THE PROCEDURE: Computed tomography colonography (CTC) is a minimally invasive radiological technique for imaging the colon and rectum. It involves the use of a spiral CT scanner to acquire multiple simultaneous tomographic sections (‘slices’) of the colon and rectum during one rotation of the x-ray source. A computer software program reformats these data to produce two dimensional images or three-dimensional reconstructions of the bowel (also referred to as ‘virtual colonoscopy’). Patients require a bowel preparation the day before the procedure. At the time of scanning, the colon is insufflated with air or carbon dioxide via a catheter placed in the rectum. The patient does not require sedation. MEDICAL SERVICES ADVISORY COMMITTEE - ROLE AND APPROACH: The Medical Services Advisory Committee (MSAC) was established by the Australian Government to strengthen the role of evidence in health financing decisions in Australia. MSAC advises the Minister for Health and Ageing on the evidence relating to the safety, effectiveness and cost-effectiveness of new and existing medical technologies and procedures, and under what circumstances public funding should be supported. A rigorous assessment of evidence is thus the basis of decision making when funding is sought under Medicare. A team from the NHMRC Clinical Trials Centre was engaged to conduct a systematic review of literature on CTC. An advisory panel with expertise in this area then evaluated the evidence and provided advice to MSAC. MSAC'S ASSESSMENT OF COMPUTED TOMOGRAPHY COLONOGRAPHY: CLINICAL NEED: Colorectal cancer is the most common cancer (excluding non-melanoma skin cancer) and the third most common cause of cancer death reported to Australian cancer registries. In 2001, there were 12,844 new cases of colorectal cancer reported and 4,754 deaths, accounting for 14.5% of all new cases of cancer and 13.1% of cancer deaths (Australian Institute of Health & Welfare (AIHW) & Australasian Association of Cancer Registries (AACR) 2004). CTC has been proposed as a minimally invasive alternative to double contrast barium enema (DCBE) and colonoscopy in patients requiring investigation or surveillance for the detection of colorectal neoplasia (cancers and polyps). CTC does not allow biopsy like colonoscopy, but can be used in patients in whom colonoscopy is contraindicated or cannot be completed. Reimbursement for CTC has been available as an interim item under the Medicare Benefits Schedule since May 2005 for two indications: (i) following an incomplete colonoscopy; and (ii) in patients with fistulous disease, obstructed colon, or megacolon in whom colonoscopy is contraindicated. Over the 6-month period, May to October 2005, 665 CTC were billed under these items in Australia with a trend of increasing CTC requests over this period. This figure does not include the number of CTCs performed for other indications, nor the number of CTCs performed on public patients treated in public hospitals. It is difficult to estimate the potential magnitude of CTC use should it be funded for the diagnosis or exclusion of colorectal neoplasia under wider indications because data about the number of DCBE and colonoscopies performed in Australia each year do not record the indication for testing. REVIEW METHODS: This review addresses two research questions to determine the potential value of CTC for the diagnosis or exclusion of colorectal neoplasia in Australia. Review question 1: What is the safety, effectiveness and cost-effectiveness of CTC versus DCBE and versus colonoscopy for the diagnosis or exclusion of colorectal neoplasia in symptomatic patients or in patients that are asymptomatic but at high risk of colorectal neoplasia due to a personal or family history of colorectal polyps or cancer? Review question 2: What is the safety, effectiveness and cost-effectiveness of CTC versus DCBE for the diagnosis or exclusion of colorectal neoplasia in symptomatic or high-risk patients who are ineligible for colonoscopy due to patient contraindications or the inability to perform or complete the test? Secondary analyses were conducted to assess the safety, effectiveness and costeffectiveness of CTC versus DCBE and versus colonoscopy to detect other specific colorectal abnormalities and all colorectal abnormalities. Literature search: A systematic review of the medical literature was undertaken using MEDLINE, Pre- MEDLINE, EMBASE, Current Contents, the Cochrane Library and Health Technology Assessment databases to identify relevant studies and systematic reviews published between January 1994 and June 2005. This search did not identify any studies comparing overall health outcomes following the use of CTC, DCBE or colonoscopy. Conclusions