Taylor, Stuart A

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UCL Discovery

CT Colonography Repor/ng and Data System Version 2023: Updated, Robust, and Relevant CT colonography (CTC) is implemented as an alterna6ve to colonoscopy in detec6ng colorectal neoplasia both in pa6ents with symptoms (1) and as part of colorectal cancer screening (2). The CTC repor6ng and data system (C-RADS) (3) was introduced in 2005 to standardize repor6ng of colonic and extracolonic findings and the associated recommenda6ons for subsequent pa6ent management. In this issue of Radiology, Yee et al (4) review the evidence behind the recommenda6ons underlying C-RADS and present an updated classifica6on of mass-like diver6cular strictures and unimportant extracolonic findings. Radiology repor6ng and data systems are widely used in medical imaging and fulfil several func6ons. Whereas they may differ in emphasis, in general, repor6ng and data systems standardize how radiologists report and categorize medical imaging findings so we are all “speaking the same language.” This promotes effec6ve communica6on between radiologists, and between radiologists and referrers. It also provides the opportunity to provide uniform recommenda6ons for pa6ents, such as discharge and/or no further inves6ga6on, addi6onal imaging, or more invasive inves6ga6ons including biopsy. Repor6ng and data systems also oUen allow for expression of the reporter’s confidence in their diagnosis and, by uniformly classifying imaging findings, create a powerful resource for audit and research.  C-RADS  fulfilled these func6ons during the 18 years since its introduc6on. It facilitates extrac6on of detailed metrics from large CTC data sets, something that would be challenging were only free text reports available. We know, for example, the expected prevalence of polyps in a CTC screening service (2) and the incidence and significance of extra colonic findings reported as indeterminate but likely unimportant (5). A modified version of C-RADs is used in the United Kingdom to benchmark CTC services based on the expected polyp detec6on rate, similar to the adenoma detec6on rates reported by colonoscopists. Such data can be scru6nized at a service level or the level of individual radiologists as part of quality assurance. In the context of research, C-RADS recommenda6ons include the op6on of CTC surveillance for 6–9-mm polyps, allowing for insights into their natural history and the importance of growth at follow-up examina6ons (6).    In crea6ng the updated C-RADS version 2023, Yee et al (4) performed a detailed literature review. This was followed by a consensus process with expert members of the American College of Radiology C-RADS commi]ee and interna6onal CTC experts to agree on the updated recommenda6ons.  Detailed guidance is given regarding prac6cal issues such as reading technique, interpreta6on pi^alls, classifica6on of polyp morphologic structure, polyp size measurement, and descriptors to be included in the CTC report. This guidance is supported by literature published since the 2005 guidelines (3). Although the updated C-RADS classifica6ons and recommenda6ons feature few changes from the original, the addi6onal suppor6ve evidence increases confidence in these recommenda6ons. For example, when classifying colonic findings, it is s6ll recommended not to report polyps that are 5 mm or smaller. These small polyps are classified into the C1 category, which means that the pa6ent is to undergo rou6ne screening intervals at 5–10 years. This recommenda6on is supported by evidence repor6ng the low incidence of advanced neoplasia or malignancy in polyps 5 mm or smaller (7), and the low prevalence of advanced neoplasia at this 5-year follow-up interval (8). It is s6ll recommended that the presence of polyps 6–9 mm should be reported (category C2a). However, in selected pa6ents, 3-year CTC follow-up instead of polypectomy is an op6on. This a recommenda6on supported by data regarding the natural history of such polyps (6).  The 2023 updated C-RADS features several changes. For colonic findings, the C2 category has been split into C2a (polyps 6-9 mm, fewer than three findings) and C2b. C2b categorizes soU-6ssue mass or mass-like area, likely benign, such as moderate to severe diver6cular myochosis coli, muscular hypertrophy, or stricture where malignancy cannot be en6rely excluded. Feedback from radiologists indicated that a classifica6on of this common finding was an unmet need in the C-RADS system, and C-RADS was therefore updated. The success of repor6ng and data systems is their ability to periodically evolve and remain fit for purpose once disseminated. The premise of the C2b category is that the reporter has a high confidence that lesion is benign. The C2b-category lesion has features that should be observed such as maintained haustral fold integrity, intact colonic mucosa at three-dimensional evalua6on, presence of diver6culosis, and lack of any shouldering to the lesion. The recommenda6on for pa6ent treatment is based on the reporter’s confidence in benignity. High confidence allows rou6ne follow-up, a reduc6on in certainty leads to shorter interval CTC follow up depending on clinical factors, and any concern for malignancy moves the lesion into the C4 category with the need for endoscopic evalua6on. The second update is in the classifica6on of extracolonic findings. Extracolonic findings at CTC are mostly of no clinical significance and addi6onal follow-up or inves6ga6on detract from the clinical and cost-effec6veness of the procedure. As CTC has become established, the prac6ce of radiologists has matured, and data suggests rela6vely low rates of follow-up for extracolonic findings (9). To simplify the repor6ng of extracolonic findings, the previous categories E1 (no findings) and E2 (unimportant findings) are now in a single E1/2 category with the explicit recommenda6on that these findings require no specific follow-up.  