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Most post-colonoscopy cancers resulted from missed, partially removed lesions
The majority of interval cancers diagnosed shortly after complete colonoscopy were lesions that were missed or not completely removed during the initial procedure in a recent study.
Researchers performed a pooled analysis of eight studies including 9,167 patients (mean age, 62 years) with sporadic colorectal neoplasia. All participants underwent colonoscopy at baseline to remove all adenomas, with patient follow-up conducted over a median of 47.2 months, during which most patients received at least one follow-up colonoscopy.
Presumptive causes of interval cancer were determined by the following algorithm: Patients with cancer detected 3 years or more after initial colonoscopy that revealed no adenomas in the same colorectal segment had “new cancer.” Lesions detected within 3 years of initial colonoscopy with no evidence of significant adenomas had “missed lesions.” Lesions detected in a segment in which adenomas were initially resected were defined as “incomplete adenoma resection,” and lesions detected within 1 year of previous colonoscopy in segments in which the initial endoscopist suspected cancer might be present were defined as “failed biopsy detection.”
During follow-up, 58 patients were diagnosed with invasive cancer (IRR=1.71 per 1,000 person-years) after prior colonoscopy indicated neoplasia clearance. Seventy-eight percent of these cancers were stage I or II, but investigators said nine colorectal cancer (CRC)-related deaths took place within the cohort.
Of 54 evaluable cancers, 52% were identified as probable missed lesions, 19% were considered likely related to incomplete resection of a noninvasive lesion and 24% were considered probable new lesions. The remaining 5% were attributed to failed biopsy detection. Seven deaths during the study occurred after missed lesions, with the other two attributed to new lesions.
“Our review suggests that many of the interval cancers might have been found earlier or perhaps excised while still an adenoma at the prior colonoscopy exam,” the researchers wrote. “These results emphasize the importance of performing colonoscopic examinations with meticulous attention to the identification and complete removal of all suspected neoplasms.”
Disclosure: Researcher Douglas J. Robertson, MD, MPH, reported serving on an advisory board for Given Imaging.