Trial cut short after benefit of breast-cancer drug is proved
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Your support makes all the difference.An international trial of a drug for breast cancer has been halted after early results showed it cut by 43 per cent the risk of the cancer returning in women already treated for the disease.
The reduction in risk - equivalent to one cancer prevented among 100 women treated per year - led the researchers to abandon the trial of 5,200 women halfway into its five-year term so that those on placebo could be offered the drug, called letrozole.
The results of the Canadian-led trial, to be published in the New England Journal of Medicine on 6 November, were so significant that they were released early online yesterday. Letrozole is one of a new class of drugs for breast cancer called aromatase inhibitors which are transforming the outlook for women with breast cancer.
Professor Ian Smith, head of the breast unit at the Royal Marsden Hospital, London, said: "This is one of the most important advances in the treatment of postmenopausal women with breast cancer, and is a further valuable step in preventing disease recurrence."
But Professor Smith was among British specialists, including Professor Jack Cuzick, at Cancer Research UK, who criticised the decision to halt the trial early because the long-term effects of letrozole may now never be known. Researchers fear it may carry risks to the bones and cognitive performance.
Professor Smith said: "There was an ethical obligation to make the results public and let the patients know. But the patients could have been asked for their consent to continue in the trial. We do not know the long-term risks of any of these aromatase inhibitors."
Recent experience has demonstrated the importance of long-term studies. A US trial of tamoxifen in preventing breast cancer in high-risk women was stopped 14 months early in 1998 after results showed it cut cases of the disease by one third. But a parallel British trial was continued for the full five years until 2001 and the results showed that the benefits of tamoxifen were almost cancelled out by an increased risk of blood clots and endometrial cancer. Tamoxifen is now not routinely recommended for the prevention of breast cancer in the UK.
In the trial of letrozole, whose brand name is Femara, the drug was given to postmenopausal women with early stage breast cancer who had already taken tamoxifen for five years afterinitial treatment. Until now there has been no drug treatment available for women who have completed five years of tamoxifen therapy, as tamoxifen itself carries increased risks after that period. The results showed that after 2.4 years of additional treatment, there were 75 cases of cancer in the Letrozole group compared with 132 in the placebo group.
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