The purpose of the study is to determine whether the continuing detection of cell-free plasma tumor DNA (ptDNA), circulating tumor cells (CTCs), and cytokines (chemicals that help the immune system communicate) in the blood can help to better evaluate the status of sarcomas over the course of therapy. 

Plasma tumor DNA is free floating DNA from the tumor found in the blood stream. Circulating tumor cells are cells that have left the tumor and moved into the blood stream. Cytokines are proteins that cells release to stimulate or calm down the immune system. 

Participants blood samples will be collected at key timepoints throughout their standard treatment and this study does not require additional study visits to participate. After the completion of treatment, blood samples will be collected every 3 months around the same time as other scans, for 12 months total. 

The results will be analyzed over time to determine if these tests are able to improve the ability to determine how therapy has impacted sarcomas.