Breast cancer drug cuts risk of healthy women getting the disease by 30 per cent

Tamoxifen is usually used to treat women once they have the disease.

But trials showed that it could reduce the chance of getting the cancer by a third - for up to 20 years.

Two studies have found that it could cut deaths from the disease among women who use it for several years.

Doctors said last night that the drug could become an option for healthy women at high risk.

Although it does have side effects including life-threatening blood clots, these disappear after women stop taking the drug. Meanwhile, the protective effects continue for up to 20 years, say experts.

The first prevention trial was begun by Professor Trevor Powles the Marsden Hospital, London, in the 1980s.

Results show the benefits of using the drug in premenopausal women - their risk of getting the disease is reduced beyond the menopause and up to 20 years later, he said.

"We did not initially get an effect but as time has gone on we've found a significant reduction in breast cancer - and the benefits keep getting bigger. Premenopausal women taking the drug are less likely to develop oestrogen sensitive cancer after the menopause, when they are most at risk."

Women in the trial were in their mid-forties. They took the drug for about six or seven years.

He added: "This is the key to its effectiveness, because it's a relatively young population given the treatment to block the effect of oestrogen on their breasts. The side effects also seem to be less in premenopausal women."

Professor Powles, lead clinician at Parkside Oncology Clinic, London, said tamoxifen was not licensed for prevention in the UK.

If the National Institute for Health and Clinical Excellence drew up guidelines for doctors, the drug could become an option for healthy women at high risk, he said.

A second study confirmed that the drug continues to reduce by a third the risk of breast cancer for several years after women stop taking it.

The International Breast Cancer Intervention Study trial, funded by Cancer Research UK, found side effects such as blood clots and womb cancer stop after women finish taking the drug.

A woman's "normal" risk of developing breast cancer over ten years is about two per cent. Women in the study had a three-fold higher risk.

Tony Howell, IBIS co-chair and professor of cancer prevention at the South Manchester University Hospitals Trust, said: "Previous studies have already shown that tamoxifen lowers the risk of developing breast cancer during active preventive treatment.

"But this is the first time that clear evidence is available on the benefits and side-effects of tamoxifen after treatment with the drug has stopped.

"These findings together with the effectiveness results suggest that over a longer follow-up time the risk of side-effects decreases while the benefit of prevention continues."

Both trials were published yesterday in the Journal of the National Cancer Institute.

Tamoxifen has been used to treat breast cancer for more than 20 years. Treatment costs just 8p a day. It can also stop breast cancer survivors from getting the disease in the other breast - cutting the risk by 45 per cent.

This led to trials to see if it would protect healthy women at high risk.