• Office of Disease Prevention, Office of the Director, National Institutes of Health, 6100 Executive Blvd, Ste. 2B03, Rockville, MD 20892, USA. jg72@nih.gov.

The randomized PLCO trial was designed to answer four primary questions: does screening for these cancers using often promoted tests reduce cancer-specific mortality? Nearly 155,000 men and women were allocated to screening or usual care arms in a 1:1 ratio under a centralized, secure randomization algorithm at ten competitively selected screening centers nationwide. Screened men received PSA blood tests and digital rectal examinations. Screened women received CA125 blood tests and trans-vaginal ultrasound. Both men and women in the screened arm received anterolateral view chest x-ray and 60 cm flexible sigmoidoscopy. Blood specimens were collected at each screening visit and buccal cell DNA was collected once from the usual care participants. Histology slides were collected for cancer cases. Participants completed a baseline questionnaire covering health and risk factors and a dietary questionnaire. Data collected on standardized machine-readable forms were scanned remotely at screening and laboratory sites utilizing PLCO dedicated, NCI provided and configured computer systems for quality checks, archiving, and analysis. Comprehensive quality assurance was implemented over recruitment, consenting, randomization, screening, data management, records keeping, patient-specific screening results reporting, follow-up, and data analysis. Performance and data quality were monitored on-site and remotely by data edits, site visits, and random record audits. Specially trained and certified professionals performed screening procedures and medical record abstracting. An independent committee of medical specialists reviewed and certified case-specific cause of death. Scientific leadership was provided by NCI Project Officers, PLCO principal investigators, external consultants, and an independent data and safety monitoring board.