Femara Beats Older Breast Cancer Drug

Aromatase Inhibitor Better Than Tamoxifen in Head-to-Head Comparison

From the WebMD Archives

Oct. 3, 2006 (Istanbul, Turkey) -- New four-year results from a major study show that postmenopausal women with early breast cancer fare better if they are treated with Femara than with tamoxifen, the standard hormone therapy.

In the study of nearly 5,000 women, those who were given Femara, an aromatase inhibitor, were less likely to have their cancercancer come back compared with those who were given tamoxifen, says Alan Coates, MD. Coates is a clinical professor in the School of Public Health at the University of Sydney in Australia.

Cancer was also less likely to spread to other parts of the body if a woman took Femara, he tells WebMD.

The findings are consistent with a preliminary analysis reported two years ago, Coates says. "But with longer follow-up, we were especially impressed that Femara also appears to prevent cancer from returning in two groups of women at particular risk of recurrence: those whose cancer had already spread to the lymph nodes at the time of diagnosis and those who had not received chemotherapy," he says.

How the Drugs Work

About 70% of women with breast cancer have tumors that are fueled by estrogen, making hormone therapy a cornerstone of regimens to prevent recurrences and improve survival after breast surgery.

For nearly 30 years, doctors have been using tamoxifen, which deprives breast cancer cells of the estrogen they need to grow. In contrast, aromatase inhibitors like Femara block an enzyme the body uses to make estrogen, thereby suppressing estrogen levels throughout the body.

The new research suggests that this differing mechanism of action means that aromatase inhibitors may fight cancer recurrence better -- and with fewer side effects -- say doctors not involved with the research.

Suayib Yalcin, MD, a cancer specialist at Hachette University in Ankara, Turkey, tells WebMD that the study confirms that aromatase inhibitors are a better choice for most postmenopausal women with early, estrogen-fueled breast cancer.

"Femara is more effective, less toxic, and more convenient than tamoxifen," he says. "In my opinion, it should be the treatment of choice."

In addition to Femara, other aromatase inhibitors include Arimidex and Aromasin.


Femara Cut Relapses, Side Effects

The new study, presented at the annual meeting of the European Society of Medical Oncology, followed 4,922 postmenopausal women who were given either tamoxifen or Femara after breast cancer surgery.

By 51 months later, Femara scored better than tamoxifen on almost every measure. It lowered the risk of relapse or dying by 18% more than tamoxifen, and it reduced distant metastases -- that is, cancercancer spread outside of the breast -- by 19% more than tamoxifen.

And in women whose cancer had already spread to the lymph nodes at the time of diagnosis and those who had not received chemotherapy, the risk of recurrence was reduced by 23% and 26% more than tamoxifen, respectively.

Also, for the first time, the longer-term results revealed emerging evidence that Femara may benefit women whose cancer had not spread to the lymph nodes at the time of diagnosis, Coates says. In this group of women, Femara reduced the risk of breast cancer coming back by 12% more than tamoxifen. In contrast, only a 2% difference was observed after two years of follow-up, he says.

As for side effects, both drugs were generally well tolerated, he says. More women on tamoxifen suffered vaginal bleeding, night sweats, and clots in the legs or lungs, Coates says.

But women taking Femara were more prone to slightly elevated cholesterol levels, joint pain, and bone fractures than those taking tamoxifen.

"But we now have drugs that can strengthen bones in women taking Femara," Coates says. "No woman who has normal bone densitybone density when she starts on Femara will develop osteoporosisosteoporosis."

The Next Step

While the study shows Femara appears to be more effective than tamoxifen, doctors are still figuring out how to best use the aromatase inhibitors.

Some studies suggest they work best right after breast cancer surgery, while others suggest women could cut their risk of recurrence even further by taking an aromatase inhibitor after they completed about five years on tamoxifen.

"What's clear is that Femara has an edge over tamoxifen," Coates says. "But whether the best strategy is an aromatase inhibitor alone, tamoxifen followed by an aromatase inhibitor, or an aromatase inhibitor followed by tamoxifen is the big question."

A second part of the current trial should offer answers to that question by next year, he says.

Breast cancer is the second biggest cancer killer of women in the industrialized world, after lung cancerlung cancer. It kills about 40,000 women each year in the U.S.

WebMD Health News Reviewed by Louise Chang, MD on October 03, 2006


SOURCES: 31st ESMO Congress, Istanbul, Turkey, Sept. 29-Oct.6, 2006. Alan Coates, MD, clinical professor, School of Public Health, University of Sydney, Australia. Suayib Yalcin, MD, Hacettepe University, Ankara, Turkey.
© 2006 WebMD, Inc. All rights reserved.