Fig. 2

Policy1-Lynch model with integrated implementation costs. (a) ‘Not LS’ includes normal IHC/MSI results (preserved immunohistochemical MMR expression) as well as abnormal IHC/MSI results (loss of immunohistochemical MMR expression) with BRAF V600E mutation or with MLH1 promoter hypermethylation. (b) High risk of LS includes abnormal IHC/MSI results without BRAF V600E mutation or without MLH1 promoter hypermethylation. (c) Timing of referral to genetic counselling varies by states. For simplicity, we assume all patients at high risk of LS are referred to genetic counselling, then offered diagnostic germline genetic testing. Therefore, CRC patients at high risk of having LS who are not compliant to genetic counselling do not take up diagnostic genetic testing, and their relatives, who may or may not be LS carriers, do not receive predictive testing and LS surveillance. (d) We do not explicitly model standard care after cancer treatment; however, stage-specific cancer treatment costs include the cost of initial treatment, the cost of follow-up appointments, blood tests and imaging, treatment for relapsed disease and palliative care. BRAF, B-Raf protooncogene; CRC, colorectal cancer; dMMR, mismatch repair deficiency; F/U, follow-up; IHC, immunohistochemistry; LS, Lynch syndrome; MLH1, mutL homolog 1 gene; MSI, microsatellite instability