Can CT colonography be an alternative to colonoscopy in patients with incomplete colonoscopy?

© Digestive Medicine Research. All rights reserved. Dig Med Res 2021;4:21 | https://dx.doi.org/10.21037/dmr-21-48 Colorectal cancer (CRC) is the third leading primary m a l i g n a n c y i n b o t h m e n a n d w o m e n ( 1 ) , a n d countermeasures against CRC have been advanced in worldwide. Colonoscopy (CS) is considered as the gold standard modality for screening of CRC (2), and the usefulness of CS for screening CRC has been reported (3). On the other hand, CS is a relatively invasive procedure, and we have encountered incidents such as perforation or difficulty in performing CS. In addition, insertion of colonoscope may induce patient’s pain and discomfort. To overcome these issues, development of the insertion method (4) and new device technology (5,6) have been reported. Although use of sedation reduces patients pain, it causes unexpected adverse event (7). CT colonography (CTC) is one of the options for difficult CS. Although no studies were found evaluating the effectiveness of CTC on CRC incidence, CRC mortality, or both (8), it has a high sensitivity for detecting large polyps in asymptomatic (9) and symptomatic (10) population and is largely superior to that of barium enema, resulting that CTC the best radiological device for surveillance of CRC (11). Another option for screening for CRC is Colon capsule endoscopy (CCE) (12)(13). CCE was first report in 2006 (6), nowadays second-generation CCE has been developed. The firstgeneration CCE had a mild sensitivity for detecting CRC and polyps (14). The second-generation CCE has a high sensitivity for detecting ≥6 mm polyps (13), approximately 80–95%, as well as CTC. In the incomplete CS cohort, the efficacies of CTC and/or CCE have been evaluated. Copel et al. (15) evaluated the efficacy of CTC included 546 patients received CTC after incomplete CS due to the technical difficulty. They reported that CTC detected additional polyps more than 6 mm in size in 13.2% of included patients. Of these patients, 63% received repeat CS, and the positive predictive value (PPV) per patient of CTC for mass lesions, large polyps, and medium polyps was 91%, 92%, and 65%, respectively (15). In a study by Sali et al., 42 patients with a positive fecal occult blood test underwent CTC after incompletion of initial surveillance CS; 50% of these patients showed polyps or mass lesions for which repeat CS was performed. CTC showed a PPV of 87.5% for polyps more than 9 mm (16). In recent metaanalysis, the performance of CTC and second-generation CCE on incomplete CS were evaluated (17). They reported that diagnostic yields of CTC and CCE were 10% (95% CI, 7–15%) and 37% (95% CI, 30–43%) for any size, 13% (95% CI, 9–18%) and 21% (95% CI, 12–32%) for more than 5 mm and 4% (95% CI, 2–7%) and 9% (95% CI, 3–17%) for more than 9 mm polyps (17). In the issue of digestive medicine research, Bazoua et al. evaluated the efficacy of CTC comparing the conventional CS in a cohort of incomplete CS. Moreover, they determined the potential of considering CTC as an alternative to CS in this group, and any risk factors or pathological causes attributed to incomplete CS. They retrospectively analyzed 102 of incomplete CS, and Editorial