Prevalence of tumor-infiltrating lymphocytes and PD-L1 expression in the soft tissue sarcoma microenvironment
The prognostic and predictive implications of programmed death-ligand 1 (PD-L1) is unknown in sarcoma. We sought to examine the immune milieu in sarcoma specimens. We evaluated PD-L1 expression by immunohistochemistry in sarcoma specimens and quantified tumor-infiltrating lymphocytes (TIL). We correlated expression with clinical parameters and outcomes. Fifty sarcoma patients treated at Memorial Sloan Kettering Cancer Center were selected. Using the DAKO PD-L1 immunohistochemistry assay and archival formalin-fixed paraffin-embedded tissue specimens; PD-L1 expression was examined. Macrophage and lymphocyte PD-L1 status was determined qualitatively. TIL was quantified. Associations between PD-L1 expression in tumor, macrophages and lymphocytes, TIL and clinical-pathological characteristics were performed. The median age was 46 years (range, 22-76), and 66% of patients were men. Tumor, lymphocyte and macrophage PD-L1 expression was noted in 12%, 30% and 58%, respectively, with the highest prevalence in gastrointestinal stromal tumors (29%). Lymphocyte and macrophage infiltration was present in 98% and 90%, respectively. There was no association between clinical features, overall survival and PD-L1 expression in tumor or immune infiltrates. Lymphocyte and macrophage infiltration is common in sarcoma, but PD-L1 tumor expression is uncommon in sarcoma with the highest frequency observed in gastrointestinal stromal tumors. There was no association between PD-L1 expression, TIL and clinicopathological features and overall survival; however, this is limited by the heterogenous patient sample and minimal death events in the studied cohort.