A leading cancer scientist has raised doubts over the ethics of a clinical trial involving 20,000 women with breast cancer who will take the drug tamoxifen.
Dr Richard Bulbrook, who did much of the initial work on tamoxifen for the Imperial Cancer Research Fund, says he is disturbed by growing evidence that the long-term risks of tamoxifen - taken by up to half a million women - outweigh its benefits. He renews warnings about the drug's links with other cancers.
And he urges women with a family history of breast cancer who take tamoxifen as a preventive treatment, to seek medical advice if they are offered it for longer than five years.
Dr Bulbrook says there is evidence from large American and Scottish trials that although tamoxifen marginally improves the survival of patients with breast cancer which has not spread to the lymph nodes, in the short term, this effect diminishes after five years.
He cites a review of 14 trials involving 17,000 women, which concluded there were more new tumours in the groups taking tamoxifen (312) compared with those in the control group. Following publication of this data, scientists in California declared the drug carcinogenic.
Writing in tomorrow's British Medical Journal, Dr Bulbrook says: "Under these circumstances, recent announcements in the British media that a trial is to be launched in Britain to look at short-term versus long-term adjuvant tamoxifen treatment in 20,000 volunteers is puzzling. Are the concordant results of the two trials described above to be ignored."
Tamoxifen has been used since the mid-1960s, but was only confirmed as a useful preventive treatment for breast cancer in 1990. The decline in breast cancer mortality in post-menopausal women in recent years has been attributed to its wider use but it remains controversial. The Medical Research Council has twice refused to fund trials of tamoxifen in healthy women because of concern about its carcinogenicity, and more than 40 side- effects.
The new trial, announced in October last year, which is questioned by Dr Bulbrook, is funded by the United Kingdom Co-ordinating Committee for Cancer Research, comprising the Cancer Research Campaign, Imperial Cancer Research Fund and the Medical Research Council.
Professor Gordon McVie, scientific director of the Cancer Research Campaign, said yesterday: "We've known about this data for a long time. The basic feeling is that these are tentative conclusions which is why we need the new trial. This balance of risk and benefits is a troubling thing and every woman who takes the drug is told about it."
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