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Femara May Be Better Than Tamoxifen

Side Effects of Breast Cancer Drugs May Determine Choice
By
WebMD Health News
Reviewed by Louise Chang, MD

Dec. 28, 2005 - It's official: Femara beats tamoxifen in preventing breast-cancer recurrence.

A large 27-nation clinical trial shows that postmenopausal women with estrogen-receptor-positive breast cancer are less likely to get new breast cancers -- especially cancers in distant parts of the body -- if they take Femara than if they take tamoxifen.

"Particularly notable was our finding of a significant [27%] reduction in the risk of distant recurrence with Femara as compared with tamoxifen," write Beat Thürlimann, MD, and colleagues. Thürlimann, a senior lecturer at the University of Basel, Switzerland, owns stock in Novartis, which makes Femara. Novartis is a WebMD sponsor.

We've heard the news before: first from Novartis, which makes the drug, and then at a meeting of cancer specialists. Now the report on the Breast International Group (BIG) 1-98 study appears in the Dec. 29 issue of The New England Journal of Medicine.

It's not that tamoxifen didn't work. Cancer-free, five-year survival was estimated at 84% for women taking tamoxifen -- only 2.6% lower than for Femara. Yet Femara had a distinct benefit, with a 27% lower risk of metastatic (distant-spreading) cancer.

Tamoxifen Still Has Large Role

Femara is the most potent member of a new class of drugs called aromatase inhibitors. These drugs almost totally shut down the body's ability to make estrogen. Estrogen-receptor-positive tumors grow in the presence of estrogen. Tamoxifen also blocks estrogen's effects, but not in the same way as Femara and its sister drugs Arimidex and Aromasin.

Other large clinical trials show that Femara and other aromatase inhibitors fight breast cancer better than tamoxifen, notes an NEJM editorial by Sandra M. Swain, MD, of the U.S. National Cancer Institute.

"It is clear ... that these trials, with close to 30,000 participants, consistently demonstrate that treatment with an aromatase inhibitor alone or after tamoxifen treatment is beneficial," Swain writes.

Choosing a Treatment Plan

Swain says many questions remain:

  • How long should treatment last?
  • Should patients take tamoxifen before an aromatase inhibitor, or after?
  • Which is best: Femara, Arimidex, or Aromasin?
  • Is taking one drug and then another beneficial?
  • Do women whose ovaries have been removed benefit from aromatase inhibitors?

And the biggest question is which drug to take. Aromatase inhibitors are still expensive, brand-name drugs. Tamoxifen is available in generic form and is much less expensive.

And aromatase inhibitors raise a woman's risk of osteoporosis. In the BIG 1-98 study, women taking Femara had a significantly higher risk of bone fracture than those taking tamoxifen.

"A woman with osteoporosis wouldn't be a good candidate for Femara," Thürlimann told WebMD last May.

Tamoxifen carries its own risks, including deadly blood clots and uterine cancer.

Women taking Femara had higher cholesterol and a higher incidence of heart trouble than women taking tamoxifen. It's not clear whether this is due to a side effect of Femara or a possible protective effect of tamoxifen.

The bottom line is that the best cancer drug for one woman isn't the best for another. Women with breast cancer -- and their doctors -- face difficult choices. The good news is that the choices are getting better and better.

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