PurposeThe registration of multi-source radiation oncology data is a time consuming and labour intensive procedure. The standardisation of data collection offers the possibility for the acquisition of quality data for research and clinical purposes. With this study we present an overview of the different tumour group data lists in the Dutch national proton therapy registry. Our goal is to provide the radiotherapy community with a flexible and interoperable data model for data exchange between centres. We highlight data variables that are needed for models used in the model-based approach (MBA), which ensures a fair selection of patients that will benefit most from proton therapy.MethodsAs a representative example of the workings of these different tumour specific knowledge graphs, we present the FAIR (Findable, Accessible, Interoperable, Reusable) data principles-compliant knowledge graph approach describing the head and neck tumour variables using radiotherapy domain ontologies and semantic web technologies. We used dosimetric and clinical variables included in the standardised head and neck tumour group items list (protrait.nl) that are used for the selection of patients candidates for proton therapy. ResultsWe successfully implemented the creation of the knowledge graph using data items from the head and neck tumour list. Furthermore, we presented the structure of an interoperable data model based on the usage of publicly available ontologies and semantic web technologies.Conclusion With this study we provide a synopsis of the different data items lists of the ProTRAIT registry, focusing on a particular knowledge graph with data items included in the head and neck tumour group list. We also highlight the importance of the FAIR data principles that can establish a standardised framework of data reusability in radiotherapy.