Results from a global study of 37,000 women treated with the drug, the largest randomised study of any cancer treatment, showed that twice as many lives could be saved if tamoxifen were used twice as widely. If all the women who could benefit from the drug in Britain were prescribed it, an extra 1,000 lives a year in this country would be saved, scientists said yesterday.
Tamoxifen, which blocks the action of the hormone oestrogen, is prescribed to one million women worldwide immediately after surgery for breast cancer but could benefit hundreds of thousands more. Oestrogen can cause any breast cancer cells remaining after surgery or chemotherapy to proliferate.
Britain has led the world in prescribing the drug to post-menopausal women but there is still a belief that it is ineffective in younger, pre- menopausal women, unnecessary in those who have had chemotherapy or in whom the cancer has not spread beyond the breast, and is not needed for more than one to two years rather than the recommended five years.
Professor Richard Peto of Oxford University said that that view was wrong on all four counts and that clinical practice must change. "Tamoxifen is already saving more lives than any other cancer drug in the world," he said. In the UK, the drug was already saving 2,000 lives a year. Professor
Peto added: "Often you can save more lives by taking seriously what you know than with a new discovery that may not be relevant for 20, 30 or 40 years."
Tamoxifen was discovered by British scientists 25 years ago but gathering the evidence of its benefits has taken decades. Professor Peto said that doctors had been slow to accept the drug because it was not toxic like other cancer drugs and they had believed that there was no gain without pain.
The latest findings, published in The Lancet, involved assembling data from 55 trials in 15 countries. Although the results showed small increases in the risk of endometrial cancer (of the lining of the womb) and of blood clots in the lungs, the drug prevented 30 times more deaths than it caused. In the UK it costs pounds 200 for a five-year course.
However, the findings only apply to women with hormone-sensitive breast cancer, 20,000 of the 30,000 new cases each year in the UK. In women who do not have hormone sensitive cancer - a quarter of those over 50 and half under 50 - the balance between the risks and benefits of tamoxifen remains unclear.
Professor Rory Collins, a study co-ordinator, said: "The best bet for those women is to get themselves into a randomised trial of tamoxifen."
The findings do not apply to the prevention of a first breast cancer in high-risk women, which is the subject of a separate trial. United States researchers decided to end the American arm of that trial last month after results showed the drug reduced the risk of a first breast cancer by 45 per cent. Half the women in the random trial were not on tamoxifen, and it was felt that it was unethical to keep them off the drug. British researchers this week decided to continue with the trial because they said there were still unanswered questions.Reuse content