Drug cuts relapse for breast cancer survivors
Source: (cancerfacts.com)
Friday, October 10, 2003
TORONTO – Oct. 10, 2003 – A new drug appears to fill in where tamoxifen leaves off in terms of preventing a recurrence of cancer in post-menopausal survivors of early-stage breast cancer.
The new drug, called letrozole, significantly reduced risk of cancer recurrence among women who had completed five years of tamoxifen therapy following surgery compared to women taking a placebo.
The Canadian-led international clinical trial was stopped early because of the positive results and researchers led by Dr. Paul Goss, of Princess Margaret Hospital in Toronto are notifying the 5,187 women in Canada, United States and Europe who have participated in the study. The results of the study were published online yesterday by the New England Journal of Medicine ahead its print publication in the Nov. 6 issue due to the importance of the findings.
"More than half of women who develop recurrent breast cancer do so more than five years after their original diagnosis," Goss said in a prepared statement. "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."
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.
"This very important advance in breast cancer treatment will improve the outlook for many thousands of women," said Dr. Andrew von Eschenbach, 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."
While tamoxifen is widely used to prevent breast cancer recurrence in post-menopausal women, it stops being effective after five years because, researchers believe, tumors become resistant to it.
A form of hormone therapy for the treatment of breast cancer, letrozole works by limiting the ability of an enzyme called aromatase to produce estrogen, a major growth stimulant in many breast cancers. Letrozole blocks production of estrogen, while tamoxifen blocks estrogen from binding to estrogen receptors on breast cancer cells.
Letrozole comes in pill form and is taken once a day. It is manufactured under the brand name Femara® by Novartis, which provided the drug for the trial.
The side effects of letrozole, a pill which is taken once a day, are very similar to those experienced by women undergoing menopause. They were generally mild in study participants. Women in the study will continue to be followed to more thoroughly assess any effects of long-term use of letrozole on bone strength or other organs. Until these are known, patients should be monitored closely. |
