Prolonged use of HRT increases breast cancer risks, researchers warn

A study says combined HRT - which includes two hormones - carries a threefold extra risk for developing lobular tumours, which form in the milk-producing glands and account for about 15 per cent of all breast cancer cases.

This type of cancer tends to be more easily treated, however, and is less likely to be fatal.

Dr Christopher Li, who led the U.S. study at the Fred Hutchinson Cancer Research Center in Seattle, Washington, said: "Previous research indicated that five or more years of combined hormone therapy was necessary to increase overall breast cancer risk.

"Our study suggests that a significantly shorter exposure may confer an increased risk."

The research follows conflicting findings on the side effects of long-term use of hormone replacement therapy, which is used to ease the symptoms of the menopause.

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In 2002, the U.S. Women's Health Initiative claimed that women using HRT were at higher risk of heart disease and strokes.

The findings were revised, however, in later analysis which showed they applied to women taking HRT for the first time in their 60s and 70s, later than is usual in the UK.

In 2003 a British study found a higher risk of breast cancer in women taking HRT for more than five years. There have since been claims by U.S. experts of a fall in new breast cancer cases because women have given up HRT.

Before the scares, an estimated 1.7million British women were using HRT to replace oestrogen lost at the menopause. There are now around a million fewer users.

Existing guidance to doctors says women should take HRT for the shortest time possible, but that it is effective to combat symptoms of the menopause.

The latest study, published in Cancer Epidemiology, Biomarkers and Prevention, comes as experts say the incidence of lobular cancer - more difficult to detect by clinical examination and X-rays - is on the rise.

Dr Li said: "Our research suggests that the use of postmenopausal HRT, specifically combined preparations, may be contributing to this."

Dr John Stevenson, consultant metabolic physician at the Royal Brompton Hospital London and chairman of Women Health Concern, said the study's findings were similar to some others, but there was also research showing no extra risk of breast cancer with three years' use.

He said: "Women taking HRT do not need to see their doctor or take any additional action."