Geographic variation in diagnostic and treatment interval, cancer stage and mortality among colorectal patients-An international comparison between Denmark and Scotland using data-linked cohorts

Background: Rurald wellers with colorectal cancer have poorer outcomes than their urban counterparts. The reasons why are not known but are likely to be complex and be determined by an interplay between geography and health service organization. By comparing the associations related to travel-time to primary and secondary healthcare facilities in two neighbouring countries, Denmark and Scotland, we aimed to shed light on potential mechanisms. Methods: Analysis was based on two comprehensive cohorts of patients diagnosed with colorectal cancer in Denmark (2010-16) and Scotland (2007-14). Associations between travel-time and cancer pathway intervals, tumour stage at diagnosis and one-year mortality were analysed using generalised linear models. Travel-time was modelled using restricted cubic splines for each country and combined. Adjustments were made for key confounders. Results: Travel-time to key healthcare facilities influenced the diagnostic experience and outcomes of CRC patients from Scotland and Denmark to some extent differently. The longest travel-times to a specialised hospital appeared to afford the most rapid secondary care interval, whereas moderate travel-times to hospital (about 20-60 min) appeared to impact on later stage and greater one-year mortality in Scotland, but not in Denmark. A U-shaped association was seen between travel-time to the GP and one year-mortality. Conclusions: This is the first international data-linkage study to explore how different national geographies and health service structures may determine cancer outcomes. Future research should compare more countries and more cancer sites and evaluate the impact and implications of differences in national health service organisation.