about the safety and effectiveness of CTC are based on four systematic reviews and 24 clinical studies that reported on CTC and/or DCBE safety and accuracy with or without comparisons with colonoscopy and 11 studies that reported on patient preferences or quality of life outcomes associated with these tests. SAFETY: CTC is a relatively safe procedure compared to DCBE and as least as safe as, or safer than, diagnostic colonoscopy. Both CTC and DCBE expose patients to ionizing radiation and are associated with a very small risk of colonic perforation. EFFECTIVENESS: CTC accuracy: CTC is generally highly sensitive and specific for the diagnosis or exclusion of cancers and polyps ≥ 10 mm in symptomatic patients and asymptomatic patients at high risk of colorectal neoplasia (11 studies of variable quality, median CTC sensitivity 84% (range 55-100%); median CTC specificity 97% (range 74-100%)). Estimates of CTC accuracy are higher for the detection of cancer alone (meta-analysis of four studies: CTC sensitivity 97% (95% CI 89-100%); CTC specificity 98% (95% CI 95-99%). These findings are consistent with results from three published systematic reviews. CTC is only moderately sensitive for the detection of lesions 6-9 mm and poorly sensitive for lesions < 5 mm (lesions 6-9 mm: six studies, CTC sensitivity range 30-80%, CTC specificity range 93-99%; lesions ≤ 5 mm: four studies, CTC sensitivity range 14- 57%, CTC specificity range 83-97%). The variation observed between studies demonstrates that CTC is less accurate in some population subgroups or settings. The extent to which patient characteristics, prevalence of disease, CTC techniques, the experience of those performing and interpreting the tests or other factors may influence CTC performance has not yet been clearly defined. Relative accuracy of CTC, DCBE and colonoscopy: Studies comparing CTC with DCBE and colonoscopy provide the best evidence to assess the relative accuracy of these tests. This evidence was limited to one study of fair quality (Rockey et al 2005) that found CTC and DCBE accuracy to be lower than noncomparative studies and systematic reviews of CTC accuracy. This study indicated that CTC is a more specific test than DCBE, but less sensitive and specific than colonoscopy for the detection of cancers and polyps ≥ 10 mm. This study also suggested that CTC may be a more sensitive test than DCBE; this difference did not reach statistical significance for lesions ≥ 10 mm, but was shown to be statistically significant for lesions 6-9 mm. Two studies of fair quality suggest that CTC may be more accurate than DCBE for the detection of all colorectal disease but less sensitive than colonoscopy; however, no studies have directly compared these tests (Munikrishnan et al 2003, Durdey et al 1987). CTC PATIENT PREFERENCES AND QUALITY OF LIFE: Three studies of fair to high quality have reported a statistically significant difference in patient preference, satisfaction and experience of pain or discomfort in favour of CTC versus DCBE (Gluecker et al 2003, Taylor et al 2005, Taylor et al 2003). The evidence reviewed also suggests that CTC may be preferred over colonoscopy. However, comparison of pain and discomfort experienced by patients undergoing both tests have shown mixed results with three of eight studies reporting results in favour of colonoscopy. ADDITIONAL CONSIDERATIONS: CTC is successful in visualising the entire colon in at least 90% of patients following an incomplete colonoscopy and may detect colorectal lesions in 18 to 27% of patients that were not identified at the initial incomplete colonoscopy (Neri et al 2002, Morrin et al 1999, Macari et al 1999, Minyue et al 2002). CTC has an advantage over DCBE for visualising the proximal colon in patients with a distal obstruction. It also has an advantage over DCBE due to technical difficulties of coating the bowel wall with barium to conduct a DCBE following a colonoscopy. CTC also offers the opportunity for detecting extracolonic lesions that cannot be identified at DCBE or colonoscopy. Rates of clinically significant extracolonic findings ranged between 1% and 13% in six studies reviewed. Incidental and clinically nonsignificant extra-colonic findings were reported in 19% to 63% of patients by three studies. The consequences of these findings have not been assessed. Clinically significant findings may be expected to change patient management, whereas insignificant findings may result in additional unnecessary investigations and patient distress. No studies were designed to compare test failure rates for CTC versus DCBE and/or colonoscopy; however, the studies reviewed suggest that CTC failure rates are at least comparable to or better than DCBE and