ESTRO 2025 - Abstract Book

S763

Clinical - CNS

ESTRO 2025

4386

Poster Discussion Pioneering Helium Ion Beam Therapy – the world’s first prospective clinical trial with scanned helium ions advancing safe and innovative radiotherapy Semi Harrabi 1,2,3 , Bastian von Nettelbladt 1,2 , Hanna Waldsperger 1,2 , Katharina Weusthof 1,2 , Lars Wessel 1,2 , Ricarda Wickert 1,2 , Line Hoeltgen 1,2 , Katharina Seidensaal 1,2 , Ivana Dockic 1,4 , Angelika Höss 3 , Malte Ellerbrock 3 , Oliver Jäkel 3,2,5 , Jakob Naumann 3 , Thomas Haberer 3 , Klaus Herfarth 1,3,2 , Jürgen Debus 1,2,3 , Andrea Mairani 3,4,6 , Thomas Tessonnier 1,3,7 1 Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany. 2 Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany. 3 Heidelberg Ion Beam Therapy Center (HIT), Heidelberg University Hospital, Heidelberg, Germany. 4 Clinical Cooperation Unit Translational Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 5 Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 6 Medical Physics, National Center of Oncological Hadrontherapy (CNAO), Pavia, Italy. 7 Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany Purpose/Objective: Helium ion radiotherapy represents an evolutionary step in particle therapy, refining the precision of proton beam therapy while avoiding some challenges associated with carbon and other heavier ions. The superior physical properties of helium ions, including their reduced lateral scattering compared to protons, enable enhanced targeting of tumor tissues while sparing adjacent healthy structures. Helium ions offer a slightly increased relative biological effectiveness (RBE) that maintains efficacy without introducing a higher level of biological complexity, such as in carbon ion therapy. This combination of improved spatial precision and balanced RBE positions helium ion therapy as a promising modality for advancing cancer treatment and further reducing the burden of radiation-induced long term sequelae. Material/Methods: The Heidelberg Ion-Beam Therapy Center (HIT) has spearheaded efforts to translate helium ion therapy into clinical practice. Through thorough beam delivery optimization and characterization, as well as rigorous preclinical studies, HIT has successfully developed the infrastructure to provide this cutting-edge treatment. Building on this foundation, a first-in-the-world prospective clinical trial has been designed to evaluate the safety and feasibility of helium ion beam therapy in patients. Conducted within the framework of Medical Device Regulation, this trial marks a critical milestone in advancing radiotherapy and establishing helium ions as a refined therapeutic option. Results: A total of 29 patients have been successfully recruited from July to October 2024, with a comprehensive safety and monitoring protocol in place. Dose prescriptions ranged from 50 to 70 Gy in 2Gy single dose for a variety of indication (mostly central nervous system (CNS) and skull base). None of the enrolled patients experienced toxicity exceeding CTCAE grade 3, underscoring the safety profile of helium ion therapy. Patients are closely monitored through weekly trial visits, with ongoing clinical assessments and radiological evaluations. In addition to standard clinical outcomes, special emphasis is placed on patient-reported outcomes, providing valuable insights into treatment-related side effects and quality of life. This holistic approach ensures a thorough understanding of both the therapeutic efficacy and the patient experience during the trial. Conclusion: The promising results lay a strong foundation for further clinical studies. Future trials, planned to start in 2025, will focus on patients with tumors in critical locations, such as the CNS and skull base, where precision is paramount. Additionally, helium ion therapy may prove particularly beneficial for vulnerable patient populations, such as pediatric patients, where sparing healthy tissue is crucial.

Keywords: helium ions, high precision radiotherapy