Colorectal cancer survival in the Nordic countries and the United Kingdom: excess mortality risk analysis of 5 year relative period survival in the period 1999 to 2000.

A deficit in colorectal cancer survival in Denmark and in the UK compared to Sweden, Norway and Finland was found in the EUROCARE studies. We set out to explore if these differences still exist. Patients diagnosed with colorectal cancer as their first invasive cancer at age 15-89 in the period 1994-2000 were identified using data from 11 cancer registries in the UK and from four Nordic countries. Five-year relative period survival using deaths in 1999-2000 following cancers diagnosed in 1994-2000 was analysed with excess mortality risk modelling. Follow-up time since diagnosis with age as an effect-modifier in the first half year was the most important factor with the highest excess risk of death immediately after diagnosis and with higher age and decreasing with length of follow-up. Variations between countries were bigger in the first half year following diagnosis than in the interval 0.5-5 years with about 30% higher risk in UK and Denmark. The differences between countries are still substantial and the order has not changed, even if the five year relative survival has improved since the EUROCARE studies. Patient management, diagnostics, and comorbidity likely explain the excess deaths in UK and Denmark during the first 6 months. The effect of stage and quality of management and treatment should be examined in population based studies with detailed patient information. Use of more detailed age-intervals than conventionally applied in survival studies proved to be important in statistical modelling and is recommended for future studies