(P 359) ROLE OF PERFUSION WEIGHTED IMAGING WITH DYNAMIC CONTRAST ENHANCED (PWI/DCE) FOR THE TREATMENT ASSESSMENT OF EXTREMITY SOFT-TISSUE NON-MYXOID UNDIFFERENTIATED PLEOMORPHIC SARCOMA

Objective: Undifferentiated pleomorphic sarcomas (UPS) are the largest subgroup of soft tissue sarcomas. Post-therapeutically demonstrate hemosiderin deposition, granulation tissue formation, fibrosis, and calcification. The aim of this study is to determine the value of advanced MRI with Perfusion-WI (PWI/DCE) in evaluating UPS treatment response.

Methods: A retrospective IRB-authorized study included 26 patients with extremity non-myxoid UPS who underwent pre-surgical imaging and surgical resection from February 2021-October 2022. Treatment-induced tumor necrosis (TIN) in surgical specimens separated cases as Good Responders (GR: TIN>90%, 13 patients), Partial-Responders (PR: 89-31%, 8 patients), and Non-Responders (NR: < 30%, 5 patients). Volumetric tumor segmentation was performed on routine advanced MRI at the Baseline (BL), Post-Chemotherapy (PC), and Post-Radiation (PRT) pre-surgical time points. DCE-PWI images were manually contoured using the MIM-licensed software, and the final contours were exported as DICOM files. A Python-based software application developed in our institution automatically extracted 7 semi-quantitative perfusion kinetic parameters. Statistical analyses compared good vs. partial/non-responders.

Results: At post-radiation (PR), 72.7% of GR displayed Capsular morphology (p=0.00007), and 100% displayed a TIC-type 2 (p=0.00002). 85.7% of partial responders showed Unipolar morphology (p=0.0001), and 71.4% expressed a TIC type 5 (p=0.0662). 60% of non-responders showed Bipolar morphology (p=0.1455), and 80% expressed a TIC type 5 (p=0.0742). The statistical analysis comparing the 7 semi-quantitative metrics separating good vs. partial/non-responders demonstrated statistical significance (p=0.0164) for wash-in rate (WiR).

Conclusion: UPS treatment assessment can rely on whole tumor PWI/DCE time-intensity curve (TIC), semi-quantitative and morphologic analysis, where TIC II, capsular enhancement, and high WiR correlate with successfully treated sarcomas with 90% or more TIN. DCE qualitative TIC and combined morphologic and semi-quantitative kinetic analysis demonstrate significant potential to serve as predictors of response in UPS.

Clinical Relevance: Perfusion Weighted Imaging (PWI) with Dynamic Contrast-Enhanced (DCE) imaging can assess treatment response in non-myxoid undifferentiated pleomorphic sarcoma.