Observational screening of the colon with subsequent referral for colonoscopy raises questions about the threshold of polyp size that necessitates referral.
Dr Robert Schoen and colleagues from Pennsylvania examined the yield at colonoscopy when a given size lesion is observed.
The investigative team assessed the yield of advanced adenoma and cancer at colonoscopy.
The yield was based on the size of the abnormality detected at flexible sigmoidoscopy.
The investigators used data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.
|A polyp less than 1 cm had a yield of 15% for advanced adenoma|
The team reported that this trial was a randomized, controlled, community-based study of flexible sigmoidoscopy.
The investigators performed subsequent colonoscopy on 10,850 subjects with a polyp visualized on screening flexible sigmoidoscopy.
For 1426 women with a polyp less than 1 cm on flexible sigmoidoscopy, the yield in the distal colon on colonoscopy was less than 1% for cancer.
For advanced adenoma in women with a polyp less than 1 cm on flexible sigmoidoscopy, the yield in the distal colon on colonoscopy was 15%.
The team found that in 2183 men, the yield was less than 1% for cancer, and 16% for advanced adenoma.
The team noted that among persons with polyps under 1 cm identified on flexible sigmoidoscopy, 6% had distal advanced adenomas that measured less than 1 cm.
However, the team observed that these individuals had villous histology or high-grade dysplasia, and 10% had adenomas of 1 cm in size or more.
Dr Schoen's team concludes, “The yield for a distal advanced adenomatous lesion when a polyp less than 1 cm is observed at flexible sigmoidoscopy is substantial.”
“It is due to the presence of advanced histology in polyps less than 1 cm and to detection of polyps that measure more than 1 cm on colonoscopy.”
“Establishing thresholds for observation versus evaluation will require careful assessment of the overall yield.”