After rising steadily for decades, the proportion of U.S. women getting mammograms to screen for breast cancer has dropped for the first time, federal researchers are reporting today.
The overall rate at which women are undergoing regular mammograms fell 4 percent between 2000 and 2005, marking the first significant decline since use of the breast X-rays started expanding rapidly in 1987, the study by the National Cancer Institute and the Centers for Disease Control and Prevention found.
The reasons remain unclear, but researchers speculated that it could be due to factors such as increasingly long waiting times to get appointments, waning fears about breast cancer, the drop in hormone use after menopause, and the ongoing debate over the benefits and risks of the exams.
Regardless of the cause, the trend is worrying breast cancer experts. They credit mammograms with playing a crucial role in reducing the death toll from breast cancer, which is the second leading cause of cancer and cancer death among U.S. women.
"This is very troubling," said Nancy Breen, who led the analysis published online today by the American Cancer Society's journal Cancer. "If women are not getting mammograms, then their cancer may not be diagnosed until later stages, which could translate into higher mortality from breast cancer."
Breast cancer strikes more than 200,000 women each year and kills more than 40,000. But the odds of surviving have been rising, in part because more women are being diagnosed by mammograms at the earliest, most treatable stages. Breast cancer experts have been growing increasingly concerned, however, by reports that mammography rates have plateaued and have perhaps started to fall. The new research is the first to document the trend nationally.
"We've been anxious to look at a national sample," Breen said. "This is the first time we had a data set to examine that represents the entire United States."
Breen and her colleagues analyzed data collected by the National Health Interview Survey, an ongoing survey of about 40,000 adults conducted by the National Center for Health Statistics to track health trends.
Data from about 10,000 women surveyed showed that the mammogram rate plateaued in 2000, began to fall in 2003 and continued to decline through 2005, the survey's most recent year. Overall, the proportion of women who said they had gotten a mammogram in the last two years declined from 70 percent in 2000 to 66 percent in 2005, according to the paper, which will be published in the June 15 issue of the journal.
Most alarming, the drop was greatest -- 6.8 percent -- among women ages 50 to 64, the age group most likely to benefit.
This is also the group most likely to take hormones after the onset of menopause. That practice fell dramatically in 2002 after a federal study found that hormone therapy raised the risk of breast cancer, heart attack and stroke.
Breen and her colleagues were also surprised that the drop was especially steep-- 6.3 percent -- among more affluent women.
"One possibility is women who stop using HRT [hormone replacement therapy] believe their risk of breast cancer has declined and so they don't feel the need for mammography," Breen said. "Another possibility is they may not be going to their doctors as often for their hormones, and so are not being told it's time for a mammogram. That's a concern because just because they are not taking HRT does not mean they are not at risk."
Shortage of mammography facilities
Another possible explanation is that a worsening shortage of mammography facilities makes it more frustrating to get an appointment.
"It can be very difficult," said Carol J. Fabian, a breast cancer specialist at the University of Kansas. "You can wait months. I think that's a big part of it."
Breen and others speculated that some of the drop may be due to the debate over the benefits of mammography. Some experts question the blanket recommendation that women routinely undergo mammograms starting at age 40, saying the risks of unnecessary treatment and anxiety from false alarms may outweigh the benefits for some women at low risk.
"Some women are beginning to balance the risks and the benefits," said Carolina Hinestrosa of the National Breast Cancer Coalition, an advocacy group. "If women are making a careful determination and an informed decision after weighing the risks and benefits, I don't necessarily think that's a bad thing."
But others argued that the benefits have been well established, particularly for women over age 50. Even though other methods, such as MRIs, are showing promise, mammograms remain the most effective widespread screening method.
"Too many women and clinicians are misunderstanding the 'controversy' about mammography," said Constance Lehman, a professor of radiology at the University of Washington. "A mammogram is the best thing a woman can do to reduce her chances of dying from breast cancer."
Another possible explanation is that the rising survival rates among breast cancer patients are making women more complacent.
"Women may also be feeling, 'Well, the death rates are dropping in the population so I don't need to get screened,' " Breen said. "That's kind of missing the point. One reason death rates are dropping is because screening rates were so high."