Hormone replacement therapy increases breast cancer risk, death risk

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Thursday June 27 ,2013 (foodconsumer.org) -- Hormone replacement therapy based on estrogen plus progestin increases the risk of breast cancer and mortality, according to a new study released in the Journal of the National Cancer Institute.

The study led by Rowan T. Chlebowski, MD, PhD from Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, CA and colleagues shows that during a 11-year follow-up, those who used estrogen plus progestin were 55 percent more likely than nonusers to develop breast cancer.

The study was based on epidemiologic data from the participants in the Women's Health Initiative randomized trial which has already shown that estrogen plus progestin increased both breast cancer incidence and all-cause death risk although most observational studies associated the hormone therapy with a favorable prognosis of breast cancers.

Among 41,449 postmenopausal women with no prior hysterectomy and mammogram negative within 2 years, 25,328 did not use hormone therapy while 16,121 used estrogen and progestin.  During the 11.3 year follow-up, 2236 women were diagnosed with breast cancer. 

Statistical analysis shows that breast cancer incidence was higher among estrogen plus progestin users than non-users, 0.60% vs. 0.42%, annualized rate, respectively, which means that hormone therapy users were 55 percent more likely to develop breast cancers.

Women starting to use the estrogen plus progestin therapy closer to menopause had higher breast cancer risk and as time from menopause increased, the increase in the risk linearly diminished.  The survival rate was similar in combined hormone therapy users and non-users.

On a population basis, estrogen plus progestin users were 32 percent more likely to die from breast cancer and 65 percent more likely to die from all causes, compared with non-users.

The researchers concluded "Consistent with WHI randomized trial findings, estrogen plus progestin use is associated with increased breast cancer incidence. Because prognosis after diagnosis on combined hormone therapy is similar to that of nonusers, increased breast cancer mortality can be expected.

An authoritative organization says that two major risk factors for breast cancer are hormone replacement therapy and medical radiation used in diagnostic tools and cancer treatment.

Early studies also linked hormone therapy to increased risk of heart disease in addition to breast cancer. (reporting by Jimmy Downs)

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