Background Among randomized trials evaluating flexible sigmoidoscopy (FSG) for its effect on colorectal cancer mortality, only the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial screened its participants more than one time. We report outcomes from the PLCO screening FSG program and evaluate the increased yield produced by a second FSG. Methods Participants were screened by 60-cm FSG in 10 regional screening centers at study entry and 3 or 5 years later, depending on the time of random assignment. Results from subsequent diagnostic intervention were tracked and recorded in a standardized fashion, and outcomes were compared according to sex and age. The protocol discouraged repeat FSG in persons with colorectal cancer or adenoma diagnosed after the initial FSG. Results Of 77 447 enrollees, 67 073 (86.6%) had at least one FSG and 39 443 (50.9%) had two FSGs. Diagnostic intervention occurred in 74.9% after a positive first FSG and in 78.7% after a positive repeat FSG. The second FSG increased the screening yield by 32%: Colorectal cancer or advanced adenoma was detected in 37.8 per 1000 persons after first screening and in 49.8 per 1000 persons after all screenings. The second FSG increased the yield of cancer or advanced adenoma by 26% in women and by 34% in men. Of 223 subjects who received a diagnosis of colorectal carcinoma within 1 year of a positive FSG, 64.6% had stage I and 17.5% had stage II disease. Conclusions Repeat FSG increased the detection of colorectal cancer or advanced adenoma in women by one-fourth and in men by one-third. Screen-detected carcinomas were early stage (stage I or II) in greater than 80% of screened persons. Colorectal cancer mortality data from the PLCO, as the definitive endpoint will follow in later publications.
Bibliographical noteFunding Information:
This work was supported by individual contracts from the Division of Cancer Prevention, National Cancer Institute, NIH, DHHS, to each of the 10 screening centers and to the coordinating center (N01-CN-25404 to University of California Los Angeles Immunogenetics Ctr., N01-CN-25476 to Westat, Inc, N01-CN-25511 to University of Pittsburgh Cancer Institute, N01-CN-25512 to Henry Ford Health System, N01-CN-25513 to University of Minnesota School of Public Health, N01-CN-25514 to University of Colorado, N01-CN-25515 to Pacific Health Research & Education Institute, N01-CN-25516 to Washington University, N01-CN-25518 to Marshfield Clinic Research Foundation, N01-CN-25522 to Georgetown University Medical Center, N01-CN-25524 to University of Utah, and N01-CN-75022 to University of Alabama at Birmingham).