Small and diminutive polyps detected at screening CT colonography: a decision analysis for referral to colonoscopy. AJR Am J Roentgenol. 2008;190:136-144. [PMID: 18094303 DOI: 10.2214/ajr.07.2646]

Computed tomographic colonography

PURPOSE OF REVIEW

Computed tomographic colonography is a new and noninvasive method to evaluate the colon. The goal of this review is to discuss the latest data and define outstanding issues related to computed tomographic colonography.

RECENT FINDINGS

Computed tomographic colonography is gaining momentum as a potential primary colon cancer screening method in the USA. Although not as accurate as colonoscopy, the accuracy of computed tomographic colonography for detection of large lesions appears to be in the 80-90% range. The field is rapidly evolving, not only in terms of technology but also in a variety of other practical areas.

SUMMARY

Current data suggest that computed tomographic colonography is a viable colon cancer screening modality in the USA. However, it is not ready for widespread implementation, largely because of lack of standards for training and reading and the fact that the number of skilled readers is limited.

Clinical management of small (6- to 9-mm) polyps detected at screening CT colonography: a cost-effectiveness analysis

OBJECTIVE

The primary aim of this model analysis was to compare the clinical and economic impacts of immediate polypectomy versus 3-year CT colonography (CTC) surveillance for small (6- to 9-mm) polyps detected at CTC screening.

MATERIALS AND METHODS

A decision analysis model was constructed incorporating the expected advanced neoplasia prevalence, frequency of measurable growth, colorectal cancer (CRC) prevalence and risk, CTC performance, and costs related to CRC screening and treatment. CRC risk was assumed to be independent of advanced adenoma size, which intentionally overestimates the risk related to small polyps. Clinical effectiveness and costs for 3-year CTC surveillance versus immediate colonoscopic polypectomy were compared for a concentrated cohort of patients with 6- to 9-mm polyps. For the CTC surveillance strategy, only cases with measurable growth (> or = 1 mm) at follow-up CTC were referred for polypectomy.

RESULTS

Without any intervention, the estimated 5-year CRC death rate from 6- to 9-mm polyps in this concentrated cohort was 0.08%, which is a sevenfold decrease over the 0.56% CRC risk for the general unselected screening population. The death rate was further reduced to 0.03% with the CTC surveillance strategy and to 0.02% with immediate colonoscopy referral. However, for each additional cancer-related death prevented with immediate polypectomy versus CTC follow-up, 9,977 colonoscopy referrals would be needed, resulting in 10 additional perforations and an incremental cost-effectiveness ratio of $372,853.

CONCLUSION

For patients with small (6- to 9-mm) polyps detected at CTC screening, the exclusion of large polyps (> or = 10 mm) already confers a very low risk of CRC. The high costs, additional complications, and relatively low incremental yield associated with immediate polypectomy of 6- to 9-mm polyps support the practice of 3-year CTC surveillance, which allows for selective noninvasive identification of small polyps at risk.

CT colonography with reduced bowel preparation after incomplete colonoscopy in the elderly

We prospectively assessed the feasibility and acceptance of computerized tomographic colonography (CTC) without bowel cathartic preparation in elderly patients after incomplete colonoscopy. A total of 136 patients underwent CTC without cathartic preparation. The time delay between conventional colonoscopy and CTC ranged between 3 and 20 days, depending on the clinical situation. Before CTC, fecal tagging was achieved by adding diatrizoate meglumine and diatrizoate sodium to regular meals. CTCs were interpreted using a primary two-dimensional (2D) approach and 3D images for further characterization. Patients were interviewed before and 2 weeks after CTC to assess preparation acceptance. CTC was feasible and technically successful in all the 136 patients. Fecal tagging was judged as excellent in 113 (83%) patients and sufficient in 23 (17%). Average CT image interpretation time was 14.8 min. Six (4.4%) cases of colorectal cancer and nine (6.6%) large polyps were detected, as well as 23 (11.3%) extracolonic findings of high clinical importance. No major side effect occurred, although 25% patients reported minor side effects, especially diarrhea. Overall, 76/98 patients replied that they would be willing to repeat the test if necessary. CTC without cathartic preparation is a technically feasible and safe procedure to complete a colonic study in the elderly, prompting its use in clinical practice.