Each Screening Center was responsible for establishing its own procedures for identifying and recruiting participants into the trial based on guidelines disseminated by the Coordinating Center and developed by NCI. Each Screening Center was also encouraged to develop and use other materials, such as introductory letters and answers to FAQs, to assist with recruitments. Once potential participants had been identified, the Screening Center collected information about them to determine their eligibility for the trial. Potential participants who were considered eligible for and interested in the study were then encouraged to enroll in the trial.
A potential participant was considered eligible for the PLCO trial if he/she did not meet any of the following exclusion criteria:
- Less than 55 or greater than or equal to 75 years of age at the time of randomization;
- Individuals undergoing treatment for cancer at the time of randomization (excluding basal-cell and squamous-cell skin cancer);
- Individuals with known prior cancer of the colon, rectum, lung, prostate (men only) or ovary (women only), including primary or metastatic PLCO cancers;
- Before October 1996, women with previous surgical removal of both ovaries were excluded from the trial; beginning in October 1996, these women were no longer excluded;
- Individuals with previous surgical removal of the entire colon, one lung, or the entire prostate (men only);
- Individuals who were participating in another cancer screening or cancer primary prevention trial;
- Males who had taken Proscar/Propecia/finasteride in the 6 months prior to randomization;
- Before April 1, 1999, women were excluded from the trial if they were currently taking or had taken Tamoxifen or Evista\Raloxifene in the 6 months prior to randomization; after April 1, 1999, women who had been or were currently taking Tamoxifen or Evista\Raloxifene were not excluded from participation;
- Males who had more than one PSA blood test in the three years prior to randomization;
- Individuals who had a colonoscopy, sigmoidoscopy, or barium enema in the three years prior to randomization;
- Individuals who were unwilling or unable to sign the informed consent form;
Randomization and Enrollment Procedures
The Study Management System (SMS) randomly assigned potential participants to either the intervention or control group and generated a unique study identification number for each participant. The PLCO trial sample is stratified by age and gender within each Screening Center with the goal of enrolling 75,000 men and 75,000 women such that these participants will fall roughly equally into four age strata: 55-59, 60-64, 65-69 and 70-74. The number of participants enrolled in PLCO exceeded the goal with a total of 78,234 women and 76,704 men.