Metastasis (from the ancient Greek meaning: 'transition') is a medical term describing the process where a tumour (generally cancer) spreads from its original location to other parts of the body via blood vessels or the lymphatic system. Brain metastasis, also referred to as 'secondary brain cancer', or a 'metastatic brain tumour', is where cancer cells have travelled to the brain from another part of the body, as opposed to 'primary brain cancer' which originates in the brain. In fact, brain metastasis is more common than primary brain tumour. Common types of cancers to metastasise to the brain include cancers of the breast, colon, kidney, lung and skin (melanoma). Most brain metastasis occurs in the cerebrum, although it can also occur in the cerebellum, brain stem and rarely spinal cord. Brain metastasis generally involves the formation of multiple tumours, although in some cases, only a single metastasis is found. The meninges (membranes that surround the brain) can also be affected, which is referred to as 'meningeal carcinomatosis' or 'leptomeningeal metastasis'.
As metastasis is caused by the presence of the original cancer, the causes are the same as for the original cancers. The reason for certain cancers having higher chances of metastasising to the brain is not entirely known.
A very common symptom is headaches, which may be caused by the pressure of the tumour in the brain (mass effect), fluid buildup in the brain (hydrocephalus), general swelling (oedema), or bleeding. As with other brain tumours, symptoms are related to the part of the brain affected and can include:
- Numbness or weakness affecting specific parts of the body (e.g. arms, legs, face).
- Cognitive issues e.g. memory, reasoning.
- Personality change.
- Issue with balance and coordination.
- Speech difficulties.
- Swallowing difficulties.
Tests / Diagnosis
Brain metastases may be identified due to…
- Neurological examination – abnormal findings found by medical staff on physical examination.
- Neuroimaging – either on MRI (magnetic resonance imaging) or CT (computed tomography) scan of the brain. These may be performed due to new symptoms, or as part of overall tests to determine how far the primary tumour has spread.
- Tissue sample – a sample of the abnormal tissues can be taken either during surgical removal of the tumour, or 'needle biopsy' and sent for laboratory analysis (histopathology).
Brain metastasis is managed within the context of the primary cancer. If the prognosis of the overall primary cancer is favourable, brain metastasis can be treated with:
- Surgery – Removal of the tumour may be performed to confirm the type of tumour, and to reduce the pressure (or mass effect) of the tumour on surrounding brain structures.
- Radiotherapy – Stereotactic radiosurgery (SRS) or whole brain radiotherapy may be offered to control metastatic deposits.
- Chemotherapy – This may be given if tumour is responsive to chemotherapy agents.