What Is A Metastatic Brain Tumour?

• Introduction
  • Definition of metastatic brain tumor
  • Importance of understanding metastatic brain tumors

• Understanding brain tumors
  • Brief explanation of brain tumors
  • Different types of brain tumors (primary and metastatic)

• Causes and risk factors

• Symptoms and diagnosis
  • Overview of common symptoms exhibited by patients
  • Diagnostic methods used to detect metastatic brain tumors

• Treatment options
  • Surgical interventions for metastatic brain tumorsRadiation therapy and its role in treating brain tumors
  • Chemotherapy and targeted therapy for metastatic brain tumors
  • Emerging treatment options and ongoing research

• Prognosis and outlook
  • Factors influencing prognosis for metastatic brain tumors
  • Coping with the emotional and physical challenges of treatment

• Conclusion
  • Recap of key points discussed
  • Encouragement to seek medical attention for any concerning symptoms
  • Hope for ongoing advancements in the treatment of metastatic brain tumors

Pretty much all of us know of cancer, the life-threatening, debilitating disease that affects humans more often than it should. However, there are many more types of cancers than what meets the eye. A tumour in the brain, for example, can be of different origins, affecting which treatment option is most preferable. Did you know that cancer can spread from one body part to the other, even the brain? This is called a metastatic brain tumour, and this article will dive into everything you need to know about it. 

What is a metastatic brain tumour? 

Brain metastasis is a process where cancer cells spread from their original position towards the brain, forming one or more metastatic brain tumours.¹ The latter, which are of a malignant form and are linked to cancer, are abnormal tissue masses that don’t die when they should. ² The metastatic tumours usually reach the brain through arterial circulation, which is responsible for carrying blood away from the heart and providing different body parts with oxygen and nutrients. The metastatic tumours grow over time, creating more and more pressure on the brain tissue. When exerting enough pressure, the tumours can lead to a change in brain tissue, leading to various symptoms.¹ 

What is the importance of understanding metastatic brain tumours? 

Metastatic brain tumours are the most common cause of brain cancer in adults, with about 20-40% of cancer patients developing brain metastases over the course of their illness. In addition, patients suffering from metastatic brain tumours do not usually live for longer than 5 months, and the condition impairs their quality of life significantly.³ However, increasing our understanding of metastatic brain cancer has, and will further allow us to develop specialised therapies which may lead to full recovery. 

Understanding brain tumours

A brief explanation of brain tumours

A tumour is an abnormal generation of cells which can lead to cancer.² Benign tumours generally stay put and do not spread to surrounding tissue or other body parts. These tumours can usually be surgically removed and pose no real threat to a person’s health. A malignant tumour; however, can spread through the body via blood or lymph, and can invade surrounding tissue. This spreading process is called metastasis. Because of its invasiveness and ability to spread easily, malignant tumours can resist localised treatments and are a much bigger threat to health.

The appearance of tumours within brain tissue is called brain tumours and can be seriously life-threatening. If a malignant form, these tumours can spread and invade healthy cerebral tissue, but also block circulation in the brain and increase pressure in the skull. The tumours can form in any part of the brain, though certain regions are more prone than others. Brain tumours are classified based on their location or the types of cells they are composed of. 

Primary vs metastatic brain tumours

Primary brain tumours originate in the brain. This means that the formation of an abnormal cell mass occurs within the cerebral tissue. Metastatic brain tumours also referred to as secondary brain tumours, are caused by metastasis of malignant tumours to the brain. This means that the malignant tumour originated elsewhere in the body, and then spread to the brain. This is about 4 times more common than primary brain tumours and can grow and disperse rapidly within the cerebral tissue, causing severe brain damage.

