The required frequency of endoscopic colorectal cancer screening following a negative examination is unclear.
In this study, researchers from the United States examined the number of adenomas and cancer in the distal colon, which was found by repeat flexible sigmoidoscopy (FSG), 3 years after a negative examination.
The team selected subjects from a randomized, controlled community-based study of cancer screening.
The subjects' mean age was 65.7 years at study entry, and 62% were male.
|14% of returning subjects had a polyp or mass detected by flexible sigmoidoscopy.|
|Journal of the American Medical Association|
Individuals underwent screening FSG at baseline. They were then screened 3 years later as part of the protocol.
Subjects were then referred to their personal physicians for further evaluation of any screen-detected abnormalities.
The researchers found that of the 11,583 participants eligible for repeat screening, 9317 returned.
The main outcome measures set by the research team included;
- Polyp or mass detection in distal colon at year 3
- Incidence of adenoma or cancer in distal colon at year 3
- Determination of reason for detection.
The team found that 14% of returning subjects had a polyp or mass detected by FSG 3 years after the initial examination.
They determined that 3% had an adenoma or cancer in the distal colon. However, advanced adenoma or cancer of the distal colon was found in 0.8% of subjects.
The researchers determined that 81% of individuals with advanced distal adenomas had lesions in a portion of the colon that had been adequately examined at the initial sigmoidoscopy.
Dr Robert Schoen's team concluded, "Repeat FSG 3 years after a negative examination will detect advanced adenomas and distal colon cancer".
"Although the overall percentage with detected abnormalities is modest, these data raise concern about the impact of a prolonged screening interval after a negative examination".