threatening disease when on HRT than to be protected against one.

"The four major trials that have been done, although in different settings and with different combinations (of HRT), really show consistent results," Professor Valerie Beral, of Britain's Cancer Research UK charity, told Reuters.

Millions of women who use HRT to relieve hot flushes and mood swings or to prevent osteoporosis were caught off guard in July after an American trial showed HRT raises the risk of stroke, breast cancer and blood clots.

Shares in HRT manufacturers like US-based Wyeth and Germany's Schering tumbled in the wake of the US trial news in July.

US FINDINGS BACKED

Beral said her analysis of four trials involving 20,000 postmenopausal women, which is published in The Lancet medical journal, confirm the findings of the US study.

"They basically support the Women's Health Initiative study," Beral said, referring to the US trial of women taking combined estrogen and progestogen HRT.

Three of the trials in the analysis studied the effects of combined HRT and one involved estrogen only.

"Putting all the data together, the results look very similar," said Beral. "What there is suggests there is no difference between the different types of HRT preparations."

For women in their 50s taking HRT for five years, the greatest risk is for developing breast cancer. Women in their 60s have a higher chance of suffering a stroke or pulmonary embolism, or blood clots in the lungs.

"These result 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," said Beral.

The review estimates that for healthy women on HRT for five years there would be a total of six extra cases of either breast cancer, stroke or clot on the lung among every 1,000 HRT users between aged 50-59.

The number would double to 12 for HRT users aged 60-69.

By contrast, there would be an estimated 1.7 fewer cases of bowel cancer or hip fracture per 1,000 HRT users aged 50-59 and 5.5 per 1,000 users between 60-69.

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

Women on the treatment for longer would have an increase in risk that accumulates with time, said Beral

"We've tried to provide risk estimates for women that they can relate to in making a decision about whether they want to take HRT or not," she added.

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