International Journal of Particle Therapy
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This document is the proceedings of the PTCOG 61 conference, containing abstracts on particle therapy research. The main findings cover advances in range verification, treatment planning, FLASH therapy, and clinical outcomes across various cancers. The clinical significance lies in demonstrating improved precision, reduced toxicity, and potential for adaptive and FLASH therapies in particle oncology.
**Background:** The Particle Therapy Cooperative Group (PTCOG) 61st Annual Conference focused on 'Integrative Particle Therapy and Complementary Care,' highlighting the integration of particle therapy into comprehensive cancer care. The conference covered clinical, physics, and biology research topics, including comparative effectiveness, novel treatment strategies, adaptive therapy, FLASH and mini-beams, and biological advantages of charged particle radiotherapy. The target audience included radiation oncologists, medical physicists, dosimetrists, residents, and radiation therapists.
**Methods:** The proceedings include oral and poster abstracts from multiple institutions worldwide. Studies employed various methodologies: clinical trials (e.g., prospective registry for Ewing sarcoma and rhabdomyosarcoma, randomized phase II trial for uveal melanoma), retrospective analyses (e.g., pediatric outcomes, financial toxicity), dosimetric comparisons (e.g., proton vs. photon for Hodgkin lymphoma, IMPT vs. IMRT for nasopharyngeal cancer), and preclinical experiments (e.g., FLASH effect in mice, microdosimetry). Physics and biology abstracts utilized Monte Carlo simulations, treatment planning system modeling, and in vitro/in vivo assays.
**Key Results:** Key clinical findings include: 2-year overall survival of 85.1% for Ewing sarcoma and 80.8% for rhabdomyosarcoma with proton therapy (O 006); significant reduction in acute and late toxicity with IMPT vs. IMRT in nasopharyngeal cancer (O 032); and a 53% lower overall toxicity score with IMPT (O 032). For physics, a multi-slit prompt-gamma camera achieved range measurement precision of ~3% with 1×10^8 protons (O 001). A neural network (ProtoNN) estimated Bragg peak location with 0.9 mm accuracy in 77 ms (O 002). FLASH studies showed that ultra-high dose rate carbon ions spared healthy tissue while providing comparable tumor control in a mouse model (O 070), and that multi-minute beam pauses did not negate the FLASH effect in mice (O 071).
**Clinical Implications:** The findings support the clinical benefits of proton therapy in reducing toxicity and improving outcomes for various cancers, particularly in pediatric and head/neck patients. Advances in range verification (prompt gamma, PET, protoacoustics) and adaptive planning (daily adaptation, AI-based prediction) promise to enhance treatment precision. FLASH therapy shows potential for widening the therapeutic window, though further research is needed for clinical translation. The conference underscores the importance of integrating particle therapy with complementary care and advancing biological optimization.