Anastrozole beats Tamoxifen for early breast cancer: Anastrozole reduced disease recurrence risk by 17%, compared with tamoxifen. (Study of 9,366 Women).

SAN ANTONIO -- The aromatase inhibitor anastrozole is markedly more effective and better tolerated than tamoxifen for adjunctive therapy in postmenopausal women with early-stage breast cancer.

Those were the major findings of the largest breast cancer treatment trial ever conducted. The study was reported at the annual breast cancer symposium sponsored by the San Antonio Cancer Institute.

After a median 30 months of treatment, there were 317 breast cancer relapses or deaths among women in the anastrozole (Arimidex) arm of the trial, compared with 379 in the tamoxifen arm and 383 in women on both agents. This equated to an overall 17% reduction in risk of disease recurrence in women on anastrozole, compared with those on tamoxifen.

The reduction in recurrence risk was 22% among women with confirmed hormone receptor--positive tumors, reported Dr. Michael Baum, professor emeritus of surgery at University College, London.

Despite these encouraging findings, Dr. Baum cautioned that further investigation is warranted before physicians should switch their breast cancer patients from tamoxifen to anastrozole.

The current study known as the Arimidex, Tamoxifen Alone or in Combination (ATAC) trial, was sponsored by AstraZeneca Pharmaceuticals, maker of Arimidex. It was a double-blind randomized study involving 9,366 women with early operable breast cancer at 380 hospitals in 21 nations. After completing primary surgery and chemotherapy if prescribed, these women with generally good-prognosis breast cancers were randomized to 1 mg/day of anastrozole, 20 mg/day of tamoxifen, or both.

The combination arm was included to see if dual therapy provided additional efficacy over that of tamoxifen alone, long considered the standard adjunctive therapy in patients with early breast cancer. It did not in any respect.