December 11, 2007
Accuracy of diagnostic mammograms varies by radiologist
Group Health team finds wide variability in nationwide study
Seattle—For women with breast symptoms such as lumps, the ability
of diagnostic mammograms to detect breast cancer accurately depends strongly
on which radiologist reads them, according to a Group Health study published
online on December 11 in the Journal of the National Cancer Institute.
“When a woman gets a mammogram, she wants to know that if she has breast
cancer, the mammogram will be likely to detect it,” said study leader
Diana Miglioretti, PhD, an associate
investigator at Group Health Center for Health Studies. “This is especially
important when the woman has a breast concern such as a lump.”
Ideally, this ability to accurately detect cancer (known as
“sensitivity”) would be consistently high, with few false-positives—biopsies
performed despite the absence of cancer. And it wouldn’t depend on which
radiologist was reading the mammograms. “But that’s not what we found,” she
added.
The research team examined how well 123 radiologists interpreted nearly
36,000 diagnostic mammograms done to evaluate breast problems, such as
lumps, from 1996 through 2003 at 72 U.S. facilities, including six from
Group Health, that contribute data to the Breast Cancer Surveillance
Consortium.
For different radiologists, sensitivity ranged from 27 percent to 100
percent; and false-positives, from 0 to 16 percent. These differences were
only partially explained by the characteristics of the patients and the
experience of the radiologists.
The radiologists who read diagnostic mammograms most accurately (with
highest sensitivity, without too many false-positives) tended to be those
who were based at academic medical centers or spent at least 20 percent of
their time on breast imaging. By contrast, unlike in Europe, most U.S. women
get mammograms interpreted by general radiologists who interpret mammograms
as only a small percentage of their practice.
"We need to reduce the wide variability among radiologists in how they
interpret diagnostic—and screening—mammograms,” said Miglioretti. “A good
way to do that may be to identify the radiologists who are least accurate at
reading mammograms—and to improve their performance with extra training.”
The national Breast Cancer Surveillance Consortium is working on ways to
accomplish these goals, including developing an interactive training
program.
“Women should get regular screening mammograms,” said Miglioretti.
“Mammography isn’t perfect, but it’s the best way we have to detect breast
cancer early, when it has the greatest chance of being cured.” She also
urged women with breast concerns, such as lumps, to try to get evaluated at
a center that has at least one breast imaging specialist: a radiologist who
spends a large percentage of the time reading mammograms and performing
breast biopsies.
Most mammograms are done to screen women with no symptoms for breast
cancer. Previous research has shown that radiologists vary widely in how
they read such screening mammograms. This new study is the largest to
examine what predicts variability in diagnostic mammograms.
Miglioretti’s coauthors included colleagues at Group Health; Harborview
Medical Center; University of Washington; University of California, San
Francisco; and Oregon Health & Science University.
Grants from the Agency for Healthcare Research and Quality, the National
Cancer Institute, and the Breast Cancer Surveillance Consortium funded the
study.
About Group Health Center for Health Studies
Founded in 1947, Group Health is a Seattle-based, consumer-governed,
nonprofit health care system that coordinates care and coverage. Group
Health Center for Health Studies conducts research related to prevention,
diagnosis, and treatment of major health problems. It is funded primarily
through government and private research grants.
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