Purpose: To assess the utility of PET/MR in assessing response to neoadjuvant radiation therapy in the treatment of high grade sarcomas.

Participants: Adult patients with potentially curable high grade sarcomas that are being treated at UNC with neoadjuvant radiation therapy followed by potentially curative surgical resection.

Procedures (methods): Patients who are being treated for potentially curable high grade sarcomas with neoadjuvant radiation therapy followed by surgical resection undergo pre-treatment, mid-treatment, and post-treatment PET/MR and the response to treatment is assessed by evaluating change in size and FDG avidity. Patients then undergo curative intent resection and are followed. Their pathology is reviewed for treatment affect as is assessed by percent necrosis, size, and resection margins. Patients are followed and assessed for recurrence.

Investigators propose that a PET/MR study at the midpoint of radiation treatment will accurately predict which patients will respond to neoadjuvant radiation therapy. The study will enroll patients with high-grade sarcomas as identified by preoperative biopsy that will be treated with neoadjuvant radiation into the study. The standard of care for these patients is to receive MRI scans at pre-treatment and post-treatment time points. Patients in this study will receive their standard pre- and post-treatment imaging in the form of PET/MR, with PET conducted simultaneously with MRI, and within the context of the study they will also receive one additional PET/MR at the end of the second week of therapy. These patients will then receive curative intent surgery and be followed in the usual fashion and assessed for local and/or distant recurrent disease. The pathology will be assessed for completeness of resection and percent of necrosis. On the basis of pathology, patients will be classified as responsive or non-responsive to therapy. Quantitative measures from PET and MRI will be computed: the change in PET tumor-mean standardized uptake value (SUV) and tumor size as assessed by MRI, from pre- to post-treatment, and from pre- to mid-treatment. The image-based quantitative measures will be correlated with the pathology outcomes to evaluate predictability of the image measures for treatment response. Patients will be followed with the intent of further correlating image measures with clinical outcomes.

Inclusion Criteria:

• Age ≥ 18 years of age (no upper age limit)
• Signed, IRB-approved written informed consent
• Must have a biopsy-proven high-grade retroperitoneal or soft tissue extremity sarcoma confirmed by independent evaluation of a UNC sarcoma specialized pathologist.
• Must have surgically curable disease as evaluated by initial imaging by our UNC surgeons.
• Must be in acceptable health to undergo radiation therapy and curative intent surgery as assessed by UNC surgeons and radiation oncologist.
• Must be able to understand and comply with study procedures for the entire length of the study.
• Must receive their neoadjuvant radiation therapy and curative intent surgery at UNC Hospitals - Chapel Hill location.
• Women of childbearing potential must have a negative serum or urine pregnancy test performed within 7 days prior to each PET/MRI

Exclusion Criteria:

• Inability to tolerate MRI (e.g., inability to lie flat for >1 hour)
• Presence of pacemaker, intracranial aneurysm clip, bladder stimulator, cochlear implant or metal near eyes or near pelvis that would create excessive imaging artifact
• Poorly controlled diabetes mellitus
• Creatinine > 1.8 mg/dL OR GFR < 30mL/min
• Body Mass Index (BMI) > 35
• Active vaginal bleeding requiring packing and emergent radiation therapy
• Pregnancy or lactating female
• History of a prior malignancy within past 5 years are excluded unless they have been disease free for 3 or more years
• Substance abuse, medical, psychological, or social conditions that may interfere with the patient's participation in the study
• Evidence of distant disease on physical exam or initial imaging
• Medical conditions precluding radiation therapy or curative intent surgery
• Previous radiation exposure precluding radiation therapy
• Had serious reaction to contrast agent
• Incarcerated or otherwise institutionalized at time of enrollment

Adult patients with potentially curable high grade sarcomas that being treated at UNC with neoadjuvant radiation therapy followed by potentially curative surgical resection were to be recruited.

Adverse events collected day of imaging up until time of surgery, an average of 10 weeks.

Small numbers of subjects limit data interpretation.