colonoscopy. COST EFFECTIVENESS: An economic model was developed to estimate the incremental cost-effectiveness of CTC compared to colonoscopy and compared to DCBE in the patients of interest. The analysis included one- and two-way sensitivity analyses of key parameters. For the comparison of CTC with DCBE, the modelled analysis shows a cost per life year saved of $25,420 of CTC compared to DCBE in the base case scenario (CTC cancer sensitivity: 59%, DCBE cancer sensitivity: 48%) with cost-effectiveness widely varying in sensitivity analyses from $4,882 per life year saved to a situation where CTC is dominated by DCBE. The base case economic analysis further indicates that CTC is less costly, but also less effective than colonoscopy. The incremental cost of colonoscopy versus CTC per life year saved is $1,659 for the base case (CTC sensitivity for cancer=59%, colonoscopy sensitivity for cancer=98%). In sensitivity analyses, the cost per life year saved for colonoscopy ranged between $13,955 and a situation where colonoscopy is more effective and associated with less costs than CTC. The results of the economic analysis must be interpreted with caution due to uncertainties around model parameters, in particular the uncertainty around the estimates of test sensitivity for cancer. REVIEW QUESTION 1: CTC VERSUS DCBE AND VERSUS COLONOSCOPY CTC is a relatively safe test compared to DCBE and colonoscopy. Evidence about CTC accuracy for the detection of cancers and polyps ≥ 10 mm compares favourably with DCBE. There is also some evidence to suggest that patients prefer CTC over DCBE. CTC is more costly than DCBE and an economic model suggests a base case incremental cost per life year saved for CTC compared to DCBE of $25,420; results of the sensitivity analysis ranged from a cost per life year saved of $4,882 for CTC compared to DCBE to a situation where CTC is dominated by DCBE (more costly and less effective). CTC is less accurate than colonoscopy for the detection of cancers and polyps ≥ 10 mm. There is also some evidence to suggest that patients prefer CTC over colonoscopy. CTC is less costly than colonoscopy and an economic model found a base case incremental cost per life year saved of $1,659 for colonoscopy compared to CTC. The cost per life year saved for colonoscopy in sensitivity analyses ranged between $13,955 and a situation where colonoscopy is more effective and associated with less costs than CTC. REVIEW QUESTION 2: CTC VERSUS DCBE IN PATIENTS WITH A CONTRAINDICATION TO COLONOSCOPY There is little evidence for a comparison of CTC versus DCBE accuracy in patients following an incomplete colonoscopy. The evidence available indicates that CTC is successful in visualising the entire colon in at least 90% of patients following an incomplete colonoscopy. CTC also has demonstrated advantages over DCBE in visualising the proximal colon in patients with a distal obstruction, the detection of extracolonic disease, and patient preferences and tolerance of testing. Another consideration favouring the use of CTC is that it can be performed immediately after a failed colonoscopy, whereas coating the bowel wall with barium can be difficult to achieve after colonoscopy. CTC is more costly than DCBE. An economic analysis based on a general model of CTC compared to DCBE in symptomatic patients found a base case incremental cost per life year saved for CTC compared to DCBE of $25,420; results of the sensitivity analysis ranged from a cost per life year saved of $4,882 for CTC compared to DCBE to a situation where CTC is more costly and less effective than DCBE. RECOMMENDATION: Computed tomography colonography (CTC) is a relatively safe procedure. CTC, double contrast barium enema (DCBE) and colonoscopy are associated with a small risk of complications. Evidence in relation to the comparison of CTC with colonoscopy indicates that CTC is less effective. MSAC recommends that public funding for CTC as a substitute investigation for colonoscopy should not be supported. On the basis of the strength of evidence pertaining to the effectiveness and costeffectiveness, MSAC recommends that public funding for CTC for exclusion of colorectal neoplasia in symptomatic or high risk patients who are either ineligible for colonoscopy due to patient contraindications or where there is an inability to perform or complete a colonoscopy, should be supported. - The Minister for Health and Ageing accepted this recommendation on 24 August 2006.
|Place of Publication||Canberra ACT Australia|
|Publisher||Commonwealth Government of Australia|
|Commissioning body||Medical Services Advisory Committee, Commonwealth of Australia, Canberra|
|Number of pages||209|
|Publication status||Published - 2006|