On September 5, 2002, the FDA granted accelerated approval to anastrozole (Arimidex®, a trademark of AstraZeneca) for the adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer. The FDA received the application on March 5, 2002, and approved it on September 5, 2002.

Investigators enrolled 9,366 postmenopausal women with operable breast cancer (84 percent hormone receptor positive) in an international, multicenter, double-blind, randomized trial (ATAC). Patients were randomly allocated to receive adjuvant treatment with either 1 milligram of Arimidex daily, 20 milligrams of tamoxifen daily, or both drugs for five years or until recurrence of the disease.

At a median efficacy follow up of 33 months, preliminary results showed that recurrence-free survival was improved in the Arimidex arm compared to the tamoxifen arm. Similar results were observed in the hormone receptor-positive population.

Women receiving Arimidex had an increase in musculoskeletal events and fractures (including fractures of spine, hip and wrist), compared with those receiving tamoxifen. More patients receiving Arimidex were reported to have an elevated serum cholesterol compared to patients receiving tamoxifen.

Women receiving Arimidex had a decrease in hot flashes, vaginal bleeding, vaginal discharge, endometrial cancer, venous thromboembolic events (including deep venous thrombosis) and ischemic cerebrovascular events compared with those receiving tamoxifen.

In the ATAC bone substudy, women receiving Arimidex had a mean decrease in both lumbar spine and total hip bone mineral density (BMD) compared to baseline.

Women receiving tamoxifen had a mean increase in both lumbar spine and total hip BMD compared to baseline. Clinical and pharmacokinetic results suggest that tamoxifen should not be administered with Arimidex. Estrogen-containing therapies should not be used with Arimidex.

The approved dose of Arimidex is one 1 milligram tablet taken daily. For adjuvant (additional) treatment of early breast cancer in postmenopausal women, the optimal duration of therapy is unknown. The FDA has required mature survival and safety data at study completion be submitted to fulfill requirements of accelerated approval.

Full prescribing information is available, including clinical trial information, safety, dosing, drug-drug interactions and contraindications.

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