Accuracy of CT Colonography for Detection of Polypoid and Nonpolypoid Neoplasia by Gastroenterologists and Radiologists: A Nationwide Multicenter Study in Japan

Abstract

OBJECTIVES:The objective of this study was to assess prospectively the diagnostic accuracy of computer-assisted computed tomographic colonography (CTC) in the detection of polypoid (pedunculated or sessile) and nonpolypoid neoplasms and compare the accuracy between gastroenterologists and radiologists.METHODS:This nationwide multicenter prospective controlled trial recruited 1,257 participants with average or high risk of colorectal cancer at 14 Japanese institutions. Participants had CTC and colonoscopy on the same day. CTC images were interpreted independently by trained gastroenterologists and radiologists. The main outcome was the accuracy of CTC in the detection of neoplasms ≥6 mm in diameter, with colonoscopy results as the reference standard. Detection sensitivities of polypoid vs. nonpolypoid lesions were also evaluated.RESULTS:Of the 1,257 participants, 1,177 were included in the final analysis: 42 (3.6%) were at average risk of colorectal cancer, 456 (38.7%) were at elevated risk, and 679 (57.7%) had recent positive immunochemical fecal occult blood tests. The overall per-participant sensitivity, specificity, and positive and negative predictive values for neoplasms ≥6 mm in diameter were 0.90, 0.93, 0.83, and 0.96, respectively, among gastroenterologists and 0.86, 0.90, 0.76, and 0.95 among radiologists (P<0.05 for gastroenterologists vs. radiologists). The sensitivity and specificity for neoplasms ≥10 mm in diameter were 0.93 and 0.99 among gastroenterologists and 0.91 and 0.98 among radiologists (not significant for gastroenterologists vs. radiologists). The CTC interpretation time by radiologists was shorter than that by gastroenterologists (9.97 vs. 15.8 min, P<0.05). Sensitivities for pedunculated and sessile lesions exceeded those for flat elevated lesions ≥10 mm in diameter in both groups (gastroenterologists 0.95, 0.92, and 0.68; radiologists: 0.94, 0.87, and 0.61; P<0.05 for polypoid vs. nonpolypoid), although not significant (P>0.05) for gastroenterologists vs. radiologists.CONCLUSIONS:CTC interpretation by gastroenterologists and radiologists was accurate for detection of polypoid neoplasms, but less so for nonpolypoid neoplasms. Gastroenterologists had a higher accuracy in the detection of neoplasms ≥6 mm than did radiologists, although their interpretation time was longer than that of radiologists.

Colon Capsule Endoscopy versus CT Colonography in Patients with Large Non-Polypoid Tumours: A Multicentre Prospective Comparative Study (4CN Study)

“…Since CTC requires a shorter time to complete the examination, CTC and CCE could be a complementary screening test. CTC has high patient acceptability and high sensitivity for polypoid lesions [8,9], whereas CCE has higher sen- sitivity for non-polypoid tumours as demonstrated in the present study. Even advanced colon cancers can be missed in failed CCE studies [32], but CTC can depict advanced colon cancers in almost 100% [8,9].…”

“…According to a previous report [13], CCE was assumed to have 93% sensitivity for polyps measuring ≥10 mm. In contrast, CTC was assumed to have 60% sensitivity for non-polypoid lesion [8,9]. In order to maintain the hypothesis as well as a type I error of 5% and power of 80%, the required sample size was estimated to be 20 for each modality.…”

“…Indeed, all of the capsules successfully went beyond the target lesions in the present study. At present, sodium diatrizoate is widely used for faecal tagging in CTC [9] and could be useful when not performing CTC but also for CCE. In approximately 10% of patients, the capsule failed to pass through the colon within the lifespan of the battery.…”

“…CTC is established as a colon screening test especially in patients with incomplete colonoscopy [17][18][19][20][21], with development of new techniques, for example, faecal tagging, automatic insufflation and recently developed software. However, the sensitivity for non-polypoid lesions by CTC was inferior to that for polypoid lesions [8,9], but data regarding sensitivity for detecting non-polypoid tumours is also still insufficient and controversial.…”

“…Particularly, depressed lesions are at high risk for cancer at the time of detection [7]. But non-polypoid lesions are more difficult to depict by not only CT colonography (CTC) but also by plain colonoscopy [8][9][10][11], because the subtle mucosal changes can be easily missed.…”