Checkpoint Inhibition In Pediatric Hepatocellular Carcinoma

Inclusion Criteria: * Age: Patients must be \<30 years of age at the time of study enrollment. * Diagnosis: Patients must have relapsed/refractory, histologically confirmed HCC to be eligible for enrollment. Patients with hepatocellular neoplasm not otherwise specified (HCN NOS) will also be eligible. * Disease Status: Participants must have measurable disease by RECIST criteria, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions) measured at ≥20 mm with conventional technique or ≥10 mm with spiral CT scan, MRI, or calipers by clinical exam. See Section 10 for the evaluation of measurable disease. * Performance Level: Karnofsky performance status ≥ 60% for patients ≥ 16 years of age or Lansky ≥ 60% for patients \< 16 years of age. * Prior Therapy: Patients must have fully recovered from the acute toxic effects of all prior anti-cancer therapy. * Patients must not have received standard or targeted treatment regimens within 14 days of initiation of treatment with pembrolizumab. * Patients must not have received prior radiotherapy within 7 days of initiation of treatment with pembrolizumab. Patients who have experienced radiation-induced adverse events must recover to a grade 1 prior to enrollment. * Organ Function Requirements: Participants must have normal organ and marrow function as defined below: * Adequate Bone Marrow Function defined as: …