Effects of proton therapy on the tumor immune system and clinical implications: A review

Proton therapy, an emerging radiation therapy technique, has gained significant attention owing to its unique physical properties and biological effects. This review aims to explore the impact of proton therapy on the tumor immune system and of its combination with other therapies. This review outlines the fundamental principles and oncological applications of proton therapy, followed by an analysis of its impact on the immune system-encompassing draining lymph nodes, peripheral blood immune cells, tumor cell immune responses, and the tumor microenvironment. We further discuss current combinatorial strategies with immunotherapy and/or chemotherapy, which point toward promising clinical directions.