Health Risks and Benefits 3 Years After Stopping Randomized Treatment With Estrogen and Progestin

March 2008

Findings Summary

The Women’s Health Initiative (WHI) Estrogen plus Progestin Study (E+P) was stopped on July 7, 2002 (after an average 5.6 years of follow-up) because of increased risks of cardiovascular disease and breast cancer in women taking active study pills, compared with those on placebo (inactive pills). The study showed that the overall risks exceeded the benefits, with women taking E+P at higher risk for heart disease, blood clots, stroke, and breast cancer, but at lower risk for fracture and colon cancer.
After stopping study pills in the E+P trial, WHI continued to collect follow-up study data from participants to evaluate the effects of stopping hormone therapy. Follow-up information for the period July 8, 2002 to March 31, 2005 was available on 95% of the women. This summary reports on the health outcomes of E+P trial participants at three years after the study pill intervention was stopped (with a mean average of 2.4 years of follow-up). The primary outcomes of interest were coronary heart disease and invasive breast cancer. A global index used to summarize the balance of risks and benefits included these two outcomes, plus stroke, pulmonary embolism, endometrial cancer, colorectal cancer, hip fracture, and death due to other causes.
Three years after stopping hormone therapy, women who had taken study pills with active estrogen plus progestin no longer had an increased risk of cardiovascular disease (heart disease, stroke, and blood clots) compared with women on placebo. The lower risk of colorectal cancer seen in women who had taken active E+P disappeared after stopping the intervention. The benefit for fractures (broken bones) in women who had taken active E+P also disappeared after stopping hormone therapy. On the other hand, the risk of all cancers combined in women who had used E+P increased after stopping the intervention compared to those on placebo. This was due to increases in a variety of cancers, including lung cancer. After stopping the intervention, mortality from all causes was somewhat higher in women who had taken active E+P pills compared with the placebo.
Based on the findings mentioned above, the study’s global index that summarized risk and benefits was unchanged, showing that the health risks exceeded the health benefits from the beginning of the study through the end of this three year follow-up. The follow-up after stopping estrogen plus progestin confirms the study’s main conclusion that combination hormone therapy (E+P) should not be used to prevent disease in healthy, postmenopausal women. The most important message to women who have stopped this hormone therapy is to continue seeing their physicians for rigorous prevention and screening activities for all important preventable health conditions.