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New Drugs Better at Treating Breast Cancer, Study Shows

Posted on: Thursday, 16 December 2004, 09:00 CST

From wire reports

A new family of drugs, known as aromatase inhibitors, is more effective at treating breast cancer in post-menopausal women than the current gold-standard drug, tamoxifen, researchers said Wednesday.

The drugs also reduced recurrence of the disease and eliminated the most severe side effects now associated with breast cancer treatment.

A major international study on more than 9,000 women with localized breast cancer showed that one of the drugs, anastrozole, raised disease-free survival by 10 percent, increased the time to recurrence by 20 percent and reduced spread of the cancer to the second breast by 40 percent compared to tamoxifen.

Trade-named Arimidex, anastrozole should now be the first choice in treating as many as half of the 213,000 American women who develop breast cancer each year, said Dr. Aman Buzdar of the University of Texas M.D. Anderson Cancer Center in Houston, a co- author of the study.

Arimidex is a much better drug, he said. I see little reason to use tamoxifen as the initial treatment in new patients with breast cancer.

Buzdar presented data from the study at the San Antonio Breast Cancer Symposium on Wednesday, and the data were published online in the medical journal Lancet.

A second study presented at the symposium showed that switching to another member of the family, exemstane , trade-named Aromasin , after two years of tamoxifen therapy was substantially more effective than sticking to tamoxifen for the normal five-year course of therapy.

The study of nearly 5,000 patients showed that women who switched to exemstane after two years had a 30 percent reduction in recurrence over the three-year study and a 54 percent reduction in cancer in the second breast, said Dr. Charles Coombes of Imperial College London.

The benefit of exemstane justifies offering treatment as early as possible, he said.

A third study of more than 3,000 women showed that switching from tamoxifen to anastrozole after two or three years reduced the risk of recurrence by 40 percent.

The studies were largely funded by the makers of the newer drugs, but experts not involved in the work were impressed by the results.

You dont have to be a rocket scientist to see that there are consistent improvements, said Dr. Derek Raghavan of the Cleveland Clinic, who was not involved in the studies.

People forget that tamoxifen already cuts recurrence of cancer by 50 percent, he said. Using one of the new drugs could reduce it by 70 percent to 80 percent, he said.

Because the three studies examined different patient populations and different drugs, a direct comparison of the percentage changes is not possible. What is clear, however, is that the aromatase inhibitors are generally more effective than tamoxifen and that using them earlier in the treatment process produces greater benefits.

Tamoxifen revolutionized breast-cancer treatment when it was introduced three decades ago. It prevents a womans estrogen from binding to cancer tissues and promoting their growth. About three- quarters of post-menopausal breast-cancer patients and perhaps 20 percent of pre-menopausal ones have tumors that are sensitive to estrogen.

But tamoxifen can have severe side effects, including the development of endometrial cancer .

None of the studies change tamoxifens status as the drug of choice for women who get breast cancer before menopause, because the newer drugs arent thought to be effective then.

The aromatase inhibitors, which were approved for sale about three years ago, work by a different mechanism, blocking the bodys production of estrogen and thereby robbing tumors of their stimulation. So far, they do not seem to produce the side effects caused by tamoxifen, although they can increase joint pain and fractures.

Results reported last year with a third member of the family, lotrezole, trade-named Femara , showed that giving it to women after they have completed five years of therapy with tamoxifen at which point that drug is no longer effective could reduce tumor recurrence over the following five years by 43 percent.

This story was compiled from reports by the Los Angeles Times and The Associated Press.

Source: Virginian - Pilot

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