Postcolonoscopy colorectal cancers were more likely to arise in the proximal colon and to show microsatellite instability.
In all, 64% of postcolonoscopy colorectal cancers were located in the proximal colon, compared with 44% of detected colorectal cancers.
Microsatellite instability (MSI) was detected in 32% of postcolonoscopy colorectal cancers, versus 13% of detected colorectal cancers.
Postcolonoscopy cancers have an estimated global prevalence ranging from 3% to 9% and an estimated pooled prevalence of 3.7%.
Risk factors for postcolonoscopy colorectal cancers include low adenoma detection rates, rural facilities, and care by physicians who are not gastroenterologists.
Tumor-specific and patient-specific factors, including location within the colon and superior survival, compared with detected cancers, raises the possibility of underlying molecular differences related to tumorigenesis.
In a study comparing 84 postcolonoscopy colorectal cancers (defined as those detected within 6-60 months of colonoscopy) with with 84 detected colorectal cancers (detected within 6 months of a colonoscopy).
MSI was the only molecular feature that was significantly more frequent in postcolonoscopy versus detected colorectal cancers.
However, postcolonoscopy colorectal cancers were significantly more likely to be early stage (86% versus 69% for detected colorectal cancers.
Five-year survival did not significantly differ between the groups.