THURSDAY, Sept. 18, 2003 (HealthDayNews) -- North American women are 2 percent to 4 percent more likely to get so-called "false-positive" results on their mammograms than European women.
But that doesn't mean early breast cancers are getting diagnosed at a higher rate here, a new study says.
University of Washington internist Dr. Joann G. Elmore reviewed data from 32 studies of community-based screening mammography programs in the United States, Europe, Asia and Australia. She found that about three more women per hundred in the United States and Canada get false-positive readings on their mammograms than do women in other parts of the world.
A false-positive reading suggests an abnormality when there isn't one.
The results of Elmore's study appear in the Sept. 17 issue of the Journal of the National Cancer Institute.
Elmore says she wasn't surprised by the higher false-positive rates. One reason she did the study was because approximately one out of 10 of her female patients were getting calls for a second mammogram after the first one indicated a possible tumor.
"But I was disturbed that we didn't see an increase in the number of women with early disease," she says. "The higher recall rate didn't give more bang for the buck in terms of early detection of invasive cancer."
The results held true even when she factored in variables like a woman's age, Elmore says.
"The United States historically has opened screenings to women in their 40s," she says, when a woman's breast tissue is denser and accurate readings are more difficult. But even after controlling for age and other variables, such as whether one or two people read the mammograms, the false-positive rate was still higher in North America.
The study did find a higher percentage of North American women diagnosed with ductal carcinoma in situ (DCIS), which is confined to the milk ducts and is the most common kind of non-invasive breast cancer.
"American radiologists are more focused on detecting DCIS," says Robert Smith, director of cancer screening for the American Cancer Society.
Elmore says more study would be needed to learn the reasons for the higher number of false-positives in North America, although she cites the fear of malpractice as one possibility. Failure or delay in cancer diagnosis is the most frequent cause for malpractice suits, particularly in cases of breast cancer, she reports in the study.
"A radiologist doesn't get sued for recommending a biopsy on a patient, but he could get sued for not recommending a biopsy," says Dr. Leonard Berlin, a radiology professor at Rush Medical College in Chicago.
Smith says the whole issue of false-positives is a difficult one.
On one hand, he says, "A reading of even 1 percent [false positive] means hundreds of thousands of women who may have to go through additional mammograms."
However, he says, studies have shown that American women aren't concerned about having a second mammogram.
"False-positives are considered a fact of life, and are accepted as part of the process, because the goal of screening is to find small cancers," he says.
That said, Smith adds, "The real challenge is to identify ways in which we can improve specificity and sensitivity in reading mammograms."
There is not much incentive for doctors to specialize in mammograms, Smith says, because the specialty is not highly respected, not highly paid, is hard work and stressful.
"You need to provide incentives to specialize in mammograms," he says.
He suggests tougher requirements for mammogram reading, as is the case in Sweden and the United Kingdom, as well as higher reimbursements and a more rational malpractice climate.
More information
The American Cancer Society explains why you should have mammograms. Also on that site is a report on another study finding a high false-positive rate for breast cancer.
