(P 453) OUTCOMES OF PLEOMORPHIC LIPOSARCOMA PATIENTS FOLLOWING MULTI-DISCIPLINARY MANAGEMENT WITHIN A TERTIARY CANCER CENTER

Objective: Given the ultra-rare incidence of pleomorphic liposarcoma (PLPS), management of this subtype of soft tissue sarcoma (STS) is based on small retrospective studies. Here we report our institutional series of outcomes for PLPS patients (pts).

Methods: Clinicodemographic and treatment-related information from all PLPS pts treated between 1/2015-4/2025 were extracted from our database. Time-to-event analyses (RFS/OS) were evaluated by Kaplan-Meier method.

Results: We identified 31 PLPS pts. The median age was 66 (26-97), and 51.6% were female. The median primary tumor size was 10 cm (1.7-37.3), with 23 (74%) arising from the extremities, and 28 (90%) FNCLCC grade 3. At presentation, 9 pts (29%) had stage II disease, 19 (61.3%) stage III, and 3 (9.7%) stage IV; 11 pts developed distant metastases on treatment. The most common sites were lungs (12/14 - 85.7%), liver (8/14 - 57%), bones (7/14 - 50%), and soft parts (6/14 - 43%). 28 pts were managed for stage II/III PLPS; 17 (60.7%) underwent neoadjuvant/adjuvant RT, 8 (28.6%) received chemotherapy, and 6 underwent resection alone. 2/28 (7.1%) were deemed inoperable. Of the 15 pts that underwent resection at our institution, all had R0/R1 margins. Median follow-up was 16 months (m). 4/26 (15.4%) and 11/26 (42.3%) pts developed local and distant relapses, respectively; 1 and 5-year distant RFS were 65.1% and 40.5%. The median OS of the entire population was 23.3 m, with 1 and estimated 5-year OS of 87.1% and 37.3%. Among 26 pts managed with curative intent, median OS was 51.9 m, with 5-year OS of 46.9%. 15 pts (45.1%) were managed for advanced disease and received at least one line of therapy. The 1st-line was doxorubicin (dox)-based in 7/15 pts (46.6%), with only two responses (13.3%). The median PFS on 1st-line was 2.9 m. Only half of the pts received a 2nd-line regimen, due to fast PD and PS deterioration. Four pts underwent anti-PD-1-based regimens, with no responses.

Conclusion: PLPS is an aggressive STS, with high metastatic potential and poor response to chemotherapy and immunotherapy. Surveillance scans may require comprehensive imaging, due to the common metastases beyond the lung in PLPS.