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Neuroscience

Glioblastoma: The Deadliest Brain Tumor

Glioblastomas (also known as GBM) are the most prevalent form of adult brain tumors, accounting for approximately 78% of all malignant tumors. They are usually very aggressive, which means they grow rapidly and spread quickly. The following article offers a brief overview of the symptoms, diagnosis, treatment, as well as different types of glioblastomas.

Abstract

Glioblastomas (also known as GBM) are the most prevalent form of adult brain tumors, accounting for approximately 78% of all malignant tumors. They are usually very aggressive, which means they  grow rapidly and spread quickly. The following article offers a brief overview of the symptoms, diagnosis, treatment, as well as different types of glioblastomas.

Introduction

Glioblastomas are an aggressive type of cancer that can occur in the brain or spinal cord. They are the rarest type of malignant Grade IV tumor, where a large portion of tumor cells, or astrocytes, reproduce and divide at any given time. These astrocytes are nourished by an ample and abnormal blood vessel supply. While predominantly consisting of abnormal astrocytic cells, the tumor can also contain a mix of different cell types and patches of necrosis, or death of body tissue. These invasive tumors are infiltrative and can spread into nearby regions of the brain, sometimes spreading to the opposite side of the brain through connection fibers in the corpus callosum, the thick band of nerve fibers that divides the cerebral cortex lobes into left and right hemispheres. This aggressive tumor may arise de novo, meaning they begin as a Grade IV tumor with no evidence of a lower grade precursor. De novo tumors are the most common form of glioblastoma, tending to be quite aggressive and more likely to affect older patients. Alternatively, secondary glioblastomas may progress from lower-grade astrocytic tumors and evolve into Grade IV tumors over time. While these tumors tend to grow slowly initially, they can progressively become aggressive. 

Diagnosis and Symptoms

Glioblastomas are generally found in the cerebral hemispheres of the brain, but can be found anywhere in the brain. Patients with glioblastomas develop symptoms rapidly due to mass effect from the tumor itself or from the fluid surrounding the tumor that causes further brain swelling. Common symptoms can be nausea, vomiting, and severe headaches, which are all related to increased pressure in the brain. Patients can also present neurological symptoms that are dependent on the location of the tumor. These symptoms could include weakness in extremities, difficulty balancing, and memory loss. The standard procedure for diagnosing glioblastomas includes a neurological exam, an imaging test, and a tissue biopsy. During the neurological exam, doctors will typically check a patient’s vision, hearing, balance, coordination, strength, and reflexes. This can aid the doctor by providing an idea of where the tumor might be located. Further imaging tests, such as an MRI and fMRI, can determine the location and size of the brain tumor. Finally, the tissue biopsy can be analyzed in a laboratory to determine the type of cells present in the tumor and their aggressiveness. 

Treatment

Glioblastoma can be difficult to treat since some cells may respond well to certain therapies, while others may not be affected at all. Because of this, the treatment plan for glioblastoma may combine several approaches. The first step in treating glioblastoma is a surgical procedure to make a diagnosis, to relieve pressure on the brain, and to safely remove as much tumor as possible. Glioblastomas are diffuse and have finger-like tentacles that infiltrate the brain, which makes them very difficult to remove completely. This is particularly true when the tumors are growing near important regions of the brain that control functions such as language, movement, and coordination. After surgery, radiation or chemotherapy may be used to slow down the growth of the residual tumor after surgery or for tumors that are inoperable. The standard of care treatment for newly diagnosed GBM depends on a variety of factors, including molecular biomarkers and age. Recurrent GBM is treated based on the patient’s response to initial treatments and assessment of disease progression. Other courses of treatments can also include targeted drug therapy, clinical trials, and palliative care.   

Prognosis and Conclusion

Long-term survivors of glioblastoma are rare, with only 6% of patients surviving more than 5 years after initial diagnosis. Several variables besides tumor size and location determine a patient’s survival chances: age at diagnosis, as younger patients often receive more aggressive, multimodal treatment; functional status, which has a significant negative correlation with age; and histologic and genetic markers. Despite advances in surgery, radiation therapy, imaging, and chemotherapy, the median survival for patients with glioblastoma remains dismal. It is a devastating cancer that deserves better therapeutic approaches and translational research, which is achievable with further research.

By Deekshita Sundararaman

Deekshita is a rising senior at Round Rock High School who is very passionate in the fields of neuroscience and psychology. She is involved in multiple medical non-profit organizations as well as research initiatives. In the future, she would like to become a neurosurgeon and help save lives.

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