Computed tomography colonography compared with conventional colonoscopy for the detection of colorectal polyps

Can Computed Tomography Colonography Replace Optical Colonoscopy in Detecting Colorectal Lesions?: State of the Art

Colorectal cancer is an important cause of morbidity and mortality worldwide. Optical colonoscopy (OC) is widely accepted as the reference standard for the screening of colorectal polyps and cancers, and computed tomography colonography (CTC) is a valid alternative to OC. The purpose of this review was to assess the diagnostic accuracy of OC and CTC for colorectal lesions. A literature search was performed in PubMed, Embase, and Cochrane Library, and 18 articles were included. CTC has emerged in recent years as a potential screening examination with high accuracy for the detection of colorectal lesions. However, the clinical application of CTC as a screening technique is limited because it is highly dependent on the size of the lesions and has poor performance in detecting individual lesions <5 mm or flat lesions, which, although rarely, can have a malignant potential.

Diagnostic accuracy of computed tomography colonography in patients at high risk for colorectal cancer: a meta-analysis

AIM

The aim was to explore the diagnostic value of computed tomographic colonography (CTC) compared with conventional colonoscopy in individuals at high risk for colorectal cancer.

METHOD

PubMed, Embase, the Cochrane Library and the Web of Science were searched by two independent reviewers for potentially eligible studies published up to 31 October 2018 that were based on a per-patient analysis. stata, meta-disc and revman were used to perform this meta-analysis. A random-effect model was used, and a subgroup analysis was conducted to explore the sources of heterogeneity.

RESULTS

A total of 14 full-text articles, involving 3578 patients, were included in this meta-analysis. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and the area under the summary receiver operating characteristic curve of CTC for detecting polyps ≥ 6 mm were 0.87 (95% CI 0.83-0.90), 0.90 (95% CI 0.86-0.93), 9.08 (95% CI 6.28-13.13), 0.14 (95% CI 0.11-0.18) and 0.94 (95% CI 0.92-0.96), respectively. For polyps ≥ 10 mm, the pooled sensitivity, specificity, positive likelihood ratio and negative likelihood ratio of CTC were 0.91 (95% CI 0.86-0.94), 0.98 (95% CI 0.95-0.99), 40.36 (95% CI 19.16-85.03), 0.90 (95% CI 0.06-0.14) and 0.98 (95% CI 0.96-0.99), respectively.

CONCLUSION

In this meta-analysis, CTC had high diagnostic accuracy for detecting polyps ≥ 6 mm and ≥ 10 mm in patients at high risk of developing colorectal cancer and it had a higher sensitivity and specificity for detecting polyps ≥ 10 mm than polyps ≥ 6 mm. However, the results should be used cautiously due to the significant heterogeneity.

The new view of colon cancer screening: forwards and backwards

Many different techniques for colon cancer screening are available. The fecal immunochemical test is best for fecal-based screening, although the DNA investigation may be more specific when further developed. Computed tomographic colonography is as good as colonoscopy for detecting colon cancer and is almost as good as colonoscopy for detecting advanced adenomas, but has limitations. The flexible sigmoidoscopic examination markedly decreases the incidence of cancer in the visualized segments, but colonoscopy is currently the best procedure for evaluating the large bowel. Techniques for retroflexion or backward view of the colon have been investigated, with all showing increased polyp detection.

Progress in the diagnosis of ileocecal lesions

The ileocecal area includes the ileocecal valve, terminal ileum, cecum, appendix, and top ascending colon. Since this area may be affected by pathologic conditions that are either common throughout the gastrointestinal system or exclusive to this area, a great variety of intestinal diseases may arise in this region, making the diagnosis of ileocecal lesions difficult. In clinic, the diagnosis of ileocecal lesions depends on the combination of disease history, clinical features, imaging and endoscopic findings. The development of advanced imaging and endoscopy technology has greatly increased the detection rate of ileocecal lesions. In this review, we discuss the use of imaging and endoscopic examinations for evaluation of ileocecal area to help ensure accurate diagnosis and appropriate treatment.

