Nivolumab With and Without Ipilimumab and Radiation Therapy in Treating Patients With Recurrent or Resectable Undifferentiated Pleomorphic Sarcoma or Dedifferentiated Liposarcoma Before Surgery

Inclusion Criteria: * Adult subjects with treatment naive primary or locally recurrent dedifferentiated liposarcoma (DDLPS) of the retroperitoneum or undifferentiated pleomorphic sarcoma (UPS) of the trunk or extremity will be eligible for inclusion in this study only if all of the following criteria apply. * Patients must be capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the consent form. * Patients must have disease determined to be surgically resectable and candidates for upfront surgery as agreed upon by a multidisciplinary consensus (Surgical Oncology, Medical Oncology, Radiation Oncology) after presentation at sarcoma multidisciplinary conference. Resectable tumors are defined as having no significant vascular, neural or bony involvement. Only cases where a complete surgical resection can safely be achieved are defined as resectable. * Patients will be evaluated by the anesthesia team prior to surgery. * Patient must have recent imaging (computed tomography \[CT\] or magnetic resonance imaging \[MRI\], as appropriate) within 4 weeks of trial enrollment, demonstrating measurable disease as defined by RECIST 1.1. * Patients must have at least one tumor amenable to serial biopsy in clinic or be willing to undergo serial biopsies through image-guided procedures during the neoadjuvant phase of the protocol. Patients must be willing to provide tumor samples at the time points. * Patients must be medicall…