Rationale and Objectives
The American College of Radiology has recently endorsed the use of computed tomographic colonography (CTC) for colon cancer screening. With advances in technology and postprocessing software, the quality of computed tomographic colonographic studies has improved, and new techniques are being developed to reduce radiation exposure and increase patient acceptance of the procedure. The aim of colorectal cancer screening is to reduce the incidence of malignancy by identifying and removing presymptomatic lesions. The aim of this study was to answer the clinical question: In an asymptomatic patient at average risk for colon cancer, is CTC equivalent to optical colonoscopy (OC) for detecting clinically significant polyps?
Materials and Methods
A systematic literature review was conducted to evaluate CTC compared to OC, using the patient, intervention, comparison intervention, outcome (PICO) search strategy. The PubMed search used Medical Subject Headings, including the terms “computed tomography colonography,” “colonoscopy,” “screening,” and “polyp.” Each of the retrieved articles was assigned a level of evidence using the Centre for Evidence-Based Medicine’s hierarchy of validity for diagnostic studies.
Results
PICO search criteria and review of abstracts identified 16 relevant studies. Using the Centre for Evidence-Based Medicine’s hierarchy of validity, there were three level 1c studies, two level 2a studies, three level 2b studies, four level 3b studies, two level 4 studies, and two level 5 studies. All relevant studies demonstrated that CTC had high or moderately high per patient and per polyp sensitivity and specificity compared to OC for clinically relevant polyps (>5 mm).
Conclusions
The majority of evidence suggests that CTC is an acceptable alternative to OC, particularly in the group of patients who are either unwilling or unable to undergo OC. The results of the large, multicenter American College of Radiology Imaging Network study are pending. This trial presented preliminary results in 2007 suggesting that the sensitivity and specificity of CTC are high and comparable to those of OC.
Currently, colorectal cancer (CRC) is the third most common type of cancer to affect adults in North America, and the approximate lifetime risk for developing this cancer in men is 6.7%, compared to 6.1% in women . In the majority of cases, the precursor to developing this type of cancer is a polyp, so screening has been advocated since the 1990s. The aim of CRC screening is to reduce the incidence of malignancy by identifying and removing presymptomatic lesions, thereby reducing CRC morbidity and mortality . However, only 42% of Americans aged >50 years have undergone any type of screening, including fecal occult blood testing, sigmoidoscopy, or optical colonoscopy (OC) . Numerous factors have been postulated to be related to the low screening rates, including a lack of awareness, patient discomfort, socioeconomic causes, and a lack of availability .
Recently, the American College of Radiology endorsed the use of computed tomographic colonography (CTC) for screening patients for colon cancer. CTC was first described in 1994 by Vining et al as a method for evaluating the colonic lumen. This technique has been significantly refined over the past decade, initially being used as a problem-solving tool for patients with incomplete colonoscopy or equivocal barium enema results. More recently, CTC has been investigated as a screening modality for patients at average risk for developing CRC. With advances in technology and postprocessing software, the quality of the resulting studies has improved, and new techniques are being developed to reduce patient radiation exposure and increase patient acceptance of the procedure. With CTC as a minimally invasive alternative to OC, it is possible that more people may be willing to undergo CRC screening, possibly resulting in the earlier detection of abnormalities, increasing the likelihood of successful intervention, and ultimately reducing the number of CRC deaths.
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Clinical scenario
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Methods
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Table 1
PubMed Search Strategy Using PICO-focused Keywords
Search Step Search Criteria Number of Retrieved Citations 1 Search “colonography, computed tomographic” (all fields) 876 2 Search “colonoscopy” (all fields) 17,823 3 Search “colonic polyp” (all fields) 9354 4 Search “colorectal neoplasms/diagnosis” (all fields) 4575 5 Search “colonic neoplasms/diagnosis” (all fields) 5164 6 Search [(#3) OR (#4)] OR (#5) 17,454 7 Search [(#1) AND (#2)] AND (#6) 360 8 Search [(#1) AND (#2)] AND (#6) 116
PICO, patient, intervention, comparison intervention, outcome.
Results were limited to studies published in the past 5 years, involving humans, and in English.