Causes and risk factors

The most common areas for primary tumours that metastasise to the brain are found in the lungs (about 50%), breast (15-20%), and skin as a form of skin cancer (melanoma, 5-10%).² Other frequent types of cancers leading to metastasis include colon, kidney, and thyroid cancer; however, pretty much all cancer subtypes can spread to the brain.³ Brain metastasis usually occurs in later stages of cancer, where the disease is already more advanced. Early treatment, and perhaps elimination, of the primary tumour, may help to avoid metastatic brain cancer. One study showed that about 60% of metastatic brain tumour patients were aged between 50 and 70 years old, and metastasis is not commonly observed in children.⁴ Next to this, overexposure to certain types of radiation, as well as specific genetic conditions causing overproduction of cells, can contribute to the development of metastatic brain tumours.

Symptoms and diagnosis

Overview of common symptoms exhibited by patients

Symptoms of brain tumours can depend on their location, as different brain regions have distinct functions.⁵ These include: 

• Headaches: this is one of the most common symptoms. It often presents itself as an early morning headache, which is a sign of intracranial pressure (increased pressure in the brain). More metastases lead to a higher incidence of headaches
• Seizures: sudden and uncontrollable bursts of activity in the brain causing behavioural, movement, and mood changes
• Personality changes
• Neurological deficits: difficulties with speech, attention, thinking, and memory 
• Loss of balance, dizziness, and nausea
• Loss of hearing 
• Vision changes
• Confusion 

More often than not, brain tumours do not immediately cause symptoms. They usually grow slowly and unnoticed, until they are large enough to exert pressure and damage brain tissue.⁶

Diagnostic methods used to detect metastatic brain tumours

Firstly, a neurological exam is usually carried out to test for symptoms. These may include balance and coordination tests, hearing and eye exams and more. The performance on these tests may also act as an indicator of the part of the brain affected by the tumour. 

The magnetic resonance imaging (MRI) technique is most commonly used to detect and diagnose metastatic brain tumours. The MRI can scan a patient’s brain and detect any lesions and their characteristics. If the patient was not previously diagnosed with cancer, a second imaging test such as computerised tomography (CT) or positron emission tomography (PET) will be carried out to identify the location of the primary tumour.

Lastly, a biopsy may be carried out in case of doubt. This is a process by which a sample of abnormal tissue is collected and analysed under a microscope to determine whether the tumour is malignant or benign and whether it is metastatic or primary. 

The earlier a patient is diagnosed, the better. Although there is no complete cure for metastatic brain cancer yet, early diagnosis will allow for effective individualised treatment aiming to control metastasis and improve quality of life. 

Treatment options

Surgical interventions 

It is important to remember that, in the case of a metastatic brain tumour, treatment is highly individualised to the patient. If the brain metastases are located in an area that is accessible in a surgical procedure, the patient may undergo an operation to remove the cancer. There is no guarantee that all of it will be removed; however, the surgeon will try to take out as much as possible. Surgical interventions will immediately improve headaches and neurological deficits, and reduce the chance of seizures. The option of surgery is therefore interesting for patients with one brain metastasis. However, if there are multiple in their brain, a different form of treatment may be more suitable. The surgery comes with risks of internal bleeding, infection and more.³ 

Radiation therapy

Radiation therapy can kill tumour cells using very high-energy beams, for example, X-rays. The advantage of using radiation therapy, as opposed to surgery, is that it reduces the risk of damaging surrounding healthy brain tissue, effectively targeting the cancer. Killing the tumour can improve the quality of life, increase the chance of survival, and reduce overall symptoms of the cancer. There are 2 types of radiation therapy generally used to treat metastatic brain tumours.⁷

Whole brain radiation

During this procedure, radiation is applied to the entire brain surface. In general, 10-15 treatments are required over the course of 2 to 3 weeks. Whole-brain radiation can lead to several side effects such as fatigue, hair loss, nausea, as well as cognitive decline if long-term.³ 

