An updated system for categorising and reporting unintended incidents in radiotherapy at a national level

BACKGROUND AND PURPOSE: Radiotherapy is a complex, multistage process that involves collaboration across professional disciplines (radiographers working in pre-treatment preparation, physicians, physicists, radiation therapists during planning and treatment. While severe errors are uncommon, they can have profound consequences for patients. The Danish Society for Medical Physics supports a Special Interest Group dedicated to improving patient safety by analysing unintended events (UEs) and near misses in radiotherapy. Here we report on the work conducted with an updated system for categorising UEs in radiotherapy in Denmark. MATERIAL AND METHODS: An updated reporting system based on the English Radiotherapy Pathway Coding (RPC) system has been taken into use in 2025. This system, including the use of a Danish system that ranks the UEs from the patients perspective, called Patient Centred Coding, is outlined and UEs reported in 2025 are summarised. RESULTS: Radiotherapy is generally a safe treatment modality, a conclusion further supported by our results from 2025. In 2025 only 339 UEs were reported, 315 of these with low risk and 24 with medium risks. The lesson learned is that the main focus in order to prevent the most harmful UEs should be on the delineation and the planning process. INTERPRETATION: Based on our experience from this work, we recommend the development of a national system for categorising and ranking UEs. We further recommend establishing a national working group that meets regularly and focuses on UEs at a national level.