New Drug Deters Breast Cancer Relapses

The original research information about this clinical trial was released online on October 9, 2003, by The New England Journal of Medicine, a month in advance of its scheduled publication date because of its potential therapeutic implications. Two editorial commentaries on the research were also released online concurrently by the Journal.

Summary: The drug Femara (letrozole) has been found in a clinical trial to improve the outcome for patients with breast cancer after tamoxifen therapy has ended. Femara is an aromatase inhibitor. It blocks estrogen production by the adrenal gland. The trial compared the effects of Femara with a placebo (sugar pill). The trial was terminated early because of Femara's documented efficacy and all women in the study were offered Femara.

Our Comments: We are delighted by this exciting and very good news. Among the questions that now need to be answered are:

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Barbara K. Hecht, Ph.D.
Frederick Hecht, M.D.
Medical Editors, MedicineNet.com


New Treatment Significantly Improves Long-term Outlook For Breast Cancer Survivors: International clinical trial concludes women should consider taking letrozole after five years of tamoxifen treatment to continue to reduce risk of recurrence

Posted Date: Thursday, October 09, 2003

A Canadian-led international clinical trial has found that post-menopausal survivors of early-stage breast cancer who took the drug letrozole after completing an initial five years of tamoxifen therapy had a significantly reduced risk of cancer recurrence compared to women taking a placebo. The results of the study appear in today's advance on-line edition of the New England Journal of Medicine.

The clinical trial has been halted early because of the positive results and researchers are notifying the 5,187 women worldwide who have participated in the study. Women on letrozole will continue taking the drug and those on the placebo can begin taking letrozole, if they wish.

"This very important advance in breast cancer treatment will improve the outlook for many thousands of women," said Andrew von Eschenbach, M.D., director of the National Cancer Institute which led the study in the United States. "This is one more example of the ability to interrupt the progression of a cancer using a drug that blocks a crucial metabolic pathway in the tumor cell."

Study researchers found that letrozole, when taken after five years of tamoxifen therapy, substantially increased the chance of remaining cancer free. In total, 132 women taking the placebo had their disease recur compared to 75 on letrozole. Overall, letrozole reduced the risk of recurrence by 43 percent, so that after four years of participating in the trial, 13 percent of the women on the placebo, but only seven percent, of those on letrozole had recurred. Deaths from breast cancer were also reduced. Seventeen women taking the placebo died of breast cancer compared to nine taking letrozole.

While tamoxifen is widely used to prevent breast cancer recurrence in post-menopausal women, it stops being effective after five years because, researchers believe, tumours become resistant to it.

"More than half of women who develop recurrent breast cancer do so more than five years after their original diagnosis," says Paul Goss, M.D., of Princess Margaret Hospital in Toronto. "For years, we have thought that we had reached the limit of what we could do to reduce the risk of recurrence with five years of tamoxifen. Our study ushers in a new era of hope by cutting these ongoing recurrences and deaths from breast cancer after tamoxifen by almost one half." Goss, a leading expert in novel hormone therapies for the treatment and prevention of breast cancer, conceived and chaired the international trial with letrozole.