Do health effects of menopausal estrogen therapy differ between women with bilateral oophorectomy versus those with conserved ovaries? To answer this question a group of investigators performed a subanalysis of the Women’s Health Initiative (WHI) Estrogen-Alone Trial,1 which included 40 clinical centers across the United States. They examined estrogen therapy outcomes by bilateral salpingo-oophorectomy (BSO) status, with additional stratification by 10-year age groups in 9,939 women aged 50 to 79 years with prior hysterectomy and known oophorectomy status. In the WHI trial, women were randomly assigned to conjugated equine estrogens (CEE) 0.625 mg/d or placebo for a median of 7.2 years. Investigators assessed the incidence of coronary heart disease and invasive breast cancer (the trial’s 2 primary end points), all-cause mortality, and a “global index”—these end points plus stroke, pulmonary embolism, colorectal cancer, and hip fracture—during the intervention phase and 18-year cumulative follow-up.
OBG Management caught up with lead author JoAnn E. Manson, MD, DrPH, NCMP, to discuss the study’s results.
OBG Management: How many women undergo BSO with their hysterectomy?
Dr. JoAnn E. Manson, MD, DrPH, NCMP: Of the 425,000 women who undergo hysterectomy in the United States for benign reasons each year,2,3 about 40% of them undergo BSO—so between 150,000 and 200,000 women per year undergo BSO with their hysterectomy.4,5
OBG Management: Although BSO is performed with hysterectomy to minimize patients’ future ovarian cancer risk, does BSO have health risks of its own, and how has estrogen been shown to affect these risks?
Dr. Manson: First, yes, BSO has been associated with health risks, especially when it is performed at a young age, such as before age 45. It has been linked to an increased risk of heart disease, osteoporosis, cognitive decline, and all-cause mortality. According to observational studies, estrogen therapy appears to offset many of these risks, particularly those related to heart disease and osteoporosis (the evidence is less clear on cognitive deficits).5
OBG Management: What did you find in your trial when you randomly assigned women in the age groups of 50 to 79 who underwent hysterectomy with and without BSO to estrogen therapy or placebo?
Dr. Manson: The WHI is the first study to be conducted in a randomized trial setting to analyze the health risks and benefits of estrogen therapy according to whether or not women had their ovaries removed. What we found was that the woman’s age had a strong influence on the effects of estrogen therapy among women who had BSO but only a negligible effect among women who had conserved ovaries. Overall, across the full age range, the effects of estrogen therapy did not differ substantially between women who had a BSO and those who had their ovaries conserved.
However, there were major differences by age group among the women who had BSO. A significant 32% reduction in all-cause mortality emerged during the 18-year follow-up period among the younger women (below age 60) who had BSO when they received estrogen therapy as compared with placebo. By contrast, the women who had conserved ovaries did not have this significant reduction in all-cause mortality, or in most of the other outcomes on estrogen compared with placebo. Overall, the effects of estrogen therapy tended to be relatively neutral in the women with conserved ovaries.
Now, the reduction in all-cause mortality with estrogen therapy was particularly pronounced among women who had BSO before age 45. They had a 40% statistically significant reduction in all-cause mortality with estrogen therapy compared with placebo. Also, among the women with BSO, there was a strong association between the timing of estrogen initiation and the magnitude of reduction in mortality. Women who started the estrogen therapy within 10 years of having the BSO had a 34% significant reduction in all-cause mortality, and those who started estrogen more than 20 years after having their ovaries removed had no reduction in mortality.
Continue to: OBG Management: Do your data give support to the timing hypothesis?