Kathi 2012-05-06 03:59:48
North American mammographers prone to more false positives, study finds
Community-based mammography screening programs in North America
are yielding a higher percentage of abnormal mammograms than
corresponding programs in other countries, but without any apparent
benefit in terms of a higher cancer detection rate, according to a study
in the September 17 issue of the Journal of the National Cancer
“This finding suggests that many, if not most, of the
presumptively abnormal mammographic interpretations in screening
programs with high percentages of abnormal mammograms turn out to be
false positives,” say study leader Joann G. Elmore, M.D., of the
Harborview Medical Center in Seattle, and her colleagues. False-positive
mammograms can lead to unnecessary follow-up procedures (e.g.,
biopsies), higher medical costs, and anxiety for the patient.
Elmore and her colleagues analyzed data from 32 studies of
community-based screening mammography programs to compare outcomes of
mammographic readings between programs in North America and those in
other countries. In each study, they looked at the percentage of
mammograms considered abnormal, the percentage of women diagnosed with
ductal carcinoma in situ (DCIS), and the percentage of women diagnosed
with minimal disease.
The percentage of mammograms deemed abnormal by North American
programs was 2 to 4 percentage points higher than it was in programs in
other countries, even after adjusting for factors such as age of women
number of mammography readers for each examination (single vs. double).
North American programs also reported a higher percentage of DCIS.
However, a higher percentage of abnormal mammograms did not appear to be
associated with a higher rate of breast cancers being diagnosed.
The authors stress caution in interpreting these findings. They
explain that a number of factors may be contributing to the observed
variation between North American programs and programs in other
countries, including differences in the population of women screened,
differences in the screening procedure, and differences in how countries
define an abnormal mammogram. Malpractice concerns and financial
incentives may also be contributing to the variation in mammography
interpretations, they say.
“Currently, it is not possible to determine which features may be
most responsible for the variability,” the authors write, adding that “a
better understanding of the sources of variability in mammography may
lead to more effective screening programs that have a lower percentage
of mammograms judged as abnormal without substantially lowering the
cancer detection rate.”
Contact: Susan Gregg-Hanson, University of Washington Harborview
Medical Center, 206-731-6397, firstname.lastname@example.org.
Elmore JG, Nakano CY, Koepsell TD, Desnick LM, D’Orsi CJ,
Ransohoff DF. International variation in screening mammography
interpretations in community-based programs. J Natl Cancer Inst
Note: The Journal of the National Cancer Institute is published
by Oxford University Press and is not affiliated with the National
Cancer Institute. Attribution to the Journal of the National Cancer
Institute is requested in all news coverage.