- Have a histologically confirmed diagnosis of STS for which olaratumab and doxorubicin would be appropriate therapy. Participants with a diagnosis of Grade 1 liposarcoma are eligible if there is histological or radiographic evidence of evolution to more aggressive disease. Participants with Kaposi's sarcoma and gastrointestinal stromal tumors (GIST) will be excluded. Participants must have potentially resectable disease (as assessed by the study investigator) and have a primary tumor lesion deemed amenable to serial biopsy.