Plasma PD-L1 levels according to histologic grade and IDH status in patients with gliomas.

Abstract

69 Background: Plasma immune biomarkers such as soluble plasma PD-L1 (sPD-L1) may serve as surrogates of the immune condition of cancer patients and be potential markers of response to different immunotherapy modalities. Very few data exist regarding sPD-L1 in patients with primary brain tumors. Our aim was to study the levels of sPD-L1 in patients with gliomas according to histologic grade and IDH mutation status. Methods: Patients (pts) with grade II to IV gliomas were prospectively enrolled. Single-time-point plasma samples were obtained prior to adjuvant radiotherapy +/- chemotherapy. sPD-L1 determined using ELISA with a rabbit polyclonal anti-PDL1/CD274 antibody as capture reagent. Results: Between February 2017 and August 2019, 44 patients (pts) with gliomas and 12 healthy controls (HC) were enrolled. N=11 grade II, n=9 grade III, n=24 grade IV; n=26 IDHwt, n=18 IDHmut. Higher sPD-L1 levels in glioma pts compared to HC (60.8 vs 47.8 ng/ml, p=0.05). Higher sPD-L1 levels in grade II vs grades III-IV (73.3 vs 60 ng/ml, p=0.09). Higher sPD-L1 in IDHmut grades II-III vs IDHwt grades II-III + IDHmut/wt grade IV (73 vs 59 ng/ml, p=0.07). Non-significantly higher sPD-L1 in grades II-III vs grade IV (73 vs 59 ng/ml, p=0.46). No difference in sPD-L1 in IDHmut vs IDHwt (63.3 vs 59.1 ng/ml, p=0.496), nor in IDHwt vs HC (59.1 vs 47.8 ng/ml, p=0.109). Trend to significance in IDHmut vs HC (63.3 vs 47.8, p=0.062). Conclusions: sPD-L1 levels were significantly higher in glioma pts compared to HC. A trend was seen towards higher sPD-L1 levels in lower-grade (grades II, III) IDHmut gliomas. These findings may indicate a different systemic immune profile for currently defined glioma groups based on histologic grade and IDH status and merit confirmation in a larger sample.