BRAIN CANCER

A brain tumour is a massive growth of abnormal cells in the brain. There are many different types of brain tumours some of them are non-cancerous (benign) and a few are cancerous (malignant). Brain tumours share some feattumourures and challenges for diagnosis and therapy with tumours elsewhere in the body. Most of the brain is separated from Blood-Brain Barrier (BBB) that exerts a much more restrictive control over substances that are allowed to pass through to other organs.

There are around 120-150 different types of brain and central nervous system tumours that have been documented so far. According to 2012 data globally there were nearly 2,60,000 reported cases of brain and nervous system cancer around the world. It is the 22nd most common cancer worldwide with 1.8% total number of new cases worldwide. And according to the mortality rate, it ranks 12th.

TYPES OF TUMORS:

A Tumor is simply a mass of cells that are classified into two types are Benign tumour and Malignant tumour.

A benign tumour composed of cells that are not cancerous. A malignant tumour comprises cancer cells. The term cancer is usually used for malignant tumours because those malignant cells grow aggressively, these abnormally growing cells are referred to as cancer cells.

Malignant tumour cells grow and spread aggressively, invading and spreading into healthy tissues areas and for the survival of these tumour cells, they tend to take the blood and nutrients from their surrounding area. When it comes to the brain it becomes a problem as the cells start growing or expanding leading to the increase of intracranial pressure or the distortion of areas of the brain, causing them to fail to work properly.

Both malignant and benign brain tumours can cause the problem of increased intracranial pressure and its consequences. Malignant brain tumour usually causes such problems more aggressively and quickly than benign brain tumours.

Not every tumour that begins in the brain spreads to the other parts of the body. But if the tumour is malignant it can invade the brain tissues and grow rapidly, whereas the benign tumours usually push the adjacent tissue rather than enter into the tissue.

Types of Grades in Brain Cancer:

The grades are classified into two types I.e. Low grade and High grade:

Low Grade is again classified into two types I.e. Grade I and Grade II

Grade I:- It is characterised as least malignant, curable via surgery alone, it's is non-infiltrative, people with grade one brain cancer have long-term survival, and the tumour is slow-growing.
Type of brain cancer that falls in Grade I are Pilocytic astrocytoma, Craniopharyngioma, Gangliocytoma, Ganglioglioma.
Grade II:- It is characterised as relatively slow-growing, a little infiltrative, and may recur as a higher grade brain tumour.
Types of Brain cancer that fall in Grade II are Diffuse Astrocytoma, Pineocytoma, Pure Oligodendroglioma.

High Grade is classified again into two types I.e. Grade III and Grade IV

Grade III:- It is characterized as malignant, infiltrative, and tend to recur as a higher grade brain tumour.
Types of brain cancers that fall in Grade III are Anaplastic astrocytoma, Anaplastic ependymoma, Anaplastic oligodendroglioma.
Grade IV:- It is characterised as the most malignant, rapid and aggressive growth of the tumour cells, widely infiltrative, rapid recurrence, and the tumour becomes Necrosis prone.
Types of brain cancer associated with Grade IV is Glioblastoma multiforme(GBM), Pineoblastoma, Medulloblastoma, Ependymoblastoma.

Types of Brain Cancer:

There are more than 150 different types of brain tumours that have been documented, but the two main groups of brain tumours are termed primary brain tumours and metastatic brain tumours.

Primary brain tumours: They include tumours that originate from the tissues of the brain or the brains immediate surroundings. Primary tumours are categorized as glial or none -glial and benign or malignant.

Malignant brain tumours: They include tumours that arise elsewhere in the body (such as the best or lung) and migrate or travel to the brain, usually through the bloodstream. Metastatic tumours are considered cancer and are malignant.

One in every four patients suffering from cancer has their brain affected from metastatic tumours. An estimated 150,000 people a year are affected. Up to 40% of people with lung cancer will develop metastatic brain tumours.

Types of Benign Brain Tumours:

Chordomas: A chordoma is a rare type of cancerous tumour that can occur along the spine from the base of the brain. Chordomas grow slowly and gradually extending into the bone and soft tissue around them. They often recur after the treatment and in 40% of cases, cancer can spread to other areas of the body such as the lungs.

The inheritance pattern of chordoma is Autosomal Dominant.
Chordomas typically occur in adults between ages 40-70 years. about 5% of chordomas are diagnosed in children. For unknown reasons, males are twice affected as females. Changes in the TBXT gene have been associated with chordoma. An inherited duplication of the TBXT gene identified in few families is associated with an increased risk of developing a chordoma.
The TBXT gene provides instruction for making a protein called "brachyury". Brachyury is a member of a protein family called T-box proteins which plays an important role during embryonic development. The Brachyury protein is especially important during the development of the spine.
In human embryos, a structure called a notochord is the precursor of the spinal column. The notochord disappears before birth, but in a small percentage of individuals, some of its cells remain in the back of the skull or the spine. In rare cases these cells begin to grow and divide uncontrollably, invading the nearby bone and soft tissue and resulting in the development of chordoma.

Craniopharyngiomas: A craniopharyngioma is a rare type of brain tumour derived from the pituitary gland embryonic tissue that occurs most commonly in children, but also affects adults. It may present at any age, even in the prenatal and neonatal periods, but peak incidence rates are childhood-onset at 5-14 years and adult-onset at 50-74 years.

