Advanced adenomas found on diagnostic colonoscopy were associated with increased risk of developing colorectal cancer, while nonadvanced adenomas were not, according to long-term follow-up results from a large screening study.
The findings come from a post hoc analysis of the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial that enrolled 154,900 individuals, of whom 15,935 underwent colonoscopy following an abnormal flexible sigmoidoscopy screening result.
With a median of 13 years of follow-up, the incidence of colorectal cancer was 20.0 per 10,000 person-years for patients who had advanced adenoma found on colonoscopy, according to a report on the study published in. By comparison, colorectal cancer incidence was 9.1 and 7.5 per 10,000 person-years for nonadvanced adenoma and no adenoma, respectively.
“By demonstrating that individuals diagnosed with an advanced adenoma are at increased long-term risk for subsequent incident CRC, these findings support periodic, ongoing surveillance colonoscopy in these patients,” wrote, of the division of gastroenterology, hepatology, and nutrition, University of Pittsburgh, and his coauthors.
Compared with patients who had no adenoma, those with advanced adenoma were significantly more likely to develop colorectal cancer (rate ratio, 2.7; 95% confidence interval, 1.9-3.7; P less than .001). By contrast, there was no significant difference in risk of colorectal cancer for patients with nonadvanced adenoma and no adenoma (RR, 1.2; 95% CI, 0.8-1.7; P = .30).
Risk of death related to colorectal cancer was also significantly increased for patients with advanced adenoma versus no adenoma, and again, the investigators said, no such difference in mortality was found when nonadvanced adenoma was compared with no adenoma.
The PLCO screening study enrolled men and women aged 55-74 years beginning in 1993, with follow-up continuing until Dec. 31, 2013.
Small, nonadvanced adenomas are commonly found in colonoscopy, occurring in approximately 30% of patients, the investigators said. In the United States, when patients have one to two nonadvanced adenomas, they are typically advised to return in 5-10 years, the researchers noted. However, evidence is lacking in terms of who should return in 5 years, as opposed to 10 years.
“If appropriately powered prospective trials were to replicate these findings, demonstrating no significant difference in cancer incidence between participants with 1 to 2 nonadvanced adenoma(s) and no adenomas, colonoscopy use could be reduced by a large extent, as a surveillance examination at 5 years would not be needed,” the study authors said.
The National Cancer Institute Division of Cancer Prevention supported the study. One author reported receiving grant support from Medtronic.
SOURCE: Click B et al. .