TUESDAY, March 4, 2008 (HealthDay News) -- An increased risk of breast cancer lingers after a woman stops taking combination hormone replacement therapy, a new study shows.
The finding, published in the March 5 issue of the Journal of the American Medical Association, was based on data from the landmark Women's Health Initiative (WHI). That trial was halted abruptly in 2002, when it was discovered that postmenopausal women taking combination hormone therapy (estrogen plus progestin) had a higher risk of cardiovascular disease, stroke, blood clots and breast cancer.
"Within a couple of years, the [raised] risk for stroke, serious blood clots and heart attack disappears, but so do the benefits to bone," added study author Marcia Stefanick, a professor of medicine at Stanford University. "The concerning issue is the risk for all cancers remains significantly elevated, mostly because of breast cancer."
Stefanick said it wasn't clear if these were new breast cancers or existing tumors that had not been detected while women were still taking hormone therapy. A study in the Archives of Internal Medicine last week found women taking combined hormone therapy for about five years had a higher risk of abnormal mammograms and breast biopsies. This, in turn, may decrease the effectiveness of these methods for detecting breast cancer.
Dr. James Liu, chairman of obstetrics and gynecology at MacDonald Women's Hospital at Case Medical Center, University Hospitals, in Cleveland, emphasized that the results applied only to women taking combination hormone therapy, and that there may indeed be a delay involved. "The good news is that these changes do reverse," he said. "There may be some lag time in the breast risk, but because the breast risk actually increases with age independent of estrogen, women still should continue to have annual surveillance."
Stefanick is chairwoman of the WHI investigator group, and Liu was the principal investigator for the WHI in Cincinnati until 2001.
The current research followed 15,730 of the original WHI participants for an average of three years after the trial ended.
The risk of cardiovascular problems was similar in the HRT and placebo groups (1.97 percent and 1.91 percent, respectively). However, there was a greater risk of overall cancer in the HRT group (1.56 percent of participants) as compared with the placebo group (1.26 percent). Most of this was explained by a heightened risk of breast cancer, the researchers said.
Lung cancer risk was slightly higher but not enough to draw any firm conclusions. "It's not such a big study that you can see all the things you need to see when you look across the population," Stefanick said. "The people who are actually studying cancer across the whole population will start to potentially identify other cancers that are related to the combination therapy."
Death from any cause was 15 percent higher in the HRT group than in the placebo group.
Putting all these factors together, the risks of combined HRT exceed the benefits, the authors stated.
"The really important message for women is they need to get a mammogram if they've stopped using hormones," Stefanick said. "They shouldn't think everything is fine. They need to get a mammogram to make absolutely sure. Once they've stopped the hormones, you have a better chance of detecting them."
Follow-up data in the estrogen-alone arm of the WHI is not yet available.
More information
The National Heart, Lung, and Blood Institute has more on the Women's Health Initiative.
