CT colonography for colorectal cancer screening: lessons from mammography

Standardized colonoscopy reporting and data system: report of the Quality Assurance Task Group of the National Colorectal Cancer Roundtable

BACKGROUND

Standardized reporting systems for diagnostic and screening tests facilitate quality improvement programs and clear communication among health care providers. Although colonoscopy is commonly used for screening, diagnosis, and therapy, no standardized reporting system for this procedure currently exists. The Quality Assurance Task Group of the National Colorectal Cancer Roundtable developed a reporting and data system for colonoscopy based on continuous quality improvement indicators.

DESIGN

The Task Group systematically reviewed quality indicators recommended by the Multi-Society Task Force on Colorectal Cancer and developed consensus-based terminology for reporting and data systems to capture these data elements. The Task Group included experts in several disciplines: gastroenterology, primary care, diagnostic imaging, and health care delivery.

RESULTS AND CONCLUSIONS

The standardized colonoscopy reporting and data system provides a tool that can be used for efforts in continuous quality improvement within and across practices that use colonoscopy.

Virtual colonoscopy in the detection of colonic polyps and neoplasms

First introduced in 1994, CT colonography (Virtual colonoscopy) has emerged as an accurate, non-invasive test that will likely play a future role in colorectal cancer screening. Over the past 3 years, there have been dramatic improvements in both hardware and software technology relating to CT colonography resulting in shorter scan times, enhanced user-friendliness and improved performance statistics. Published results show the accuracy of CT colonography to be comparable to conventional colonoscopy for detection of polyps >6mm in size with few false-positives. While many of the technical aspects of CT colonography have now been standardised current interest focuses on the development of faecal tagging agents to avoid full bowel catharsis and the use of low dose multislice CT acquisition to reduce patient radiation exposure. This chapter will summarise the development of CT colonography to date, document its published performance in detection of colorectal polyps and cancers, and review its current and potential future uses.

CT Colonography of Colorectal Polyps:A Metaanalysis

OBJECTIVE

For proper evaluation of the accuracy of CT colonography, prospective multiinstitutional trials would be ideal. Until these trials are available, data can be collectively analyzed. The purpose of this study is to use metaanalysis to assess the reported accuracy of CT colonography compared with conventional colonoscopy for detecting colorectal polyps.

MATERIALS AND METHODS

Articles comparing CT colonography and conventional colonoscopy were identified, and a standardized form was used to extract relevant study data. Fisher's exact test and the Mantel-Haenszel test were used for pooling of data. A 95% confidence interval (CI) was selected to determine sensitivity and specificity, and the Kruskal-Wallis exact test was used to identify trends relating to polyp size. Meta-analysis methods were used to test strength of results. Comparisons were made for the percentage of polyps detected grouped by size (> or = 10 mm, 6-9 mm, < or = 5 mm) and the percentage of patients identified who had polyps of the same size.

RESULTS

Fourteen studies fulfilled all the study inclusion criteria and gave a total of 1,324 patients and 1,411 polyps. The pooled per-patient sensitivity for polyps 10 mm or larger was (sensitivity [95% CI]) 0.88 (0.84-0.93), for polyps 6-9 mm it was 0.84 (0.80-0.89), and for polyps 5 mm or smaller it was 0.65 (0.57-0.73). The pooled per-polyp sensitivity for polyps 10 mm or larger was 0.81 (0.76-0.85), for polyps 6-9 mm it was 0.62 (0.58-0.67), and for polyps 5 mm or smaller it was 0.43 (0.39-0.47). Sensitivity for detection of polyps increased as the polyp size increased (p < 0.00005). The pooled overall specificity for detection of polyps larger than 10 mm was 0.95 (0.94-0.97).

CONCLUSION

The specificity and sensitivity of CT colonography are high for polyps larger than 10 mm.

Acceptance by patients of multidetector CT colonography compared with barium enema examinations, flexible sigmoidoscopy, and colonoscopy

OBJECTIVE

The purpose of this study was to compare patient acceptance of multidetector CT colonography, total colonoscopy, flexible sigmoidoscopy, and double-contrast barium enema to ascertain any overall preference. SUBJECTS AND METHODS. One hundred sixty-eight patients underwent CT colonography followed by either flexible sigmoidoscopy (n = 59) or colonoscopy (n = 109). A 25-point questionnaire with principal components relating to satisfaction, worry, and physical discomfort was administered after CT colonography and after endoscopy, and a follow-up questionnaire was administered 1 week after the procedures. Questionnaires were also completed by 140 patients undergoing double-contrast barium enema examinations. Responses were compared using Wilcoxon's matched pairs test and the Mann-Whitney test.

RESULTS

Overall satisfaction was greater with colonoscopy (p = 0.01), but CT colonography caused less discomfort (p = 0.002), was better tolerated (p = 0.005), and was the preferred follow-up investigation of those expressing a preference (p = 0.003). Compared with flexible sigmoidoscopy, CT colonography caused less pain (p = 0.004), was more acceptable (p = 0.04), and was preferred as the follow-up investigation (p < 0.001). Tolerance of colonoscopy was significantly less in women (p = 0.03), but such was not the case for CT colonography (p = 0.58). Patients undergoing CT colonography were less worried (p < 0.001), were more satisfied (p = 0.001), and suffered less discomfort (p < 0.001) than those having barium enema.

CONCLUSION

Patients' experiences with barium enema examinations were significantly worse than with any other test. Although patients were most satisfied with colonoscopy, they reported more pain during both colonoscopy and sigmoidoscopy than during CT colonography, and they also found CT more acceptable. In patients expressing a preference, CT colonography was the preferred follow-up investigation.

Colon cancer screening with virtual colonoscopy: promise, polyps, politics

Virtual colonoscopy (CT colonography) promises to become a primary method for colorectal cancer screening and return radiologists to a major role in colon cancer prevention. Results from major centers in the United States show accuracy to be comparable to conventional colonoscopy for detection of polyps of significant size--that is, greater than 10 mm--with few false-positives. The advent of virtual colonoscopy has also heightened awareness of the natural history of colonic polyps, particularly in terms of identifying an appropriate target size for detection in colorectal screening programs. Small polyps (<10 mm) are often either hyperplastic on histology or are unlikely to progress to frank cancer in the patient's lifetime and are therefore of little clinical significance for the average adult. Thus, the rationale for detecting and removing each and every colonic polyp regardless of size has come under increasing scrutiny in the context of cost-benefit analysis of various test strategies for colorectal cancer screening. Virtual colonoscopy may allow patients to obtain reliable information about the status of their colonic mucosa noninvasively and thus make a more informed decision as to whether to proceed to conventional colonoscopy for polypectomy.

Virtual colonoscopy: a new tool for colorectal cancer screening

Virtual colonoscopy or computed-tomography colonography is a promising new method for colorectal cancer screening. Helical computed tomography is used to generate high-resolution, two-dimensional axial images of the abdomen and pelvis. Three-dimensional images of the colon simulating those obtained with conventional colonoscopy can be reconstructed from the data obtained. Favorable attributes of virtual colonoscopy include its safety, high patient acceptance, and ability to provide a full structural evaluation of the entire colon. Multiple studies of virtual colonoscopy have been published in the literature in the past year regarding technique, image display, image reconstruction, clinical trial results, and feasibility as a screening tool. This manuscript will review the various studies in each of these areas.