Mammography screening may be effective in reducing breast cancer mortality in certain populations, but it can pose harm to women who participate. The limitations are best described as false-positives (related to the specificity of the test), overdiagnosis (true-positives that will not become clinically significant), false-negatives (related to the sensitivity of the test), discomfort associated with the test, radiation risk and anxiety.
Table 3 provides an overview of the estimated benefits and harms of screening mammography for 10,000 women who undergo annual screening mammography over a 10-year period.
Table 3. Estimated Benefits and Harms of Mammography Screening for 10,000 Women Who Undergo Annual Screening Mammography Over a 10-Year Perioda
No. of Breast Cancer Deaths Averted With Mammography Screening Over Next 15 yb
No. (95% CI) With ≥1 False-Positive Result During the 10 yc
No. (95% CI) With ≥1 False Positive Resulting in a Biopsy During the 10 yc
No. of Breast Cancers or DCIS Diagnosed During the 10 y That Would Never Become Clinically Important (Overdiagnosis)d
b Number of deaths averted are from Welch and Passow.The lower bound represents breast cancer mortality reduction if the breast cancer mortality relative risk were 0.95 (based on minimal benefit from the Canadian trials[3,4]), and the upper bound represents the breast cancer mortality reduction if the relative risk were 0.64 (based on the Swedish 2-County Trial).
c False-positive and biopsy estimates and 95% confidence intervals are 10-year cumulative risks reported in Hubbard et al.and Braithwaite et al.
d Overdiagnosed cases are calculated by Welch and Passow.The lower bound represents overdiagnosis based on results from the Malmö trial,whereas the upper bound represents the estimate from Bleyer and Welch.
e The lower-bound estimate for overdiagnosis reported by Welch and Passowcame from the Malmö study.The study did not enroll women younger than 50 years.