Abdominal Radiology

ª Springer Science+Business Media, LLC, part of Springer Nature 2018

Abdom Radiol (2018) https://doi.org/10.1007/s00261-018-1514-3

CT colonography: the ideal colorectal cancer screening test David H. Kim Department of Radiology, University of Wisconsin School of Medicine and Public Health, E3/311 Clinical Science Center, 600 Highland Ave, Madison, WI 53792-3252, USA

The marked technological advances in multi-detector CT over the past two decades have allowed a revolutionary change regarding bowel imaging. With the ability of fast volumetric acquisition of the abdomen and pelvis with thin z-axis slice thickness, the bowel can be exquisitely imaged to diagnose previously difficult-to-detect entities such as small bleeding sources in the small bowel and subcentimeter precancerous polyps in the colon. CT colonography (CTC) represents the cross-sectional replacement for the dated fluoroscopic standard of the double-contrast barium enema. CT colonography is now the screening option of choice for colorectal cancer (CRC) by imaging [1]. There is a wealth of trial and observational data which demonstrate accurate polyp and cancer detection [2–5]. In addition, over a decade of clinical use has reinforced the capabilities of this technology. A strong argument can be made that of all potential CRC screening tests, CTC may represent the best overall option for colorectal cancer screening. Unlike stool-based evaluations, including the newer stool DNA tests, which work mainly by detecting early cancers, CTC can detect important precancerous polyps to prevent cancers from occurring in the first place as well as detect the early cancers. Unlike colonoscopy which holds a risk for significant complications including perforations, CTC has a wide safety profile because it is essentially an imaging exam. Coupled with a selective polypectomy approach based on size, CTC can avoid unnecessary polypectomies for pseudodisease as opposed to colonoscopy where many benign polyps with no future cancer risk are removed. CTC also allows additional evaluation for aortic aneurysms and osteoporosis in the general population (i.e., opportunistic screening) which holds tremendous additional benefit.

Correspondence to: David H. Kim; email: [email protected]

The adoption for CTC use in colorectal cancer screening has been slow over the years. This has resulted from a combination of factors including lack of national insurance coverage, contrary messages from gastroenterologists given the perceived competition with colonoscopy, and the general lack of interest in interpreting these exams by radiologists. This is unfortunate as colorectal screening rates remain unacceptably low among the eligible population with the current tests in widespread use. The additional of CTC would undoubtedly increase the total numbers of screened individuals and help to decrease future cancer incidence. Studies have been shown to increase screening rates overall when introduced in a given population [6]. It is felt that discussion regarding CTC starts the conversation for screening in general which then can occur with any of the options. Hopefully, the issues holding back CTC use will continue to dissipate in the coming years. CTC would be a valuable addition to the existing tests to combat this largely preventable cancer. It is our distinct pleasure to present this special feature issue of Abdominal Radiology on CT colonography. An impressive list of leading CTC researchers present comprehensive articles encompassing several key areas in CT colonography. Drs. Pickhardt, Johnson, and Yee begin with a historical overview of CTC, highlighting important trials and events from research and development to clinical implementation. Dr. Chang outlines the key technical issues to ensure a consistent quality exam while Dr. Park covers the various interpretative strategies to optimize accurate polyp detection. Interpretative pitfalls as well as the important issue of serrated polyps are discussed. Drs. Yee and McFarland discuss radiation and extracolonic findings which are two important ancillary issues that are often raised with CTC. And finally, Drs. Dachman and Barish explain C-RADS which represents the structured reporting system for CTC as well as highlight the ACR national data registry (NRDR) which ensures continuous quality improve-

David H. Kim: CT colonography

ment. We hope that these articles serve as an important resource for our Abdominal Radiology readership as CTC becomes more prevalent in the CRC screening arena.

References 1. Yee J, Kim DH, Rosen MP, et al. (2014) ACR appropriateness criteria colorectal cancer screening. J Am Coll Radiol 11:543–551 2. Johnson CD, Chen MH, Toledano AY, et al. (2008) Accuracy of CT colonography for detection of large adenomas and cancers. N Engl J Med 359:1207–1217

3. Johnson CD, Herman BA, Chen MH, et al. (2012) The National CT Colonography Trial: assessment of accuracy in participants 65 years of age and older. Radiology 263:401–408 4. Kim DH, Pickhardt PJ, Taylor AJ, et al. (2007) CT colonography versus colonoscopy for the detection of advanced neoplasia. N Engl J Med 357:1403–1412 5. Pickhardt PJ, Choi JR, Hwang I, et al. (2003) Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med 349:2191–2200 6. Benson M, Pier J, Kraft S, et al. (2012) Optical colonoscopy and virtual colonoscopy numbers after initiation of a CT colonography program: long term data. J Gastrointest Liver Dis 21:391–395