CT colonography, colonoscopy or barium enema for diagnosis of colorectal cancer in older symptomatic patients (SIGGAR1)
CT colonography (CTC) is a new health technology for whole-colon examination that is disseminating at a rapid rate, based on results suggesting that it is as sensitive as colonoscopy for colonic cancer and large polyps but safer and more acceptable to patients.
In the UK the use of CTC as a screening tool is controversial but a systematic review of the literature suggests that it is very sensitive for cancer and may thus have an important role in the NHS for rapid, accurate, acceptable, safe, and cost-effective investigation of symptomatic patients, most of whom are older and less tolerant of colonoscopy.
CTC will be compared with the accepted standards of total colonoscopy and barium enema in two parallel, prospective multicentre randomised trials (randomised 2 to 1 in favour of the standard test), with choice of the standard test depending on local factors such as availability and expertise. The detection or exclusion of significant colorectal neoplasia (cancer and/or polyps >1cm) will be determined for each of the three tests, including the number and nature of any additional tests required to confidently exclude cancer and the incidence, nature, and significance of incidental extracolonic lesions detected by CTC.
The frequency and nature of procedure-related adverse events will be recorded and psychological morbidity associated with each investigative pathway will be measured using validated questionnaires. Patient specific records of costs and outcomes including influence of test conversion and multiple investigations will be obtained and cost utility models developed to compare management plans with outcome cost. The investigators will also update systematic reviews and use these and the data collected to populate models that summarise the health effects and costs of alternative diagnostic approaches in patients of differing ages, risks, and preferences. Notably, the frequency, relevance, morbidity, and costs associated with incidentally discovered lesions will be assessed.
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