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Long-term Risk of False-Positive Screening Results and Subsequent Biopsy as a Function of Mammography Use¹

¹ From the Departments of Surgery (K.B., J.A.C., K.S.H., B.L.S., K.K.T., J.S.M.), Pathology (J.S.M.), and Radiology (D.B.K., R.M., E.F.H.), Massachusetts General Hospital, Yawkey 7939, 55 Fruit St, Boston, MA 02114; and Departments of Pathology (J.S.M.), Surgery (K.S.H., B.L.S., K.K.T.), and Radiology (D.B.K., E.F.H.), Harvard Medical School, Boston, Mass. Received January 21, 2005; revision requested March 23; revision received May 18; accepted June 21; final version accepted November 2. Supported by departmental funds from the Massachusetts General Hospital Division of Surgical Oncology. Address correspondence to J.S.M. (e-mail: michaelj{at}helix.mgh.harvard.edu).

Purpose: To retrospectively determine the long-term risk of false-positive mammographic assessments and to evaluate the effect of screening regularity on the risk of false-positive events.

Materials and Methods: Institutional review board approval was obtained, and informed consent was waived. Retrospective analysis was performed for the occurrence of false-positive assessments among 83 511 women who underwent 314 185 mammographic examinations from January 1, 1985, to February 19, 2002. Data were collected from a database that had been assembled prospectively. Two categories of false-positive events were examined: biopsies that did not reveal cancer and false-positive mammographic assessments. Rates of false-positive events were compared by using a ² analysis, and 95% confidence limits were calculated. Because comparisons of multiple pairs were considered, all P values that demonstrated statistical significance exceeded the requirement of the Bonferroni correction.

Results: While the overall rates of biopsies that did not reveal cancer and of false-positive mammographic assessments were similar to those found in other studies, most of the burden of false-positive events was borne by women who underwent intermittent screening. Long-term rates of false-positive events were lower among women who underwent regular screening than among those who underwent intermittent screening. In the 5-year group, 2.9% of women who underwent five mammographic examinations over the next 5 years had biopsy results that did not reveal cancer, whereas 4.6% of women who underwent three mammographic examinations over the next 5 years had biopsy results that did not reveal cancer. For women who underwent regular screening, the risk of undergoing biopsies that did not reveal cancer declined over time to 0.25% per year after several years of screening, a value that is lower than the risk of these events among women who did not undergo screening. The rate of false-positive mammographic assessments was also lower for women who underwent regular screening than for those who underwent intermittent screening.

Conclusion: Prompt annual attendance for mammographic screening reduces the occurrence of false-positive mammographic results.

© RSNA, 2006

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