The reputation of the breast cancer drug tamoxifen has taken another serious knock following the publication of two European trials that show it is not a cancer preventative.

The drug had been heralded as a major step forward in cancer prevention last April when a US trial found that the drug reduced the risk of breast cancer by 45 per cent. So sensational was the finding that the trial was stopped prematurely so that other women could benefit from the drug.

But the new trials suggest that the drug is no better than a sugar pill in preventing cancer. The UK trial, involving 2,494 healthy women aged between 30 and 70 with a family history of breast cancer, found the rate of breast cancer was the same, whether the woman took tamoxifen or not.

An Italian study had similar results. No protective effect was found after an average follow up period of 46 months in a population of 5,408 healthy women who had had a hysterectomy.

The UK researchers say they are not surprised. "We had serious concerns about the US trial at the time it was stopped," said Dr Trevor Powles from the Royal Marsden Hospital, London. He said the Americans had not followed up the results for long enough. Although the preventative qualities were evident after three years or so, at six years there was no difference between placebo and tamoxifen.

The true value of the drug as a preventative will not be known for another seven years, he predicts (BMJ, 1998; 317: 162).