Japanese National Computed Tomographic (CT) Colonography Trial

The investigators will evaluate the sensitivity of CTC in detecting colorectal polyps and cancers (at least 6 mm in diameter) in 1,500 subjects at increased risk of colorectal cancer (CRC), using optical colonoscopy as the reference standard. The primary endpoint will be sensitivity in the detection of colorectal polyps and cancers that are at least 6 mm in diameter. The secondary endpoints will include specificity and predictive values in the detection of colorectal polyps and cancers.

This clinical study will also evaluate the differences of the detection accuracies between human readings with and without computer-aided detection (CAD) that automatically detects colonic lesions in CTC images and presents the detected lesions to the readers. This clinical study will also compare performance between radiologists and gastroenterologists in detecting colorectal lesions in CTC images.

All the CTC images and their interpretations, optical colonoscopy reports and images, and pathology reports of resected colorectal lesion will be prospectively collected from 12 Japanese hospitals participating in the trial. All patients' information will be completely anonymized at each site before any analysis of the data takes place.

Inclusion criteria

• Outpatients who are eligible for optical colonoscopy.
• Aged 20 years or older.
• Major functions of organs of the subjects are in a good condition.
• Signed informed consent forms are obtained from the patients.

Exclusion criteria

• Known colorectal polyps or cancers at any site at the time of enrollment.
• Patients with inflammatory bowel disease.
• Fulfillment of clinical criteria for diagnosis of FAP or HNPCC (Amsterdam criteria).
• Serious medical conditions that may increase the risk of optical colonoscopy or are so severe that screening would have no benefit.
• Previous colorectal surgery.
• Gastric or intestinal stenosis, abdominal adhesions, bowel obstruction or perforation, toxic megacolon.
• Evidence of an increased risk in carrying out bowel preparation or CTC exams.
• Possibility of pregnancy.
• Optical colonoscopy or barium enema carried out within the last 3 years.
• Patients with psychological conditions that contraindicate colonoscopy or that make them irrelevant to participate in the trial.
• Iodine hypersensitivity.
• Severe thyroid disease.
• Claustrophobia.
• Severe deafness.
• Subjects whose eligibility for this clinical trial is not appropriate by other reasons.