Replacement Hormone Therapy Can Double Clot RiskMay 23, 2008 | Parker Waichman LLP
A French review of a variety of studies just revealed that menopausal women who take hormone-replacement therapy (HRT) pills more than double their risk of developing a potentially fatal blood clot. The review of 17 studies suggested that the risk was also significantly higher during the first year of HRT. The findings appear in the British Medical Journal.
HRT relieves serious menopausal symptoms such as hot flashes and was popular until a 2002 study—The Women’s Health Initiative—suggested it could raise the risk of breast and ovarian cancer, strokes, and other life-threatening conditions. Arterial blood clots are a common cause of heart attacks and strokes; vein blood clots can kill if they move to the lungs. "This meta-analysis ... showed that current use of oral oestrogen increases the risk of (blood clots) by two-fold to three-fold," Pierre-Yves Scarabin and Marianne Canonico of the Paul Brousse Hospital in France wrote. Earlier trials linked HRT drugs to blood clots; however, the French review marks the first systematic meta-analysis—a review of what myriad studies found—to truly assess the risk.
Analysis of eight observational studies and nine randomized controlled trials found that HRT via patch showed no significant increased risk, unlike the pills. Perhaps due to the different way oestrogen—oral estrogen—is absorbed. Further research is needed to confirm the findings, the team said. When taken orally, oestrogen enters through the digestive system and is processed by the liver, which might impair the balance between clotting and anti-clotting factors in the blood, the researchers said.
Meanwhile, in January, U.S. researchers reported HRT significantly raises the risk of an uncommon type of breast cancer. The study found women who took combined estrogen/progestin HRT for three years or more had four times the usual risk of lobular breast cancer. The study, published in the January issue of Cancer Epidemiology, Biomarkers and Prevention, is one of dozens of studies looking to clarify the dangers of taking HRT to treat menopause symptoms. "Previous research indicated that five or more years of combined hormone-therapy use was necessary to increase overall breast-cancer risk," Dr. Christopher Li of the Fred Hutchinson Cancer Research Center, who led the study, said. "Our study, the first specifically designed to evaluate the relationship between combined HRT and lobular breast cancers, suggests that a significantly shorter length of exposure to such hormones may confer an increased risk," he added. According to the American Cancer Society, lobular breast cancer accounts for about 10 percent of all invasive breast cancers, the cancers that most threaten to spread to other parts of the body.
Historically, doctors believed HRT could protect women from chronic diseases, especially heart disease. But use of HRT plunged after the 2002 Women's Health Initiative study confirmed HRT could raise the risk of certain cancers, strokes, and other serious conditions. Research since also indicates that the incidence of breast cancer dropped by 8.6 percent between 2001 and 2004 in the U.S., in conjunction with the decline in HRT use.