(P 292) OUTCOMES IN PLEOMORPHIC LIPOSARCOMA OF THE EXTREMITY AND TRUNK: IS MULTIMODALITY THERAPY INDICATED?

Objective: In comparison to the more common histologic subtypes of liposarcoma (e.g., well differentiated/dedifferentiated; myxoid round cell), pleomorphic liposarcoma (PLPS) is poorly understood but generally regarded as more aggressive, with a high risk of distant metastasis. In this study, we sought to 1) assess outcomes after surgery for primary, non-metastatic PLPS and 2) explore indications for multimodality therapy (e.g., perioperative chemotherapy, radiation therapy) in this ultra-rare malignancy.

Methods: Clinicopathologic data were retrospectively collected for eligible adult patients treated from 2002-2019 at our sarcoma referral center. Descriptive data was summarized and Kaplan-Meier plots were constructed for overall survival (OS) and crude cumulative incidences (CCI) of disease-specific death (DSD), local recurrence (LR) and distant metastasis (DM). Univariable models were performed to assess the association of specific variables of interest (e.g., tumor size) on outcome.

Results: In total, 51 PLPS patients were included in this study. Mean tumor size was 9.7 cm. Tumors originated mostly in the extremity (67%), were deep in location (73%), and high grade (FNCLCC 3/3, 78%). All patients underwent complete (R0/R1) resection. Chemotherapy was given in 33% of patients and radiation therapy in 69%. With a median follow-up of 62 months, OS was 76% at 5 years. CCI of DSD, LR and DM at 5 years was 16%, 2% and 26%. Greater tumor size was observed to be strongly associated with worse OS (p = 0.002) and DSD (p = 0.006). Survival did not seem to be affected by pre-referral inadequate excision once patients (n = 18) underwent re-excision at our center. A separate subgroup of patients (n = 14) was identified with smaller (mean: 5.4 cm), superficial, lower grade tumors who underwent surgery alone without any DSD.

Conclusion: In primary, non-metastatic PLPS, adequate surgery combined with perioperative chemotherapy and radiation therapy, when appropriate, is associated with favorable outcomes. Subgroups with potentially better clinical outcomes likely exist suggesting heterogeneity within PLPS. Multidisciplinary collaborative efforts across sarcoma centers are needed to better characterize these subgroups and determine the optimal strategies for management.