October 23, 2014

How can radiologists detect breast cancer more accurately?

Research suggests having them do diagnostic workups of some of their own recalled cases

SEATTLE—Flash quiz: Do you remember taking tests in school and getting immediate feedback on how you did? Maybe learning promptly what you did right—and where you should have made different choices—helped to improve your future performance.

“Likewise, some people believe that radiologists do better at distinguishing cancer from noncancerous spots if they learn quickly what the outcome of a diagnostic workup is—by seeing a woman through that workup,” said Diana Buist, PhD, MPH, a senior investigator at Group Health Research Institute. “But this idea had never been tested.”

That’s why Dr. Buist led a study of more than 650,000 screening mammograms interpreted by 96 radiologists in the Breast Cancer Surveillance Consortium (BCSC). These mammograms were linked to cancer registries to evaluate how well radiologists did screening mammography. She and a BCSC team found consistently higher rates of cancer detection for those radiologists who interpreted more diagnostic mammograms that resulted from recall of screening mammograms that they had interpreted than for radiologists who interpreted fewer of these mammograms.

The study report, called “Effect of radiologists’ diagnostic workup volume on interpretive performance,” is in the November issue of Radiology, and Dr. Buist is on a Radiology podcast (skip to 16:38 – 37:45 for Dr. Buist’s discussion of the effect of workup volume on performance).

Putting it all together

When radiologists interpret screening mammograms, they decide whether to call patients back for diagnosis. Some radiologists read only screening mammograms—not diagnostic ones and many times a different radiologist is reading the diagnostic mammogram exam than the radiologist who saw something on the screening exam, Dr. Buist explained. But what if radiologists do the diagnostic work on some of their screening mammograms that they have recalled for diagnosis? Then, the research team found, radiologists tend to read screening mammograms with higher sensitivity and cancer detection rate—although also with more false alarms. (When a woman without breast cancer is called back after screening mammography for extra testing, she has a “false positive.”)

So making radiologists work up some of their own recalled cases and interpret more mammograms (which has previously been linked to fewer false alarms) could improve screening performance—and cancer detection, the research team concluded.

“Our study found that breast cancer screening could be more accurate if every year radiologists interpreted not only a minimum number of mammograms, but also at least 50 diagnostic workups that resulted in screening exams that they interpreted as needing additional imaging,” Dr. Buist said. What her team didn’t expect to find was that radiologists who worked up more of the screening exams they thought were abnormal also tended to have higher false-positive rates. The same team previously reported in the same journal that radiologists who interpret more mammograms and spend some time reading diagnostic mammograms do better at determining which suspicious breast lesions are cancer.

Dr. Buist is chairing an Institute of Medicine panel that will convene in 2015 to evaluate evidence that has evolved since the last report was issued in 2005. She is also an affiliate investigator at the Fred Hutchinson Cancer Research Center, an affiliate professor in the Departments of Epidemiology and Health Services at the University of Washington School of Public Health, and a senior scholar in residence at AcademyHealth.

Her BCSC coauthors included Diana Miglioretti, PhD, of Group Health Research Institute and the University of California, Davis; Melissa Anderson, MS, of Group Health Research Institute; and colleagues at the American Cancer Society; the National Cancer Institute; Oregon Health & Science University (OHSU); Washington University; Dartmouth University; University of Vermont; University of North Carolina; and University of California, San Francisco (UCSF).

This research was supported by the National Cancer Institute BCSC (U01CA63740, U01CA86076, U01CA86082, U01CA70013, U01CA69976, U01CA63731, U01CA63736, U01CA70040, HHSN261201100031C). Portions of the data collection were supported by the National Cancer Institute and the Agency for Healthcare Research and Quality (R01 CA107623) and the National Cancer Institute (K05 CA104699).

Breast Cancer Surveillance Consortium

The Breast Cancer Surveillance Consortium (BCSC) is the nation's largest and most comprehensive collection of breast cancer screening information. It's a research resource for studies designed to assess the delivery and quality of breast cancer screening and related patient outcomes in the United States. The BCSC is a National Cancer Institute-funded collaborative network of seven mammography registries with linkages to tumor and/or pathology registries. The network is supported by a central Statistical Coordinating Center. Currently, the Consortium's database contains information on over 9.9 million mammographic examinations, 2.4 million women, and 120,800 breast cancer cases (100,500 invasive cancers and 20,300 ductal carcinoma in situ). For more information, visit http://breastscreening.cancer.gov.

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