CT Colonography Improves Participation in Cancer Screening

Jennifer Garcia

November 14, 2011

November 14, 2011 — Participation in colorectal cancer screening is significantly improved with computed tomographic (CT) colonography compared with traditional colonoscopy and has a similar diagnostic yield for advanced neoplasia, according to a study published online November 15 in The Lancet Oncology.

Members of the general population were invited for colorectal cancer screening by colonoscopy or noncathartic CT colonography. Of the 5924 participants invited for colonoscopy, 1276 (22%) underwent the procedure compared with 982 (34%) of the 2920 CT colonography invitees (relative risk [RR], 1.56; 95% confidence interval [CI], 1.46 - 1.68; P < .0001).

The diagnostic yield for advanced neoplasia was 8.7 per 100 participants for the colonoscopy group and 6.1 per 100 participants for the CT colonography group (RR, 1.46; 95% CI, 1.06 - 2.03; P = .02). For lesions 10 mm or greater, the diagnostic yield for advanced neoplasia was similar for both techniques 1.5 per 100 invitees for colonoscopy and 2.0 per 100 invitees for CT colonography — indicating that both procedures can be used successfully for population-based screening, according to the researchers.

"The decision about the preferred method for colorectal cancer screening in population-based screening can be guided by the results of our trial, which showed more participants with noncathartic CT colonography, a higher yield for colonoscopy, but a similar diagnostic yield for both methods in the detection of advanced neoplasia per 100 invitees, " write Esther M. Stoop, MD, from the Department of Gastroenterology and Hepatology, Erasmus University Medical Centre, Rotterdam, the Netherlands, and colleagues.

From June 8, 2009, to August 16, 2010, members of the general population of Amsterdam and Rotterdam between 50 and 75 years of age were invited to participate in colonoscopy or CT colonography cancer screening. Participants were randomly assigned per household by using an algorithm based on sex, age, and socioeconomic status.

The researchers noted that the demographic characteristics of the 2 groups were similar; however, the participation rate was lower among those in the advanced-age group and lower socioeconomic status categories. Participation did not differ between men and women. Individuals with symptoms that could be related to colorectal cancer within the previous 3 months were instructed to contact their family physician instead.

For patients in the colonoscopy group, bowel preparation consisted of 2 L of polyethylene electrolyte glycol solution, 2 L of transparent fluid, and a low-fiber diet for 2 days. The procedure was performed under conscious sedation, and all detected lesions were removed during the same procedure. If removal was not possible, biopsy samples were obtained for histopathology.

For patients in the CT colonography group, noncathartic preparation consisted of 2 times 50 mL of iodinated contrast agent given the day before the examination, 50 mL given 1.5 hours before the examination, and a low-fiber diet for 1 day. Participants with 1 or more large lesions (≥ 10 mm) were referred for colonoscopy. All polyps detected during follow-up colonoscopy were removed, irrespective of size. Individuals with lesions 6 to 9 mm were offered surveillance CT colonography.

The researchers discuss whether cathartic vs noncathartic preparation for CT colonography may have affected their results. Previous studies showed that iodine tagging similar to that used in this study yielded results similar to those achieved with cathartic preparation.

The study authors report that only 1 other, much smaller, randomized trial has compared participation and diagnostic yield of colonoscopy and CT colonography. The diagnostic yield for colonoscopy in that study was similar to what was seen in this study; however, the participation rate and the diagnostic yield of CT colonography were higher. This may have been due to differing exclusion and referral criteria, explain Dr. Stoop and colleagues.

Although follow-up data for individuals offered surveillance CT colonography are not yet available, the study authors predict that on the basis of the diagnostic yield of the colonoscopy group, the diagnostic yield of CT colonography has been underestimated.

Complication rates were similar in both groups and were related primarily to postpolypectomy bleeding (2 patients in the colonoscopy group and 3 in the CT colonography group). Detection rates overall were similar to those documented in other studies.

Noncathartic CT colonography requires limited bowel preparation, is less invasive, and has a low risk for complications. These features probably contribute to its perception as a less burdensome procedure. The authors caution, however, that its limitations need to be considered, primarily that detected lesions will necessitate subsequent colonoscopy. In addition, exposure to ionizing radiation with CT colonography is a potential disadvantage, but the procedure would probably still have a favorable benefit-risk ratio if that were taken into account, according to the researchers.

Dr. Stoop and colleagues explain that given the identical invitation process for both procedures, the difference in participation rates is most likely explained by the expected burden of procedure-related complications. Increasing public education and involvement of general practitioners will lead to increased participation of all screening techniques, observed the researchers.

Screening has been shown to reduce colorectal cancer mortality both by early detection of cancers and by endoscopic removal of adenomas. "[T]o know which screening technique is preferable, other factors such as cost-effectiveness, influenced by higher participation rate of CT colonography and higher yield per participant for colonoscopy, and experienced burden should be studied," the study authors conclude.

"Results from this trial show a significant 55% improvement in screening participation with CT colonography over colonoscopy, which is a crucial component to the overall success of a screening programme," writes Perry J. Pickhardt, MD, from the Department of Radiology, School of Medicine and Public Health, University of Wisconsin-Madison, in an accompanying commentary.

Dr. Pickhardt notes that the diagnostic yield of CT colonography would be improved in this setting with the use of cathartic preparation and the application of 3-dimensional reading. Additionally, cathartic preparation would allow for same-day polypectomy.

"The implication that CT colonography would lead to greater participation in colorectal screening over colonoscopy is a crucial finding, since this modality could operate in parallel with existing colonoscopic screening," writes Dr. Pickhardt.

The study was funded by The Netherlands Organization for Health Research and Development, the Centre for Translational Molecular Medicine, and the Nuts Ohra Foundation (Amsterdam, the Netherlands). The study authors have disclosed no relevant financial relationships. Dr. Pickhardt disclosed having been a consultant for Medicsight, Viatronix, and Bracco and a cofounder of VirtuoCTC.

Lancet Oncol. Published online November 15, 2011. Study abstract Editorial extract

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