Table 2
Levels of Evidence as Adapted from the Oxford Centre for Evidence-Based Medicine
Levels of Evidence Diagnostic Tests 1a Systematic review with homogeneity of level 1 diagnostic studies or clinical decision rule with 1b studies from different clinical institutions 1b Cohort study with good reference standards and validation of clinical decision rule tested within a single clinical institution 1c Studies with results that have very high sensitivity and/or specificity, such that a positive result rules in the diagnosis and a negative result rules out the diagnosis 2a Systematic review of level 2 diagnostic studies with homogeneity 2b Exploratory cohort study with good reference standards looking for significant factors or clinical decision rule after derivation or validated only on split samples or databases 3a Systematic review including 3b or studies of higher levels of evidence 3b Non-consecutive study or study without a consistently applied reference standard 4 Case-control study with either poor or non-independent reference standards 5 Expert opinion
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Results
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Table 3
Summary of CT Colonography Compared to Colonoscopy Results with Levels of Evidence for Articles retrieved from PubMed Search Using PICO-focused Keywords
Reference Year N Sensitivity (%) Specificity (%) PPV (%) NPV (%) CT Scanner Level of Evidence Johnson et al. † 2008 2531 78–90 86–88 23–40 98–99 16 slice 1c Pickhardt et al. † ‡ 2003 1233 89–94 80–96 — — 4,8 slice 1c Iannoccone et al. † 2003 158 96 97 94 98 4 slice 1c Mulhall et al. † 2005 — 48–85 92–97 — — — 2a Halligan et al. 2005 — — — — — — 2a Pickhardt et al. ∗ 2004 1233 86–92 — — — 4,8 slice 2b Iannoccone et al. ∗ 2005 88 86–100 82–100 70–100 91–100 4 slice 2b Vogt et al. ∗ 2004 115 91–100 82–83 — — 4 slice 2b Copel et al. † 2007 546 — — 33–65 — 4,8 slice 3b Yun et al. ∗ 2007 113 89–91 — 76–87 — 16 slice 3b Wessling et al. 2005 78 81–100 86 — — 4 slice 3b Macari et al. ∗ 2004 68 53–100 90 Δ — — 4 slice 3b Edwards et al. 2004 93 — — 73 — 1 slice 4 Kim et al. 2007 246 — — — — — 4 Rozen 2006 — — — — — — 5 Rex 2005 — — — — — — 5
CT, computed tomographic; FN, false negatives; FP, false positives; NPV, negative predictive value; PPV, positive predictive value; TN, true negatives; TP, true positives.
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Discussion
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Conclusions
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References
1. Rabeneck L.: Population-based colorectal cancer screening; an overview of Ontario’s program. Oncol Exchange 2007; 6: pp. 25-27.
2. Quintero E., Parra-Blanco A.: Noninvasive diagnostic tools in colorectal cancer mass screening. Curr Colorect Cancer Rep 2007; 3: pp. 29-34.
3. Swan J., Breen N., Coates R.J., et. al.: Progress in cancer screening practices in the United States: results from the 2000 National Health Interview Survey. Cancer 2003; 97: pp. 1528-1540.
4. Umar S., Richmond E., Griebel D.J.: Colorectal cancer prevention: diet, drugs or nothing. Curr Colorect Cancer Rep 2007; 3: pp. 16-23.
5. McAlearney A.S., Reeves K.W., Kickinson S.L., et. al.: Racial differences in colorectal cancer screening practices and knowledge within a low-income population. Cancer 2008; 112: pp. 391-398.
6. Shih Y.C., Zhao L., Elting L.S.: Does Medicare coverage of colonoscopy reduce racial/ethnic disparities in cancer screening among the elderly?. Health Aff (Millwood) 2006; 25: pp. 1153-1162.
7. Vining D.J., Gelfand D.W., Bechtold R.E., Scharling E.S., Grishaw E.K., Shifrin G.Y.: Technical feasibility of colon imaging with helical CT and virtual reality. [abstract] AJR Am J Roentgenol 1994; 162: pp. S104.
8. Haynes B.: Of studies, syntheses, synopses, summaries, and systems: the “5S” evolution of information services for evidence-based healthcare decisions. Evid Based Nurs 2007; 10: pp. 6-7.
9. Dodd G.D.: Evidence-based practice in radiology: steps 3 and 4—appraise and apply diagnostic radiology literature. Radiology 2007; 242: pp. 342-353.
