Brain Metastasis

Being far more prominent than primary brain tumour, brain metastasis is the most common form of malignant brain tumour. Historically, there were slim hopes for patients diagnosed with brain metastasis. However, with recent advancements in cancer management, patients with brain metastases are more likely to have positive prognoses after treatment.

Different parts of the brain have different functions. Therefore, the symptoms of brain metastases are dependent on the location and size of the tumours. 

Some patients may experience milder symptoms while some may suffer from multiple symptoms. The symptoms may include: 

• Seizure (partial or generalized tumours)
• Dizziness (prevalent in cerebellar tumours)
• Headache or vomiting (when metastasis occurs in a large area, causing pressure effects)
• Endocrine problems (when the hypothalamus or pituitary gland is involved)
• Cognitive function impairment (when frontal lobe or temporal lobe is involved)
• Motor function impairment of the limbs
• Sensory impairment of the limbs
• Facial numbness, pain or difficulty in swallowing (when cranial nerves or brainstem are affected)
• Speech problem, either expressive or receptive (when the dominant hemisphere is involved)
• Visual problem (if the occipital lobe is affected or the optic tract is compressed)
• Incontinence

These symptoms can present similarly to a stroke or other neurological diseases. A thorough investigation is essential for a definitive diagnosis.

• Neurological examination 
  • Clinical examination is a simple but useful tool for preliminary diagnosis and subsequent investigations.
• CT Scan
  • CT scan is widely utilised as they are more accessible. Although being less sensitive than MRI scans on tumour detection and characterisation, they are commonly used as the first screening modality in emergency. CT scan can also detect complications like hemorrhage or hydrocephalus.
  • A contrast CT can reveal more details of the image. It is an alternative to MRI especially some patients are not suitable for that, e.g. with pacemaker insertion.
• MRI Scans
  • Magnetic resonance imaging (MRI) with contrast enhancement is currently the highest standard for detecting brain lesions. MRI is more sensitive and specific than other imaging modalities in determining the presence, location, and number of metastases. However, MRI scans often take longer to complete.
• Biopsy
  • If the nature of the tumour is uncertain, a biopsy should be performed for diagnosis.
  • Genetic mutations can also be detected in the biopsied specimen to provide a guide for pharmacological management.

Surgery

• Surgery can quickly relieve any mass effects caused by brain metastases. However, it is only suitable for cases with milder metastases, tumours involving only one side of the brain or tumours on the exterior as extracting tumours from both sides or deep parts of the brain is risky.
• Before surgery, the patient’s general health condition has to be assessed. Older patients or those who are medically ill are not recommended to be under the surgery, as they are higher in risk.
• One major limitation of surgery is the potential irreversible neurological deficit after operation. Some parts of the brain are not operable. For example, resecting tumor at the motor cortex may cause limb paralysis. 

Whole Brain Radiotherapy (WBRT)

• Palliative whole brain radiation therapy (WBRT) is commonly used for patients with multiple brain metastasis.
• Side effects of whole brain radiotherapy include fatigue, hair loss, mild headache, nausea and vomiting. These occur usually in the first three months after radiotherapy. Oral steroids are usually prescribed with WBRT to reduce these side effects.
• WBRT may affect the patient’s quality of life and long-term neurocognitive function. However, it is rare to be severely affected.

Stereotactic radio-surgery (SRS)

• An effective treatment for localised and small brain metastatic tumours, which are tumours less than 3cm in diameter. 
• Compared with open surgery, it can provide similar effects in disease control.
• SRS shrinks tumours over a long time, which is unideal for tumours causing mass effects in the brain. 
• With recent advancements in radiotherapy technology, SRS in treating multiple brain metastasis has been more feasible and efficient.

Drug Therapies

• In the past, drug therapies were considered ineffective against brain metastasis due to the “blood brain barrier”. 
• Nowadays, with the development of novel anti-cancer systemic treatment, drugs have been designed to improve the drug penetration into the brain. Many targeted therapies and immunotherapies had been proven to be effective for both intracranial and extracranial diseases with similar response rate. 
• For example, Osimertinib, a third-generation anti-EGFR targeted agent for metastatic lung cancer, can effectively control brain metastasis with lung primary.

Patients with brain metastasis form a heterogeneous group in terms of their general condition, primary cancer, number and site of occurrence. Each patient will receive a tailored management plan. To provide the best possible treatment, a multi-disciplinary team (MDT) approach can be used. For example, the use of SRS after surgical resection of the brain metastasis in hope of reducing the risk of relapse.

Smart patient (by Hospital Authority): Brain tumour

The Hong Kong Anti-Cancer Society: Brain tumour (Chinese only)

Hong Kong Neuro-oncology Society: Brain tumour education booklet (Chinese only)

American Society of Clinical Oncology (ASCO): Brain metastasis

Canadian Cancer Society: Brain metastases

Special thanks to Ms. Gobby Wing-Tung Kwong, Ms. Katrina Tung-Yee Tse (Class M25), medical student of Li Ka Shing Faculty of Medicine, the University of Hong Kong, and Dr. Tai-Chung Lam, Department of Clinical Oncology, the University of Hong Kong for authoring and editing this article.

Last updated on 1 Nov 2021.