From tumor-centric to ecosystem-based hypotheses in brain tumor research and care: Proceedings from The second Brain Tumor Meeting by the Sea organized by Julie Gavard and Eric Chevet, held in St Malo (France), 23-25 March 2026.

Brain tumors remain among the most lethal cancers, largely due to their remarkable heterogeneity, plasticity, and resistance to therapy. The second Brain Tumor Meeting by the Sea (Saint-Malo, France, 2026) brought together researchers, clinicians, and patient representatives to discuss emerging concepts shaping the future of neuro-oncology. A recurring theme was the shift from a tumor-centric perspective toward an ecosystem-based view that integrates tumor cells, microenvironmental cues, developmental context, and patient-centered dimensions. Advances in patient-derived models, multi-omics approaches, spatial technologies, and artificial intelligence are refining tumor classification and revealing novel therapeutic vulnerabilities. Discussions highlighted cellular plasticity and stress-adaptation mechanisms as key drivers of tumor evolution and treatment resistance. They also emphasized the need for identifying dynamic biomarkers and developing more physiologically relevant disease models. Beyond biological discoveries, the meeting underscored the importance of strengthening interactions among research, clinical care, and patient communities. Together, these advances support a more integrated framework for understanding brain tumors and developing future therapeutic strategies.