The cause of craniopharyngioma is unknown.
About 120 cases are diagnosed each year in the United States in patients under the age of 19. More than 50% of the patients with craniopharyngioma are under 18 years.
Craniopharyngiomas do not appear to be inherited in families.

Gangliocytomas: It is a rare type of central nervous system (CNS) tumour made up of mature neurons. Gangliocytomas may occur in all age groups but most often occur in people between the age of 10-30 years. The most common site is the temporal lobe of the brain, but they can arise anywhere in the CNS including the cerebellum, brainstem, floor of the third ventricle, and spinal cord.

These tumours are mostly associated with epilepsy.
Ganglocytomas are generally slow-growing and usually don't become malignant.
Treatment involves surgical removal of the tumour.

Types of Malignant Brain Tumours:

Gliomas are the most prevalent type of adult brain tumour, accounting for 78% of malignant brain tumours. They arise from the supporting cells of the brain tumours. They arise from supporting cells of the brain called glia. These are sub-divided into Astrocytomas, Ependymal cells and Oligodendroglial cells.

Anaplastic astrocytoma: It is a rare, cancerous type of brain tumour. Arises from star-shaped brain cells called astrocytes. These cells surround and protect nerve cells in the brain and spinal cord. An anaplastic astrocytoma grows slowly, but sometimes it may grow rapidly. Anaplastic astrocytomas are not inherited they are sporadically but can be associated with few rare genetic disorders. Astrocytomas can have a genetic link when they are associated with a few rare disorders such as Neurofibromatosis Type 1, Li-Fraumeni syndrome, Turcot syndrome, and Tuberous sclerosis. Astrocytomas occur frequently in people with one of these diseases.
Other astrocytic tumours: As is the case for most other non-diffuse gliomas, other astrocytes tumours tend to grow slowly and are thought to be more encapsulated. They most commonly occur in children and young adults. Tumours in this category include polycystic astrocytoma (grade1) and subependymal giant cell astrocytoma (SEGA). Pilocytic astrocytomas are the most common pediatric gliomas and are associated with numerous genetic abnormalities, the most common being a fusion between the KIAA1549 and BRAF genes. This leads to the overexpression of BRAF, which in turns leads to unregulated cell growth. SEGAs are highly associated with a syndrome known as tumour sclerosis and are therefore associated with mutations in the tumour sclerosis complex genes 1&2.
Ependymal tumours: These tumours arise from ependymal cells, which line a region of the brain known as the ventricular system, where cerebrospinal fluid (CSF) is created and is circulates. The CSF has many functions, including nutrients transfer to and from the brain and protection against shock injuries. The most common subtypes of ependymal tumours are low-grade (grade II) and anaplastic (grade III) ependymoma. Genetic abnormalities present depend on the subtype and location of the tumour. The gene fusion of RELA and C11orf95 leads to the activation of multiple other genes and drives ependymal tumour formation.
Oligodendrogliomas: Oligodendrogliomas arise from oligodendrocytes, which are responsible for the formation of the myelin sheath of neurons in the central nervous system. The myelin sheath insulates the axon, the “cable” by which the electrical current generated by a neuron is propagated. IHD1 and IDH2 mutations are also characteristic of diffuse oligodendroglial tumours. The deletion of the short arm of chromosome1 (1p) and the long arm of chromosome19 (19q), collectively known as 1p/19q co-deletion, is a known feature of these glial tumours.

The telomerase reverse transcriptase (TERT) gene encodes an important subunit of telomerase. Telomeres are located at the end of the chromosome and shorten with each cell division. Telomerase is a protein that can elongate telomeres. Mutations in the promoter region of TERT can be present in diffuse oligodendrogliomas and lead to overexpression of telomerase, which can lead to uncontrolled elongation of telomeres and an infinite replication potential in tumour cells

Signs and symptoms:

The general signs and symptoms of brain tumours include the following:

Headaches, which may be severe and worsen with activities.
Seizures: People may experience different types of seizures. Certain drugs can help prevent or control them. Motor seizures otherwise known as convulsions are sudden involuntary movements of a person's muscles.
Personality change or memory change
Nausea
Fatigue
Sleep problems
Change in the ability to walk or perform daily activities.

Symptoms of a brain tumour can be general or specific. A general symptom is caused by the pressure of the tumour on the brain or spinal cord. Whereas specific symptoms are caused when a specific part of the brain is not working well because of the tumour.

Family History: About 5% of brain tumours may be linked to hereditary genetic factors or conditions.

Diagnosis:

Most brain tumours are not diagnosed until after symptoms appear. Often a brain tumour is initially diagnosed by an internist or a neurologist. An internist is a doctor who specializes in problems with the brain and central nervous system. After asking the patients about their medical history and doing the physical tests the doctors may recommend the following diagnostic test for the confirmation of brain tumours.

Magnetic Resonance Imaging (MRI)
Tissue sampling/ biopsy/ surgical removal of a tumour
CT scan
Positron emission tomography (PET) or PET-CT scan
A cerebral arteriogram also called a cerebral angiogram
Lumbar puncture or spinal tap
Myelogram
Molecular testing of the tumour
Neurological, vision, and hearing test
Electroencephalography (EEG)
Evoked potentials

Treatment overview:

In brain tumour care, different types of doctors often work together to create a patient's overall treatment plan that combines different types of treatment. It is called a multidisciplinary team this team may include different health professionals, such as physician assistants, nurse practitioners, oncology nurses, social workers, pharmaceuticals, counsellors, dietitian, rehabilitation specialists, and others.

Treatment options and recommendations depend on several factors such as