High Norwegian prostate cancer mortality: evidence of over-reporting

Abstract

Objective: This study aimed to determine the level of misattribution of prostate cancer deaths in Norway based on the county of Vestfold in the years 2009–2014. Materials and methods: The study included 328 patients registered as dead from prostate cancer (PCD; part I of death certificate), 126 patients with prostate cancer as other significant condition at death (OCD; part II of death certificate) and 310 patients who died with a diagnosis of prostate cancer not registered on the death certificate (PC-DCneg) in Vestfold County in 2009–2014. The complete cohort with patients’ names and dates of birth was provided by the Norwegian Institute of Public Health and the Norwegian Cancer Registry. The true cause of death of all patients was evaluated based on patient journals. Results: Over-reporting of prostate cancer deaths in the PCD group was 33% while under-reporting in the OCD and PC-DCneg groups was 19% and 5%, respectively. The correlation between registered and observed causes of death was 0.81 (95% confidence interval 0.78–0.83). Misattribution of prostate cancer deaths increased significantly with patient age and decreasing Gleason score. Conclusions: Prostate cancer mortality statistics in Norway are relatively accurate for patients aged <75 years at death. However, overall accuracy of cause of death assignment is significantly reduced by misattribution among older patients (> 75 years), who represent the large majority of prostate cancer deaths. Over-reporting of prostate cancer deaths among elderly people may not be an exclusively Norwegian phenomenon and may affect prostate cancer mortality statistics in other countries.