BDNF and central nervous system cancer: Plasma levels of BDNF were significantly lower in glioblastoma patients compared to healthy controls. BDNF, along with sTREM‐1 and sHLA‐G, demonstrated a good discriminatory capability for glioblastoma patients, with the best performance achieved when combined (AUC = 0.9534, sensitivity 79.2%, specificity 94.1%). In grade IV glioma, BDNF levels were significantly decreased, suggesting its potential as a diagnostic marker.