A Review of the Current Role of Proton Therapy in Modern Oncology

Proton therapy (PT) is a high-precision form of radiotherapy. The interest in clinical application in oncology of PT is related to its ballistic selectivity capable to adequately cover the tumor target with high homogeneity, high conformality and sparing the surrounding organ at risk (OAR), mainly in the middle-low dose area, with a potential significant reduction of toxicity and development of radio-induced second tumors. PT has gained a renewed interest in very recent years after its first pioneering beginning in Berkeley in 1954 due to the advancement in treatment planning, delivery systems (gantry), radiobiological knowledge and clinical imaging. This fact has permitted the transit of PT from laboratory research structures to modern clinically-oriented treatment facilities. The results of PT in some specific sites such as ocular tumors and base of the skull tumors are well known approaching local control rates at five years of 100% and 90%, respectively. Indications are now evolving towards the treatment of other very common tumors such as lung, head and neck, liver: all of them show very attractive response rates. A particular interest is now growing for pediatric tumors considering the possibility of reducing not only the dose to OAR but also the integral dose. Integration with chemotherapy represents another challenge thanks to the possibility of increasing dose intensity of chemotherapy or total radiation dose and/or reducing the toxicity of the combined treatment.