Stereotactic Body Proton Radiotherapy for the Treatment of Liver Cancer

Inclusion Criteria: * Age \>= 18 years * Radiologically presumed or histologically proven, newly diagnosed or recurrent, hepatocellular carcinoma * Clinical stage T0-T4N0M0 (American Joint Committee on Cancer \[AJCC\] 8th edition). * One to three discrete Liver Reporting and Data System-5 (LIRADS-5) lesions that can be encompassed within a single radiation treatment plan * Patients treated with external beam radiation as a bridge to transplant are allowed * Minimum single lesion size \>= 1 cm, maximum cumulative diameter =\< 15 cm * Vascular involvement (including portal vein, inferior vena cava \[IVC\] and/or hepatic vein) is allowed * Target lesion must be amenable to a SBRT regimen utilizing proton beam therapy (i.e. SBPT) * Prior local liver treatment including surgery, percutaneous ablation, transarterial bland or chemoembolization (TACE), or Y-90 radioembolization is allowed if completed at least 6 weeks prior to treatment start date * Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 to 2 * Life expectance \>= 3 months based on medical comorbidities, tumor extent and other clinical factors as determined by treating physician * Child Pugh score of A or B7 * Absolute neutrophil count (ANC) \>= 1000 cells/mm\^3 (within 45 days of study entry) * Platelets (Plt) \>= 30,000 cells/mm\^3 (the use of transfusion or other intervention to achieve the minimum platelet level is allowed) (within 45 days of study entry) * Hemoglobin (Hgb) \>= 8.0 g/dL (the…