San Antonio – U.S. breast cancer rates plunged an unprecedented 7 percent in 2003, the year after millions of women stopped taking menopause hormones when a study showed the pills raise the risk of tumors.
The startling new analysis, reported Thursday at the San Antonio Breast Cancer Symposium, does not prove a link between hormone therapy and breast cancer, but strongly suggests it, many experts said.
“When I saw it, I couldn’t believe it,” statistician Donald Berry of the University of Texas M.D. Anderson Cancer Center in Houston said of the drop.
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.
The drop 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.
“It’s a big deal … amazing, really,” said another 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 200,000 cases of breast cancer had been expected that year; the drop means that about 14,000 fewer women actually were diagnosed with the disease.
A separate study by the American Cancer Society, currently in press with a medical journal, also documents the drop. 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.”
