A groundbreaking advance in the field of particle therapy has been achieved with the first successful treatment of a living animal tumor using radioactive ion beams (RIB), marking a decisive step towards more precise and effective cancer treatments. This milestone emerges from the EU-funded BARB project, driven by Professor Marco Durante and his team at the GSI Helmholtzzentrum für Schwerionenforschung and FAIR, in close collaboration with scientists from Ludwig-Maximilians-Universität Munich (LMU). The results, published in the prestigious journal Nature Physics, provide compelling evidence of the feasibility and enormous potential of a novel approach that uses radioactive ions not only to eradicate tumors but also to image them in real-time during therapy.
The BARB project—or Biomedical Applications of Radioactive Ion Beams—builds on a vision nearly half a century old yet only now truly realized, thanks to recent instrumental and accelerator advances. The core innovation lies in the simultaneous utilization of therapeutic and diagnostic radiation emitted by radioactive ions during treatment. This capability addresses range uncertainty, a long-standing challenge in particle therapy that arises because clinicians cannot precisely ascertain the ion beam’s stopping location once it penetrates the body. Small errors in range lead to either underdosing the tumor or damaging surrounding healthy tissue. The BARB team’s approach overcomes this by harnessing the positron emission from radioactive ions to generate in-beam positron emission tomography (PET) images, thus allowing real-time tracking of the beam’s path inside the body.
At the heart of this achievement is a sophisticated detector system developed by researchers at LMU Munich, designed specifically for small animal research. This high-resolution in-beam PET scanner can detect the annihilation photons produced as emitted positrons interact with electrons in the tissue, thereby precisely localizing the radioactive beam as it deposits its therapeutic dose. Originally developed under the ERC Consolidator Grant project “SIRMIO,” the PET detector has been further optimized within BARB to handle the unique challenges posed by radioactive carbon ion beams, enabling image-guided treatment with unprecedented accuracy.
Professor Marco Durante highlights the transformative nature of this advance: “Particle therapy is growing rapidly as one of the most precise forms of radiation treatment, but its clinical impact is limited by uncertainties in imaging during treatment. Our work demonstrates that using the same ion beam for therapy and in situ imaging breaks this barrier, paving the way for highly accurate, safe, and versatile particle therapies.” The ability to verify dose delivery in real time has exciting implications, particularly for treating tumors near critical structures—such as spinal cords or vital organs—where even millimeter-scale inaccuracies can have severe consequences.
The researchers presented proof of concept by treating osteosarcoma, a malignant bone tumor, in mice. The tumor was located in a sensitive neck region in close proximity to the spinal cord, traditionally a prohibitive area for intensive radiation due to potential neurological damage. By employing a radioactive carbon ion beam (^11C isotope), the group administered a high therapeutic dose of 20 gray directly to the tumor with submillimeter precision. The mice experienced complete tumor control without paralysis or other significant neurological side effects, underscoring the method’s safety and efficacy at preclinical scale.
This breakthrough is facilitated by the tandem integration of advanced accelerator facilities and nuclear imaging instrumentation. The “FAIR Phase 0” experiments at GSI/FAIR provided the intense beams of radioactive ions necessary to perform these realistic therapies, overcoming previous limitations where available beam intensities and control were insufficient. Moreover, collaboration between research pillars APPA and NuSTAR at FAIR, and international partners such as LMU and QST-Chiba, exemplifies how interdisciplinary approaches accelerate cutting-edge biomedical developments.
One of the key technical challenges addressed was real-time image reconstruction paired with continuous PET data acquisition during irradiation. Co-first author Giulio Lovatti, working as a doctoral student at LMU, emphasized the complexity of extracting meaningful beam localization from PET signals under ongoing beam delivery conditions. Their solution enabled the first demonstration of fully image-guided tumor therapy using radioactive ion beams, a milestone expected to refine treatment planning and delivery in future clinical settings.
Beyond cancer therapy, the BARB project opens new avenues in radiation oncology and other medical fields. The approach to image-guided irradiation could enhance the treatment of metastases difficult to target precisely and enable safer therapies for small, sensitive areas, including non-malignant cardiac applications such as ventricular ablations for arrhythmias. Such versatility illustrates the broad translational significance of this methodology.
Looking forward, the team plans to investigate additional short-lived isotopes for radioactive ion therapy that may generate even stronger imaging signals with faster feedback, optimizing treatment monitoring efficiency and accuracy. The future integration of these therapies with the fragment separator Super-FRS under construction at FAIR promises to increase radioactive beam intensities, thereby enabling more effective and clinically applicable protocols.
The success of BARB also lays important groundwork for Professor Durante’s subsequent ERC Advanced Grant project, “Heavy Ion FLASH (HI-FLASH),” which explores ultra-high dose-rate irradiation techniques. This continuity reflects a vibrant and rapidly evolving research landscape, wherein fundamental nuclear physics insights increasingly drive medical technologies that directly benefit patients.
In conclusion, the work presented by the BARB collaboration represents a paradigm shift in particle therapy—a sophisticated synergy of physics, biology, and medical technology that moves beyond traditional radiation treatments. By transforming the ion beam itself into both a precise weapon against tumors and an intrinsic imaging tool, this pioneering research ushers in a new era of safe, efficient, and personalized radiotherapy, paving the way for future clinical translation and improved patient outcomes worldwide.
Subject of Research: Animals
Article Title: Image-guided treatment of mouse tumours with radioactive ion beams
News Publication Date: 19-Aug-2025
Web References: DOI: 10.1038/s41567-025-02993-8
References: Nature Physics publication by the BARB collaboration
Image Credits: © GSI/FAIR
