Results of Breast Cancer Study Confirm Benefit

(Ivanhoe Newswire) -- The verdict is in. A complete analysis of the international trial on the drug letrozole (Femara) confirms earlier studies that show the drug reduces breast cancer recurrence in women previously treated with tamoxifen (Nolvadex).

Letrozole is an aromatase inhibitor that suppresses the production of estrogen. Because estrogen stimulates the growth of breast tumors that express the estrogen receptor, drugs that block the action of estrogen are useful in treating those tumors. Tamoxifen is the most commonly used estrogen-blocking drug, but becomes ineffective after five years of treatment. Doctors say that's likely because tumor cells become resistant to it or even dependent on it.

In this recent international trial, researchers tested whether letrozole could reduce the recurrence of tumors and increase survival in postmenopausal women with breast cancer who had already completed five years of treatment with tamoxifen. More than 5,000 women received either letrozole or a placebo for an additional five years after tamoxifen treatment.

The study was halted in October 2003 because early results showed tumors in women taking the drug were significantly less likely to recur than in those on the placebo.

In this final review, new results were uncovered. Paul E. Gross, M.D., Ph.D., from the Massachusetts General Hospital Cancer Center in Boston, says, "The most important new findings … are that letrozole treatment can improve the survival of women with node-positive disease and can reduce the chance metastasic tumors will develop."

The study also shows the risk of recurrence was nearly 5-percent lower in women receiving letrozole than in the placebo group. Women receiving letrozole also had a 39-percent lower risk of metastasis.

Women on letrozole were more likely to develop osteoporosis, but there was no significant difference in reported fractures between the two groups. There was also no increased risk of cardiovascular problems in the letrozole group. Dr. Gross says more studies are needed to investigate how long treatment with letrozole should continue and whether the drug will also be helpful for women who previously stopped taking tamoxifen or for those who never took that drug.

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SOURCE: Journal of the National Cancer Institute, 2005;97:1262-1271