Accuracy of Finnish Cancer Registry colorectal cancer data: a comparison between registry data and clinical records

Background: The population-based Finnish Cancer Registry (FCR) is an important resource for research and healthcare politics in Finland. The aim of this study was to validate the accuracy of the colorectal cancer (CRC) data within the FCR. Material and methods: FCR data are based on independent cancer report forms (CRFs) from both clinicians and pathologists. Data from patients diagnosed with CRC during a randomized, population-based CRC screening program between 2004 and 2012 were extracted from the FCR and compared to data extracted from the original clinical patient records of these individuals by two gastrointestinal surgeons. The study focused on tumour characteristics and primary treatment. Accuracy was measured by calculating Cohen's kappa coefficient (kappa), which considers the possibility of agreement by chance. Results: Altogether, 1475 patients were studied. kappa was 0.74 for stage, 0.87 for tumour location (right/left), 0.78 for a more detailed location, 0.72 for tumour histology, 0.46 for surgical removal of the primary tumour, and 0.43 for chemotherapy. Among those who underwent surgery, the radicality of surgical treatment had a kappa of 0.24. In total, 173 (12%) patients were lacking a CRF from a clinician. Conclusion: The FCR data had good accuracy regarding tumour characteristics, but poor accuracy in treatment information. The main reason for this suboptimal accuracy was missing CRFs from treating clinicians. Awareness of these findings is crucial when research and decision making is based on FCR data. Measures have since been taken to improve the completeness of FCR recording.