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New ASCO Technology Assessment Recommends Aromatase Inhibitors as Adjuvant Therapy

Alexandria, VA – November 15, 2004 - Adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer should include an aromatase inhibitor in order to lower the risk of tumor recurrence, according to an updated technology assessment from the American Society of Clinical Oncology (ASCO).

This new technology assessment updates ASCO’s previous recommendation on adjuvant hormonal therapy for this specific group of women. These new recommendations, based on results from multiple large randomized trials, indicate that aromatase inhibitors are appropriate either following a course of tamoxifen or used as initial treatment. Options include treatment with tamoxifen for 2 to 5 years, followed by treatment with aromatase inhibitors, or treatment for 5 years with an aromatase inhibitor alone.

“These findings show a modest but consistent improvement in disease-free survival among women who received an aromatase inhibitor compared to those who did not,” said Eric P. Winer, MD, Director of the Breast Oncology Center at the Dana Farber Cancer Institute in Boston, Massachusetts, and lead author of the Technology Assessment. “In women with hormone receptor-positive early breast cancer, hormones can influence the growth of the cancer. In postmenopausal women, aromatase inhibitors can block estrogen production and reduce estrogen levels by more than 90 percent.”

The ASCO panel recommends the following general guidelines for use of aromatase inhibitors:

* Postmenopausal women with hormone receptor-positive breast cancer may substitute an aromatase inhibitor for tamoxifen as initial adjuvant therapy.Alternatively, women can still begin treatment with tamoxifen and plan to switch to an aromatase inhibitor after 2 to 5 years.It not clear at this time which strategy is superior.

* Postmenopausal women who are currently taking tamoxifen may considering switching to an aromatase inhibitor after 2 to 5 years of tamoxifen therapy.

* Women who switch to an aromatase inhibitor may continue this therapy for 2 to 3 more years, but no longer than 5 years. Women are advised that the result of treatment with an aromatase inhibitor for longer than 5 years has not been studied and should only be done in the context of a clinical trial.

* There are no data to recommend taking tamoxifen after an aromatase inhibitor.

In addition, women who develop invasive hormone receptor-positive breast cancer while taking tamoxifen for breast cancer risk reduction, and women who cannot take tamoxifen because of high risk of severe side effects, or who have tried tamoxifen and had to stop because of severe side effects, might be advised to consider using an aromatase inhibitor.

The three types of aromatase inhibitors highlighted in ASCO Technology Assessment are anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin). Doctors do not yet know if these drugs can be used interchangeably. In addition, the long-term side effects of aromatase inhibitors are not known. Early data suggest that when compared with tamoxifen, aromatase inhibitors may reduce the chance of blood clots and uterine cancer and may increase the risk of osteoporosis and fractures.

“While researchers await more mature results and findings from additional trials using the aromatase inhibitors in the adjuvant setting, many patients and physicians have elected to use the third-generation aromatase inhibitors either as initial therapy in the adjuvant setting or following a course of tamoxifen,” Winer said.

ASCO also released a new evidence-based technology assessment, Aromatase Inhibitors for Early Breast Cancer, the patient version of the clinical practice recommendations. The patient guide will be available online at on November 15.

Source: American Society of Clinical Oncology

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