Abstract 
Introduction: 
Malignant primary brain tumors are classified according to histologic grading and high grade tumors are among the most aggressive cancer. Thus, accurate diagnosis and progression detection is imperative for brain tumor patients. Although some of serum biomarkers have been reported for brain tumor, none of them are currently used in routine practice because of imprecision or inconvenience. We sought to identify potential biomarker for diagnostic or prognostic prediction in primary brain tumors. 
Methods:
A total of 74 patients were retrieved from supratentorial glioma patient cohort designed for intraoperative goal-directed therapy between 2013 and 2015. Data analysis included patient demographics, co-morbidities, tumor histology, and serum biomarkers, including lactate, lactate dehydrogenase, fibrillary acidic protein, S100B, neuron-specific enolase, and neutrophil gelatinase-associated lipocalin. 
Results:
Serum lactate level is significantly higher in patients with high grade tumors than that of low grade tumors (p=0.011). However, the remaining biomarkers were not significantly different. Receiver operating characteristic analysis of serum lactate yielded area under the curve of 0.705 in discriminating high grade from low grade brain tumors. Using cut-off values of 2.0 mmol/L, serum lactate measurement yielded a sensitivity of 45% and specificity of 90.7% in the prediction of high grade gliomas. Elevated lactate was also significantly related to poor progression-free survival with hazard ratio (HR) of 1.658 and 95% confidence interval (CI) from 1.078 to 2.548 (p = 0.021) and overall survival (HR, 2.049; CI, 1.006–4.174; p = 0.048 ).
Conclusions:
  Elevated preoperative serum lactate level predicts higher grading of primary brain tumor. High serum lactate is significantly associated with poor progression-free survival for patients with brain tumor. Serum lactate measurement may have potential as a practical biomarker in the treatment planning of brain tumor.

Preoperative serum lactate measurement as a prognostic biomarker for patients with primary brain tumor