CT colonoscopy in 2007: the next standard for colorectal cancer screening in average-risk subjects?

Over a decade has passed since computed tomographic colonography (CTC) was first described as a potential tool for the detection of colonic polyps. Today CTC is highly specific, but the range of reported sensitivities is wide. Patient or scanner characteristics do not fully account for this variability, but collimation, the number of CT detectors, the mode of imaging, and operator expertise do explain some of the discrepancies. In the present issue of Endoscopy, Kim et al. [1] describe the meticulous technique they used at the University of Wisconsin and explain how they have organized an active CTC-based screening program for colorectal carcinoma (CRC). However, the role of CTC in CRC screening is still debatable, and their interesting paper raises three major issues which ought to be discussed:

the clinical relevance of diminutive (< 6 mm) and small (< 1cm) polyps, policy differences between the USA and European countries relating to the organization of CRC screening in a population setting, the need or otherwise to conduct randomized studies to show a decrease in mortality or incidence prior to implementation of a national screening program.

References

• 1 Kim D. et al . Computed tomographic colonography for colorectal screening.  Endoscopy. 2007;  39 542-547
• 2 Mulhall B P, Veerappan G R, Jackson J L. Meta-analysis: computed tomographic colonography.  Ann Intern Med. 2005;  142 635-650
• 3 Summers R M, Yao J, Pickhardt P J. et al . Computed tomographic virtual colonoscopy computer-aided polyp detection in a screening population.  Gastroenterology. 2005;  129 1832-1844
• 4 Church J M. Clinical significance of small colorectal polyps.  Dis Colon Rectum. 2004;  47 481-485
• 5 Gschwantler M, Kriwanek S, Langner E. et al . High-grade dysplasia and invasive carcinoma in colorectal adenomas: a multivariate analysis of the impact of adenoma and patient characteristics.  Eur J Gastroenterol Hepatol. 2002;  14 183-188
• 6 Nusko G, Mansmann U, Altendorf-Hofmann A. et al . Risk of invasive carcinoma in colorectal adenomas assessed by size and site.  Int J Colorect Dis. 1997;  12 267-271
• 7 Butterly L F, Chase M P, Pohl H, Fiarman G S. Prevalence of clinically important histology in small adenomas.  Clin Gastroenterol Hepatol. 2006;  4 343-348
• 8 Souques M, Lassalle M, Guldner L. et al . Colorectal polyps and cancers diagnosed by pathologists in Ile de France Region. Crisapif-Petri study.  Gastroenterol Clin Biol. 2006;  30 587-593
• 9 Eide J. Risk of colorectal cancer in adenoma-bearing individuals within a defined population.  Int J Cancer. 1986;  38 173-176
• 10 Hur C, Chung D C, Schoen R E, Gazelle G S. The management of small polyps found by virtual colonoscopy: results of a decision analysis.  Clin Gastroenterol Hepatol. 2007;  5 237-244
• 11 Kudo S E, Kashida H. Flat and depressed lesions of the colorectum.  Clin Gastroenterol Hepatol. 2005;  3 (7 Suppl 1) S33-S36
• 12 Hurlstone D P, Cross S S, Adam I. et al . Efficacy of high magnification chromoscopic colonoscopy for the diagnosis of neoplasia in flat and depressed lesions of the colorectum: a prospective analysis.  Gut. 2004;  53 284-290
• 13 Tsuda S, Veress B, Toth E, Fork F T. Flat and depressed colorectal tumours in a southern Swedish population: a prospective chromoendoscopic and histopathological study.  Gut. 2002;  51 550-555
• 14 Jaramillo E, Watanabe M, Slezak P, Rubio C. Flat neoplastic lesions of the colon and rectum detected by high-resolution video endoscopy and chromoscopy.  Gastrointest Endosc. 1995;  42 114-122
• 15 Rembacken B J, Fujii T, Cairns A. et al . Flat and depressed colonic neoplasms: a prospective study of 1000 colonoscopies in the UK.  Lancet. 2000;  355 1211-1214
• 16 Hart A R, Kudo S, Mackay E H. et al . Flat adenomas exist in asymptomatic people: important implications for colorectal cancer screening programmes.  Gut. 1998;  43 229-231
• 17 Hur C, Gazelle G, Zalis M, Podolsky D. An analysis of the potential impact of computed tomographic colonography (virtual colonoscopy) on colonoscopy demand.  Gastroenterology. 2004;  127 1312-1321
• 18 Ladabaum U, Song K. Projected national impact of colorectal cancer screening on clinical and economic outcomes and health services demand.  Gastroenterology. 2005;  129 1151-1162
• 19 Hur C, Gazelle G S, Hsu E H. et al . The effect of prior colonic imaging on endoscopic productivity: potential impact of computed tomographic colonography.  Clin Gastroenterol Hepatol. 2005;  3 1124-1127
• 20 Zalis M E, Barish M A, Choi J R. et al . CT colonography reporting and data system: a consensus proposal.  Radiology. 2005;  236 3-9
• 21 Brenner D J, Georgsson M A. Mass screening with CT colonography: should the radiation exposure be of concern?.  Gastroenterology. 2005;  129 328-337
• 22 Bosworth H B, Rockey D C, Paulson E K. et al . Prospective comparison of patient experience with colon imaging tests.  Am J Med. 2006;  119 791-799
• 23 Taylor S A, Halligan S, Saunders B P. et al . Acceptance by patients of multidetector CT colonography compared with barium enema examinations, flexible sigmoidoscopy, and colonoscopy.  AJR Am J Roentgenol. 2003;  181 913-921
• 24 Phillips K A, Liang S Y, Ladabaum U. et al . Trends in colonoscopy for colorectal cancer screening.  Med Care. 2007;  45 160-167
• 25 El-Serag H B, Petersen L, Hampel H. et al . The use of screening colonoscopy for patients cared for by the Department of Veterans Affairs.  Arch Intern Med. 2006;  166 2202-2208
• 26 Heresbach D, Manfredi S, D’Halluin P N. et al . Review in depth and meta-analysis of controlled trials on colorectal cancer screening by faecal occult blood test.  Eur J Gastroenterol Hepatol. 2006;  18 427-433