The millions of U.S. women who quit taking menopause hormones after a big federal study found that the pills raised the risk of breast cancer now have more reason to be glad they stopped.
A new analysis reveals that U.S. breast cancer rates plunged more than 7 percent in 2003 and strongly suggests that the reason is less hormone use.
"It's a big deal ... amazing, really," said one of the researchers, Dr. Rowan Chlebowski of Harbor-UCLA Medical Center in Los Angeles. "It's better than a cure" because these are cases that never occurred, he said.
About 14,000 fewer women were diagnosed with the disease than had been expected, researchers reported Thursday at the San Antonio Breast Cancer Symposium.
Cancers take years to form, so going off hormones would not instantly prevent new tumors. But tumors that had been developing might stop growing, shrink or disappear, so they were no longer detected by mammograms, doctors theorized.
Cases dropped most among women 50 and older the age group taking hormones. The decline was biggest for tumors whose growth is fueled by estrogen the type most affected by hormone use.
In fact, when both factors were combined older women with estrogen-positive tumors the drop was 12 percent.
The decline was seen in every single cancer registry that reports information to the federal government, and no big change occurred with any other major type of cancer. These are strong signs that the breast cancer decline is no statistical fluke or error, reports AP.
A separate study by the American Cancer Society, currently in press with a medical journal, also documents the drop in cases. Lead author Ahmedin Jemal attributes two-thirds of it to a decline in hormone use and the rest to mammography use leveling off, resulting in fewer tumors being detected.
"We are really trying to look at the big picture," he said. "You cannot rule out the effect of screening."
Breast cancer is the most common major cancer in American women and the second leading cause of cancer deaths in women. About 213,000 new cases are expected to occur in the United States this year and more than 1 million worldwide.