This paper is based on the Liver Focus Group supported by IBA. An International group of 22 liver cancer experts from 18 institutions were brought together in Miami, Florida to discuss the optimal utilization of PBT for primary and metastatic liver cancer. A primary rationale for PBT is sparing uninvolved liver and PBT should be considered if mean liver dose (MLD) and low dose liver constraints cannot be achieved with XRT.

A consensus is reached among the experts that PBT should be more strongly considered for HCC patients with the following:

• At least CP-B cirrhosis

• High tumor-to-liver ratio

• Larger tumor size

• Smaller uninvolved liver volume

• Higher number of tumors

• Prior RT to the liver. Future studies should focus on identifying which patient subgroups achieve the greatest clinical advantage from PBT to guide treatment decision making.