Fundamental Physical Principles and Clinical Applications of Proton Therapy: A Comprehensive Review
Authors
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Crownbirth Ebipade Eki
Delta State University, Abraka
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Anita Franklin Akpolile
Delta State University, Abraka
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Godwin Kparobo Agbajor
Delta State University, Abraka
Keywords:
Proton therapy, Bragg peak, Stopping power, Linear Energy Transfer, Pencil Beam Scanning, Radiobiological Effectiveness, FLASH radiotherapyAbstract
Proton therapy is an advanced modality in external beam radiotherapy that exploits the unique depth-dose distribution of accelerated protons to achieve improved tumor targeting compared with conventional photon-based techniques in selected anatomical geometries. This review synthesizes the fundamental physical principles underlying proton therapy, including proton-matter interactions, stopping power, linear energy transfer (LET), the Bragg peak, and the generation of the spread-out Bragg peak (SOBP). Accelerator technologies such as cyclotrons and synchrotrons, beam delivery methods including passive scattering and pencil beam scanning, and treatment planning approaches incorporating proton computed tomography and range verification are examined. The radiobiological effectiveness of protons is discussed alongside emerging evidence for FLASH proton therapy, which delivers ultra-high dose rates (>40 Gy/s) currently under early-stage clinical investigation. Clinical applications are supported by Level I evidence from randomized controlled trials (e.g., the 2025 Lancet trial demonstrating 90.9% versus 81.0% five-year overall survival for oropharyngeal cancer), Level II evidence from prospective cohort studies, and Level III evidence from meta-analyses showing reduced toxicity and secondary malignancy risks in pediatric cancers and central nervous system tumors. Despite challenges such as range uncertainty and high facility costs, proton therapy continues to evolve as a component of precision oncology in appropriately selected patients. This review underscores how fundamental physics principles translate into measurable clinical benefits when applied to specific tumor sites and patient populations.
Author Biographies
Crownbirth Ebipade Eki
Department of Physics, Delta State University, Abraka, Delta State.
Anita Franklin Akpolile
Department of Physics, Delta State University, Abraka, Delta State.
Senior Lecturer
Godwin Kparobo Agbajor
Department of Physics, Delta State University, Abraka, Delta State
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