Postcolonoscopy Cancer Still Mostly Associated With Missed Lesions, but Failed Resections Are Also Important

Postcolonoscopy Cancer Still Mostly Associated With Missed Lesions, but Failed Resections Are Also Important

Douglas K. Rex, MD, MASGE, reviewing Leung LJ, et al. Gastroenterology 2022 Nov 30.

Postcolonoscopy colorectal cancer (PCCRC) is a dreaded event. Previous studies have found that PCCRC is associated with a lower adenoma detection rate (ADR), nongastroenterologist performance of colonoscopy, proximal location, and high-yield indications such as positive fecal blood tests. Some studies also suggest the serrated pathway contributes disproportionately to PCCRC. 

Most PCCRC has been attributed to missed lesions. The World Endoscopy Organization (WEO) created a PCCRC classification according to the root cause; this study applied the WEO system to a very large bank of PCCRCs in a large U.S. health care system.

The authors randomly selected 523 of 1497 colonoscopies that had resulted in PCCRC diagnoses 6 months to 10 years after colonoscopy. Of the included cases, 197 (37%) were classified as “likely new CRC,” which the WEO system defines as PCCRC that has arisen more than 4 years after colonoscopy. Among these, 9 (4.6%) had an advanced adenoma detected at the prior colonoscopy in the same colon segment as the subsequently diagnosed PCCRC, 16 (8.1%) had an advanced adenoma in a different segment, and 13 (6.7%) had an incomplete colonoscopy or inadequate preparation.

Among the 63% diagnosed within 4 years of colonoscopy, 236 (70.2%) had a complete examination with adequate preparation and were classified as “possible missed lesion, prior examination adequate,” and 52 (15.5%) were “possible missed lesion, prior examination negative but inadequate.”  There were 11 cases (3.3%) with advanced adenomas in the same bowel segment and classified as “detected lesion, not resected” and 37 (11.0%) with advanced adenomas in the same segment and classified as “likely incomplete resection of previously identified lesion.”

Douglas K. Rex, MD, FASGE


These results support prior conclusions that missed lesions cause most PCCRCs. However, factors such as incomplete examination, poor preparation, and lesions that are detected but either not resected or ineffectively resected each contribute to PCCRC. There is no proof that PCCRC arising after 4 years is “likely new cancer,” and this study supports that some PCCRCs arising in this time frame are not. The same database could be used to determine whether ADR predicts the occurrence of PCCRC specifically arising after 4 years, which could clarify whether the concept of “likely new cancer” is valid.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.


Leung LJ, Lee JK, Merchant SA, Jensen CD, Alam A, Corley DA. Post-colonoscopy colorectal cancer etiologies in a large integrated United States healthcare setting. Gastroenterology 2022 Nov 30. (Epub ahead of print) (

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