What patients value in data reuse for oncology research: a multi-stakeholder qualitative study to inform the European Health Data Space implementation in Belgium and beyond

The reuse of health data is critical for advancing health research, yet it raises complex ethical, legal, and societal challenges. In the European Union, the recently adopted European Health Data Space (EHDS) aims to harmonize access to and reuse of health data for research and innovation, while safeguarding individual rights. However, questions remain about what patients value in data reuse and how their values can be embedded in governance frameworks. Belgium, with its strong research tradition and central role in EU policymaking, offers an important testbed for these questions. We conducted a qualitative study combining semi-structured interviews with 39 professionals (policy and governance representatives, researchers, physicians, industry, law and ethics experts, and supporting actors) and three focus groups with ten oncology patients and patient representatives. The interviews explored professional perspectives on data reuse and informed the design of the focus groups. Data were analyzed using the framework method, integrating inductive and deductive coding. Patient-researchers were involved throughout the study design, data collection, and interpretation. Participants unanimously recognized the value of health data reuse at both individual (improved healthcare) and collective (advancing scientific research) levels. Patients emphasized the importance of transparency, feedback about research results, and opportunities for meaningful involvement in data governance. While patients were generally willing to share their data, they highlighted conditions such as trust in the system, strong data protection, and safeguards against misuse. Both professionals and patients considered the EHDS a positive step for facilitating research but expressed concerns about its practical implementation. All participants recognized the value of both individual and collective control over health data, though challenges of representation and resource constraints were noted when it came to patient involvement. This study provides the first in-depth investigation in Belgium of what patients and professionals value in relation to health data reuse, particularly in the context of the EHDS. Findings underscore that the legitimacy of the EHDS will depend on embedding patient values into its implementation through transparency, participatory data governance, and legal and technical safeguards. The results provide actionable insights for policymakers, researchers, and practitioners to build a value-oriented and socially legitimate health data ecosystem at national and EU levels.