1714P - PD-L1 expression as a potential therapeutic target and prognostic biomarker in well-differentiated and dedifferentiated liposarcoma

Abstract

BackgroundFor liposarcoma (LPS), the mainstay of treatment is still surgical resection. Recently, some researchers suggested that immune checkpoint inhibitor may have a clinical activity in well-differentiated (WD) and dedifferentiated (DD) LPS. We aimed to evaluate the expression level of programmed death ligand 1 (PD-L1) and determine its relationship with clinical outcomes in WD/DD LPS. MethodsAll patients diagnosed with WD/DD LPS at Asan medical center from 1989 to 2017 were identified and their clinical information were obtained from our medical database. PD-L1 testing was performed with previously-collected surgery or biopsy tissue by Immunohistochemistry (IHC). ResultsTotal 152 patients who were pathologically diagnosed with WD (n=74) or DD (n=78) LPS and had available tissue for PD-L1 IHC assay were included in this retrospective analysis. The median age was 58 years (range, 19—87) with males comprising 59.2%. By primary site, abdomen-pelvis (69.7%) was most frequently involved. Most patients (98.7%, n=150) were presented with localized disease at the time of diagnosis and every patient with localized disease except one with high-perioperative risk (n=149) underwent curative-intent surgical resection. PD-L1 positive (tumor proportion score ≥1%) rate was 31.1% and 51.3% in WD and DD LPS, respectively. In WD LPS, PD-L1 positivity, as well as abdomen-pelvis origin, R1/2 resection, and no adjuvant radiotherapy, was associated with shorter recurrence-free survival (RFS) (vs. PD-L1 negativity, 31.3 vs. 99.8 months; P=0.014) and remained significant in the multivariate analysis (HR, 2.7, P=0.028). In DD LPS, on the other hand, PD-L1 expression had no statistical significance in multivariate model for RFS. Overall survival was not properly compared due to the small number of death events. ConclusionsOur findings indicate that decent portion of WD/DD LPS patients were positive for PD-L1 expression, and it might be a negative prognostic biomarker in surgically-resected WD LPS. This provides a rationale for future clinical trials of immune checkpoint inhibitor for patients with PD-L1-positive WD/DD LPS. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.