PD-L1 expression in soft tissue sarcomas and its prognostic implication.

Abstract

e14261 Background: The expression rate of PD-L1 in human malignant tumors paid a lot of attention and has been reported to vary from 19% to 92%, and the expression of PD-L1 was associated with poor prognosis of various human and may predicted the response to immune checkpoint inhibitors. The purpose of this study to investigate the expression of PD-L1 and its clinic-pathological feature in soft tissue sarcomas (STS). Methods: We collected Paraffin embedded tissue of 50 Patients with STS retrospectively from the archives of Pathology and oncology Department, Ain Shams University Hospitals from 2011-2017.then we correlated between PD-L1 expression and the clinico-pathological features. For PD-L1 expression we followed the Cologne 6-step proportional scoring system, using the rabbit monoclonal antibody (E1L3N 13684) and Tumors with > /10% membranous stained cells were considered to be positive for expression. The differences among variables were calculated by chi-square test. Results: PD-L1 expression was found in 12 (24%) of cases. Of all sarcoma subtypes , desmoid tumors had the highest prevalence of PD-L1 expression noted in 2/3 (66%) of samples followed by GIST 2/4(50%), then liposarcoma 3/11(27%). In addition, there were 2 rhabdomyosarcoma cases with tumor positivity for PD-L1 expression. We found that STS patients with PD-L1 expression have shorter survival with a median OS 11 vs 19 months (p-value = 0.1) as well as a mean PFS 6 vs 11 months (p-value = 0.1) in PD-L1 positive and negative respectively; this finding considered as clinically significant, but not reached to statistical significant . Conclusions: We report here that PD-L1 expression is as prognostic factor for poorer outcome. This finding may be clinically significant but does not reach the statistically significant levels due to small number of samples included. Its role beyond that of a prognostic biomarker remains to be established in the context of larger clinical trials. Clinical trial information: 31/2017.

Evaluation of PD-L1 Expression in Undifferentiated Pleomorphic Sarcomas, Liposarcomas and Chondrosarcomas

“…The lack of established protocols for evaluating PD-L1 immunohistochemistry staining in sarcomas is a major challenge, given that different histological subtypes might have different cutoff values. Existing studies often adapt pre-existing protocols [ 22 , 23 ], but the absence of consensus results in interstudy variation in cutoffs for positive expression.…”