Detection of metastasis in myxoid liposarcoma: WB-MRI versus CT-CAP.

OBJECTIVE

To describe the incidence and distribution of skeletal and extraskeletal metastases in myxoid liposarcoma (MLS) on staging whole-body MRI (WB-MRI) and CT chest, abdomen, and pelvis (CT-CAP), to inform initial staging protocols.

MATERIALS AND

METHODS

Retrospective review of staging WB-MRI and CT-CAP performed within 60 days in 57 histologically proven MLS cases at a quaternary sarcoma center (October 2018 to August 2022). Findings were classified by consensus as normal, indeterminate, or metastasis (bone, lung, and soft tissue). Primary tumor characteristics were compared between metastatic and nonmetastatic cases.

RESULTS

Fifty-seven patients (25 female, 32 male; mean age 46 years) comprised 55 new diagnoses and two recurrences. Median WB-MRI to CT-CAP interval was 0 days (IQR 0 to 8). Among new diagnoses, WB-MRI classified 76% as normal, 13% indeterminate, and 11% metastatic; CT-CAP proportions were 82%, 11%, and 7%. All bone metastases and indeterminate osseous lesions on WB-MRI were occult on CT-CAP or outside the CT field of view (FOV). All extrapulmonary soft tissue lesions within the CT FOV were seen on both. Small pulmonary nodules (< 5 mm) were seen only on CT. All metastases occurred in deep tumors; mean maximum dimension and volume were significantly larger with metastases (19.3 vs. 10.6 cm, p = 0.035; 1566 vs. 399 cm3, p = 0.007).

CONCLUSION

Osseous metastases and indeterminate lesions were more frequent on WB-MRI than CT-CAP, whereas extrapulmonary soft tissue metastases were seen on both within the CT FOV. CT chest retained value for small pulmonary nodules. These findings support prospective evaluation of WB-MRI plus CT chest for initial staging in MLS.