Myxoid liposarcoma: treatment outcomes, metastatic pattern and volumetric analysis

Myxoid liposarcoma (MLPS) is a rare subtype of soft tissue sarcoma. This entity has a specific clinical behavior, characterized with a distinct pattern of hematogenous spread, as well as with a unique radiosensitivity and chemosensitivity. Oncologic results, metastatic patterns and treatment response after multimodal therapy were evaluated in a unicentric patient cohort.

Patients with myxoid liposarcoma were retrospectively analyzed in a single institution analysis (n = 31). Oncologic outcomes were evaluated in 28 patients with localized MLPS treated with multimodal therapy in curative intent. Metastatic pattern was analyzed in additional 3 patients with initially metastatic disease. In patients treated with concomitant MR-guided hyperthermia in the preoperative setting (n = 7), tumor size response was evaluated longitudinally during radio(-chemo)therapy in thermometry MRIs and before surgery (based on preoperative imaging).

The median follow-up was 4.1 ± 1.0 years. The most common anatomic localization was the lower extremity (78.6%). The 5‑year rates for oncologic outcomes in 28 patients treated in curative intent were 91.7% (± 8.0%) for overall survival (OS), 77.4% (± 11.0%) for local control (LC), 60.1% (± 10.6%) for distant metastasis-free survival (DMFS) and 55.4% (± 11.1%) for disease free survival (DFS). Excellent 5‑year LC (94.7 ± 5.1%) was demonstrated for the cohort excluding 5 patients treated for local recurrences. Most patients had good pathologic response (< 10% vital tumor tissue) following neoadjuvant treatment (82.4%, 14/17). However, this did not correlate with oncologic outcomes. A specific pattern of distant metastases has been observed, with predilection for soft tissues as the most common metastatic site. Furthermore, no isolated pulmonary metastases were observed. The MR analysis demonstrated a significant tumor size reduction (≥ 25%) of the initial tumor volume in 85.7% (n = 6/7) patients. No local recurrences and no distant metastases were observed in patients with significant MR size reduction.

Sequential MRIs during preoperative radiotherapy of myxoid liposarcoma show distinct patterns of the known size reduction of this specific subentity. Our analysis of metastatic patterns demonstrate mostly soft tissue metastases, no patient experienced isolated pulmonary metastases.