Brain cancer is a diagnosis no one wants to hear---brain tumours can be very debilitating and interfere with normal brain function. Metastases, or secondary brain tumours, are formed from cancer present in another region of the body. However, regardless of what the originating cancer is, the prognosis of brain metastases is never good. Radiation is a common therapy prescribed for brain cancer patients to treat metastatic brain tumours, but the survival rate is not very high.
Metastases are formed when part of a tumour from another cancer in the body breaks off. The separated section of the tumour travels up the bloodstream to the brain, where the cancerous cells affect the healthy brain cells. Most metastatic brain tumours form from lung cancer, breast cancer, bowel cancer, colon cancer, kidney (renal) cancer and skin cancer (malignant melanoma).
Whole Brain Radiation Therapy
Whole brain radiation therapy (WBRT) is the treatment most widely used for metastatic brain cancers. Whole brain radiation therapy works by targeting radiation at the tumour formation. Radiation can be a dangerous treatment on the brain, as radiation can also damage healthy brain cells. This therapy is usually done over a period of 2 weeks. However, the period of time can be longer depending on the size of the tumour.
Whole brain radiation therapy is not without its side effects. Significant neurotoxicity has been reported with whole brain radiation therapy, which has resulted in both acute and chronic effects that can be detrimental to the patient. Acute effects of whole brain radiation therapy include hair loss, nausea, lethargy, vomiting, otitis media and severe cerebral oedema. The chronic effects of whole brain radiation are atrophy, leukoencephalopathy, radiation necrosis, neurological deterioration and dementia.
The prognosis of metastatic brain radiation is not very good. Without treatment, the survival rate of a metastatic brain cancer is 1 month. When the metastasis is treated with whole brain radiation therapy, the survival rate raises only slightly to 3 to 4 months. One of the reasons for the low survival rate is many of the brain metastases are resistant to radiation; the specific tumours that are radiation resistant are non-small cell lung, renal, colon and melanoma.
Prognosis is better for metastatic brain cancer patients when whole brain radiation therapy is combined with surgery. The radiation and surgery combination gives patients a higher chance of survival and a better quality of life; however, surgery is only recommended for patients where the tumour is accessible.