Stereotactic radiosurgery

Multiple beams can target the tumour, exposing it to a high dose of radiation and killing it. Typically, only one session is needed to kill the metastases, and multiple tumours can be targeted in one session. The treatment is especially beneficial for patients with multiple brain metastases. This procedure can also lead to side effects, including vertigo, headache, seizures, and nausea. However, unlike whole-brain radiation, there is little to no risk of long-term cognitive decline.³

Chemotherapy

Chemotherapy uses drugs to kill the cancer cells. It is not usually used as a first-line treatment for brain metastases, instead seen as a last option when surgery or radiation therapy is not possible.³ Several factors are limiting the efficiency of chemotherapy for metastatic brain cancer, with most studies only showing a small improvement. The main issue is the blood-brain barrier, a sort of protective shield selecting which substances are allowed to enter the brain tissue or not, can block drugs from entering the brain tissue and reaching the tumour(s), rendering them pretty much ineffective. Additionally, the cells in the metastases may have increased resistance, meaning the drugs can’t kill them.⁸ 

Emerging treatment and ongoing research

Targeted therapies

The drugs used in targeted therapy can focus on certain abnormalities found only in cancer cells. They can block these abnormalities, eventually causing these cancer cells to die. There are several studies still investigating which agents are most effective, but this form of therapy seems to be very promising to increase overall survival.⁹ 

Immunotherapy

Our body has an immune system that usually kills all cells that shouldn’t be there. However, cancer cells have a special feature where they produce proteins normally produced by the body, camouflaging them from our immune cells. However, immunotherapy can interfere with this process, eventually helping our immune system to seek out, find, and eliminate cancer cells.¹¹ 

There is always ongoing research for new ways to treat metastatic brain tumours, which are tested in clinical trials. Upon discussion with their healthcare provider, patients may be able to join some of these trials.³  

Prognosis and outlook

Prognostic factors

The prognosis for patients with metastatic brain tumours is generally poor, and the condition can significantly decrease one’s quality of life. However, several prognostic distinctions have been made, allowing for patient-tailored therapy choices.³ For example, a good prognosis would encourage the choice for a more intensive treatment, improving survival and quality of life. Patients with a less favourable prognosis will mainly look at controlling symptoms and stabilising metastasis. Next to age, the most important prognostic factors are: 

• Key performance status (KPS): this describes the patient’s level of day-to-day functioning. This includes their ability to care for themselves, their daily activity, physical abilities, and cognitive state
• Number of metastases: The treatment use will also depend on the amount of tumours within the patient’s brain
• Primary tumour control: This refers to the percentage of the primary tumour under control of treatment/being killed

Coping with the emotional and physical challenges of treatment

Multiple forms of therapies can help the patient improve their day-to-day life with the illness. Physical therapy can help regain strength and motor skills, and speech therapy can improve any potential speech difficulties. Occupational therapy can help patients get back to ‘normal’ life and help them regain independence. Supportive, also named palliative care, is also used to help relieve pain and other symptoms of cancer. Caregivers will aim to improve the patient’s quality of life and help them manage their illness. Additionally, they can provide emotional and psychological support for family members and friends. Next to this, gentle exercise and stress management techniques may be useful to help patients cope.¹⁰

Summary

Metastatic brain tumour is a secondary cancer caused by the migration of cancer cells from their original site to the brain. It is a debilitating illness, severely impacting neurological functioning and overall quality of life. There is no complete cure yet; however, several interventions such as surgery, radiation therapy, and chemotherapy, have been proven effective in killing the tumours and improving symptoms. Further, early treatment of the primary cancer may help completely avoid the development of metastatic brain tumours. Living with the illness can be difficult, but multiple support systems can help both the patient and their family cope. 

If you have any persistent signs or symptoms that concern you, it is important to contact your doctor immediately. Additionally, make sure to let them know of any previous history of cancer if you have one.

Metastatic brain cancer probably seems like a scary condition, especially as it currently does not have a cure. However, the existing treatments have already improved a significant amount, and recent technological advancements have given hope to researchers to ameliorate them further.