Estrogen plus progestin more dangerous than thought
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A new study shows women who have used a hormone therapy based on estrogen and progestin have a higher risk of developing fatal breast cancer, compared with women who do not use the hormone therapy.
Rowan T. Chlebowski, MD, PhD of Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, California and colleagues found women who had used estrogen and progestin for an average of 5.6 years were 25 percent more likely to develop breast cancer and were twice as likely to die from the disease.
Hormone replacement therapy based on estrogen plus progestin was tested in a clinical trial known as The Women's Health Initiative Study and was found to drastically increase risk of breast cancer, heart disease and stroke among women.
The study involved more than 161,000 women ages 50 to 79.
Chlebowski previously reported in the February 2009 issue of the New England Journal of Medicine that women faced a 100 percent increased risk of developing breast cancer during 5.6 years of using estrogen plus progestin.
The risk of breast cancer after intervention was inconsistent. Some researchers found the risk of breast cancer after the therapy dropped quickly while others observed otherwise.
In the current study published in Journal of American Medical Association, Chlebowski et al. said both invasive breast cancer incidence and mortality were increased among women who used the combined hormone therapy for 5.6 years and were followed up for 7.9 years.
The goal of the current study was to look at the associations between use of the hormone therapy and mortality and incidence of invasive breast cancer among postmenopausal women using the estrogen and progestin therapy during a 11-year follow-up through Aug 2009.
The study involved a total of 16,608 postmenopausal women ages 50 to 79 who received 0.625 mg per day of conjugated equine estrogen and 0.25 mg per day of medroxyprogesterone acetate.
The researchers found women receiving estrogen plus progestin were more likely to develop breast cancer compared with women in the placebo group. The risk for breast cancer and invasive breast cancer was increased by 25 percent and 75 percent, respectively.
They also found women in the study group were twice as likely as the controls to die from breast cancer and 57 percent more likely to die from all causes, compared with controls.
Chlebowski concluded "Estrogen plus progestin was associated with greater breast cancer incidence, and the cancers are more commonly node-positive. Breast cancer mortality also appears to be increased with combined use of estrogen plus progestin."
The trial of estrogen plus progestin was discontinued in 2002 after the association was found between use of the hormones and increased risk of breast cancer, heart disease and stroke.
However, the combined hormone therapy may still be prescribed to women for a short-term use to help them overcome hot flashes.
David Liu and editing by Aimee Keenan Greene
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