Background: 

Angiosarcoma (AS) is an uncommon highly aggressive sarcoma that exhibits endothelial differentiation and represents less than 1% of all STS, with an annual incidence of 300 cases in the US. In locally advanced or metastatic disease, initial responses to cytotoxic chemotherapy are common; however, the duration is limited, and most patients will eventually succumb to metastatic disease. Common regimens used include weekly paclitaxel, gemcitabine + docetaxel and immunomodulatory agents such as steroids + cyclophosphamide. Unfortunately, once metastasized, median OS is only 3 to 12 months. Targeted therapies for AS including VEGF blocking have limited efficacy and the predictive value of recurrent genetic alterations is still not well characterized. More recently, we’ve seen reports of exceptional responses with use of Immunotherapy (IO) in some AS patients1,2. However, predictor factors for IO-response in sarcoma are in an early stage of development. Understanding distinct molecular drivers as well as immune microenvironment appears to be crucial to predict these responses3 . Herein, we performed molecular analyses to identify new, potential treatment options including immunotherapy for patients with AS.