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[NOTE: Keep in mind that HRT — Hormone Replacement Therapy — uses the same artificial hormones that are used in chemical birth control methods.]

Prempro is a “drug that relieves hot flashes but raises the risk of the two biggest cancer killers in women” according to Rowan Chlebowski, Los Angeles Biomedical Research Institute.

Prempro is a combination of the hormones estrogen and progestin used by 15% to 20% of post-menopausal women in the USA.

Chlebowski et al reported in JAMA (Oct 2010) that, compared with a placebo, Prempro increased women’s risk of breast cancer, that their cancers were more likely to have spread to their lymph nodes, and that they were more likely to die of breast cancer.

These findings come from a government-sponsored study known as the Women’s Health Initiative. One part of the study randomly assigned 16,000 women, aged 50-79, to either Prempro or a placebo.

That study was halted in July 2002 because long-term Prempro use was found to raise the risk of breast cancer, heart attack and stroke.

Participants had been taking their pills for an average of 5.5 years.

These findings join a growing list of studies questioning the safety of hormone therapy.

Last year, the same researchers reported in The Lancet that, compared with a placebo, Prempro raises the number of lung cancer deaths, although it does not increase the number of lung cancer cases.

In February 2009, Chlebowski et al reported that Prempro users had a marked decrease in breast cancer risk within two years of quitting treatment.

In this second Prempro study just released, researchers followed about 13,000 women for an average of 8 years after they had stopped taking their pills.

So far, about 1.3 extra breast cancer deaths per 10,000 women per year have occurred in those on Prempro.

In a statement, Prempro manufacturer Pfizer noted: “The increased risk of breast cancer compared to placebo has been included in Prempro’s label since its introduction in 1995. This analysis does not alter that risk…”

Because the extra breast cancer deaths in Prempro users were relatively few, Peter Bach of Memorial Sloan-Kettering Cancer in New York writes in an editorial in JAMA, doctors “might conclude that a brief period of hormone therapy for relief of menopausal symptoms is safe.”

But, Bach continues, no one has proven that.

He calls for additional studies to determine whether lower doses or shorter duration could relieve symptoms without increasing cancer risk.

[21 Oct 2010, Thursday, USA TODAY, McLean, VA, Rita Rubin, p A3]