A team from Nottingham, England, investigated the use of flexible sigmoidoscopy and colonoscopy in the surveillance of colorectal adenoma.
They conducted a randomized trial in which the two techniques were compared at one, two, and five-year intervals. Recurrent adenomas were stratified into "high" or "low" risk categories.
A total of 776 patients were separated into "high" (n = 307) and "low" (n= 469) recurrence risk groups. They were then randomized to flexible sigmoidoscopy or colonoscopy, at varying intervals.
|A surveillance interval of 5 years, for recurrent adenoma, was effective.
Only 81 recurrent adenomas (30/81 were greater than 1 cm in diameter) were detected in the 2,307 person years of follow-up, within the surveillance study.
The researchers found that adenoma recurrence was significantly higher in the high-risk group (relative rate 1.82).
However, recurrence rates per 1,000 person years were low, and not significantly different in those surveyed by colonoscopy or flexible sigmoidoscopy.
Loss to follow-up was found to be greatest in those having an annual examination, compared with two- or five-yearly surveillance examinations.
Despite surveillance, invasive cancer developed in 4 patients, compared with an expected value of 9.12 for the general population in England. Of these 4 patients who developed cancers, only one was detected by surveillance examination.
Author J. N. Lund, of the University Hospital, Nottingham, said on behalf of fellow colleagues, "Adenoma recurrence rates were much lower than expected in both high- and low-risk groups. This suggests that endoscopic surveillance should be targeted at high-risk groups.
"A surveillance interval of five years was as effective as shorter intervals in terms of cancer prevention, and was associated with similar compliance to two-yearly examinations," it was concluded.