Does stage at diagnosis explain the difference in survival after breast cancer in Denmark and Sweden?

Breast cancer survival differs 9 percentage points between the neighbouring countries of Denmark and Sweden. The authors' aim was to analyse whether this was caused by early detection in Sweden. The extent of disease and outcome was compared in two population-based breast cancer cohorts in 1983-1989. Breast cancer management was decentralized in Denmark without mammography screening whereas treatment in Sweden was centralized and the population partly screened. Ten- and 15-year relative survival was 15% and 6% higher in Sweden (p<0.001) with corresponding differences in crude and disease-specific survival. Stage distribution was significantly more favourable in the Swedish cohort. In multivariate analysis age, tumour size, extent of axillary surgery, and spread affected survival; however, the impact of region persisted (p<0.001). Reanalysis without screening-detected patients only slightly affected the impact of region. It was concluded that early detection had significant impact on survival but other regional differences might be of importance.