Screening for cancer: is it cost effective?

Screening is defined as the presumptive identification of unrecognized disease or defect by the application of tests, examinations, or other procedures that can be applied rapidly and carried out in the general population or in individuals at high risk. When considering immunochemical or biochemical cancer markers, it might be more appropriate to describe these tests as risk-factor monitors and introduce the concept of two interpretations of these tests: in asymptomatic populations as indicators of probability of cancer, and in patients with previously treated cancer as predictors of recurrence despite initial treatment described as "curative." The successes of screening with alpha-fetoprotein for hepatocellular carcinoma and with catechol metabolites in neuroblastoma are discussed. The major emphasis will be the possible use of CA 125 and prostate-specific antigen (PSA) in risk-factor assessment of ovarian cancer and prostate cancer, respectively. It is important to understand in what context a PSA value > 10 micrograms/L indicates a 67% probability of cancer.