Current Topics of Proton Radiobiology

Proton therapy is a cutting-edge modality over conventional photon radiotherapy because of its great advantage of conformal physical dose deposition. However, it is not fully understood about its biological effects compared to photon irradiation. Here I summarized current topics of proton radiobiology, including “relative biological effectiveness (RBE) of protons,” “gene expression and signal transduction induced by protons,” and “non-targeted response with protons.” The current radiobiological status and knowledge may have significant implications for proton therapy in terms of not only development of biologically corrected treatment planning but also suppression of molecular and cellular processes that are fundamental to tumor growth and invasion. In addition, one of the important future research directions is to combine or fuse with other therapeutic modalities; especially, a combination of proton therapy with immunotherapy is attracting attention.