Using Proton Therapy to Treat Left Atrial Undifferentiated Pleomorphic Sarcoma: Clinical Course and Technical Challenges

statements were evaluated through a two-round anonymous voting process, with consensus predefined as agreement by at least 75% of voters.Results: A total of 60 statements were evaluated, achieving consensus for all reviewed items.Fifty statements (83%) were rated as appropriate for proton therapy use, eight (13%) as uncertain and two (3%) as inappropriate.Following expert discussion, several statements were reformulated or merged to improve consistency and clinical applicability.The final recommendations address paediatric and adult indications, tumour site-specific scenarios and clinical situations in which proton therapy is most likely to provide meaningful benefit within the current Spanish setting, taking into account limited access to facilities.Conclusions: This SEOR-SPROMP multidisciplinary consensus provides structured, evidence-informed clinical recommendations for proton therapy use in Spain, complementing national health system indications.The RAND/UCLA methodology enabled robust multidisciplinary agreement while reflecting real-world access constraints.These recommendations support equitable patient selection, streamline referral processes and provide a framework for the future expansion of proton therapy services.