Overview

Metastatic brain tumours are cancers that grow in the brain through a primary cancer growing in another part of the body. The primary cancer may be lung, colon, breast, lymphoma, leukaemia etc. They frequently occur in the cerebrum (80%), the cerebellum (13-16%) and the brainstem (3%). Fifty percent of the time, multiple metastatic brain tumours are present. Most are diagnosed after their primary cancer has been diagnosed and treated. About one-third of people with metastatic brain tumours have not been previously diagnosed with cancer, and their central nervous system symptoms are the first indication of cancer. In about half of these people, the primary site will never be found.

Many tumours or cancer types such as breast cancer, lung cancer, kidney cancer, melanoma, or bladder cancer can spread to the brain. Some types of cancer, such as colon cancer, only spread infrequently or in the case of prostate cancer, very rarely.

Brain tumours can directly destroy brain cells or they may indirectly damage cells by producing inflammation, compressing other parts of the brain as the tumour grows, inducing brain swelling and causing increased pressure within the skull.

Symptoms

Headache initially the headache comes and goes, and is usually common in the morning. It gradually increases in duration, frequency and severity.

Weakness: one side of the body is weak.

Behavioural changes: some examples include impairment of judgement, reasoning, memory loss, rapid mood changes and mental confusion.

Neurological: drowsiness, changes in vision, speech disturbance, balance problems, clumsy unsteady walk, dizziness and vomiting.

Seizures: may be the first indication.

Prevention

The best way to prevent metastatic brain tumours is to reduce risk factors contributing to development of other cancer types. Hence, you should:

• keep a well balanced, high-fibre diet as poor nutrition and low-fibre diet may contribute to development of intestinal cancers
• stop smoking as it can cause lung cancer
• limit or moderate consumption of alcohol as excessive use is often associated to liver cancer
• limit exposure to the sun or use sunscreen as excessive exposure can cause melanoma (skin cancer)
• for women, monthly self-examination of the breast and/or regular mammogram screening (especially if you are above 40 years) can detect breast cancer at their earliest, most curable stages

Diagnosis

The diagnosis is based on the medical history, neurological examination and CT or MRI scans. If there is no history of cancer, it is necessary to undergo more extensive testing to determine the primary cancer such as blood, urine and stool tests, chest X-ray, colonoscopy, chest / abdominal CT scan and mammography.

Treatment Options

Treatment goals depend on the patient and other factors. The goal may be cure or relief of symptoms.

Surgery
This may be in the form of :

1. Biopsy: removal of a small piece of tumour to confirm the exact nature of the tumour or to help diagnose the primary cancer if it has not yet been determined.

2. Resection: this is recommended if the patient's health is good, there are no other metastases in other parts of the body, the primary cancer does not respond positively to radiation therapy, and there is a single metastasis that can be approached surgically without causing undue neurological damage. Resection is usually followed by whole-brain radiation.

Radiation Therapy
Radiation kills cancer cells directly or interferes with their growth. Two types of radiation therapy are available.

1. Conventional radiation therapy: The whole brain is radiated over 1-2 weeks. It may be the only treatment used for patients with lymphoma or small cell lung cancer because these cancers are very radiosensitive. Whole brain radiation often follows surgical resection. 60-80% of all patients respond to radiation therapy by experiencing relief of symptoms.

2. Radiosurgery: The Gamma Knife machine uses 201 narrow beams of gamma rays, precisely aimed at the tumour from many directions encircling the head. Each part of the brain through which the beams pass receives only a small amount of the total dose, while enabling a large dose to be delivered to the tumour. This method necessitates knowledge of the exact location of the tumour, and this is achieved by fixing a special ring (Leksell stereotactic frame) to the head under local anaesthetic and doing a MRI Scan with the stereotactic frame in place.

Radiosurgery is appropriate for metastases of diameter 3cm or less. It does not require hospitalisation and there is no risk of infection or surgical complications. However it does not offer the opportunity for histological confirmation of the diagnosis, the results of treatment is not immediate.

Chemotherapy

Chemotherapy is recommended for spinal fluid metastases and is still under investigation for use against metastatic brain tumours. If the primary tumour is hormone dependent, hormones or hormone-blocking drugs may be used. Breast cancers that are oestrogen-receptor positive are treated with tamoxifen which may also shrink the metastatic tumours. Prostate cancer metastases may also be treated by hormones. Steroids may be effective in patients with lymphoma.

Steroids

Steroids such as Dexamethazone, act rapidly to decrease the symptoms of raised intracranial pressure due to brain swelling that accompanies metastatic brain tumours but do not kill the tumour cells. Improvement is noticeable within six to twenty-four hours. This therapy is effective in sixty to eighty percent of patients with metastatic brain tumours. Steroids are frequently prescribed during the course of radiation therapy to reduce the swelling caused by radiation.

Steroid use is monitored by the doctor because of its potential side effects e.g. gastric pain and haemorrhage, aggravation of diabetes mellitus, reduced ability of the body to fight infection etc.