gms | German Medical Science

Background: Adherence with colorectal cancer (CRC) screening using fecal occult blood tests (FOBTs) is low. Accordingly, researchers are actively pursuing the development of a blood test (BT) for CRC screening. Pilot studies have focused on the BT’s sensitivity for detecting invasive CRC, while there is limited evidence regarding its sensitivity for detecting precursor lesions (i.e., adenomas). We assessed the cost-effectiveness of a hypothetical BT that does not detect precursor lesions (beyond chance detection) in comparison to the currently recommended FOBTs.

Methods: We used a previously-developed microsimulation model, SimCRC, to calculate life-years and lifetime costs (payers’ perspective) for a cohort of US 50-year-olds to whom non-invasive screening for CRC is offered annually from age 50 to 75. For FOBTs (i.e., Hemoccult II, Hemoccult SENSA and fecal immunochemical test) we used established estimates regarding test performance and costs (respectively, specificities of 98%, 93%, 95%, sensitivities for small adenomas of 5%, 12%, 10%, sensitivities for large adenomas of 12%, 24%, 22%, sensitivities for CRC of 40%, 70%, 70% and per test costs of $5, $5, $22). For the BT we assumed a specificity of 95%, a sensitivity of 90% for CRC, a sensitivity of 0% for adenomas of all sizes, and a base-case per test cost of $22. We performed sensitivity analyses on the screening interval, test characteristics and screening adherence and performed threshold analysis on the cost of the BT.

Results: At the base-case cost estimate of $22, the BT was dominated by the FOBTs in all scenarios, even when its sensitivity for CRC was assumed to be 100% or when adherence for BT strategies was assumed to be substantially higher than for FOBTs (80% versus 50%). Compared with Hemoccult SENSA and the fecal immunochemical test, BT strategies saved 13-18 fewer life-years while the costs were about $450,000 to $600,000 higher (outcomes expressed per 1000 50-year-old individuals, discounted at 3% annual rate). The BT remained dominated even when the unit cost of the test was lowered to zero.

Conclusions: The detection of adenomas appears to be a crucial aspect in the development of BTs that are aimed to improve non-invasive screening for CRC. Sequentially-designed diagnostic studies focusing first on adenomas, which are more prevalent, rather than on CRC could be a resource-saving approach to identify promising marker candidates.