Hospital variation in surgical outcomes for gastric cancer: the impact of case-mix and treatment across a global cohort

BACKGROUND: There is substantial global variation in demographics, disease burden, and treatment for gastric cancer patients. Benchmarking is an instrument to assess such variation and enables to investigate to which extent case-mix and treatments explain differences in outcomes. We aimed to evaluate hospital-level variation in surgical outcomes following gastrectomy for gastric cancer before and after adjusting for case-mix and treatment-related factors. METHODS: were used to quantify the variance in outcome explained by case-mix and treatment-related factors. RESULTS: A total of 7818 patients from 41 hospitals were included, with contributions ranging from 12 to 2554 patients per hospital (IQR: 49-146). Observed 30-day mortality and severe complications ranged from 0 to 9.7% (IQR: 3.2%) and 5.3 to 31% (IQR: 7.7%), respectively. Larger variation between hospitals was observed for retrieval of > 15 lymph nodes (IQR: 12.3%), prolonged hospitalization (IQR: 14.4%) and readmissions (IQR 11.3%). This variation was reduced in the crude model, while adjusting for case-mix and treatment-related factors did not significantly reduce variation for any outcome. Case-mix factors had a limited contribution to the explained variance, except for 30-day mortality (33.9%) and negative resection margins (31.7%). Adding treatment-related factors increased the explained variance for 30-day mortality by 40.8%, but had low impact (< 10%) on the variance in most surgical outcomes. CONCLUSIONS: Case-mix and treatment factors are not the primary drivers of variation in surgical outcomes following gastrectomy. Case-mix adjustment can improve the validity of global comparisons for 30-day mortality, but does not seem essential for comparing other investigated outcomes.