Proton Beam Therapy in Clinical Oncology: Indications, Outcomes, and Future Directions

Abstract

Proton beam therapy (PBT) is an advanced form of radiation therapy that offers distinct physical and dosimetric advantages over conventional photon-based radiotherapy. The characteristic Bragg peak enables protons to deposit most of their energy at a defined depth within the tumor while minimizing the radiation dose delivered to surrounding healthy tissues. This review discusses the principles, clinical applications, advantages, limitations, and future directions of PBT in clinical oncology. Evidence from various cancer types indicates potential benefits in reducing normal-tissue exposure and treatment-related toxicities, particularly in pediatric malignancies, head and neck tumors, thoracic cancers, breast cancer, and selected skull-base tumors. PBT techniques, including passive scattering, pencil beam scanning, and intensity-modulated proton therapy, have improved dose conformity and treatment precision. However, uncertainties related to proton range, relative biological effectiveness, tumor motion, imaging, and anatomical changes remain important challenges. The high cost of proton therapy facilities and limited availability also restrict its widespread use, while evidence of superior clinical outcomes compared with modern photon therapy remains inconsistent for several cancers, including prostate cancer. Recent developments involving artificial intelligence, adaptive proton therapy, FLASH proton therapy, compact accelerator systems, and advanced imaging may further improve treatment accuracy, safety, and accessibility. Overall, PBT represents a promising modality for selected oncology patients, but continued clinical research and long-term comparative studies are required to establish its role and cost-effectiveness across different cancer indications.