Standardizing Late-Effects Data Capture in Childhood Cancer Survivorship: A FHIR-Based Follow-Up Questionnaire

Advances in paediatric oncology have led to a growing population of childhood cancer survivors at risk of long-term and late effects requiring lifelong follow-up. However, follow-up data collection remains heterogeneous, limiting interoperability and reuse across care settings and research infrastructures. Within the PanCareSurPass project, we aimed to standardize the follow-up questionnaire used in the Survivorship Passport (SurPass) and implement it as a computable artefact based on HL7 FHIR (Fast Healthcare Interoperability Resources). Starting from CTCAE (Common Terminology Criteria for Adverse Events), we developed a survivorship-oriented extension to support longitudinal documentation of late effects during routine clinical follow-up, including in adulthood. The questionnaire was modelled using FHIR Questionnaire and QuestionnaireResponse resources and integrated into the PanCareSurPass FHIR Implementation Guide to support both primary clinical use and secondary use of data in alignment with the European Health Data Space. This work provides a reusable foundation for interoperable late-effects data capture, supporting continuity of care and enabling observational studies and registries across Europe.