UICC World Cancer Congress 2006

Objective: Helicobacter pylori (Hp) infection is responsible for ~40% of all cases of gastric cancer (GC), the second leading cause of cancer-related deaths worldwide. Our objective was to develop a model capable of evaluating the cost-effectiveness of Hp screening and treatment programs.

Methods: Our computer-based model simulates the natural history of intestinal-type GC in China and Columbia, two high-risk regions with Hp seroprevalence of >70%. Health states reflect disease progression and include gastritis, atrophy, metaplasia, dysplasia, and invasive cancer. Initial probabilities reflecting movement between states were derived from country-specific cohort studies and the literature. We calibrated the model to age-specific prevalence of precancerous lesions and GC incidence to elucidate unobserved parameters for which data were not available.

Results: In both China and Columbia, the lifetime GC risk was ~3% although the shape of the age-specific cancer incidence curve differed. The risk of progression between precancerous health states, as derived from our calibration exercises, differed between countries. For example, probabilities of progression among the precancerous health states were up to 2.5 times higher in China while those for progression to invasive cancer were up to 1.5 times higher in Columbia. Differences may reflect risk factors, such as smoking, diet, and genetics.

Conclusions: Natural history models calibrated to different epidemiologic settings can leverage region-specific data in order to understand and reflect geographical variation of risk factors and their role in disease progression. This model is being used to estimate the costs and benefits of GC prevention programs from a population perspective.