CT colonography (virtual colonoscopy) for primary colorectal screening: challenges facing clinical implementation

Abstract

Computed tomographic colonography (CTC), also referred to as virtual colonoscopy, is a minimally invasive test for the detection of colorectal polyps. Although its initial performance characteristics for evaluating lowprevalence populations were rather disappointing [1, 2], a larger multicenter trial in asymptomatic adults subsequently showed that CTC has the potential to be an effective primary screening tool [3]. Key features in the latter study that help explain this improved performance include the use of the three-dimensional endoluminal display for primary polyp detection, oral contrast for tagging of residual fluid and stool, segmental unblinding of CTC results at optical colonoscopy (OC), and use of only multidetector CT scanners [3]. As we await further validation of this rapidly evolving technique, actual clinical implementation of primary CTC screening should proceed without delay by those who are currently able to achieve an acceptable accuracy. The need for immediate action is self-evident, as far too many people are dying from a disease that could have been prevented by effective routine screening in more than 95% of cases [4]. There are many important challenges that are likely to be encountered as CTC screening transitions from the realm of research to daily clinical practice (Table 1). This update focuses primarily on three specific issues: (a) development of a logical diagnostic algorithm for CTC screening, (b) identifying the most appropriate group of patients to be screened by CTC, and (c) establishing a mutually beneficial working relationship with gastroenterology. Additional challenges and issues that are also important but are not covered in report include demonstrating the relative cost effectiveness of CTC screening, reimbursement by third-party payers, dedicated training of radiologists, and establishment of standard practice guidelines and accreditation. In the end, I believe that none of these challenges will prove to be insurmountable.