10. Staunton M.: Evidence-based practice in radiology: steps 1 and 2—asking answerable questions and searching for evidence. Radiology 2007; 242: pp. 23-31.
11. Pickhardt P.J., Choi J.R., Nugent P.A., Schindler W.R.: The effect of diagnostic confidence on the probability of optical colonoscopic confirmation of potential polyps detected on CT colonography: prospective assessment in 1,339 asymptomatic adults. AJR Am J Roentgenol 2004; 183: pp. 1661-1665.
12. National Health Service Centre for Evidence-Based Medicine. Levels of evidence and grades of recommendations. Available at: http://www.cebm.net/level_of_evidence.asp .
13. Mulhall B.P., Veerappan G.R., Jackson J.L.: Meta-analysis: computed tomographic colonography. Ann Intern Med 2005; 142: pp. 635-650.
14. Halligan S., Altman D.G., Taylor S.A., et. al.: CT colonography in the detection of colorectal polyps and cancer: systematic review, meta-analysis, and proposed minimum data set for study level reporting. Radiology 2005; 237: pp. 893-904.
15. Pickhardt P.J., Choi J.R., Hwang I., Butler J.A., et. al.: Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med 2003; 349: pp. 2191-2199.
16. Johnson C.D., Chen M-H, Tolendano A.Y., et. al.: Accuracy of CT colonography for detection of large adenomas and cancers. N Engl J Med 2008; 359: pp. 1207-1217.
17. Iannaccone R., Laghi A., Catalano C., et. al.: Detection of colerectal lesions: lower-dose multi-detector row helical CT colonography compared with conventional colonoscopy. Radiology 2003; 229: pp. 775-781.
18. Iannaccone R., Catalano C., Mangiapane F., et. al.: Colorectal polyps: detection with low-dose multi-detector row helical CT colonography versus two sequential colonoscopies. Radiology 2005; 237: pp. 927-937.
19. Vogt C., Cohnene M., Beck A., et. al.: Detection of colorectal polyps by multislice CT colonography with ultra-low-dose technique: comparison with high-resolution videocolonoscopy. Gastrointest Endosc 2004; 60: pp. 201-209.
20. Copel L., Sosna J., Kruskal J.B., Raptopoulos V., Farrel R.J., Morrin M.M.: CT colonography in 546 patients with incomplete colonoscopy. Radiology 2007; 244: pp. 471-478.
21. Yun J., Ro H.J., Park J.B., et. al.: Diagnostic performance of CT colonography for the detection of colorectal polyps. Korean J Radiol 2007; 8: pp. 484-491.
22. Wessling J., Domagk K., Lugenring N., et. al.: Virtual colonography: identification and differentiation of colorectal lesions using multi-detector computed tomography. Scand J Gastroenterol 2005; 40: pp. 468-476.
23. Macari M., Bini E., Jacobs S., et. al.: Colorectal polyp and cancers in asymptomatic average-risk patients: evaluation with CT colonography. Radiology 2004; 230: pp. 629-636.
24. Edwards J.T., Mendelson R.M., Fritschi L., et. al.: Colorectal neoplasia screening with CT colonography in average-risk asymptomatic subjects: community-based study. Radiology 2004; 230: pp. 459-464.
25. Kim D.H., Pickhardt P.J., Hoff G., Kay C.L.: Computed tomographic colonography for colorectal screening. Endoscopy 2007; 39: pp. 545-549.
26. Rozen P.: Report of the World Organization for Digestive Endoscopy Colorectal Cancer Screening Committee Meeting, Chicago, 2005. Eur J Cancer Prevent 2006; 15: pp. 95-102.
27. Rex D.K.: Colonoscopy is justified for any polyp discovered during computed tomographic colonography. Am J Gastroenterol 2005; 100: pp. 1903-1908.
28. Mandel J.S., Bond J.H., Church T.R.: Reducing mortality from colorectal cancer by screening for fecal occult blood. N Engl J Med 1993; 328: pp. 1365-1371.
29. Kronborg O., Fenger C., Olsen J., Jorgensen O.D., Sondergaard O.: Randomised study of screening for colorectal cancer with fecal occult-blood test. Lancet 1996; 348: pp. 1647-1671.
30. Garber A.M., Phelps C.E.: Economic foundation of cost effectiveness analysis. J Health Econ 1997; 16: pp. 1-31.
31. Brown M.L., Fintor L.: Cost-effectiveness of breast cancer screening: preliminary results of a systematic review of the literature. Breast Cancer Res Treat 1993; 25: pp. 113-118.
