New analysis of a large federal study suggests menopause hormones taken for five years increases the risk for breast cancer twofold, revealing compelling findings of the dangers associated with these still widely used pills.
The new findings, presented last week at the San Antonio Breast Cancer Symposium, will likely put to rest any doubts that the risks outweigh the benefits for most women.
In recent years, breast cancer rates have declined, largely, due to millions of menopausal women that have stopped taking hormone therapy and fewer women are starting taking it, said Dr. Rowan Chlebowski, M.D., Ph.D., the study’s leader of Harbor-UCLA Medical Center in Los Angeles.
“This is excellent news: Even if you’ve been taking hormones for a long time, quitting will still lower your risk of cancer within about two years,” said Dr. Claudine Isaacs, Medical Director of the Cancer Assessment and Risk Evaluation program (CARE) at Georgetown University.
The findings are based on the Women’s Health Initiative (WHI), which tested progestin and estrogen pills that doctors believed could prevent heart disease, bone loss and other medical conditions in women following menopause. The study was halted in 2002 after researchers found that HRT increased the risk of adverse events including blood clots, heart attack and breast cancer in hormone users.
Since that time, experts have continued debating about whether the risks apply to those women just starting on hormones after entering menopause, usually in their 59s, and take them for less time. The federal study included women mostly in their 60s and well past menopause.
Experts recommend using hormone therapy only when symptoms are severe and to use the lowest dosage possible for the shortest amount of time. New findings still support those recommendations and while they remain the same, what has changed is “whether hormone treatment should be started at all,” Chlebowski said.
Most short-term pill users are not at risk for developing breast cancer. The increased risk from hormone use over a few years accounts for a few extra cases of breast cancer per 1,000 hormone users. However, with each year of use, the risk increases.
The WHI was made up of two parts. The first part of the study included 16,608 women who were randomly assigned a placebo or Wyeth’s Prepmro (estrogen and progestin).
Researchers detected a 26 percent higher risk of breast cancer in women given Prempro prompting the study to be halted.
But, that average was based on the 5 ½ years the women were on the pills. For the new study, researchers followed 15,387 of these women through July 2005 and marked breast cancer cases as they occurred.
Researchers found a pattern – at the start of use, risk increased, peaked when the study ended and fell when hormone users stopped taking their pills. The risk of breast cancer for pill takers was twice that of the others at the peak.
In the second part of the study, 16,121 women who had taken hormones for about seven years and another group of 25,329 women that had never used hormone pills were examined.
In retrospect researchers found hormone users had begun with a double risk of breast cancer compared to the others and it fell as use stopped. Among hormone users at the start of the study, use dropped to 41 percent in 2003.
The use of hormone products has declined by 70 percent in the general population, since the onset of the study, said Dr. JoAnn Manson, study co-author and preventive medicine chief at Harvard’s Brigham and Women’s Hospital in Boston.
While that figure corresponds with a large decline in breast cancer cancers, some researchers speculate that this could be due to a drop in mammograms, which would in turn mean fewer cancers are being reported but not necessarily occurring.
In the future, researchers will observe women who took only estrogen, which is generally recommended for women who have had a hysterectomy. #