Circulating Tumor DNA in Soft Tissue Sarcoma

Inclusion Criteria: * Patients must have histologically confirmed high-risk extremity or retroperitoneal liposarcoma, leiomyosarcoma and undifferentiated pleomorphic sarcoma. * Patients must have archival tissue from the diagnostic biopsy available. * Deemed appropriate for preoperative or postoperative radiotherapy and curative surgery following patient assessment by radiation oncologist and surgical oncologist. * Age 18 years or older. * Eastern Cooperative Group (ECOG) performance status ≤ 2 * Ability to understand and willing to sign a written informed consent document and comply with study requirements. Exclusion Criteria: * Patients with benign histology * Patients with prior malignancy within previous 5 years or concurrent malignancy other than adequately treated basal cell carcinoma of skin or carcinoma in-situ of cervix. * Patients with planned neo-adjuvant chemotherapy. * Patients with regional nodal disease or unequivocal metastases * Uncontrolled inter-current illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.