Following Tamoxifen with Aromatase Inhibitors

A new study published in the Journal of Clinical Oncology suggests that postmenopausal women who take tamoxifen for three years may then benefit from switching to a new class of drugs called aromatase inhibitors.

Studies have shown that breast cancer growth often depends on the presence of estrogen. Tamoxifen is a drug that is extremely effective in blocking the action of estrogens. But after about five years, it appears that tamoxifen stops working effectively.

Aromatase inhibitors also work on estrogen-sensitive cancers, but in a different way. They do not block the action of estrogen but rather work by preventing estrogen production in the first place.

Dr. Francesco Boccardo of the National Cancer Research Institute in Genoa, Italy and colleagues studied 380 postmenopausal breast cancer patients who had been using tamoxifen for three years. Approximately half of the patients continued on tamoxifen therapy for another two years while the other half were given low-dose aminoglutethimide, an aromatase inhibitor.

After a median follow-up period of 61 months, Boccardo's team observed no significant difference in "cancer-related events" between the two groups. However, in terms of overall survival, they noted "a significant trend favors aminoglutethimide in overall survival and breast cancer-specific survival."

They cautioned that more patients in the aromatase inhibitor group complained of drug-related side effects and more of them discontinued treatment, but "the number of cardiovascular events and, in general, life-threatening adverse events was higher in the tamoxifen arm," they wrote.

"Switching patients from tamoxifen to aminoglutethimide treatment resulted in comparable event-free survival, but longer overall survival was achieved in patients who were switched to aminoglutethimide as compared with those who continued to receive tamoxifen," they concluded.

The researchers noted that additional studies are underway to test the effectiveness of new, more active and more tolerable aromatase inhibitors. If these outcomes are positive, they added, "sequencing tamoxifen with an aromatase inhibitor could become a preferable alternative to tamoxifen alone in early breast cancer patients."

SOURCES:
Journal of Clinical Oncology, November 15, 2001; 19:4209-4215
36th Annual Meeting of the American Society of Clinical Oncology, May 20-23, 2000, New Orleans, LA
American Cancer Society (http://www.cancer.org)

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