Decrease in breast cancer risk persists in estrogen trial follow-up

Postmenopausal women who were evaluated after taking conjugated equine estrogen (CEE) had neither an increased nor decreased risk of coronary heart disease (CHD), and a decrease in breast cancer risk persisted, according to a post-intervention follow-up of the Women’s Health Initiative (WHI) Estrogen-Alone Trial, published in the Journal of the American Medical Association.

The WHI Estrogen-Alone Trial was stopped early after a mean of 7.1 years of follow-up due to an increased risk of stroke. The intervention phase was a double-blind, placebo-controlled, randomized clinical trial comparing 0.625 mg/d of CEE with placebo in 10,739 postmenopausal U.S. women 50 to 79 years of age with prior hysterectomy.

Researchers with the Fred Hutchinson Cancer Research Center in Seattle, Wash., and other facilities found a lower breast cancer post-intervention risk in the CEE group of 0.26% compared to 0.34% in the placebo group. The post-intervention risk for CHD among women assigned to CEE was 0.64% compared to 0.67% in the placebo group. The risk of deep vein thrombosis was lower at 0.17% compared to 0.27% in the placebo group. Risk of stroke was no longer elevated in women receiving CEE at 36% compared to placebo at 41%. Hip fracture risk did not differ greatly at 36% with CEE and 28% with placebo.

Younger women had more favorable health outcomes compared to older women for CHD (P=.05 for interaction); total myocardial infarction (P=.007 for interaction); colorectal cancer (P=.04 for interaction); total mortality (P=.04 for interaction); and global index of chronic diseases (P=.009 for interaction).