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92 CT colonography vs optical colonoscopy: an Alberta-based cost effectiveness analysis for colorectal cancer screening
  1. Orysya Svystun,
  2. Marilyn Zeman,
  3. Michael Seidler,
  4. Christopher Fung
  1. University of Alberta, Edmonton, Canada


Objectives The sensitivity and specificity of computerized tomographic colonography (CTC) has approached that of (OC). This has led to the acceptance of CTC as an alternative for colorectal cancer screening by some guidelines. CTC’s less invasive nature and lower risk of complications may improve compliance and in turn patient outcomes; however, cost and need for colonoscopy if lesions are detected remain an obstacle for implementation. As a result, we set out to determine the cost effectiveness of CTC allowing for its drawbacks and advantages when compared to OC within a local context.

Method Using a decision analysis software, an economic analysis was performed comparing CTC to OC for colorectal cancer screening in asymptomatic patients over 50 years of age. The ten-year primary outcome measures were study cost, cost difference of screening 100,000 patients, and the cost of one quality adjusted life year gained (QALY). The sensitivities, specificities, and polyp prevalence rates were derived from literature. Cost of each test was calculated from local data. Within the primary model, which reflects the screening recommendations of guidelines that have accepted CTC, in the case of a normal OC, reassessment would not be necessary for 10 years whereas in an asymptomatic average risk population CTC must be repeated every five years. This analysis was also performed with both CTC and OC being conducted every ten years.

Results The calculated cost of OC is $764.36 compared to $580.01 for CTC. When a polypectomy is performed, the fee of OC increases by at least $232.29. Relative to CTC, which would need to be performed twice in ten years, OC would save $39.6 million in screening 100,000 patients in one decade. The incremental cost effectiveness ratio (ICER), or the additional cost per life year gained of OC compared to CTC was calculated to be $3390.76. If the interval for CTC is increased to ten years it would become more cost effective than OC for colorectal cancer screening, saving the healthcare system $18.4 million per 100,000 patients over a decade in comparison.

Conclusions Although CTC costs less to perform than OC, when a ten year screening interval is utilized and QALY is set at $50 000, OC is the cost-effective method of colorectal cancer screening if the 5-year CTC screening interval is maintained.

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