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Letrozole Improves Breast Cancer Survival

Offers better results than tamoxifen, but side effects may influence choice, experts say

WEDNESDAY, Dec. 28, 2005 (HealthDay News) -- Postmenopausal breast cancer patients who take letrozole, one of a new class of drugs called aromatase inhibitors, reduce their risk of cancer recurrence compared with women taking tamoxifen, a breast cancer drug used widely for more than two decades, researchers report.

Tamoxifen has greatly reduced the risk of recurrence and death in women who have estrogen-receptor-positive breast cancer, meaning cancer that is fueled by the hormone estrogen. The drug reduces the risk of recurrence by 47 percent and the risk of death by 26 percent for five years after surgery.

Now a new study finds that letrozole further improves both recurrence and survival rates. The report appears in the Dec. 29 issue of the New England Journal of Medicine.

"Letrozole improves outcome better than tamoxifen for postmenopausal women with hormone-receptor-positive breast cancer," said study author Richard D. Gelber, a professor in the Department of Biostatistics and Computational Biology at the Dana-Farber Cancer Institute, in Boston.

In their study, Gelber and his colleagues selected 4,003 women to receive letrozole and 4,007 to receive tamoxifen. During more than two years of follow-up, the researchers found that 84 percent of the women taking letrozole did not have a recurrence of breast cancer, compared with 81.4 percent of the women taking tamoxifen.

Gelber said that aromatase inhibitors are being used more often, and he expects their use will continue to grow. "As people become more comfortable with the side-effect profiles relative to tamoxifen, there is likely to be increasing use."

The side effects differ between the two drugs, Gelber explained. For example, thromboembolism (blood clots), endometrial cancer, and vaginal bleeding are side effects of tamoxifen, while side effects of letrozole include the risk of fractures, cardiac events and high cholesterol.

"There are tradeoffs," Gelber said. "That's why a discussion with the doctor is important to decide whether tamoxifen or an aromatase inhibitor is best. Aromatase inhibitors add to the arsenal of treatments that can improve results for these women. The drug could be used following tamoxifen or might, for some patients, replace the use of tamoxifen."

One expert believes that women should receive an aromatase inhibitor at the start of treatment.

"My personal bias is that starting with an aromatase inhibitor, a woman has a lower risk of recurrent cancer than with tamoxifen," said Dr. Aman Buzdar, a professor of medicine and oncology at the University of Texas M.D. Anderson Cancer Center, in Houston. "When you look at the safety profile, letrozole is more favorable overall than tamoxifen."

Buzdar recommends aromatase inhibitors to his postmenopausal patients with estrogen-receptor-positive breast cancer. "In addition, if a patient is on tamoxifen, I go over the studies with them, which clearly demonstrate that switching them is better than continuing with tamoxifen," he said.

Another expert is more cautious, believing that treatment must be tailored to individual patients.

"While aromatase inhibitors are great on the breast cancer standpoint, seeing some modest increase in survival, one has long-term concerns," said Dr. Patricia A. Ganz, a professor of medicine at UCLA's Schools of Medicine and Public Health.

"For postmenopausal women, aromatase inhibitors have an edge," Ganz said. "I would encourage this therapy for women who have a high risk of recurrence. But for somebody who has a teeny weenie tumor in the breast, I would recommend tamoxifen, because of the difference in side effects."

More information

The National Cancer Institute can tell you more about breast cancer.

SOURCES: Richard D. Gelber, Ph.D., professor, Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston; Patricia A. Ganz, M.D., professor, medicine, UCLA Schools of Medicine and Public Health, Division of Cancer Prevention and Control Research, Jonsson Comprehensive Cancer Center, Los Angeles; Aman Buzdar, M.D., professor, medicine, M.D. Anderson Cancer Center, University of Texas, Houston; Dec. 29, 2005, New England Journal of Medicine
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