Clinical question When patients undergo repeated screenings for multiple cancers, how often do false-positive results occur?

Bottom line Almost half the healthy adults undergoing repeated multimodal cancer screening will have at least one false-positive result by the time they have had 14 screening procedures. Many people seem to believe there is no harm in screening; however, these results are a sobering reminder that screening healthy populations may not be so benign. (Level of evidence = 1b)

Synopsis These authors report data from patients aged 55 to 74 years who represented the intervention wing of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Women in this wing were offered annual can cer antigen 125 testing and transvaginal ultrasonography for ovarian cancer for 4 years, chest radiography for lung cancer at baseline and yearly for 2 years in nonsmokers or 3 years in smokers, and flexible sigmoidoscopy for colorectal cancer at baseline and at 3 or 5 years. Men were offered the same tests for lung and colorectal cancers, and also received annual digital rectal examinations and prostate-specific antigen blood tests for 4 years. The investigators declared a false-positive result if a screening test result was abnormal, but the cancer went undiagnosed after 3 years of follow-up. At the end of 3 years of follow-up, each patient could have had up to 14 screening tests. Among the 68,436 patients, more than 40% had at least one false-positive result. Approximately 33% of the women and 50% of men had at least one false-positive. Approximately 3% had minimally invasive diagnostic procedures, 16% underwent moderately invasive procedures, and nearly 2% underwent major surgery. Flexible sigmoidoscopy and chest radiography, for men and for women, were the tests yielding the highest rates of false-positive results. This study did not include screening mammography. Adding mammography to the above would increase the number of falsepositive results and invasive procedures for women.

Croswell JM, Kramer BS, Kreimer AR, et al. Cumulative incidence of false-positive results in repeated, multimodal cancer screening. Ann Fam Med. 2009;7(3):212-222

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