Flexible sigmoidoscopy screening for colorectal neoplasia in average-risk people: evaluation of a five-year rescreening interval

OBJECTIVE: To determine the prevalence of colorectal neoplasia detected by rescreening people with average risk five years after initial screening by flexible sigmoidoscopy. DESIGN: Prospective survey of results of a colorectal cancer screening program. PARTICIPANTS: People aged 55-64 years with no symptoms or family history of colorectal cancer who were recruited from the community for flexible sigmoidoscopy screening five years previously (July 1995 to December 1996) and had no colorectal neoplasms detected. SETTING: Fremantle Hospital, Western Australia, a community-based teaching hospital, December 2000 to June 2001. MAIN OUTCOME MEASURES: Number and size of colorectal neoplasms (adenomas or cancer) compared between rescreened patients and initial screening population (all 982 people screened between July 1995 and December 1996). RESULTS: 803 people were eligible for rescreening; 138 were no longer at the recorded address, and 361 of the remaining 665 (54%) were rescreened. Rescreening found a significantly lower prevalence of colorectal adenomas than initial screening (8% [95% CI, 5%-11%] versus 14% [95% CI, 13%-15%]; P < 0.05) and also a lower percentage of adenomatous polyps over 5 mm in diameter (32% [95% CI, 15%-49%] versus 51% [95% CI, 46%-56%]; no significant difference). CONCLUSION: Average-risk people who have been screened for colorectal neoplasms, with none found, have a low prevalence of neoplastic lesions five years later. Longer rescreening intervals need to be considered.