The subjects in the PLCO Cancer Screening Trial have been described previously.27 Briefly, from 1992 through 2001, more than 150,000 subjects between the ages of 55 and 74 years from 10 study centers across the United States were randomly assigned to undergo a specific cancer-screening regimen (screening group) or receive routine medical care (control group) to evaluate the effects of screening on disease-specific mortality. At baseline, all study subjects provided written informed consent and completed a questionnaire regarding demographic and risk-factor characteristics.28
