CT Colonography versus Colonoscopy for the Detection of Advanced Neoplasia

To the Editor: We raise two issues regarding the nonrandomized comparison of computed tomographic colonography (CTC) and optical colonoscopy (OC) reported by Kim et al. (Oct. 4 issue). 1 First, the prevalence of cancer in the OC group (0.1%) was 10 to 20% of the expected prevalence, whereas the prevalence of cancer in the CTC group was more consistent with that in a screening population. 2 , 3 Since the symptom prevalence in the groups was equal, the unequal cancer prevalence suggests that the OC group had more patients with prior negative screening, which is associated with low rates of cancer and advanced . . .