Cancer of the Brain and Brain Tumours
Understanding the brain
- Different types of brain tumour
- Brain Tumours may be benign tumours and primary malignant tumours. The following is a brief description of the main types.
- Meningiomas are usually benign. They arise from cells in the meninges (the tissues that surround the brain).
These arise in the cerebellum and are high grade malignant tumours. They are uncommon in adults, but are one of the most common brain tumours in children
These are malignant primary brain tumours that arise from glial cells. There are various types, depending on the cell of origin. For example:
- Astrocytomas (originating from astrocyte cells.)
There are various types of astrocytoma. They include:
- Low-grade astrocytomas.
- Anaplastic astrocytoma. This is a high-grade tumour.
- Glioblastoma multiforme. This is a high grade tumour which tends to grow quite quickly. It is the commonest type of primary malignant brain tumour in adults.
- Oligodendrogliomas (originating from oligodendrocytes). These can vary in their grade.
- Ependymoma (originating from ependymal cells). These are rare, but are usually low grade.
Primitive neuroectodermal tumours (PNETs)
These are very similar to medulloblastomas and mainly occur in children.
There are various types of tumour which arise from the different cells in the pituitary gland. They tend to be benign. However, the cells of the tumour may produce large quantities of hormones which can cause various symptoms. As they grow, they may also cause pressure symptoms. The optic nerves (the nerves of sight) are near to the pituitary and so a growing pituitary gland tumour may press on an optic nerve and affect vision.
Acoustic neuroma (schwannoma)
This is a benign tumour which arises from schwann cells which cover the nerve that goes to the ear. Symptoms can include deafness on the affected side and vertigo.
There are various other rare types of benign and primary malignant brain tumours.
What is metastatic brain cancer?
Metastatic brain cancer is a mass of cells that originated in another body organ and has spread into the brain tissue. Metastatic tumors in the brain are more common than primary brain tumors
What are the symptoms and signs of brain cancer?
Although there are few early signs, the most common symptoms of brain cancer are weakness, difficulty walking, seizures, and headaches.
Other common symptoms are nausea, vomiting, blurry vision, or a change in a person's alertness, mental capacity, memory, speech, or personality.
Methods of detecting a brain tumour:
If a person has symptoms that suggest a brain tumor,following tests may be needed.
- Physical exam
- Neurologic exam
- CT Scan
- MRI (magnetic resonance imaging) with gadolinium: A substance called gadolinium is injected into a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. Sometimes a procedure called magnetic resonance spectroscopy (MRS) is done during the MRI scan.
An MRS is used to diagnose tumors, based on their chemical make-up.
- SPECT scan (single photon emission computed tomography scan): A procedure that uses a special camera linked to a computer to make a 3-dimensional (3-D) picture of the brain. A small amount of a radioactive substance is injected into a vein or inhaled through the nose. As the substance travels through the blood, the camera rotates around the head and takes pictures of the brain. There will be increased blood flow and more chemical reactions (metabolism) in areas where cancer cells are growing. These areas will show up brighter in the picture. This procedure may be done just before or after a CT scan.
- PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the brain. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do
- Angiogram - Dye injected into the bloodstream flows into the blood vessels in the brain to make them show up on an x-ray. If a tumor is present, the doctor may be able to see it on the x-ray.
- Skull x-ray - Some types of brain tumors cause calcium deposits in the brain or changes in the bones of the skull. With an x-ray, the doctor can check for these changes.
- Spinal tap - A sample of cerebrospinal fluid (the fluid that fills the spaces in and around the brain and spinal cord) is taken out.. A laboratory checks the fluid for cancer cells or other signs of problems.
- Myelogram - This is an x-ray of the spine. A spinal tap is performed to inject a special dye into the cerebrospinal fluid. The patient is tilted to allow the dye to mix with the fluid. This test helps the doctor detect a tumor in the spinal cord.
- Biopsy - The removal of tissue to look for tumor cells is called a biopsy. A pathologist looks at the cells under a microscope to check for abnormal cells. A biopsy can show cancer, tissue changes that may lead to cancer, and other conditions. A biopsy is the only sure way to diagnose a brain tumor.
- Surgeons can obtain tissue to look for tumor cells in three ways:
- Needle biopsy - The surgeon makes a small incision in the scalp and drills a small hole into the skull. This is called a burr hole. The doctor passes a needle through the burr hole and removes a sample of tissue from the brain tumor.
- Stereotactic biopsy - An imaging device, such as CT or MRI, guides the needle through the burr hole to the location of the tumor. The surgeon withdraws a sample of tissue with the needle.
- Biopsy at the same time as treatment - Sometimes the surgeon takes a tissue sample when the patient has surgery to remove the tumor.
Sometimes a biopsy is not possible. If the tumor is in the brain stem or certain other areas, the surgeon may not be able to remove tissue from the tumor without damaging normal brain tissue. The doctor uses MRI, CT, or other imaging tests instead.
Treatment depends upon the tumour type, patient's age and general condition
Surgery --Surgery is used to diagnose and treat adult brain tumors
Even if the doctor removes all the cancer that can be seen at the time of the surgery, some patients may be given chemotherapy or radiation therapy after surgery to kill any cancer cells that are left. Treatment given after the surgery, to lower the risk that the cancer will come back, is called adjuvant therapy.
Radiation Therapy -There are two types of radiation therapy.
External radiation therapy –
Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type of tumor and where it is in the brain.
Other types of radiation therapy
- Radiosensitizers: Drugs that make tumor cells more sensitive to radiation therapy. Combining radiation therapy with radiosensitizers may kill more tumor cells.
- Hyperfractionated radiation therapy: Hyperfractionated radiation therapy is radiation treatment in which the total dose of radiation is divided into small doses and the treatments are given more than once a day. Hyperfractionated radiation therapy is used as a standard treatment for a brain stem glioma.
- Accelerated-fraction radiation therapy: Radiation treatment in which the total dose of radiation is divided into small doses and the treatments are given more than once a day. The total dose of radiation is also given over a shorter period of time (fewer days) compared to standard radiation therapy.
- Intraoperative radiation therapy: A cancer treatment that uses high-energy x-rays to kill cancer cells during cancer surgery.
- Stereotactic radiosurgery: A type of radiation therapy that uses a rigid head frame attached to the skull to aim high-dose radiation beams directly at the tumors. This causes less damage to nearby healthy tissue. This is also called stereotaxic radiosurgery and radiation surgery. This procedure does not involve surgery.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. To treat brain tumors, a dissolving wafer may be used to deliver an anticancer drug directly to the brain tumor site after the tumor has been removed by surgery. The way the chemotherapy is given depends on the type of tumor and where it is in the brain.