The flat adenoma may be a more aggressive pathway in colorectal carcinogenesis.
Dr Michael O'Brien and colleagues from across America histopathologically reclassified sessile adenomas from the National Polyp Study cohort as either flat or polypoid.
The researchers compared their results to the initial classifications and surveillance pathology.
In total, the researchers noted 933 sessile adenomas as having been detected during 1980–1990.
The research group reclassified those adenomas as follows: (1) adenoma thickness (AT): ≤1.3 mm, and (2) adenoma ratio (AR): adenoma thickness <2× normal mucosa thickness.
Using logistic regression, the researchers were able to assess whether flat adenomas had an effect on risk for high-grade dysplasia initially.
In addition, the research team employed the Cox proportional hazards model to assess the risk for advanced adenomas at surveillance.
|Flat adenomas represented 27% of all baseline adenomas.|
|Clinical Gastroenterology and Hepatology|
The analysis encompassed 8401 person-years of follow-up evaluation. AT and AR measures of adenoma flatness were 95% concordant.
The researchers were able to show that, by the AT measure, flat adenomas (n = 474) represented 27% of all baseline adenomas.
Flat adenomas were found to be no more likely to exhibit high-grade dysplasia than sessile (polypoid) or pedunculated adenomas.
Dr Michael O'Brien concluded, "Patients with flat adenomas at initial colonoscopy were not at greater risk for advanced adenomas at surveillance compared with those with polypoid adenomas only, after adjustments for multiplicity, age, and family history of colorectal cancer."
He added, "Flat adenomas identified in the National Polyp Study cohort at baseline were not associated with a higher risk for high-grade dysplasia initially, or for advanced adenomas at surveillance."