To Evaluate The Cost-effectiveness Of IHC Detection Of MSI In Patients With Advanced Gastric Cancer

Objective:GC is a common gastrointestinal tumor.In China,the incidence and mortality rate of gastric cancer has been high for a long time,and its age-standardized 5-year survival rate is 27.4%.Microsatellite instability can effectively predict the prognosis of gastric cancer patients and has a guiding effect on gastric cancer immunotherapy.For microsatellite instability,there are mainly 2 types of detection methods:immunohistochemical detection and polymerase chain reaction detection.Immunotherapy has achieved excellent clinical efficacy in recent years,opening a new direction for the treatment of patients with advanced gastric cancer.However,a comprehensive evaluation of a clinical treatment plan needs to consider not only therapeutic effects but also health economics aspects,so a scientifically sound evaluation system is still necessary to test the long-term benefits of treatment.The aim of this study is to apply decision analysis Markov model to evaluate the cost effectiveness of immunohistochemical detection of microsatellite instability on the efficacy of advanced gastric cancer patients,to further guide the treatment of advanced gastric cancer patients,and to provide theoretical support for their clinical decisions.Methods:(1)A decision tree model was constructed to detect MSI with no detection,immunohistochemistry(IHC)and polymerase chain reaction(PCR)and guide treatment in patients with advanced GC: In the decision tree part,the patients with advanced GC were divided into three groups: no detection,immunohistochemical detection of MSI and polymerase chain reaction(PCR)detection of MSI.Then the Markov state and the transition between the states were determined according to the natural course of gastric cancer,and the Markov model was constructed.(2)To determine the prevalence of gastric cancer,the sensitivity and specificity of immunohistochemical and polymerase chain reaction(PCR)detection,detection cost and transfer probability between Markov states;(3)According to the characteristics of the incidence of gastric cancer,the initial age of the cohort was determined to be 68 years old,one month as a cycle,the total cycle number was 5 years,and the sample size was 100,000 people.Immunohistochemical detection and polymerase chain reaction(PCR)detection were simulated by Using Treeage Pro 2011 Monte Carlo simulation method for gastric cancer patients.(4)Cost-effectiveness analysis and incremental analysis were carried out after conversion of simulated resource input and health utility values at a discount rate of 3%.QALY was used to evaluate health benefits(QALY,calculated by e Q-5D scale based on Chinese population preference).Cost effectiveness ratio(CER)and incremental cost effectiveness ratio(ICER)are used in the cost effectiveness analysis.(5)Sensitivity analysis of possible influencing factors.Results:1.IHC detection of MSI and treatment with Pembrolizumab significantly reduced end-point mortality compared with no detection and PCR detection of MSI.2.Compared with non-detection and PCR detection of MSI,detection of MSI with IHC and immunotherapy instruction increased the cost by 10,1152.9821 yuan per person,and1.89523 QALys per person.For each additional QALY obtained,the additional investment cost is 53,372.44513 yuan.It is significantly lower than the per capita GDP of China in 2021(80,976 yuan),indicating that the detection and treatment of advanced gastric cancer patients have a high cost-effectiveness value.3.One-dimensional sensitivity analysis results show that the cost of immunotherapy has the most obvious impact on ICER,that is,with the decrease of immunotherapy cost,the cost saved by each additional QALY obtained by IHC detection regimen increases.Probability sensitivity analysis shows that: Compared with no test,IHC test has a stable probability of cost-effectiveness when the willingness to pay is significantly lower than 2021 GDP per capita.Conclusion:1.In patients with advanced GC in China,the detection of MSI by IHC and the guidance of immunotherapy require extra investment,but it can delay the disease process and improve the quality of life of patients,thus achieving obvious clinical effects.From the social point of view,it has higher socio-economic value.2.The cost of detecting MSI by IHC is lower than that by PCR,and the use of IHC to detect MSI and guide Pembrolizumab in patients with advanced gastric cancer is cost-effective and should be extended.3.The decision analysis of Markov model and cost-effectiveness analysis method by IHC detection method can realize quantitative optimization of clinical treatment plan and guide clinical decision making.4.This study is an interdisciplinary application of clinical medicine,evidence-based medicine,diagnostic decision-making and clinical pathology,and provides important ideas and directions for clinical diagnosis programs.