Advancing Particle Therapy to Improve Cancer Care: Report on “2nd World Forum on Particle Therapy”

Purpose Charged particle therapy (PT), including proton beam therapy (PBT) and carbon ion radiation therapy (CIRT), offers potential advantages for selected patients. A key challenge remains in how to expand access to PT to maximize clinical benefit. Methods Eighty-one international PT leaders convened at the 2nd World Forum to discuss strategies for advancing PT globally. Results Recent PBT trials have shown reduced toxicity in oropharyngeal and advanced esophageal cancer, improved local control in hepatocellular carcinoma, and improved survival in patients with leptomeningeal and oropharygeal cancer. In contrast, there was no difference in toxicity nor progression-free survival in low-to-intermediate risk prostate cancer, and no cognitive benefit seen in adult glioblastoma. Additional trials results are awaited. Vendor financial support has been instrumental in enabling many studies. CIRT trials remain limited, though several are ongoing. Further development and harmonization of relative biological effectiveness (RBE) models is crucial. Helium therapy and oxygen therapy require exploration. Heavy ions may enhance immune response through more complex DNA damage than X-rays. This potential synergy with immunotherapy should be explored further. Second-generation trials should leverage the biological advantages of PT, target promising sites and diseases, include molecular diagnostics, and explore hypofractionation. Indications for PBT are expanding, supported by emerging evidence. More studies are needed, including developments in clinical endpoints and integration of biological data on tumors and normal tissues. Follow up of all PT patients is needed, with pooling of international data. Trials are needed to define the role of heavier ions and their immune effects. Conclusions Large, definitive, “Champion Studies,” demonstrating survival benefit over established therapy are essential. International collaboration with strong administrative and financial support will be key. A meeting to develop such a study is strongly recommended. The faster and more efficiently the community can work, the more patients will benefit.