Establishing the role of CT colonography within the Bowel Cancer Screening Programme

Aim: To critically assess the evidence base to help establish the most desirable role for computed tomographic colonography (CTC) in bowel cancer screening. Introduction: Bowel cancer develops over time from polyps. Early detection improves outcomes of this major health problem, so a targeted UK screening programme has been introduced. Currently, faecal occult blood test is followed by optical colonoscopy (OC) in positive cases. CTC is currently only used where OC is contraindicated or incomplete. The optimum role for CTC in screening is controversial. The ongoing debate must consider a range of factors in the context of the screening scenario and in light of evolving CTC protocols and guidance. Findings: Diagnostic ability: CTC's sensitivity is more variable and lower than OC, but technological improvements such as computer-aided detection (CAD) and better understanding of optimal technique promise improved results. There remain uncertainties around surveillance periods, clinically-significant lesion size, and the cost of extra-colonic findings. The linkages between these factors are unclear. Furthermore, many findings are based on populations that are not necessarily transferable to the screening situation. Risks: CTC involves radiation, but the risk is considered low, especially in a screening population. Technological advances promise further dose reductions. Perforation and the use of contrast agents may also present small risks. Patient acceptability: CTC is generally considered less unpleasant than OC, but patient acceptability may still be lower in a secondary screening role. Availability & cost: CTC may be cost-effective in primary screening, but expanding capacity is slow and expensive. The likely cost of investigating and treating extra-colonic findings is unclear. Conclusions: CTC is a new technique which, though promising, still has many uncertainties which are interlinked. It is currently difficult to determine the most desirable screening role, especially as bowel cancer screening itself is still new and evolving. Further research specific to the screening scenario is required. (C) 2013 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.