We read with interest the two excellent studies on interval colorectal cancers (CRC) following colonoscopy and wish to present important data relevant to the prevention of interval CRC. In a pooled multicohort analysis, Robertson and coauthors found that invasive cancer was diagnosed in 0.6% of patients after clearing colonoscopy among eight large North American trials, and concluded that half of these were likely missed lesions.1 In a population-based study, le Clercq and coauthors reported that CRC found following colonoscopy were more likely to have non-polypoid morphology than prevalent cancers.2

We previously described that non-polypoid colorectal neoplasms (NP-CRN) harbour more advanced pathology than polypoid neoplasms.3 Indeed, due to their subtle appearance, NP-CRN may be a key contributor to interval CRC. The learning curve in their detection is largely unknown.

Using available data, we summarised the learning curve (see …