Risk for CRC with young-onset adenomas may vary by stage
A cohort study in U.S. veterans younger than age 50 years found that those with advanced adenomas had an eightfold increased risk for incident colorectal cancer (CRC) versus those with normal results, whereas cumulative CRC incidence and mortality at 10 years were relatively low overall.
While younger patients with advanced adenomas on colonoscopy may be at higher risk for incident colorectal cancer (CRC), any adenoma in this age group does not appear to increase overall risk, a recent study found.
Researchers conducted a cohort study of U.S. veterans ages 18 to 49 years who underwent colonoscopy from 2005 to 2016. The primary exposure of interest was young-onset adenoma on baseline colonoscopy. The researchers defined normal colonoscopy as a colonoscopy without any documented adenoma or without a pathology report including a diagnosis of adenoma or malignancy. They categorized young-onset adenomas as advanced if they were conventional adenomas of 10 mm or greater or adenomas with villous histology or high-grade dysplasia of any size. They defined nonadvanced adenomas as conventional adenomas that were smaller than 10 mm and had no histological features of an advanced adenoma.
Median follow-up was 4.7 years. The researchers used Kaplan-Meier curves to calculate cumulative incident and fatal CRC risk in veterans with versus without young-onset adenoma, in those with versus without advanced young-onset adenoma, and in those with versus without nonadvanced young-onset adenoma on baseline colonoscopy. They used Cox models to estimate incident and fatal CRC risk in adults with advanced or nonadvanced young-onset adenomas versus those with normal colonoscopy. The study results were published April 13 by the American Journal of Gastroenterology.
The study included 54,284 veterans who were younger than age 50 years and had undergone colonoscopy, 7,233 (13%) who were diagnosed with any young-onset adenoma on baseline colonoscopy. Cumulative 10-year incidence of CRC was 0.11% (95% CI, 0.00% to 0.27%) after any adenoma diagnosis, 0.18% (95% CI, 0.02% to 0.53%) after a diagnosis of advanced young-onset adenoma, 0.10% (95% CI, 0.00% to 0.28%) after a diagnosis of nonadvanced adenoma, and 0.06% (95% CI, 0.00% to 0.09%) after normal colonoscopy. Participants who had advanced adenomas had an eightfold higher risk for incident CRC than those with normal colonoscopy (hazard ratio [HR], 8.0; 95% CI, 1.8 to 35.6). There was no significant association between increased CRC risk and nonadvanced adenoma versus normal results on colonoscopy in unadjusted Cox models (HR, 0.8; 95% CI, 0.1 to 6.1) or between advanced adenoma and fatal CRC risk versus normal colonoscopy, although the confidence interval was wide.
“The low absolute CRC risk observed among individuals with young onset adenoma in our study may suggest that these individuals do not need more aggressive surveillance than what is already recommended for adults ages ≥50: 7 to 10 year follow up after diagnosis of 1-2 non-advanced adenomas <10 mm in size; 3 to 5 year follow up after diagnosis of 3-4 non-advanced adenomas <10 mm in size; and 3 year follow up after diagnosis of an advanced adenoma,” the authors wrote. “A decision to engage in more aggressive surveillance should also take into account issues of resource utilization, access, and overall healthcare cost.” Limitations of the study included potential lack of generalizability and small event numbers, they noted.