Breast cancer drug may improve on old one - studies
By Maggie Fox

WASHINGTON- A new class of breast cancer drug seems to work even better than the standard tamoxifen in fighting the disease, at least in some women, researchers said on Monday.

They said it was too soon to say if the new drugs, called aromatase inhibitors, should replace tamoxifen as a favored drug, but they shrank tumors better and helped more women survive.

Breast cancer is the second biggest cancer killer of women in the industrialized world, after lung cancer. It kills 40,000 women each year in the United States.

Several studies presented at a breast cancer conference in San Antonio show one brand of aromatase inhibitor called Femara, made by Swiss drugmaker Novartis under the generic name letrozole, may work in a wider range of women than tamoxifen.

"Letrozole is associated with a higher rate of tumor shrinkage ... and a better one- and two-year survival than tamoxifen," Duke University's Dr. Matthew Ellis, who presented one study to the conference, said in a telephone interview.

Femara is a member of a new class of drugs called aromatase inhibitors, which work differently from tamoxifen to prevent certain kinds of breast cancer. Tamoxifen is made under the name Nolvadex by AstraZeneca Plc but is now available generically as well.

"It has a very simple mechanism of action that is not prone to the problems that tamoxifen is," Ellis said. "It reduces the ability of the body to make estrogen."

About 80 percent of women with breast cancer have what is called estrogen receptor positive cancer caused by the female hormone's effect on cells.

Ellis, working with researchers in Germany, Spain, France and Britain, followed 324 women taking either tamoxifen or Femara. They saw tumors shrink in 60 percent of women taking Femara for four months, compared to 41 percent of women taking tamoxifen.

New drugs block estrogen better. "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," Ellis, who is a paid consultant to Novartis, which also funded the study, said in a statement.

In a second study, Dr. Martine Piccart of the Jules Bodet Institute in Brussels, Belgium, and colleagues followed 453 women taking Femara and 454 taking tamoxifen.

Overall median survival was 34 months with Femara and 30 months with tamoxifen. Piccart said 64 percent of patients were alive two years after starting Femara, compared to 58 percent of tamoxifen patients.

Ellis' team worked with women whose breast cancer had progressed to the late stages, but another study presented at the conference showed a related drug, Arimidex, could help women with early breast cancer.

Made by AstraZeneca under the generic name Anastrozole, Arimidex also reduced breast cancer deaths.

After a median of 30 months' treatment and 33 months of follow-up, 317 of 3,125 women given Arimidex suffered relapses, compared to 379 of 3,116 women taking tamoxifen - a 17 percent reduction.

"This advance is as important for women fighting early breast cancer as the advent of tamoxifen was 20 years ago," Michael Baum of University College Hospital in London, who presented the results, said.

"The results of the (latest) study ... may support the use of anastrozole, rather than tamoxifen, as the future treatment of choice," he added.

Tamoxifen mimics some of the action of estrogen and by doing so blocks its cancer-causing effects - usually. But sometimes it does not, and tamoxifen can increase the risk of a very rare form of cancer of the uterus.

Femara and related drugs stop the action of an enzyme called aromatase, which converts androgen, a precursor hormone, into the female hormone estrogen.

Women taking letrozole make almost no estrogen. Tamoxifen has been shown to reduce cases of breast cancer in healthy women who are known to have a high risk of the disease.

The researchers said it was too soon to tell if the new drugs would have the same effect.

A third company, Pharmacia, makes an aromatase inhibitor called Aromasin. - Reuters