**Abstract**

Brain tumor is an abnormal growth of mass of cells in (or) around the brain. Brain tumors can be malignant (cancerous) or being non-cancerous. It is the most common malignant primary intracranial tumors of central nervous system. Brain tumor can affect brain function if they grow large enough to press on surrounding nerves, blood vessels and tissues. Only one third of tumors formed in the brain are formed as cancerous cells. Brain tumors release molecular information to the circulation. Liquid biopsies collect and analyse tumor component in the body fluid and there is an increasing interest in investigation of liquid biopsies as substitute from tumor markers. Tumor-derived biomarkers include nucleic acids, proteins and tumor-derived extracellular vesicles that accumulate in blood (or) cerebrospinal fluid. Circulating biomarkers like O-6-methylguanine DNA methyl transferase, epidermal growth factor, isocitrate dehydrogenase, circulating tumor cells, circulating cell free micro RNAs, circulating extracellular vesicles plays and important role in causing a cancer. Brain tumor can be treated by surgery, radiation therapy (or) targeted therapy. Radiation therapy is often given afterwards. As a consequence, the most recent review reviewed the present state of research with the hopes of discovering a new brain tumor inhibitor that may be used to treat advanced malignancies.

**Keywords:** brain tumor, bio-markers, circulating bio-marker, O-6-methylguanine DNA methyl transferase

#### **1. Introduction**

A brain tumor is one of the most malignant tumors in humans. It accounts for approximately 1.35% of all malignant neoplasm and 29.5% of cancer-related death [1]. Brain and CNS tumors include tumors of the brain, cranial nerves, spinal nerves, spinal cord, and the meninges. The tumor can be broadly classified as malignant and non-malignant (or benign) tumors. The world health organization (WHO) classification specifies a grading system ranging from grade, whereas, grade III/IV are malignant or high grade [2]. A brain tumor is a diverse group of neoplasm with different types of primary brain tumor (or) metastatic cancer. The most common malignant brain tumors are glioblastoma that originates from glial cells [3]. Metastatic brain tumors (MBTs) account for the majority of an intra-axial brain tumors in adult patients. It is estimated that up to one-third of patients diagnosed with a primary malignancy will develop central nervous system metastatic lesions during their disease course [4]. Pediatric central nervous system (CNS) tumors are the second most common childhood malignancy and the most

common solid tumor in children [5]. Early diagnosis and treatment of brain tumors are imperative to prevent permanent damage to the brain (or) death of the patient. At the level of medical data analysis, the features election and classification process are the ones intensively used to identify the patient data whether it is normal (or) abnormal [6]. Once the tumor is detected under the microscope. It is often too late for effective treatment prognosis in patients is correlated with the stage of disease at the time of detection and therefore, it is important to find markers that allow the early detection of the tumor. The treatment options for patients with brain metastases include corticosteroids, surgery, chemotherapy, whole-brain radiation therapy, and stereotactic radiosurgery [7]. A patient with a brain tumor suffers from a significant problem called neurocognitive dysfunction. To diagnose the neurocognitive dysfunction in the brain tumor needs new strategies for the early initiation of appropriate neurocognitive rehabilitation. Raman spectroscopy technique is used for the differentiation of brain tumors. This leads to accurate identification of two essential factors such as brain tumor boundary and the complete resection of the tumor which is important for removal of glioma tumor in brain surgery [8].
