The increased risk of developing breast cancer for women who take Hormone replacement therapy (HRT) is very small, researchers suggest in this week’s issue of the British Medical Journal.

Recent studies of HRT have led to “often confusing information,” say Dr. John Boyages and colleagues at the University of Sydney in Australia. Their point is that the effect of HRT on breast cancer risk may be lower in an elderly population because of the reduced number of years remaining at risk.

Boyages’ team compiled data from several sources to calculate individual risk for women living to age 79. Information on the use of HRT was derived from the 2001 Australian health survey, while the annual incidence of breast cancer was pulled from the Cancer Council New South Wales Web site, and cumulative breast cancer risk for the population was obtained from the Million Women study.

The researchers estimate that using HRT for about five years, starting at age 50, hardly affects the cumulative breast cancer risk up to age 79. The risk associated with no HRT was 6.1 percent; with estrogen only, 6.3 percent; and with use of combined estrogen-progesterone HRT, 6.7 percent.

The extended use of estrogen for 10 years increases risk by 0.5 percent, and by 0.9 percent for 15 years.

The authors point out that upon cessation of HRT, the risk quickly returns to the same level as no usage.

“The indications for hormone replacement therapy vary and decisions regarding its use must be made at an individual level,” Boyages and his associates advise. “Our analysis provides women and clinicians with better information to make these choices.”

SOURCE: British Medical Journal, August 6, 2005.