Stereotactic body proton therapy for liver metastases

Although surgical resection is the gold standard, stereotactic body radiotherapy (SBRT) is often the preferred treatment for metastatic liver tumors due to size, multi-focality, tumor distribution or patient co-morbidities limiting surgical options. The major dose-limiting concern in the use of SBRT for liver tumors is the risk of radiation-induced liver disease (RILD). This can limit the number of patients who may be candidates for conventional SBRT. The use of protons for SBRT is potentially attractive given the dosimetric advantages inherent to proton radiotherapy potentially offering a way to maximize tumor control via dose escalation while avoiding excessive radiation to the remaining liver and other organs at risk. In this review we discuss the physical attributes and rationale for stereotactic body proton therapy (SBPT) for the treatment of liver metastases.