REVIEW ARTICLE - MEDICAL DECISION-MODELS OF HELICOBACTER-PYLORI THERAPY TO PREVENT GASTRIC-CANCER

The aim of the present article is to study the utility of Helicobacter pylori eradication programmes in decreasing the incidence of gastric cancer. Three types of decision models are employed to pursue this aim , i.e. decision tree, present value, and declining exponential approxi mation of life expectancy (DEALE). 1) A decision tree allows one to mo del the interaction of multiple variables in great detail and to calcu late the marginal cost, as well as the marginal cost-benefit ratio, of a preventive strategy The cost of gastric cancer, the efficacy of H. pylori therapy in preventing cancer, and the cumulative probability of developing gastric cancer exert the Largest influence on the marginal cost of cancer prevention. The high cost of future gastric cancer and a high efficacy of therapy make screening for H. pylori and its eradi cation the preferred strategy. 2) The present value is an economic met hod to adjust future costs or benefits to their current value using a discount rate and the length of time between now and a given time poin t in the future. It accounts for the depreciation of money and all mat erial values over time. During childhood, the present value of future gastric cancer is very low. Vaccination of children to prevent gastric cancer would need to be very inexpensive to be practicable. Cancer pr evention becomes a feasible option, only if the time period between th e preventive measures and the occurrence of gastric cancer can be made relatively short, 3)The DEALE provides a means to calculate the incre ase in life expectancy that would occur, if death from a particular di sease became preventable. Life expectancy of the general population is hardly affected by gastric cancer. For life expectancy to increase ap preciably by vaccination or antibiotic therapy directed against H. pyl ori infection, these interventions would need to be focused towards a sub-population with an a priori high risk for gastric cancer.