Annual hospital volume and colorectal cancer survival in a population-based nationwide cohort study in Finland

Purpose: To examine the annual hospital volume of surgery in relation to survival in colorectal cancer. Previous studies on hospital volume and survival following colorectal cancer surgery are conflicting. Methods: All 49 032 patients who underwent resection for colorectal cancer in 1987–2016 in Finland were included, with complete follow-up until December 31, 2019. Primary outcome was 5-year mortality. Cox regression provided hazard ratios (HR) with 95% confidence intervals (CI) for quartiles of annual hospital volume for colorectal surgery, adjusted for calendar period, age, sex, comorbidity, stage, tumor location and oncological therapy. Additionally, colon and rectal cancer surgery were assessed separately. Sensitivity analysis of patients with confirmed curative intent was conducted. Results: Compared to highest quartile (≥108 resections annually), lowest hospital volume (≤37 resections annually) was associated with slightly increased 5-year all-cause mortality (adjusted HR 1.07, 95% CI 1.02–1.12). A pre-planned subgroup-analysis suggested a slightly improved 5-year survival in high-volume institutions for rectal cancer, but not colon cancer surgery. Sensitivity analysis including only those operated with confirmed curative intent suggested no differences between hospital volume groups in colorectal, colon or rectal cancer for 5-year all-cause mortality. Conclusions: Higher hospital volume is associated with slightly improved all-cause 5-year mortality in colorectal cancer surgery, but this effect may be limited to rectal cancer surgery only. Volume-outcome relationship in rectal cancer surgery should be investigated further using large datasets. These results do not support centralization of colon cancer surgery based on hospital volume only.