A metastatic brain tumour is cancer that started in another part of the body and spread to the brain.
Causes, incidence, and risk factors
Many tumour or cancer types can spread to the brain, the most common being lung cancer, breast cancer, melanoma, kidney cancer, bladder cancer, certain sarcomas, and testicular and germ cell tumours. Some types of cancers only spread to the brain infrequently, such as colon cancer, or very rarely, such as prostate cancer.
Growing brain tumours may place pressure on nearby parts of the brain. Brain swelling due to these tumours also causes increased pressure within the skull.
Metastatic brain tumours are classified depending on the exact site of the tumour within the brain, type of tissue involved, original location of the tumour, and other factors. Rarely, a tumour can spread to the brain, yet the original site or location of the tumour is unknown. This is called cancer of unknown primary (CUP) origin.
Metastatic brain tumours occur in about one-fourth of all cancers that metastasize (spread through the body). They are much more common than primary brain tumours (tumours that start in the brain) and occur in approximately 10-30% of adult cancers.
Symptoms
- Decreased coordination, clumsiness, falls
- Rapid emotional changes or strange behaviours
- Fever (sometimes)
- General ill feeling or lethargy
- Headache – recent or a new, more severe type type for the person
- Memory loss, poor judgment, difficulty solving problems
- Numbness, tingling, pain, and other changes in sensation
- Personality changes
- Seizures – new for the person
- Speech difficulties
- Vision changes – double vision, decreased vision
- Vomiting – with or without nausea
- Weakness of a body area
Note: Specific symptoms vary. The symptoms commonly seen with most types of metastatic brain tumour are those caused by increased pressure in the brain.
Signs and tests
An examination reveals neurologic changes that are specific to the location of the tumour. Signs of increased pressure within the skull are also common. Some tumours may not show symptoms until they are very large.
Then, they suddenly cause rapid decline in the person’s neurologic functioning.
The original (primary) tumour may already be known, or it may be discovered after an examination of tumour tissues from the brain indicates that it is a metastatic type of tumour.
A CT scan or MRI of the brain can confirm the diagnosis of brain tumour and identify the location of the tumour. MRI is usually better for finding tumours in the brain.
Cerebral angiography is occasionally performed. It may show a space-occupying mass, which may or may not be highly vascular (filled with blood vessels).
A chest x-ray, mammogram, CT scans of the chest, abdomen, and pelvis, and other tests are performed to look for the original site of the tumour.
An EEG may reveal abnormalities in the nerve signalling in the brain.
An examination of tissue removed from the tumour during surgery or CT scan-guided biopsy is used to confirm the exact type of tumour. If the primary tumour can be located outside the brain, the primary tumour is usually biopsied rather than the brain tumour.
A lumbar puncture (spinal tap) is sometimes also performed to test the cerebral spinal fluid to look for cells related to the tumour.
Treatment
Treatment depends on the size and the type of the tumour, the initial site of the tumour, and the general health of the person. The goals of treatment may be relief of symptoms, improved functioning, or comfort.
Radiation to the whole brain is often used to treat tumours that have spread to the brain, especially if there is more than one tumour.
Surgery may be used for metastatic brain tumours. Some may be completely removed. Tumours that are deep or that infiltrate brain tissue may be debulked (removing much of the tumour’s mass to reduce its size).
Surgery may reduce pressure and relieve symptoms in cases when the tumour cannot be removed.
Chemotherapy for brain metastases is not as helpful as surgery or radiation for many types of cancer.
Stereotactic radiosurgery: this is a form of radiation therapy that focuses high-powered x-rays on a small area of the brain.
Medications for some symptoms of a brain tumour may include the following:
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- Corticosteroids such as dexamethasone to reduce brain swelling
- Osmotic diuretics such as urea or mannitol to reduce brain swelling
- Anticonvulsants such as phenytoin or levetiracetam to reduce seizures
- Pain medication
- Antacids or antihistamines to control stress ulcers
When widespread cancer is discovered, treatment may focus primarily on relief of pain and other symptoms. This is called palliative or supportive care.
Comfort measures, safety measures, physical therapy, occupational therapy, and other interventions may improve the patient’s quality of life. Legal advice may be helpful in forming advanced directives, such as power of attorney, in cases where continued physical or intellectual decline is likely.
Expectations (prognosis)
In general, the probable outcome is fairly poor. For many people with metastatic brain tumours, the cancer spreads to other areas of the body. Death often occurs within 2 years.
Complication
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- Brain herniation (fatal)
- Loss of ability to function or care for self
- Loss of ability to interact
- Permanent, progressive, profound neurologic losses.
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