Screening for Colorectal Cancer in Older Patients (PLCO Screening Trial)

PRIMARY OBJECTIVES: I. To determine whether screening with flexible sigmoidoscopy (60-cm sigmoidoscope) can reduce mortality from colorectal cancer in women and men aged 55-74 at study entry. SECONDARY OBJECTIVES: I. To assess screening variables, other than mortality, for each of the interventions including sensitivity, specificity, and positive predictive value. II. To assess the incidence, stage, and survival of cancer cases. III. To investigate the mortality predictive value of biologic and/or prognostic characterizations of tumor tissue as intermediate endpoints. IV. To conduct biomolecular and genetic research into factors associated with cancer carcinogenesis and promotion, as well as the early detection of these factors. OUTLINE: Participants in the overall PLCO study are stratified by screening center, gender, and age (55-59 vs 60-64 vs 65-69 vs 70-74). Participants are randomized to 1 of 2 arms (control vs screening). ARM I (Control): Participants receive standard medical care. Participants complete a Diet History Questionnaire (DHQ) at baseline. ARM II (Colorectal Screening): Participants undergo a colorectal examination with a flexible sigmoidoscope at baseline and year 5. A scheduling and tracking procedure is implemented to ensure regular attendance at repeat screens for participants screened negative or for those who are designated suspicious or positive at screening but for whom subsequent diagnostic procedures do not reveal colorectal cancer (follow-up diagnostic procedures are through their own medical care environment). Participants diagnosed with colorectal cancer via a screening test are referred for treatment in accordance with current accepted practice for appropriate stage of disease, patient age, and medical condition; a procedure is provided for contact with qualified medical personnel to insure appropriate therapy. Participants complete a Dietary Questionnaire (DQX) at baseline and DHQ at year 3. An Annual Study Update (ADU) (previously referred to as the Periodic Survey of Health \[PSH\] questionnaire) is mailed to each participant annually for 13 years to identify all prevalent and incident colorectal cancers as all deaths that occur among both screened and control subjects during the trial. After completion of screening, participants are followed up for at least 13 years.