Brain metastases are tumors formed when cancer from another organ spreads to the brain through the bloodstream. Treatment is planned according to the number, size and location of the metastases and the overall course of the disease.
What are brain metastases?
Brain metastases (secondary brain tumors) occur when cancer that started elsewhere in the body reaches the brain through the bloodstream and forms new tumor deposits. In adults, metastases account for a large proportion of the tumors found in the brain.
The cancers that most commonly spread to the brain include lung cancer, breast cancer, melanoma (skin cancer), and kidney and colorectal cancers. A metastasis may be a single lesion or there may be several lesions in different parts of the brain.
As advances in cancer treatment have improved survival, the number of patients diagnosed with brain metastases has also increased. Treatment today takes a multidisciplinary approach that considers the patient's general condition and quality of life.
Symptoms
Symptoms vary with the location and size of the metastasis. Some metastases cause no symptoms and are detected on imaging performed during cancer follow-up.
- Headache, nausea and vomiting
- Seizures
- Weakness or numbness on one side of the body
- Speech disturbance
- Visual disturbance
- Loss of balance and coordination
- Forgetfulness, personality and behavioural changes
Diagnosis
Contrast-enhanced brain MRI is the most valuable investigation. It shows the number and size of metastases and the surrounding swelling (oedema), guiding treatment planning. In patients without a known cancer, whole-body imaging may be performed to find the source of the brain lesion; where necessary, the diagnosis is confirmed by examining tissue obtained by biopsy or surgery.
Treatment Approach
Treatment decisions are made jointly by neurosurgery, radiation oncology and medical oncology. The main options are:
- Surgery: May be preferred for single or few metastases that are large, cause significant mass effect, or require tissue for diagnosis. Radiosurgery or radiotherapy is usually added to the tumor bed after surgery.
- Radiosurgery (Gamma Knife, CyberKnife): Delivers a high, focused dose to single or multiple metastases of suitable size while sparing the surrounding brain. It is often given in a single session without hospital admission.
- Whole-brain radiotherapy: May be used in selected patients with many metastases.
- Systemic therapies: Chemotherapy, targeted therapies and immunotherapy are planned by medical oncology according to the type of primary cancer.
- Supportive treatment: Corticosteroids to reduce swelling and anti-seizure medication may be needed.
After treatment, regular MRI scans are used to monitor the response of treated lesions and to detect any new ones.