Radiation Therapy With Protons or Photons in Treating Patients With Liver Cancer

Inclusion Criteria: * Pathologically (histologically or cytologically) or radiographically-proven (based on the American Association for the Study of Liver Diseases \[AALSD\] criteria) unresectable or locally recurrent hepatocellular cancer prior to registration * Appropriate stage for study entry based on the following diagnostic workup: * All patients must have computed tomography (CT) scan chest/abdomen/pelvis with multiphasic liver CT scan prior to registration; if CT contrast is contraindicated, CT chest without contrast and magnetic resonance imaging (MRI) of abdomen is permitted * Participants must have measurable disease at study entry, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded) as \> 2 cm with conventional techniques or as \> 1 cm with spiral CT scan * Patient must have 3 or fewer single or multinodular tumors; for patients with a single lesion, lesion must be 15 cm or less in greatest dimension; for patients with two lesions, no lesion may be greater than 10 cm in greatest dimension; for patients with three lesions, no lesion may be greater than 6 cm in greatest dimension; portal vein involvement or thrombosis combined with a single lesion that is \>= 1 cm and =\< 15 cm in greatest dimension is allowed * Age \>= 18 * Zubrod performance status 0-1 within 30 days prior to registration * Negative urine or serum pregnancy test for women of childbearing potential within 7 days prior t…