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Is Computed Tomographic Colonography Being Held to a Higher Standard?

Samita Garg, MD; and Dennis J. Ahnen, MD
[+] Article, Author, and Disclosure Information

From Denver Veterans Affairs Medical Center, University of Colorado Cancer Center, and University of Colorado Denver School of Medicine, Denver, Colorado.

Acknowledgment: The authors thank William R. Brown, MD, and Gregory Austin, MD, for their helpful review of the manuscript.

Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M09-1103.

Requests for Single Reprints: Dennis J. Ahnen, MD, Denver Veterans Affairs Medical Center 111E, 1055 Clermont Street, Denver, CO 80220; e-mail, dennis.ahnen@ucdenver.edu.

Current Author Addresses: Drs. Garg and Ahnen: Denver Veterans Affairs Medical Center 111E, 1055 Clermont Street, Denver, CO 80220.

Author Contributions: Conception and design: D.J. Ahnen.

Analysis and interpretation of the data: D.J. Ahnen, S. Garg.

Drafting of the article: D.J. Ahnen, S. Garg.

Critical revision for important intellectual content: D.J. Ahnen, S. Garg.

Final approval of the article: D. Ahnen.

Administrative, technical, or logistic support: D.J. Ahnen.

Collection and assembly of data: D.J. Ahnen.

Ann Intern Med. 2010;152(3):178-181. doi:10.7326/0003-4819-152-3-201002020-00009
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Recent guidelines for colorectal cancer screening have reached different conclusions on whether computed tomographic colonography (CTC) is an acceptable screening option, and the Centers for Medicare & Medicaid Services recently decided not to cover CTC screening. The rationale against recommending or covering CTC screening includes concerns about radiation exposure, false-negative rates for small polyps, the discovery of extracolonic findings, variability in performance, a lack of targeted studies, a higher adenoma rate in the Medicare-eligible age group, and an absence of evidence that covering CTC would increase overall screening rates. Similar concerns can be raised for other recommended and covered colon cancer screening tests, but it seems that CTC is being held to a new and higher standard.





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Is Computed Tomographic Colonography (CTC) an option for colorectal cancer?
Posted on February 28, 2010
Giancarlo Spinzi
Valduce Hospital- Como- Italy
Conflict of Interest: None Declared

Garg and Ahnen (1) discussed the decision of USPTF and CMS not to approve CTC for colo-rectal screening. They did not mention the problem of small polyps and flat lesions. Although flat colo-rectal lesions were once thought to be rare, studies of western populations have shown that approximately 40% of adenomatous lesions detected at colonoscopy were flat (2). The malignant risk of flat adenomatous lesions is controversial, but large prospective epidemiologic studies have shown that flat lesions have an increased risk of harboring high-risk displasia and of progressing to invasive carcinoma (3). They are difficult to detect using CTC and can be a significant source of false-negative results (4). There is no clear consensus about which CTC techniques are optimal to visualize flat lesions. The colon should be well distended because lesions that present as thickened folds are difficult to see unless the colon is distended and IV enhancement may be helpful although it is not routinely used for screening CTC (5). I agree with the concerns of USPSTF and CMS about CTC as an acceptable option in their guidelines.


1) Garg S, Ahnen DJ. Is Computed Tomographic Colonography being held to a higher standard?. Ann Intern Med 2010; 152: 178-181

2)Hurlstone DP, Cross SS, Adam I et al. A prospective clinicopathological and endoscopic evaluation of flat and depressed colo-rectal lesions in the United Kingdom. Am J Gastroenterol 2003; 98: 2543-2549

3)Rembacken BJ,Fujiii T, Cairns A, et al. Flat and depressed neoplasms: a prospective study of 1000 colonoscopies in UK. Lamcet 2000; 355: 1211- 1214.

4) Park SH, HA HK, Kim MJ, et al. False-negative results at multi-detector row CT colonography: multivariate analysis of causes for missed lesions. Radiology 2005; 235: 495-502.

5) Park SH, Ha HK, Kim AY, et al. Flat polyps of the colon: detection with 16-MDCT colonography-preliminary results. AJR 2006; 186: 1611-1617

Conflict of Interest:

None declared

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