Colorectal cancer: CT colonography and colonoscopy for detection--systematic review and meta-analysis

PURPOSE

To perform a systematic review and meta-analysis of published studies assessing the sensitivity of both computed tomographic (CT) colonography and optical colonoscopy (OC) for colorectal cancer detection.

MATERIALS AND METHODS

Analysis followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. The primary data source was the results of a detailed PubMed search from 1994 to 2009. Diagnostic studies evaluating CT colonography detection of colorectal cancer were assessed by using predefined inclusion and exclusion criteria, in particular requiring both OC and histologic confirmation of disease. Studies that also included a mechanism to assess true-positive versus false-negative diagnoses at OC (eg, segmental unblinding) were used to calculate OC sensitivity. Assessment and data extraction were performed independently by two authors. Potential bias was ascertained by using Quality Assessment of Diagnostic Accuracy Studies guidelines. Specific CT colonography techniques were cataloged. Forest plots of per-patient sensitivity were produced on the basis of random-effect models. Potential bias across primary studies was assessed by using the I(2) statistic. Original study authors were contacted for data clarification when necessary.

RESULTS

Forty-nine studies provided data on 11,151 patients with a cumulative colorectal cancer prevalence of 3.6% (414 cancers). The sensitivity of CT colonography for colorectal cancer was 96.1% (398 of 414; 95% confidence interval [CI]: 93.8%, 97.7%). No heterogeneity (I(2) = 0%) was detected. No cancers were missed at CT colonography when both cathartic and tagging agents were combined in the bowel preparation. The sensitivity of OC for colorectal cancer, derived from a subset of 25 studies including 9223 patients, was 94.7% (178 of 188; 95% CI: 90.4%, 97.2%). A moderate degree of heterogeneity (I(2) = 50%) was present.

CONCLUSION

CT colonography is highly sensitive for colorectal cancer, especially when both cathartic and tagging agents are combined in the bowel preparation. Given the relatively low prevalence of colorectal cancer, primary CT colonography may be more suitable than OC for initial investigation of suspected colorectal cancer, assuming reasonable specificity.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101887/-/DC1.

Finding polyps at colonoscopy previously noted on CT colonography

Colon screening examinations have been shown to discover neoplastic lesions at an early stage. Even the most careful studies by colonoscopy and by computed tomographic colonography (CTC) can overlook tumors with a diameter greater than 5 mm. Advances in technology have continually improved the ability to find polyps, which will lead to a real decrease in colorectal cancer incidence.

Diagnostic accuracy of CT colonography and optical colonoscopy evaluated using surgically resected specimens

OBJECTIVE

The aim of this study was to clarify the diagnostic ability of CT colonography (CTC) using surgically resected specimens to avoid inaccuracy associated with optical colonoscopy (OC).

SUBJECTS AND METHODS

CTC and OC were performed in 152 consecutive patients with colorectal cancer. Forty patients had simultaneous lesions other than the ones for which the surgery was intended, and these lesions were used as the gold standard. In 24 patients without stenosis, the sensitivity and positive predictive values (PPV) of CTC and OC were evaluated. In 16 patients with stenosis, the diagnostic ability of CTC for lesions located proximal to the stenosis was assessed.

RESULTS

Sensitivity of CTC and OC was 81% and 66% (P = 0.16), and PPV was 90% and 100% (P = 0.13), respectively. For 22 lesions larger than 5 mm, the sensitivity of CTC and OCS was 96% and 91% (P > 0.50), and PPV was 100% and 100%, respectively. In patients with stenosis, sensitivity and PPV were 89% and 80%, respectively. These results were not significantly different from those in patients without stenosis.

CONCLUSIONS

CTC is a reliable modality for the diagnosis of colorectal polyps. It is also useful to evaluate the colon proximal to severe stenosis which could not be observed by OC.