Differences in survival from prostate cancer in Denmark, Iceland and Sweden

Register-based studies have shown large survival differences among prostate cancer patients in the Nordic countries. The aim of this study was to determine the background of such differences in Denmark, Iceland and Sweden.

Patients with prostate cancer were identified through population-based cancer registers in the three countries. Clinical findings at diagnosis were retrieved from hospital records. In Sweden, clinical information was gathered from regional population-based prostate cancer registers. Country-specific incidence and excess mortality rates were compared, with adjustment for prognostic factors.

The relative survival in the cohorts was comparable to that in previous population-based studies. Significant differences in excess mortality rates were found across countries, which diminished or disappeared after adjustment for patient characteristics, i.e. metastatic status, clinical T stage and prostate-specific antigen level. A difference in the proportion of patients with metastatic disease was the main explanation of the differences in survival among countries, while the incidence rates of metastatic cancer were similar.

Register-based studies of the relative survival of prostate cancer patients are influenced by national differences in clinical presentation at diagnosis. Differences in the proportion of patients with metastatic spread explained most of the difference in relative survival among patients in Denmark, Iceland and Sweden. Future country comparisons of relative survival should include adjustment for differences in patient characteristics, such as stage, prostate-specific antigen level and screening intensity.