OBJECTIVES: Colorectal cancer (CRC) simulations models have been extensively used to compare the cost and effectiveness of CRC screening in different contexts. These models sometimes included strategies focus on individuals with specific CRC risk factors such as familial history. To our knowledge, no models included strategies based on a validated risk equation. This study presents the results of a model incorporating such equation.

METHODS: A microsimulation model of CRC screening was constructed, calibrated and validated for the French context. The model simulate the natural history of CRC, from adenomas to CRC and includes a screening module. A validated CRC risk equation predicting the risk of advance neoplasia (AN) at colonoscopy was incorporated into the model and provided risk groups (RG) for each individual. The model was used to assess the cost effectiveness of fecal occult blood testing (FOBT) with an immunological test (iFOBT) at different thresholds (30 and 10μgHb/g) and colonoscopy every 5 years to the absence of screening in 5 RG. Test efficacy was based on literature and costs on French prices. Participation rates were 29.1% for iFOBT and 25% for colonoscopy.

RESULTS: Individuals were distributed in the 5 RG as follows: 41% had a risk < 5% of AN (0), 17% 5%-7.5% (1), 17% 7.5-10% (2), 15% 10-14% (3) and 10% a risk greater than 14% (4). Versus no screening, iFOBT (30μgHb/g) was associated with ICERs of €51,000/QALY in RG0, €8,900/QALY in RG1, €3,500/QALY in RG2, €1,900/QALY in RG3 and €900/QALY in RG4. Similarly, iFOBT (30μgHb/g) was dominated in RG0 and associated to ICERs of €30,000/QALY, €6,000€/QALY, €4,600/QALY and €2,300/QALY (RG0-RG4). Finally, colonoscopy was associated with ICERs of €442,000/QALY, €84,600/QALY, €50,125/QALY, €29,000/QALY and €16,200/QALY (RG0-RG4).

CONCLUSIONS: The results suggest that using a risk equation to offer risk adapted screening strategies might improve overall screening effectiveness while maximizing efficacy.