Elevated cancer risk seen in ex-hormone users

March 4, 2008

NEW YORK (Reuters Health) - Participants in the Women's Health Initiative (WHI) trial who stopped using estrogen plus progestin when the study was terminated in 2002 appear to be at increased risk for subsequent fatal and nonfatal malignancies compared with subjects who had received placebo, new research shows.

The WHI trial was intended to run for 8 to 9 years, but it was stopped after a mean of 5.6 years after estrogen/progestin use was linked to an increased risk of invasive breast cancer and appeared to yield no overall health benefit. The goal of the present study, reported in the Journal of the American Medical Association for March 5, was to determine the health outcomes of 15,730 participants 3 years after the intervention had stopped.

The risk of cardiovascular events in ex-hormone and ex-placebo users was comparable, with annualized rates of 1.97% and 1.91%, respectively, Dr. Gerardo Heiss, from the University of North Carolina School of Public Health in Chapel Hill, and colleagues found. This runs counter to what was noted during the WHI trial when hormone use was linked to an increased risk of such events.

As noted, women who had received hormone therapy were more likely to develop cancer than were controls during the postintervention phase, with annualized rates of 1.56% and 1.26%, respectively.

Breast cancers were more common in ex-hormone users than in ex-placebo users. However, the relative risk seen was lower than that noted during the trial.

"All-cause mortality was somewhat higher in the (estrogen + progestin) than in the placebo group (1.20% vs 1.06%)," the report indicates.

Women treated with hormone therapy had a global index of risks and benefits that was 12% higher than that of controls, indicating that the risks of this therapy outweigh the benefits.

"Following termination of use of conjugated equine estrogens plus medroxyprogesterone acetate of 3.5 to 8.5 years, clinical vigilance seems warranted with respect to a sustained higher risk of malignancies," the researchers conclude.