Brain Cancer

The brain is the center of thought, emotion, memory, speech, and many more, and it is the most sophisticated organ in the human body. A hard skull protects the brain where it floats in a fluid called Cerebrospinal Fluid (CSF). The brain is generally set apart from the rest of the body, and functions rather differently too. Most of the brain cells are called astrocytes, and they basically support and serve the 10 billion working cells that are called neurons. These neurons make about 13 trillion connections with one another to sustain life within the human body.

Brain tumors can arise at any time and damage this complex organ in various ways. Some risk factors are environmental, like radiation from previous cancer treatment. Other risk factors are mainly due to immune system disorders, and rarely do they run in the family. Therefore, abnormalities of genes (mutations) are the main cause for brain cancer.

It all starts in a single cell anywhere in the brain, since any type of cell there can become cancerous. Unlike cancer in other organs of the body, brain tumors spread locally and cause a lot of damage to the normal tissue in the place where they originated.

Most brain tumors are primary, and the two most common types are astrocytomas that start in the astrocytes, and glioblastomas multiforme. Primary brain tumors, which originate in or around the brain rarely spread to other another organ, though cancer in other organs, like the lungs, can spread or metastize to the brain. Such tumors are called metastic brain cancers and they are treated differently.

The symptoms or signs which hint to the existence of a brain tumor include:

? Blurred vision

? Personality changes

? Seizures

? Malaise

? Intellectual decline

? Headaches

? Vomiting

? Emotional liability

? Nausea

If a patient’s symptoms suggest the presence of a brain tumor, a few examinations could be done. First, a physical examination is done, and the patient’s complete medical history is studied. If there is a problem, imaging studies will show the tumor if it is present. Early detection and treatment usually don’t affect the chances of survival. The two most common imaging studies used are the magnetic resonance imaging (MRI) and the computed tomography (CT) scan. The difference is that a CT is a type of cross-section X-ray, but an MRI uses strong magnets and radio waves instead. Other imaging studies like the position emission tomography (PET) and the angiography are less used because they only produce specific information dealing with certain aspects of a tumor.

All these examinations are then used to diagnose the tumor, but to achieve definite results, a biopsy is needed where a neurosurgeon removes some of the cancerous tissue for examination under a microscope to determine the best treatment and the chances of survival.

Due to the unique characteristics of brain cancer, treatment is extremely difficult and a cure is not possible since it would have to (1) treat the whole brain, (1) get to places where the blood flow does not reach, (3) kill every single cancerous cell without damaging the rest of the functional brain.

Unfortunately, such a cure has yet to be discovered, and the best treatment nowadays is called standard therapy. First, surgery is performed removing about 90% of the tumor. Radiotherapy and Chemotherapy follow to achieve the maximum therapeutic benefit. Since most brain cancer is not caused by any definite causes, and occurs for no apparent reason, it cannot be prevented, especially in children (astrocytoma and the medulloblastoma).

Because many parts of the brain are essential to life, a tumor that starts in any of these areas may be impossible to remove, and can eventually be life threatening.

Tumor Clinical Features Treatment & Prognosis

Glioblastoma multiforme Presents commonly with nonspecific complaints and increased intracranial pressure. As it grows, focal deficits develop. Course is rapidly progressive, with poor prognosis. Total surgical removal is usually not possible, and response to radiation therapy is poor.

Astrocytoma Presentation similar to glioblastoma multiforme but course more protracted, often over several years. Cerebellar astrocytma, especially in children, may have a more benign course. Prognosis is variable. By the time of diagnosis, total excision is usually impossible; tumor often is not radiosensitive. In cerebellar astrocytoma, total surgical removal is often possible.

Medulloblastoma Seen most frequently in children. Generally arises from roof of fourth ventricle and leads to increased intracranial pressure accompanied by brain stem and cerebellar signs. May seed subarachnoid space. Treatment consists of surgery combined with radiation therapy and chemotherapy.

Ependymoma Glioma arising from the ependyma of a ventricle, especially the fourth ventricle; leads early signs of increased intracranial pressure. Arises also from central canal of cord. Tumor is not radiosensitive and is best treated surgically if possible.

Tumor Clinical Features Treatment & Prognosis

Brain stem glioma Presents during childhood with cranial nerve palsies and then with long-tract sings in the limbs. Signs of increased intracranial pressure occur late. Tumor is inoperable; treatment is by irradiation and shunt for increased intracranial pressure.

Cerebellar hemangioblastoma Presents with disequilibrium, ataxia of trunk or limbs, and signs of increased intracranial pressure. Sometimes familial. May be associated with retinal and spinal vascular lesions, polycythemia, and hypernephromas. Treatment is surgical.

Pineal tumor Presents with increased intracranial pressure, sometimes associated with impaired upward gaze (Parinaud’s syndrome) and other deficits indicative of midbrain lesion. Ventricular decompression by shunting is followed by surgical approach of tumor; irradiation is indicated if tumor is malignant. Prognosis depends on histopathologic findings and extent of tumor.

Craniopharyngioma Originates from remnants of Rathke’s pouch above the sella, depressing the optic chiasm. May present at any age but usually in childhood, with endocrine dysfunction and bitemporal field defects. Treatment is surgical, but total removal may not be possible.

Acoustic neurinoma Ipsilateral hearing loss is most common initial symptom. Subsequent symptoms may include tinnitus, headache, vertigo, facial weakness or numbness, and long-tract signs. (May be familial and bilateral when related to neurofibromatosis.) Most sensitive screening tests are MRI and brain stem auditory evoked potential. Treatment is excision by translabyrinthine surgery, craniectomy, or combined approach. Outcome is usually good.

Meningioma Originates from the dura mater or arachnoid; compresses rather than invades adjacent neural structures. Increasingly common with advancing age. Tumor size caries greatly. Symptoms vary with tumor site. Tumor is usually benign and readily detected by CT scanning; may lead to calcification and bone erosion visible on plain x-rays of skull. Treatment is surgical. Tumor may recur if removal is incomplete.

Primary cerebral lymphoma Associated with AIDS and other immunodeficient states. Presentation may be with focal deficits or with disturbances of cognition and consciousness. May be indistinguishable from cerebral toxoplasmosis. Treatment is by whole-brain irradiation; chemotherapy may gave an adjunctive role.

Standard Therapy

To date, the best treatment for malignant astrocytoma and glioblastoma multiforme (GBM) is a combination of:

? Surgery (Gross total removal, i.e. 80 – 99%)

? Radiotherapy (5,000 – 6,000 Rads)

? Chemotherapy (BCNU)

Growth Dynamics (GBM):

? Growth Fraction = 20% (Only a percentage of the tumor is growing at any one time)

? Cell Cycle Time = 2 – 5 Days (This is how long it takes a growing cell to reproduce)

? Cell Loss = 80 – 90% (A high percentage of cells spontaneously die off)

? Doubling Time = Around 7 Days