Metabolic navigation during brain tumor surgery: analysis of a series of 403 patients

Introduction. Metabolic navigation with 5‑ALA is one of methods for intraoperative imaging in neuro‑oncology.Aim. To perform a comparative analysis of sensitivity of metabolic navigation with 5‑ALA during surgery of primary and secondary brain tumors of various histological nature and degree of malignancy.Materials and methods. During the period from 2013 to 2020, our group have performed surgery to 403 patients using metabolic navigation: microsurgical resections were performed in 384 people with brain tumors, 220 of them were with glial tumors, 101 were with intracranial meningiomas, 63 were with metastatic brain damage. Among patients with metastases, 39 patients had a solitary injury, 16 had a multi‑focal injury, so 72 cases of metastatic nodes were considered in this group. Stereotactic biopsies with 5‑ALA‑assistance were performed in 19 people. Metabolic navigation was performed with the drug 5‑ALA, which was taken orally at a dose of 20 mg/kg 2 hours before surgery. Intraoperative fluorescence was evaluated using microscope with a fluorescent module.Results. Metabolic navigation using microscope has a high sensitivity when employed during microsurgery (including repeated implementation of surgery) in cases of anaplastic gliomas (65 % in total, 58 % with bright glow), glioblastomas (94 % in total, 53 % with bright glow), intracranial meningiomas (94 % in total, 64 % – with bright glow). The use of 5‑ALA has significant limitations in sensitivity in cases of diffuse gliomas (46 % – in total, 27 % – with bright glow) and brain metastases (in total 87 % – for the solid part, 52 % – for the bed, with bright glow – 51 %). In diffuse gliomas, the glow areas had significantly higher proliferative index and cell nuclei density than the fluoronegative zones. Among the most important factors affecting the glow of gliomas it can be noted: the status of the IDH1 mutation, the volume of the contrasting part of the glioma according to MRI data, the methionine accumulation index according to positron emission tomography, the tumor blood flow indicators according to the arterial spin marking method – ASL perfusion.Conclusions. Implementation of 5‑ALA navigation with the use of microscope provides high sensitivity in cases of glioblastomas, anaplastic gliomas (especially for detecting of non‑contrasting part of tumor that is not visually altered in the white light of operating microscope) and brain meningiomas. The method is less effective in low‑grade gliomas and intracranial metastases.