ATLANTA – Research on two continents signaled more bad news for menopause hormones, offering the strongest evidence yet that they can raise the risk of breast cancer and are tied to a slightly higher risk of ovarian cancer.
New U.S. government numbers showed that breast cancer rates leveled off in 2004 after plunging in 2003 -- the year after millions of women stopped taking hormones because a big study tied them to higher heart, stroke and breast cancer risks. Experts said the leveling off shows that the 2003 drop in the cancer rate was real and not a fluke.
From 2001 to 2004, breast cancer rates fell almost 9 percent -- a dramatic decline, researchers report in Thursday's New England Journal of Medicine. The trend was even stronger for the most common form of the disease -- tumors whose growth is fueled by hormones. Those rates fell almost 15 percent among women ages 50 to 69, the group most likely to have been on hormone pills.
At the same time, a study of nearly 1 million women in the United Kingdom showed that those who took hormones after menopause were 20 percent more likely to develop ovarian cancer or die from it than women who never took the pills. That study was published online by the London-based journal The Lancet.
For consumers, the new research doesn't change the advice to use the lowest dose for the shortest time possible for hot flashes and other menopause symptoms that can't otherwise be controll The drop was seen in all of the cancer statistics registries reviewed in the study, and no other cancer rate changed as dramatically -- strong signs that hormones were playing a role, specialists said.
The 2004 rate held steady at about 126 cases per 100,000.
Stopping hormone use may have stopped some cancers from growing and caused them to disappear, scientists speculate. Or it may have just slowed them down so that they won't appear until years later, said Ahmedin Jemal, an American Cancer Society researcher. Only time will tell which is true, he said.
Wyeth Pharmaceuticals, which makes top-selling hormone pills Prempro and Premarin, criticized the study as overly speculative. Company spokesman Dr. Joseph Camardo said hormone prescriptions continued to fall in 2004 but breast cancer rates did not decline proportionately.
Ravdin said the company's criticism does not invalidate the cancer trends.
Breast cancer is the most common major cancer in American women and the second leading cause of cancer deaths in women. About 180,000 new cases are expected to occur in the United States this year and more than 1 million worldwide.
Ovarian cancer is far less common. The British study found that even with the 20 percent greater risk from hormones, the actual risk was very low: 2.6 of every 1,000 hormone users developed ovarian cancer over five years compared to 2.2 in 1,000 non-hormone users.
Still, that means about 1,000 extra ovarian cancer deaths from 1991 through 2005, said study leaders at the Cancer Research UK Epidemiology Unit in Oxford.
Hormone use has declined already, and the new report should cause it to fall further, Dr. Steven Narod of the University of Toronto wrote in an editorial accompanying the study in The Lancet.
"We hope that the number of women dying of ovarian cancer will decline as well," he wrote.
Camardo, Wyeth's spokesman, said hormone labels already warn about an elevated risk of ovarian cancer.
New England Journal: www.nejm.org
Women's Health Initiative study: http://www.nhlbi.nih.gov/whi/index.html
American Cancer Society: www.cancer.org
National Cancer Institute: www.cancer.gov
The Lancet: www.thelancet.com