Prevention and Screening

North American screening programs identify more mammograms as abnormal but do not detect more breast cancers than programs in other countries

Compared with community-based mammogram screening programs around the world, North American screening programs appear to interpret a higher percentage of mammograms as abnormal. However, this approach does not appear to detect more cancers per 1,000 screens, according to a recent study supported in part by the Agency for Healthcare Research and Quality (HS10591). The study did show more cases of ductal carcinoma in situ (DCIS) found by North American screening programs.

Joann G. Elmore, M.D., M.P.H., of the University of Washington, Seattle and Harborview Medical Center, and her colleagues reviewed published reports to identify international screening mammography programs. They identified the population screened, examination technique, and clinical outcomes. The researchers examined the percentage of mammograms judged to be abnormal, positive predictive value of an abnormal mammogram (PPV_A), positive predictive value of a biopsy performed (PPV_B), and percentages of breast cancer patients with DCIS and minimal disease (DCIS and/or tumor size 10 mm or less).

The percentage of mammograms judged to be abnormal were 2-4 percentage points higher in North American screening programs than they were in programs from other countries, after adjusting for factors such as women's age. The percentage of mammograms judged to be abnormal had a negative association with PPV_A (cancer detected) and PPV_B (biopsies conducted), but there was a positive association with the frequency of DCIS cases diagnosed and number of DCIS cases diagnosed per 1,000 screens. The wide variation in mammography interpretation noted in the studies reviewed for this article was likely due to multiple factors. These ranged from the characteristics of the population screened and features of the mammography exam to physicians interpreting the mammogram and features of a country's health care system.

See "International variation in screening mammography interpretations in community-based programs," by Dr. Elmore, Connie Y. Nakano, Thomas D. Koepsell, M.D., M.P.H., and others, in the September 17, 2003, Journal of the National Cancer Institute 95(18), pp. 1384-1393.

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