Pre- and post-operative plasma glial fibrillary acidic protein levels in patients with newly diagnosed gliomas

Therapies that disrupt or repair blood-brain barrier integrity can result in major changes in MRI images even when the tumor volume remains constant. Thus, a reliable blood-based tumor biomarker could significantly improve clinical care and research studies in these patients. This study was performed to assess plasma concentrations of glial fibrillary acidic protein (GFAP) in patients with high- and low-grade gliomas before and after debulking surgery. Pre-operative plasma was collected from 33 patients with radiation- and chemotherapy-naïve gliomas. Additional plasma was collected 24-48 h post-operatively from 23 of these patients. Plasma GFAP (pGFAP) concentrations were determined using an electrochemiluminescent immunoassay and were analyzed as a function of tumor grade, tumor GFAP expression, the integrity of the blood-brain barrier, and post-operative status. Detectable pGFAP levels (≥ 0.04 ng/mL) were found pre-operatively in 52 % of patients and post-operatively in 96 %. Detectable pGFAP was more common in patients with WHO grade IV (100 %) than WHO grade III (56 %) or WHO grade II gliomas (20 %). No patient with undetectable GFAP had WHO grade IV glioma. Higher pGFAP concentrations were also associated with contrast enhancement but not related to tumor GFAP expression. GFAP is commonly detected in the plasma of patients with high-grade gliomas. pGFAP levels rise rather than fall following debulking surgery which is probably a result of surgical trauma. GFAP remains a potentially informative plasma biomarker for gliomas. Longitudinal studies are required to correlate pGFAP levels with patient outcomes.