Neoadjuvant Dual Checkpoint Inhibition and Cryoablation in Relapsed/Refractory Pediatric Solid Tumors

Inclusion Criteria: * Informed Consent: Guardian/parent or patient capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol. Written informed consent obtained from the patient/legal representative prior to performing any protocol-related procedures, including screening evaluations. * Age: \>1 year and \<40 years at time of enrollment on study. * Diagnosis: histologically confirmed solid tumors (at time of original diagnosis or relapse), including osteosarcoma, Ewing sarcoma family of tumors, and rhabdomyosarcoma for disease-specific arms. For non-statistical cohort, other types of tumors are eligible, including but not limited to melanoma, hepatic tumors, Wilms tumor, neuroblastoma, and non-rhabdomyosarcoma soft tissue sarcomas. * Measurable/Evaluable Disease: Patients must have at least TWO measurable/evaluable solid target lesions. * Candidate for Cryoablation Therapy: Patients must have at least one tumor available for cryoablation therapy. * Therapeutic options: The patient's cancer must have relapsed after or failed to respond to frontline curative therapy and there must not be other potentially curative treatment options available. Curative therapy may include surgery, radiation therapy in past, chemotherapy, or combination of these modalities. * Performance Status: Karnofsky ≥50% for patients \>16 years of age and Lansky ≥60% for patients ≤16 years of age. …