There are limitations with C-RADS, and the intent was to come up with a practical reporting scheme based on the data that were available, Dr. Zalis said.
Surveillance and screening intervals, especially for small polyps, and more advanced decision models will be forthcoming. And additional reporting for CTC may include some sort of confidence indicator, he said.
A confidence indicator would allow an interpreting clinician to communicate a level of confidence to an endoscopist so he or she can decide how hard to look for something before declaring that it is a false positive.
“Of course there will be nuances that we can't capture on the first round, but we needed to start somewhere, and we expect the criteria will expand with experience,” he added.
Dr. Zalis disclosed that he has received grant and research support from GE Healthcare Inc.
Classification of CTC Findings
These 10 categories, provided by Dr. Zalis, represent the C-RADS classification of colonic and extracolonic findings on computed tomographic colonography, with a few examples (but not a comprehensive list) for each category:
Colonic Findings
▸ C0: Inadequate study/awaiting prior comparisons. Use this category in cases of inadequate prep or insufflation, or when the image can't be read because of excess fluid or feces.
▸ C1: Normal colon or benign lesion. Use this category for cases of no polyp greater than 6 mm, and continue routine screening.
▸ C2: Indeterminate lesion. Use this category for cases of fewer than three polyps 6–9 mm.
▸ C3: Polyp, possibly advanced adenoma. Use this category for cases of three or more polyps 6–9 mm or any polyp 10 mm or larger; a follow-up colonoscopy is recommended.
▸ C4: Colonic mass, likely malignant. Use this category when a lesion compromises the bowel lumen, or there is evidence of extracolonic invasion; surgical consultation is recommended.
Extracolonic Findings
▸ E0: Limited exam. Use this category when an exam is compromised by an artifact so that evaluation of extracolonic soft tissues is limited.
▸ E1: Normal exam or anatomic variant. Use this category when no extracolonic abnormalities are visible, or if there is an anatomic variant such as a retroaortic left renal vein.
▸ E2: Clinically insignificant finding. Use this category when no work-up is indicated, such as for simple cysts or a vertebral hemangioma.
▸ E3: Likely insignificant finding, incompletely characterized, such as a minimally complex renal cyst. Use this category when a work-up may be needed, based on practice and patient preference.
▸ E4: Potentially significant finding. Use this category for a solid renal mass or liposarcoma, and be sure to communicate the details to the referring physician.