Exemestane vs. tamoxifen after 2-3 years' tamoxifen

Switching to exemestane after 2 to 3 years of treatment with tamoxifen improves disease-free and overall survival in postmenopausal women with estrogen-receptor–positive early breast cancer, according to the results of a randomized, controlled trial from Europe.

Researchers included almost 5,000 women who had unilateral invasive disease but who were disease-free after 2 to 3 years of treatment with tamoxifen. Half the women were then switched to the aromatase inhibitor exemestane, while the other half continued taking tamoxifen for the remainder of 5 years.

After a median follow-up of 4.5 years, the unadjusted hazard ratio was 0.76 (95% CI, 0.66–0.88, P=0.0001) in favor of exemestane. The absolute benefit by the end of treatment was 3.3% (95% CI, 1.6–4.9). In terms of number of deaths, 222 occurred in the exemestane group versus 261 in the tamoxifen group.

Coombes RC, Kilburn LS, Snowdon CF, et al. Survival and safety of exemestane versus tamoxifen after 2-3 years' tamoxifen treatment (Intergroup Exemestane Study): a randomised controlled trial. Lancet. 2007;369:559-570.