Abstract
Despite demographic and socio-economic similarities between the Netherlands and Belgium, differences in survival for patients with esophageal and gastric cancer between the two countries exist. This population-based study investigated these survival differences with the aim of identifying explaining factors. We analyzed data from the Netherlands Cancer Registry (N = 26,980) and the Belgian Cancer Registry (N = 15,097) for patients diagnosed with esophageal or gastric cancer between 2010 and 2016. Survival differences were examined using relative survival, stratified for tumor location and stage. Factors that potentially mediated the survival differences were tested via multivariable excess hazard models controlling for baseline population mortalities. Five-year relative survival probability was significantly lower for patients from the Netherlands with esophageal cancer (EC) or gastric cancer (GC) (EC: 21% (20%-22%), GC: 20% (19%-21%)) compared to Belgian patients (EC: 24% (23%-25%), GC: 27% (25%-29%)). Across tumor stages, relative survival of patients with esophageal and gastric cancer was lower among patients from the Netherlands. Multivariable excess hazard modeling showed that survival differences of patients with stage IV disease disappeared when adjusting for treatment. This was not observed among patients with stage I-III gastric cancer, where survival differences remained after adjustment for treatment. Survival of patients with esophageal cancer and gastric cancer is generally higher in Belgium. For patients with stage IV disease, this difference can most likely be attributed to differences in treatment. Although treatment explains part of the survival differences for patients with curable disease, other causes remain largely unknown.