Menopausal hormone therapy, long linked to a slight increase in breast cancer risk, also makes mammograms less reliable and may delay diagnosis of breast cancer.
Those findings, published in today’s Journal of the American Medical Association, are the latest bad news about estrogen-progestin therapy.
A federally financed study, the Women’s Health Initiative, has produced a cascade of data over the last year about the negative health effects of hormone therapy, prompting millions of American women to abandon the drugs that physicians once viewed as menopausal cure-alls.
These are the findings of the last year:
July: Women on hormones had more heart attacks, strokes, blood clots, and breast cancer than women on placebo. These harms outweighed a decrease in colon cancer and hip fractures.
March: Women on hormones had no better quality of life, including general health, energy, depression, and sexual satisfaction, than women on placebo.
May: Women on hormones were not protected from normal declines in mental function and were at higher risk for developing dementia.
The Women’s Health Initiative halted the estrogen-progestin part of the study prematurely in July because, after five years on hormones, the women’s increased health risks became apparent.
An estimated three million women continue to take hormones, primarily to relieve menopausal hot flashes and vaginal dryness, uses still approved by the FDA.
The latest data on breast cancer confirm and contradict previous, less-rigorous studies.
The new data found a 24 percent increase in breast cancer risk, not much different from other studies. (For the average woman, that would increase the lifetime risk of developing breast cancer from 1 in 8 to about 1 in 7.)
But although some previous studies found that hormone users tended to have highly curable, slow-growing tumors, the Health Initiative found that hormone users were just as likely to have aggressive cancers as nonusers.
What’s more, hormone users had more abnormal mammograms and their tumors were bigger and more advanced at diagnosis. This may be because hormones increase breast density, making mammograms less reliable, or because hormones stimulate cancerous growth or both, say the researchers, from UCLA, Stanford University, Brown Medical School and other institutions across the country.
In an editorial in the journal, two breast-cancer researchers said hormones’ effect on the breast created a double-whammy that is “almost unique” in medicine.
“An agent increases the risk of developing a disease while simultaneously delaying its detection,” wrote Northwestern University epidemiologist Peter H. Gann and surgeon Monica Morrow.
Morrow happens to be the coauthor of a 1999 study that concluded hormone use did not increase breast-cancer risk except for rare, highly curable types.
But her study, like all the important research on hormone therapy prior to the Women’s Health Initiative, relied on circumstantial evidence, comparing women who chose to use hormones to those who didn’t.
Even though hormone therapy has been popular since the 1960s, the Health Initiative is the first study to randomly give hormones or placebo to a large enough number (more than 16,000) of healthy postmenopausal women to draw unbiased conclusions.
Even Wyeth Laboratories, maker of Prempro, the estrogen-progestin brand used in the study, stands by the results.
“This is the most rigorous, definitive study to date,” Wyeth medical director Victoria Kusiak said.
Wyeth’s first-quarter sales of Prempro and related products dropped from about $550 million last year to $342 million this year. And the company, which just recently closed the books on the fen-phen diet drug class-action lawsuits, faces another legal tempest, as personal-injury lawyers rush to state and federal courts on behalf of hormone users. At least five class-action lawsuits have been filed, including one in Pennsylvania.
Wyeth spokeswoman Natalie DeVane said: “As a company, we believe any claims brought against us related to Prempro or the Women’s Health Initiative would be without factual or legal basis.”
Although Prempro pills were used in the study, the researchers say they have no evidence that other brands are safer.