Proton therapy in the palliative setting

Given its sharp dose fall off and ability to spare healthy surrounding tissue, proton beam therapy (PBT) has traditionally been used to treat various types of malignancies in the definitive setting, with strong, empirical data supporting its utility and safety. In the palliative setting, however, photon therapy has generally remained the standard of care in radiation treatment delivery due to lower cost, and greater availability. However, recent data suggest that the use of PBT may provide benefit in terms of symptom management and disease control in patients with locally advanced or recurrent disease who do not qualify for definitive therapy or with metastatic disease. Additionally, due to its unique dosimetric properties, PBT may confer less overall toxicity, thus helping preserve or improve the quality of life in this patient population, especially for those who are nearing end of life. While there is a need for further study, initial data analyzed from both retrospective and prospective single-institution and multi-institution trials are promising. This review aims to explore the efficacy and safety of PBT in the palliative setting among adults and to summarize pertinent studies that support its usage. To the authors' knowledge, this is the first review of the literature pertaining to PBT used in the palliative setting across multiple disease sites.