Population-based Aarhus Sarcoma Registry: validity, completeness of registration, and incidence of bone and soft tissue sarcomas in western Denmark

BACKGROUND The aim of the present study was to validate the data in the Aarhus Sarcoma Registry (ASR), to determine if this registry is population-based for western Denmark, and to examine the incidence of sarcomas using validated, population-based registry data. METHODS This study was based on patients with bone and soft tissue sarcoma treated at the Sarcoma Centre of Aarhus University Hospital between January 1, 1979 and December 31, 2008. The validation process included a review of all medical files by two researchers using a standardized form. The Danish Cancer Registry was used as a reference to assess the completeness of registration of patients in the ASR. Crude and World Health Organization age-standardized incidence, as well as age-, gender-, and year-specific incidences were estimated. RESULTS The validation process added 385 to the 1442 patients who were registered in the ASR. Before validation, on average, 70.5% of the data for the variables was correct. Validation improved the average completeness of the registered variables from 83.7% to 99.3%. The 1827 patients in the ASR after validation include 85.3% of the patients registered in the Danish Cancer Registry. The overall World Health Organization age-standardized incidence of sarcoma in the trunk or extremities in western Denmark in the period 1979-2008 was 2.2 per 100,000, being 0.8 for bone sarcomas and 1.4 for soft tissue sarcomas. CONCLUSION The validation process significantly improved the completeness of the variables and the quality of the ASR data. ASR is now a valuable population-based tool for epidemiological research and quality improvement in the treatment of sarcoma. It is our recommendation that documented validation of registries should be a prerequisite for publishing studies derived from them.