Proton-based stereotactic radiosurgery and stereotactic body radiation therapy

Proton beam radiation has a unique depth-dose distribution with lower surface dose, peaked energy loss at the end of the traveling range, and negligible exit dose compared to photon radiation that allows better sparing of normal tissues and potential dose escalation to the tumor. With advanced proton beam delivery and imaging guidance systems and years of successful proton treatment experience, clinicians are moving forward to implement proton beam in stereotactic body radiation therapy (SBRT). Major challenges in implementing stereotactic body proton therapy (SBPT) still exist such as the proton range uncertainty, radiobiological modeling, and inter-fractional motion management. Recent studies have demonstrated the safety and efficacy of utilizing SBPT in treating central nervous system (CNS), lung, and liver tumors. However, more clinical trials involving large patient cohorts are needed to evaluate the long-term clinical outcomes of SBPT. In addition to the technical challenges, consensus guidelines on treating selected patients with SBPT are needed to ensure treatment quality. Lastly, more effort on SBPT insurance approval is needed to further expand its clinical application. This study introduces the fundamental and new technologies utilized in SBPT and summarizes the current status of SBPT implementation in treating CNS, lung, and liver tumors.