Less pitfalls and variation in population based cancer survival comparisons within the European Union: Lessons from colorectal cancer patients in neighbouring regions in Denmark and Germany - The Fehmarn Belt project

Improved data quality and comparability than presently used in the large international survival studies is needed. If stage and treatment is taken into account, more valid international comparisons of cancer survival are possible. Reporting and follow-up must be improved and cases only known from death certificates (DCO) minimised. A high proportion DCO (excluded from analyses) may produce higher survival, whereas a low the opposite. Co-morbidity and socio-economic status should be included alongside other prognostic variables in survival studies. Barriers towards proper follow-up and monitoring of outcome e.g. privacy legislation must be considered with a view to future patient mobility.