U.S. Breast Cancer Rate Stabilizes
Thursday, September 7, 2006
The decades-long rise in the rate of new breast cancer cases in American women appears to have leveled off, indicating that the nation may have reached a long-sought turning point in the battle against the feared malignancy.
After climbing steadily since the 1980s, the breast cancer rate stopped rising in 2001 and may have started to fall in 2003, according to the latest federal data. While it will take more years before it becomes clear whether the change marks the start of a lasting trend, the statistics appear to indicate a tantalizing shift, experts said.
"I think we're finally beginning to see a change -- that it's leveling off -- and we may even be seeing the start of a decline," said Brenda K. Edwards of the National Cancer Institute, who led a team that reported the change in an annual report on cancer released today. "We have to be cautious. But I think it's real."
The new report did not examine why breast cancer incidence would have plateaued, but Edwards and others said it could be the result of a combination of factors. Among them: The use of mammography appears to have peaked, the number of women delaying childbearing may have stabilized, and the use of hormones after menopause has plummeted.
"These are just some hypotheses. There may be other factors we don't know about," said Ahmedin Jemal of the American Cancer Society, who helped prepare the analysis of data collected by cancer registries around the country. "Breast cancer is influenced by many factors. It's very complex."
Although the death rate from breast cancer has been dropping because of earlier diagnosis and improved treatment, the new numbers mark the first sign that the rate of women getting breast cancer may have stopped increasing.
Whatever the cause, that would mark a milestone with major public health implications because of the large number of women diagnosed with the disease. Nearly 213,000 women find out they have breast cancer and nearly 41,000 die of the disease each year, making it the most common cancer in women and the second-leading cancer killer after lung cancer.
"The fact that it's the most frequently diagnosed cancer in women means small changes in statistics have a substantial impact on a large number of women," Edwards said. "Even a small decrease or change would represent a fair number of women."
"It's good news -- very happy news," said Nancy E. Davidson, who directs the breast cancer center at Johns Hopkins University in Baltimore. "We've been concerned because breast cancer has been rising for some time. The notion that it's plateauing is very good news."
Some advocates, however, expressed doubt about the numbers, saying cancer reporting is highly unreliable.
"I don't trust the accuracy of these numbers," said Barbara Brenner of Breast Cancer Action, a San Francisco-based advocacy group. "There's still way too many women getting breast cancer."
Other experts, while less skeptical that the rate had leveled off, also expressed caution.
"It's too soon to know whether we're turning the tide," said Carolina Hinestrosa of the National Breast Cancer Coalition. "It appears to be leveling off, but to confirm that you need another data point."
The breast cancer rate began rising in the 1980s, driven by factors including better detection with increased used of mammography, more women delaying childbearing, rising obesity rates and perhaps the popularity of hormones to treat symptoms of menopause. Although the rate slowed in the '90s, it continued a slow but steady rise throughout the decade.
That trend line appears to have finally hit a plateau in 2001, according to the "Annual Report to the Nation on Cancer," which is prepared by the National Cancer Institute, the American Cancer Society, the North American Association of Central Cancer Registries and the Centers for Disease Control and Prevention.
The rate at which women were diagnosed with breast cancer fell from 137.3 per 100,000 women in 2001 to 133.8 in 2002 -- in statistical terms, essentially no change -- but then fell to 124.2 in 2003, a significant drop.
While more data will be needed to confirm whether this will continue, Edwards said she is confident that at the least the incidence has hit a plateau.
"It does take several data points to see a pattern," Edwards said. "But the news for us is breast cancer incidence, which we've been seeing increase for so many years, that increase has stopped."
Although more research will be needed to explore the reasons, the change coincided with a leveling-out of mammography use and in the number of women waiting to have children, and it came a year after millions of women stopped using hormone-replacement therapy because of the discovery that it increases the risk of breast cancer and does not protect against heart disease, Edwards and others said.
"It is plausible the number of women who went off hormone- replacement therapy could have impacted the number of breast cancers that are being reported," Edwards said.
Several experts said the leveling off was consistent with other trends.
"The fact that the incidence has leveled off is good, because it shows that our screening is being effectively used and that there are no ongoing factors in the environment increasing the incidence," said breast cancer researcher and author Susan Love of the University of California at Los Angeles. "We could be at a turning point."
Researchers are eagerly awaiting the first analysis of the 2004 numbers, which are just starting to come in, to see whether the drop in 2003 continued or whether the numbers simply stayed flat.
"I can tell you many of us are anxiously awaiting to see our data from 2004," Edwards said, speculating that the number might tick back up slightly, in part because there may have been some underreporting in 2003. But she did not expect to see any resumption of the increase. "I think we have plateaued for a while."