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Colorectal cancer (CRC) incidence and death were increased in patients found to have advanced adenomas on colonoscopy, according to a new analysis of the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial.

At a median follow-up of 12.9 years, advanced adenoma patients had significantly increased risk of CRC diagnosis (rate ratio 2.7, 95% CI 1.9 to 3.7, P<0.001) and CRC death (RR 2.6, 95% CI 1.2 to 5.7, P=0.01) compared with patients with no adenoma, reported Robert E. Schoen, MD, MPH, of the University of Pittsburgh, and colleagues.

"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," the authors wrote in the .

Among patients with non-advanced adenoma, no significant differences were seen for CRC risk (RR 1.2, 95% CI 0.8 to 1.7, P=0.30) or CRC mortality (RR 1.2, 95% CI 0.5 to 2.7, P=0.68) compared with patients with no adenoma on colonoscopy.

For patients with up to two non-advanced adenomas, current guidelines in the U.S. recommend colonoscopy follow-up at anywhere from 5 to 10 years, a decision left to the discretion of the physician.

"If appropriately powered prospective trials were to replicate these findings demonstrating no significant difference in cancer incidence between participants with one to two non-advanced 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 authors wrote.

Patients in the study were part of the PLCO trial. Of 154,900 patients randomized to flexible sigmoidoscopy, 64,650 of 77,442 ultimately took part in the screening.

The study looked at 15,935 patients who underwent colonoscopy following an abnormal finding on flexible sigmoidoscopy. Of those, 50.1% had no adenoma (7,985 patients), 31.8% had a non-advanced adenoma (5,068 patients), and 18.1% had an advanced adenoma (2,882 patients).

Patients in the study had a median age of 64 (55 to 74), were mostly white (90.7%), and men made up the majority (59.7%). Those with a history of colon, lung, prostate, or ovarian cancers were excluded from the trial.

There were 196 total cases of CRC through end of follow-up: 70 from the advanced adenoma group, 55 from the non-advanced group, and 71 in the group with no adenomas. Per 10,000 person-years, the rate of CRC diagnosis in the advanced adenoma group was 20.0 (95% CI 15.3 to 24.7) , 9.1 (95% CI 6.7 to 11.5) in the non-advanced group, and 7.5 (95% CI 5.8 to 9.7) for in the group with no adenomas.

Study limitations included limited statistical power due to its post-hoc nature and lack of patient history of previous adenoma removal. Also, the group with no adenomas may not be truly representative of someone with a negative colonoscopy, since their results followed an abnormal or positive finding on flexible sigmoidoscopy.