Exemestane

Postmenopausal women with hormone receptor-positive breast cancer can take an aromatase inhibitor instead of tamoxifen as adjuvant therapy, the American Society of Clinical Oncology concluded in a technology-assessment statement.

Aromatase inhibitor adjuvant therapy may be associated with a higher rate of osteoporosis, but initial data indicate equal or better effectiveness than tamoxifen therapy in preventing cancer recurrence--particularly in women on tamoxifen therapy for 2-3 years and then switched for the remainder of 5 years, the statement said.

The statement reflects what is already common clinical practice, commented Richard Elledge, M.D., medical director of the breast care center at Baylor College of Medicine, Houston.

But there is still no real information to guide clinicians in selecting the patients who may be most appropriate for an aromatase inhibitor instead of tamoxifen, and there is need for even more long-term data, he added.

Longer-term data from two pivotal trials are expected to be announced in the next few months, said Dr. Elledge, a researcher who was not involved with the statement.

"This still remains an area undergoing rapid evolution," he said. "Right now, we just have this sea change."

Two nonsteroidal aromatase inhibitors, anastrozole and letrozole, are approved in the United States as first- or second-line treatment of hormone receptor-positive metastatic breast cancer, and one steroidal aromatase inactivator, exemestane, is approved for hormone therapy for women with metastatic breast cancer after disease progression or after antiestrogen therapy.

In metastatic disease treatment, all three agents have been equivalent or superior to tamoxifen in trials, the statement said.

As adjuvant therapy in postmenopausal patients with early-stage disease, the largest trial reported a disease-free survival rate of 92% for anastrozole, compared with 89% for tamoxifen, at a median follow-up of 4 years. That trial also reported that the patients on anastrozole had fewer thromboembolic events and uterine abnormalities than the patients on tamoxifen, but they had a higher fracture rate.

Two studies have compared tamoxifen taken for 5 years with tamoxifen taken for 2-3 years followed by a switch to an aromatase inhibitor for the remaining time; switching resulted in a 32% reduction in recurrence in both studies.

There is reason to think one would not want to start a patient on an aromatase inhibitor and then switch him or her to tamoxifen, but there are no clinical data on this strategy, the statement also said.

BY TIMOTHY F. KIRN

Sacramento Bureau

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