The potential of CT colonography for colorectal cancer screening in Japan

Abstract

Colorectal cancer remains a leading cause of mortality worldwide, and early detection is essential for improving outcomes. CT colonography (CTC) has emerged as a promising alternative to optical colonoscopy for colorectal cancer screening. This article explores the potential of CTC in Japan, focusing on quality control, patient acceptability, complications, and its role in screening programs. CTC has demonstrated high sensitivity and specificity for detecting colorectal polyps, with its diagnostic performance comparable to colonoscopy for lesions ≥ 10 mm. Techniques such as fecal tagging and dual-position imaging significantly enhance diagnostic accuracy. However, the variability in diagnostic outcomes underscores the need for rigorous interpretation training and quality control. The American College of Radiology recommends training with at least 50 cases verified by colonoscopy. Despite its advantages, the adoption of CTC in Japan remains limited due to low awareness among medical professionals, a shortage of trained radiologists, and the absence of specific guidelines endorsing its use. Patient acceptability for CTC is high due to its non-invasive nature, shorter examination time, and reduced bowel preparation requirements compared to colonoscopy. Nonetheless, complications such as bowel perforation, albeit rare, necessitate careful risk assessment. While CTC has been recognized in the U.S. and Europe for screening and diagnostic follow-up, its integration into Japan's colorectal cancer screening guidelines is crucial to expand its utilization. To maximize the benefits of CTC, efforts must focus on standardizing methodologies, establishing quality indicators, and generating robust evidence on mortality reduction and cost-effectiveness.

Keywords: CT colonography; Colorectal neoplasms; Mass screening; Quality control.

Fig. 1

a On standard fly-through imaging, submersed lesions are typically obscured and not visualized. b Following the application of electronic cleansing, the tagged residual fluid was effectively removed, enabling clear identification of the lesion (►). c Endoscopic view of the lesion, which was subsequently resected and pathologically confirmed as an 8-mm adenoma

Fig. 2

Sessile Serrated Lesion (SSL), which has recently attracted attention as the third pathway of carcinogenesis, often presents as a flat lesion with mucus attached to its surface. a A 57-year-old female underwent CT colonography following a positive screening result, revealing a 15 mm type II a lesion in the ascending colon. ► identifies the sessile serrated lesion. b When electronic cleansing was applied, the lesion disappeared (►). c On the multi-planar reconstruction image, the lesion appeared to resemble tagged mucus. d An endoscopic image of the same lesion. The pathological diagnosis was SSL

Fig. 3

A 90-year-old male was scheduled for CT colonography as part of a detailed examination for abdominal pain. Bowel preparation included Diatrizoate meglumine and a bowel cleansing agent. On the day of the examination, the patient developed respiratory failure and was urgently hospitalized. a A chest CT scan taken on the same day revealed pneumonia in both lower lobes of the lungs, leading to a diagnosis of aspiration pneumonia caused by the bowel preparation agents. b A plain chest X-ray taken two days later showed significant worsening of the pneumonia. Despite intensive care, including steroid pulse therapy, the patient died on that day

Fig. 4

A 66-year-old female was scheduled for CT colonography to investigate the cause of her constipation. She took a bowel preparation agent containing barium starting the day before the examination, but no bowel movements occurred. On the day of the examination, she presented with fever, abdominal pain, and low blood pressure, entering a state of shock and requiring hospitalization. a, b Tagged stool was observed from the ascending colon through the sigmoid colon, while untagged stool was found in the rectum. The patient was diagnosed with sepsis secondary to obstructive colitis and died the following day

Fig. 5

The total number of colorectal examinations conducted nationwide (including both outpatient and inpatient) based on insurance claims. CTC CT Colonography, BE Barium Enema