COLUMBUS, Ohio--Standardized descriptions of mammographic findings and standardized reporting of final assessments continue to play an important role in improving the predictive value of mammography, Lawrence W. Bassett, MD, said at the Ohio State University James Cancer Hospital and Research Institute's Third Oncology Update.
Using standardized terms, such as the nomenclature defined by the American College of Radiology Breast Image Reporting and Data System (BI-RADS), radiologists can review and compare various studies with more confidence, allowing more effective communication with other radiologists, said Dr. Bassett, who is the Iris Cantor Professor of Breast Imaging at UCLA.
Databases created by collecting standardized descriptions of abnormalities, and the course of the treatment and disease that followed, could be used to develop algorithms to predict prognosis based on a description of the initial lesion, Dr. Bassett said.
Accurate computer-aided diagnosis using standardized descriptions may also become possible. At Duke University a computer using artificial intelligence reviewed mammographic findings described with standardized terms (Baker et al: Radiology 198:131-135, 1996). The computer's ability to make a diagnosis and recommendations for biopsy were impressive, Dr. Bassett said, and its specificity was better than that of a human.
In the meantime, radiologists can improve their medical practice by measuring the predictive value of their imaging techniques and comparing it to emerging national goals, Dr. Bassett said. The positive predictive value (PPV) of mam-mography is defined as the number of cancers found at biopsy divided by the number of cases recommended for biopsy after an abnormal mammogram.
The ideal PPV will vary according to the priorities of those involved. In some parts of Europe, for instance, where cost effectiveness of health-care delivery is a high priority, the PPV is 50% to 75%.
A random survey conducted by the FDA of 50 US facilities showed a PPV of 21% (Brown et al: AJR 165:1373-1377, 1995). The problem with a low PPV is that a large number of biopsies for benign conditions can discourage referring physicians from ordering screening mammograms, Dr. Bassett said.
A less aggressive approach to biopsy producing a PPV of 25% to 40% has been described as a desirable goal (Linver et al: AJR 165:19-25, 1995). With this approach, Dr. Bassett said, more than 50% of the tumors discovered at biopsy should be stage 0 or I with a node positivity rate of less than 25%. More than 30% of the cancers should be minimal.
Physicians can use several strategies to increase the PPV of their practice. Among the most valuable is to initiate a complete workup for abnormalities found on screening mammograms. This may include using magnification mammog-raphy or taking a number of special views, he said. Ultrasonography will identify 20% to 30% of the abnormalities as definitely benign, he noted.
Another method is the medical audit, which involves collecting and analyzing data regarding the mammography report and any subsequent outcome data such as biopsy or clinical follow-up. An audit is a useful way for mammographers to see whether their practice is operating under current guidelines. Medical audits are part of the Mammography Quality Standards Act of 1992.