CT Colonography Versus Optical Colonoscopy for Screening Asymptomatic Patients for Colorectal Cancer:

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.

Key Words: Evidence-based medicine, methods standards, radiology, CT colonography, optical colonoscopy, polyp, colon cancer