Second Prempro study shows link to cancer risks
Published: Thursday, October 21, 2010 at 8:38 a.m.
Last Modified: Thursday, October 21, 2010 at 8:40 a.m.
If you wanted to sell a new drug that relieves hot flashes but raises the risk of the two biggest cancer killers in women, the Food and Drug Administration “would say you’re crazy,” says cancer specialist Rowan Chlebowski.
Yet, says Chlebowski, of the Los Angeles Biomedical Research Institute, that describes Prempro, a combination of the hormones estrogen and progestin used by 15 percent to 20 percent of postmenopausal women in the USA.
This week, Chlebowski and his coauthors reported in The Journal of the American Medical Association that, compared with a placebo, Prempro increased women’s risk of breast cancer and that their cancers were more likely to have spread to their lymph nodes. And, the scientists write, women who took the hormones were more likely to die of breast cancer.
Their findings are the latest to question 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 doesn’t increase the number of lung cancer cases.
These findings come out of a government-sponsored study known as the Women’s Health Initiative. One part of the study randomly assigned 16,000 women ages 50 to 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 1/2 years.
In February 2009, Chlebowski and his co-authors reported that Prempro users’ breast cancer risk appeared to drop markedly within two years of quitting treatment.
For this week’s breast cancer analysis, researchers followed nearly 13,000 of the women for an average of eight 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 maker Pfizer said it is reviewing Chlebowski’s data. “The increased risk of breast cancer compared to placebo has been included in Prempro’s label since its introduction in 1995,” the statement reads. “This analysis does not alter that risk, nor does it dispute hormone therapy’s effectiveness.”
Because the excess 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 see if lower doses or shorter doses could relieve symptoms without increasing cancer risk.
Cynthia Pearson, executive director of the National Women’s Health Network, agrees. “This is so important to women’s health,” Pearson says. “I would love more information.”
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