Hormone Therapy Found to Increase Breast Cancer Risk

A major clinical trial of the risks and benefits of hormone therapy for postmenopausal women has been halted early because of the finding that it increases the risk of invasive breast cancer. The results were published in the July 17, 2002, issue of The Journal of the American Medical Association (JAMA).

The study involved 16,608 women, aged 50-79, with an intact uterus who were enrolled in the study between 1993 and 1998 at more than 40 US clinical sites. The women were randomly assigned to a daily dose of estrogen (0.625 mg) plus progestin (2.5 mg) or to a placebo. The results showed that during one year, among 10,000 postmenopausal women taking these hormones, eight more (26%) will have invasive breast cancer than will a similar group of 10,000 women not taking these hormones. Similarly, seven more will have a heart attack (29%), eight more will have a stroke (41%), and 18 more (100%) will have blood clots, including eight with blood clots in the lungs.

Some benefits were also found: a 37% reduction in cases of colorectal cancer, a 33% reduction in hip fractures, and a 24% reduction in total fractures. The study was conducted by the US National Heart, Lung, and Blood Institute (NHLBI). Although the study was scheduled to run until 2005, it was stopped after an average follow-up of 5.2 years.

"Women with a uterus who are currently taking estrogen plus progestin should have a serious talk with their doctor to see if they should continue it,” said Jacques Rossouw, acting director of the Women's Health Initiative, a group participating in the study. "If they are taking this hormone combination for short-term relief of symptoms, it may be reasonable to continue since the benefits are likely to outweigh the risks. Longer term use or use for disease prevention must be re-evaluated given the multiple adverse effects noted.”