Circulating Tumor DNA in Soft Tissue Sarcoma

This study is investigating whether tiny fragments of cancer DNA floating in the blood (called "circulating tumor DNA" or ctDNA — like a liquid biopsy) can be used to monitor soft tissue sarcoma (cancer in muscles, fat, or connective tissue) and detect early signs of recurrence after treatment. **You may be eligible if...** - You are 18 years or older - You have been diagnosed with a specific high-risk soft tissue sarcoma (liposarcoma, leiomyosarcoma, or undifferentiated pleomorphic sarcoma) in the limbs or abdomen - Tissue from your original biopsy is available for research - Your doctor has recommended pre- or post-surgery radiation therapy combined with surgery aimed at curing the cancer - You are in generally good health **You may NOT be eligible if...** - Your tumor is non-cancerous (benign) - You have had another cancer within the past 5 years (with some exceptions for minor skin cancers) Talk to your doctor to see if this trial is right for you.