New drug 'stops breast cancer from developing'

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Breast cancer, the most common malignant disease in women, can be prevented by treating healthy patients with drugs before it develops, scientists reported yesterday.

Breast cancer, the most common malignant disease in women, can be prevented by treating healthy patients with drugs before it develops, scientists reported yesterday.

The first results of a trial involving 7,000 women at high risk of breast cancer but who had no signs of the disease showed that giving the hormonal drug tamoxifen cut their risk of developing the cancer by a third. The benefit was the same whatever the age of the woman and whatever the level of risk.

The finding, presented at the European Breast Cancer Conference in Barcelona, raises hopes of opening up a second front in the battle against breast cancer by stopping the disease before it appears. There are 38,000 new cases of breast cancer a year in Britain and in 2000 there were 12,770 deaths.

The role of tamoxifen in preventing a recurrence of breast cancer in women who have already had it is one of the great medical success stories of the past decade, with a 26 per cent increase in survival rates among post-menopausal women, thanks to the drug. The improvement has been so startling that doctors speak openly of tamoxifen as a "cure" for the disease.

Now the International Breast Intervention Study (Ibis), run in six countries and co-ordinated from the UK, has demonstrated that tamoxifen can also prevent breast cancer in healthy women, who have never had the disease. This raises the prospect of preventive drugs being prescribed to the thousands of women at high risk of the cancer because of their family history.

But scientists from Cancer Research UK, who led the trial, also reported that more women had died of other causes while taking tamoxifen and warned it was still too early to tell whether the side-effects from the treatment outweighed the benefits.

Tamoxifen is known to increase the risk of thrombosis (blood clots) and of endometrial cancer (cancer of the lining of the womb). In the trial, 25 women died who were taking tamoxifen, more than double the 10 deaths among women given a placebo.

The higher death rate in the tamoxifen group led the researchers to publish the preliminary results yesterday so that women would know of the risks. But the trial would continue, they said.

Professor Jack Cuzick, the lead investigator, said the benefits of tamoxifen in preventing breast cancer were now indisputable. Although nobody could yet say with certainty how many lives could be saved, he added: "For high-risk women, we calculate that deaths from breast cancer within 10 years of diagnosis would be reduced by 18 per cent."

Blood clots were the most important side-effect of tamox-ifen, he said. "Every effort should be made to reduce this risk although we must keep it in perspective ... We know there is a link between blood clots and surgery. It would seem a wise precaution to discontinue tamoxifen before any major surgery ... and not to recommence it until one month after surgery."

Professor Gordon McVie, joint director general of Cancer Research UK, said: "These preliminary findings from the Ibis trial confirm that tamoxifen can prevent breast cancer in healthy women. These findings are obviously very encouraging ... Although there have been more deaths [in the tamoxifen group] this is thought to be a chance finding not related to tamoxifen. The trial will continue and we hope that the women involved will continue to participate."

The Ibis trial, begun in 1998, is the biggest to test the preventive effects of tamoxifen and involves women from Britain, Finland, Switzerland, Belgium, Australia and New Zealand. The results presented yesterday showed there had been 68 cases of breast cancer among the tamoxifen group compared with 101 among those taking the placebo, a reduction in incidence of the disease of a third.

The researchers also presented an update on previous smaller studies run in America, at the Royal Marsden hospital in London and in Italy. When combined, the four studies showed an overall reduction in breast cancer of 38 per cent. None of the previous three studies showed an increase in deaths from other causes among the tamoxifen group.

The next aim for the researchers is to identify women at highest risk of the disease for whom the benefits of tamoxifen given preventively would clearly outweigh the risks, or to develop a more selective drug that works in the same way as tamoxifen, but without the side-effects.

The researchers said other such drugs were "coming along" and would be available in the next few years.