Immu-13. Pd-l1 Expression Predicts Survival in Newly Diagnosed Glioblastoma Patients Receiving Vaccine Immunotherapy but Not Standard Therapy Alone
Year: 2017
Type: conference-abstract
Abstract: While PD-L1 expression on tumors and immune cells can mediate immunosuppression, limited data exists about the correlation of PD-L1 to clinical outcomes in GBM. Here we evaluate outcomes of GBM patients treated with standard radiation and temozolomide therapy alone, or with concurrent vaccine immunotherapy, stratified by PD-L1 expression on tumor and circulating myeloid cells. Newly diagnosed GBM patients treated with standard chemoradiation (n=71) or a clinical trial of heat shock protein vaccination (n=32) had tumor PD-L1 expression evaluated by immunohistochemistry (SP142 clone) and characterized as negative-low (0-5%), medium (5-50%), or high (>50%) expression. PD-L1 expression on circulating myeloid cells (CD11b+) was evaluated by flow cytometry at surgery, and patients were divided into PD-L1hi/PD-L1lo subsets relative to the median. Radiographic progression and overall survival were recorded. Among patients treated with standard chemoradiation, significant tissue PD-L1 expression (medium-high) was observed in 36%. Myeloid cell PD-L1 expression ranged from 3-81% with a median of 21%. No correlation between tumor and myeloid PD-L1 expression was observed (R2=0.008; p=0.53). PFS for the peripheral PD-L1hi vs. PD-L1lo groups was 9.5 vs. 8.8 months (HR =0.76; p=0.37). No difference was observed in OS for these groups (HR = 0.75; p=0.40). By comparison, in patients treated with vaccine therapy, PFS for the peripheral PD-L1hi vs. PD-L1lo groups was 11.3 vs. 27.2 months (HR=3.1, p=0.009), and OS was 18.0 vs. 44.7 months (HR 3.3, p=0.007). Tumor characterization as PD-L1 negative-low vs. medium-high did not impact PFS (HR=0.84, p=0.69) or OS (HR=0.89, p=0.56). Expression of PD-L1 on tumor and circulating myeloid cells in GBM patients receiving standard chemoradiation did not significantly impact survival. In patients treated with concurrent vaccine immunotherapy, only myeloid cell PD-L1 expression correlated with survival. These results suggest that checkpoint inhibition for GBM may only be effective when combined with other immunotherapeutic strategies.
Source: Neuro-Oncology
Language: English
Subfield: Genetics
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2767449605