What is the utility of whole-body PET/MRI in the staging of myxoid liposarcoma?

Abstract

Myxoid liposarcoma is a soft tissue sarcoma with a unique predilection for metastasis to atypical sites compared to other soft tissue sarcoma histologic subtypes. Does a whole-body (PET/MRI or PET/CT) staging approach, compared to current National Comprehensive Cancer Network (NCCN) guidelines, improve our ability to identify metastatic disease in myxoid liposarcoma? A retrospective analysis identified 31 patients diagnosed with myxoid liposarcoma between 2015 and 2022. Ten patients were staged with standard guidelines and 21 with a whole-body PET modality. Patients who did not complete any staging or had their definitive care performed outside our institution were excluded. In the whole-body group, three (14.3%) patients were found to have metastatic disease on initial presentation, while none had metastatic disease in the standard group. During post-treatment surveillance, two patients in the standard group (n = 10) had new metastases discovered by CT chest with/without MRI spine. Three patients in the whole-body group developed new metastases, which were discovered by whole-body PET/MRI in one and MRI spine in two patients. The median SUVmax of the primary tumor site was 2.8 (range 2.3, 3.4), and for metastasis detected on follow-up imaging, the median SUVmax was 3.2 and 2.6 for the whole-body and standard groups, respectively. Whole-body PET modalities for staging myxoid liposarcoma appear to detect initial metastatic disease and new disease during surveillance, at least as well as current NCCN guideline-recommended modalities. Given that the avidity of myxoid liposarcoma is low, the added value of PET imaging may be limited.