Late Diagnosis, Smoking History and Socioeconomic Inequality in Gastric Carcinoma: A Decomposition Approach

Background: An association between cancer survival and socioeconomic status (SES) has been evaluated for many different cancers but calculating socioeconomic inequality in survival is very late. In this study we aimed to determine associations between socioeconomic inequality and survival risk factors in patients with gastric carcinoma (GC). Methods: In this cross-sectional study, we enrolled 235 patients with confirmed GC. SES data were retrieved from three sources pathological records, official death certificates and telephone interviews. Polychoric correlation matrix was used to reduce the number of variables. Inequality was measured by concentration index (CI) and we decomposed CI to determine contribution in inequality. All analyses were performed by standard statistical software STATA (version 11.2). Results: The overall CI for late diagnosis (2 stage onwards) and positive history of smoking were -0.020 (95% CI = -0.041 - 0.004) and -0.105 (95% CI = -0.110 - -0.076), respectively. Results of decomposition shows past medical history of gastrointestinal diseases (29%) and history of smoking (18%) have the largest contributions in inequality in GC survival. Conclusions: Results of this study showed risk factors in GC survival such as smoking, having a past medical history of gastrointestinal diseases and late diagnosis are more prevalent among people of lower SES.