32. Ladabaum U., Song K., Fendrick A.M.: Colorectal neoplasia screening with virtual colonoscopy: when, at what cost, and with what national impact?. Clin Gastroenterol Hepatol 2004; 2: pp. 554-563.
33. Heitman S.J., Manns B.J., Hilsden R.J., et. al.: Cost-effectiveness of computerized tomographic colonography versus colonoscopy for colorectal cancer screening. CMAJ 2005; 173: pp. 877-881.
34. Kiberd B.: Colon cancer screening. CMAJ 2006; 174: pp. 975.
35. Peltekian K.: Colon cancer screening. CMAJ 2006; 174: pp. 975.
36. Pickhardt P.J., Hassan C., Laghi A., Zullo A., Kim D.H., Iafrate F., Morini S.: Cost-effectiveness of colorectal cancer screening with computed tomography colonography: the impact of not reporting diminutive lesions. Cancer 2007; 109: pp. 2213-2221.
37. Pickhardt P.J., Hassan C., Laghi A., et. al.: Small and diminutive polyps detected at screening CT colonography: a decision analysis for referral to colonoscopy. AJR Am J Roentgenol 2008; 190: pp. 136-144.
38. Pickhardt P.J.: By-patient performance characteristics of CT colonography: importance of polyp size threshold data. Radiology 2003; 229: pp. 291-293.
39. Marshall J.B., Barthel J.S.: The frequency of total colonoscopy and terminal ileum intubation in the 1990s. Gastrointest Endosc 1993; 39: pp. 518-520.
40. Winawer S.J., Zauber A.G., Ho M.N., et. al.: Prevention of colorectal cancer by colonoscopic polypectomy. N Engl J Med 1993; 329: pp. 1977-1981.
41. Hixson L.J., Fennerty M.B., Sampliner R.E., Garewal H.S.: Prospective blinded trial of the colonoscopic miss-rate of large colorectal polyps. Gastrointest Endosc 1991; 37: pp. 125-127.
42. Chung D.J., Huh K.C., Choi W.J., Kim J.K.: CT colonography using 16-MDCT in the evaluation of colorectal cancer. AJR Am J Roentgenol 2005; 184: pp. 98-103.
43. Johnson C.D., Harmsen W.S., Wilson L.A., et. al.: Prospective blinded evaluation of computed tomographic colonography for screen detection of colorectal polyps. Gastroenterology 2003; 125: pp. 311-319.
44. Gluecker T.M., Johnson C.D., Harmsen W.S., et. al.: Colorectal cancer screening with CT colonography, colonoscopy, and double-contrast barium enema examination: prospective assessment of patient perceptions and preferences. Radiology 2003; 227: pp. 378-384.
45. Hara A.K., Johnson C.D., MacCarty R.L., Welch T.J.: Incidental extracolonic findings at CT colonography. Radiology 2000; 215: pp. 353-357.
46. Beebe T.J., Johnson C.D., Stoner S.M., Anderson K.J., Limburg P.J.: Assessing attitudes toward laxative preparation in colorectal cancer screening and effects on future testing: potential receptivity to computed tomographic colonography. Mayo Clin Proc 2007; 82: pp. 666-671.
47. Iannaccone R., Laghi A., Catalano C., et. al.: CT colonography without cathartic preparation for the detection of colorectal polyps. Gastroenterology 2004; 127: pp. 1300-1311.
48. Van Gelder R.E., Nio C.Y., Florie J., et. al.: Computed tomographic colonography compared with colonoscopy in patients at increased risk for colorectal cancer. Gastroenterology 2004; 127: pp. 41-48.
49. Huda W.: Radiation dosimetry in diagnostic radiology. AJR Am J Roentgenol 1997; 169: pp. 1487-1488.
50. Wise K.N.: Solid cancer risks from radiation exposure for the Australian population. Australas Phys Eng Sci Med 2003; 26: pp. 53-62.
51. Johnson C.D., Toledano A.Y., Herman B.A., et. al.: American College of Radiology Imaging Network A6656. Computerized tomographic colonography: performance evaluation in a retrospective multicenter setting. Gastroenterology 2003; 12: pp. 688-695.