Study: Letrozole Better Than Tamoxifen for Women With Advanced Breast Cancer

Letrozole (Femara®) appears to be more effective than tamoxifen as a treatment for postmenopausal women with locally advanced or metastatic breast cancer, according to researchers at Duke University Medical Center.

The new drug was able to shrink breast cancer tumors better than tamoxifen in a study of postmenopausal women presented at the 24th Annual San Antonio Breast Cancer Symposium.

After four months of taking letrozole, 60 percent of the women taking letrozole showed tumor shrinkage compared to 41 percent of women taking tamoxifen. Patients taking letrozole also underwent fewer mastectomies than women taking tamoxifen.

Letrozole slows cell division, thus slowing tumor growth, better than tamoxifen, say the researchers. Letrozole works by depriving the tumor of estrogen, and without estrogen, tumor cells that rely on the hormone for growth cannot divide and stop growing.

"We are very excited by letrozole's potential because it appears to block the growth-promoting effects of estrogen within cancer cells better than tamoxifen does," said Dr. Mathew Ellis, an oncologist at Duke and lead author of the study. "Estrogen is involved in up to 80 percent of all breast cancers, so blocking its effects is vital to successful treatment."

"Although our results are preliminary, letrozole appears to block estrogen more effectively than does tamoxifen, suggesting that letrozole may work for women whose tumors are relatively resistant to tamoxifen," said Ellis.

Researchers believe that letrozole may be a potential replacement for more toxic chemotherapy treatments in some patients, or could be taken along with other drugs like Herceptin for maximum effect.

Its distinct mechanism of action makes letrozole different from current drugs like tamoxifen and other, more toxic chemotherapy agents, said Ellias.

Researchers caution that further studies are needed in larger groups of women before a change in therapy procedures can be recommended.

Other Sources: Duke University