Uneven Between-Hospital Distribution of Patient-Related Risk Factors for Adverse Outcomes of Colorectal Cancer Treatment: A Population-Based Register Study

Purpose: The purpose of this study was to elucidate between-hospital variation in the prevalence at the time of diagnosis of patientrelated risk factors for adverse outcomes of colorectal cancer (CRC) treatment.Patients and Methods: A register-based national cohort of 44,471 patients diagnosed with CRC and registered in the Danish Colorectal Cancer Group database in 2009-2018 was included in the study. Patient-related risk factors present at diagnosis were collected from national Danish registers within the areas of demography, lifestyle factors, comorbidity, participation in screening, disease-related factors and socioeconomic factors. Prediction models of short-term postoperative outcomes and mortality were modelled to examine the potential aggregated impact of patient-related risk factors on outcomes, and variations between hospitals were examined.Results: The most conspicuous variations found were for old age (75+ years), ranging from 31% (95% confidence interval (95% CI): 29-33%) to 46% (95% CI: 43-48%), Union for International Cancer Control Stage I ranging from 12% (95% CI: 10-14%) to 21% (95% CI: 19-22%), Stage IV ranging from 23% (95% CI: 21-25%) to 35% (95% CI: 34-37%) and American Society of Anesthesiologists score & GE;III ranging from 18% (95% CI: 16-19%) to 40% (95% CI: 37-43%). Clinically significant variations were found in predicted probability of 30-day surgical complications which varied from 17% (95% CI: 16-17%) to 23% (95% CI: 22- 23%) and 90-day postoperative mortality which varied between 3.2% (95% CI: 3-3.4%) and 5.5% (95% CI: 4.9-6%).Conclusion: Marked variation in the prevalence of patient-related risk factors for adverse outcomes of colorectal cancer treatment exists between hospitals in Denmark. It seems reasonable to take these differences into account when comparing outcomes between hospitals.