Does the expression of glial fibrillary acid protein (GFAP) stain in glioblastoma tissue have a prognostic impact on survival?

Objective. - Several parameters are known to predict the survival of glioblastoma (GB), including extent of resection and MGMT promotor methylation. Staining for glial fibrillary acidic protein (GFAP) is a common component of routine histological work-up, but its clinical utility in GB is unclear. The aim of the present study was to analyze the predictive value of quantitative GFAP measurements for survival of patients with GB. Methods. - All subjects in our institutional database of patients with primary GB who underwent surgery between 2011 and 2014 with examination of immunohistochemical staining of GFAP were included. Percentage GFAP staining was measured in 5% increments (5-100%). Univariate and multivariate analyses were performed between GFAP values and survival data. Clinically relevant cut-offs for GFAP staining were identified by receiver operating characteristic (ROC) curves. Results. - The final cohort consisted of 272 GB patients with available quantitative GFAP measurements (mean age, 62 (+/- 11.1) years, 117 females [43%]). Overall survival was 11.4 months (+/- 8.6). Median GFAP value was 70% (range, 5-100%). The ROC curve showed the clinically relevant cut-off for GFAP at 75% (area under the curve: 0.691). Accordingly, GB patients with GFAP > 75% presented poorer survival on Kaplan-Meier survival estimation (P= 0.021). Multivariate analysis adjusted for age, extent of resection, preoperative Karnofsky performance status scale, IDH1 mutation and MGMT methylation status confirmed the independent predictive value of GFAP >= 75% for overall survival (P= 0.032). Finally, patients with GFAP >= 75% showed significantly poorer long-term survival than those with GFAP < 75%: 5.8% vs. 15.2% (P= 0.0183) and 0.8% vs. 8% (P = 0.0076) for 2- and 3-year survival, respectively. Conclusion. - Quantitative immunohistochemical assessment of GFAP staining could provide a novel biomarker for overall and especially long-term survival of patients with GB. Prospective multi-center validation of the prognostic value of GFAP for GB survival is needed. (C) 2020 Elsevier Masson SAS. All rights reserved.