Overall, the updated C-RADS are useful and will improve u6lity in day-to-day clinical prac6ce. It will be interes6ng how the C2b category will be used, and how comfortable radiologists will be in recommending follow-up for lesions for which their level of confidence of benignity is less than high. Whereas short interval follow-up (eg, months) may be reasonable, to wait up to 3 years may risk missing a cancer. In clinical prac6ce, radiologists may have a low bar in classifying mass-like lesions, which are not clearly benign as either needing short-interval follow-up or as C4, requiring endoscopy. It will be important to perform an ongoing audit of the use of the C2b category and pa6ent outcomes regarding clinically important colonic pathology. It is also important to acknowledge that C-RADS  has primary u6lity  when CTC is  used as a screening tool. Worldwide, CTC is more oUen used for the inves6ga6on of pa6ents with symptoms . The treatment of pa6ents who may be older and frailer than the screening popula6on frequently diverges from the follow-up recommenda6ons in C-RADS and is reliant on clinical considera6ons.  The updated C-RADS classifica6on of colonic and extracolonic findings will be useful in all pa6ent popula6ons. One area of CTC repor6ng not yet addressed by C-RADS is extracolonic screening, par6cularly bone density, sarcopenia, and cardiometabolic predictors such as aor6c calcifica6on and liver steatosis. It is possible that these findings have greater importance for pa6ent longevity than do colonic observa6ons, but further research is required into the clinical and cost-effec6veness of rou6ne repor6ng, together with the role ar6ficial intelligence will have in detec6on and quan6fica6on (10). It is likely that this will be addressed in the next itera6on of C-RADS.  References 1 Halligan, S. et al. Computed tomographic colonography versus barium enema for diagnosis of colorectal cancer or large polyps in symptoma6c pa6ents (SIGGAR): a mul6centre randomised trial. Lancet 381, 1185-1193, doi:10.1016/S0140-6736(12)62124-2 (2013). 2 Pickhardt, P. J. & Kim, D. H. Colorectal cancer screening with CT colonography: key concepts regarding polyp prevalence, size, histology, morphology, and natural history. AJR. American journal of roentgenology 193, 40-46, doi:10.2214/ajr.08.1709 (2009). 3 Zalis, M. E. et al. CT colonography repor6ng and data system: a consensus proposal. Radiology 236, 3-9, doi:10.1148/radiol.2361041926 (2005). 4 Yee J, Dachman A, Kim D, et al. CT Colonography Repor6ng and Data System (C-RADS): version 2023 Update. Radiology (In-Press) 5.  Pooler, B. D., Kim, D. H. & Pickhardt, P. J. Indeterminate but Likely Unimportant Extracolonic Findings at Screening CT Colonography (C-RADS Category E3): Incidence and Outcomes Data From a Clinical Screening Program. AJR. American journal of roentgenology 207, 996-1001, doi:10.2214/ajr.16.16275 (2016). 6 Pooler, B. D. et al. Growth rates and histopathological outcomes of small (6-9 mm) colorectal polyps based on CT colonography surveillance and endoscopic removal. Gut, doi:10.1136/gutjnl-2022-326970 (2023). 7 Ponugo6, P. L., Cummings, O. W. & Rex, D. K. Risk of cancer in small and diminu6ve colorectal polyps. Diges:ve and liver disease : official journal of the Italian Society of Gastroenterology and the Italian Associa:on for the Study of the Liver 49, 34-37, doi:10.1016/j.dld.2016.06.025 (2017). 8 McComiskey, D. A., Barre], B., Flemming, J., McKay, K. & Sala, E. Colorectal Cancer Outcomes in a Large Nega6ve Computed Tomography Colonography Screening Cohort. Canadian Associa:on of Radiologists journal = Journal l'Associa:on canadienne des radiologistes 70, 452-456, doi:10.1016/j.carj.2018.09.009 (2019). 9 Pooler, B. D., Kim, D. H. & Pickhardt, P. J. Extracolonic Findings at Screening CT Colonography: Prevalence, Benefits, Challenges, and Opportuni6es. AJR. American journal of roentgenology 209, 94-102, doi:10.2214/ajr.17.17864 (2017). 10 Pickhardt, P. J. et al. Opportunis6c Screening: Radiology Scien6fic Expert Panel. Radiology 307, e222044, doi:10.1148/radiol.222044 (2023).   Author biography Dr Stuart Taylor is a professor of medical imaging in the Center for Medical Imaging, University College London. His research interests focus on cross-secAonal imaging of the bowel, parAcularly in inflammatory bowel disease and colorectal cancer. Dr Taylor is a fellow of the Academy of Medical Sciences, NIHR senior invesAgator, and immediate past president of BSGAR. He sits on the execuAve commiKee of ESGAR.  @Profstuartaylor   Stuart.taylor@ucl.ac.uk  

CT Colonography Reporting and Data System Version 2023: Updated, Robust, and Relevant

https://discovery.ucl.ac.uk/10197210/3/Taylor_CT%20Colonography%20Reporting%20and%20Data%20System%20Version%202023_AAM.pdf

CT Colonography Reporting and Data System Version 2023: Updated, Robust, and Relevant

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