Late mortality among five-year survivors of cancer in childhood and adolescence Differences between the Nordic Countries

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Abstract
The present study was aimed at assessing differences between the Nordic countries, if any, in late mortality among five-year survivors of childhood cancer. All cases diagnosed before the age of 20 years, between 1960 and 1989, were collected from all Nordic cancer registries. In total, 13 689 patients were identified as five-year survivors and during the extended follow-up 12.3% of them died. Mortality was analysed by decade of diagnosis, for all sites, and for leukaemia, Hodgkin's lymphoma, and central nervous system tumours separately. Analyses were done within a Cox proportional hazards regression framework with adjustments made for gender and age at diagnosis. Hazard ratios were calculated in relation to a weighted Nordic mean based on the proportion of five-year survivors in each country. Overall late mortality was significantly higher in Denmark and Finland than in Norway and Sweden. This could not be explained by inverse differences in five-year survival. The differences diminished over time and had disappeared in the last period. The pattern was similar for both genders. The disappearance of the differences was most probably the effect of a closer collaboration between Nordic paediatric oncologists with development and implementation of common protocols for treatment of childhood cancers in all countries.