Drug Dramatically Reduces Breast Cancer Recurrence

The results were reported in the October 9, 2003, online edition of the New England Journal of Medicine.

The Canadian-led study involved 5,187 women worldwide. The researchers found that when women took letrozole after five years of tamoxifen therapy, they greatly increased their chance of remaining cancer-free. In all, 132 women taking the placebo had their disease recur, compared to 75 on letrozole, reducing the risk of recurrence by 43%. After four years of participating in the trial, 13% of the women on placebo but only 7% of those on letrozole had a recurrence of cancer. Deaths from breast cancer were also reduced by half. The trial was halted early because of the dramatic positive results.

Although tamoxifen is widely used to prevent breast cancer recurrence in postmenopausal women, the drug stops being effective after five years because tumors appear to become resistant to it. Letrozole is one of a new class of drugs called aromatase inhibitors. These work by limiting the ability of an enzyme called aromatase to produce estrogen, which stimulates the growth of many breast cancers. Astra-Zeneca has a drug of the same type called anastrozole (Arimidex).

"More than half of women who develop recurrent breast cancer do so more than five years after their original diagnosis,” said Paul Goss, M.D., of Princess Margaret Hospital (Toronto, Canada; www.uhealthnet.on.ca). "Our study ushers in a new era of hope by cutting these ongoing recurrences and deaths from breast cancer after tamoxifin by almost one-half.” Dr. Goss conceived and chaired the international trial, which was coordinated by the National Cancer Institute of Canada Clinical Trials Group in partnership with the US National Cancer Institute and its Clinicial Trials Cooperative Group.




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