Testing the Addition of Nivolumab to Chemotherapy in Treatment of Soft Tissue Sarcoma

Inclusion Criteria: * Histologically confirmed cutaneous or visceral angiosarcoma, where curative treatment is either not possible or curative modality therapy is declined by the subject. Note: If a subject declines curative modality therapy, the reason must be documented (e.g. excessive morbidity to necessary surgery) * Note: Radiation induced angiosarcomas are permitted * All local diagnostic slides AND 5 x 4-6 micron unstained slides from diagnostic tumor tissue should be available for retrospective central pathology review * Must have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. Per RECIST v1.1, clinical lesions will only be considered measurable when they are superficial and \>= 10 mm diameter as assessed using calipers or ruler (e.g. skin nodules). For the case of skin lesions, documentation by color photography including a ruler to estimate the size of the lesion is required. When lesions can be evaluated by both clinical exam and imagining, imaging evaluation should be undertaken since it is more objective and may also be reviewed at the end of the study. The same method of measurement should be used throughout the study, preferably performed by the same investigator. Areas previously radiated must have demonstrated disease progression at some point over the past 6 months and growth must be subsequent to the last line of anti-cancer directed therapy (e.g. chemotherapy, radiation therapy, surgery) * Not pregnant and not nu…