What is Brain Metastasis

Brain metastases are the most feared and common complication of widespread cancer in the body, and as such are a significant cause of death and ill health amongst people with cancer. Metastasis is the mechanism by which cancer spreads from the place from which it initially began (the ‘primary’) to distant locations in the body. For instance a cancer beginning in the lung and spreading (metastasising) to the brain.

Statistics on Brain Metastasis

Brain metastases occur in approximately 15% of adult cancer patients and 6% of child cancer patients.

Risk Factors for Brain Metastasis

The majority of brain tumours are spread from past or current cancers of the lung , breast and colon.

Progression of Brain Metastasis

Most cancer cells reach the brain via the bloodstream. Less commonly they may travel by direct spread from surrounding structures such as the skull or sinuses in the head. Brain cancers disrupt the function of surrounding brain tissue by displacing or compressing structures as the tumour increases in size.

How is Brain Metastasis Diagnosed?

MRI scanning is commonly used for patients with suspected brain cancers, although CT scanning is also used. Sometimes a surgical procedure is necessary to confirm the diagnosis.
In the event of brain metastases where the primary site of the cancer is unknown, a search for the source is undertaken with chest x-ray, mammography and ultrasound of the abdomen, so that this may be treated as well.

Prognosis of Brain Metastasis

Prognosis of brain metastases tends to be poor. Outlook is better for those with solitary tumours which have been surgically removed. In most cases, treatment aims not for a cure, but rather to relieve symptoms and improve quality of life.

How is Brain Metastasis Treated?

The initial treatment of patients with brain metastases is directed at controlling brain swelling and preventing seizures. Steroid therapy should be started in most patients with metastatic tumors and anticonvulsant drugs may be required in patients with seizures. If the primary site of the cancer is found, this will also be treated.
Further therapy often includes irradiation and, in selected patients, surgical removal of the lesion (particularly of an MRI-documented solitary metastasis) and chemotherapy. Studies have shown extended survival following resection so this should be considered where possible. Unfortunately only a minority of patients have single lesions and many patients have conditions which make them unsuitable candidates for surgery (pre-existing medical problems, inaccessible tumours).

Brain Metastasis References

  1. Brada M, Cruickshank G. Radiosurgery for brain tumours. BMJ 1999;318:411-412 [1]
  2. Khosla A. Brain metastases. eMedicine 2005. [available online: http://www.emedicine.com/radio/topic101.htm]
  3. Kumar and Clark. Clinical Medicine, 5th ed. WB Saunders, Toronto (2002).
  4. Newton H. Neurologic Complications of Systemic Cancer. Am F Phys. 1999. [available online: http://www.aafp.org/afp/990215ap/878.html]
  5. Tierney L, McPhee S. Current medical diagnosis and treatment (40th ed.). McGraw-Hill, 2001, New York.