Definition & Overview

Brain metastasis, also known as metastatic brain tumor and metastasis to the brain, begins as cancer in a different part of the body and spreads to the brain over time. The term “metastasis” refers to the spreading of the cancer cells from one part of the body to another. These cancer cells get lodged in that secondary part and become a tumor. Sometimes, the spreading of cancer cells results in a single tumor, usually in the case of breast and kidney cancers. In some cases, multiple tumors form in the case of lung, skin and colon cancers.

Metastatic brain tumors may be accidentally discovered even before the primary cause of cancer is known. There have been cases where patients have undergone a routine MRI or brain scan for the diagnosis of a different, unrelated disease, and brain metastasis is discovered. Once brain metastasis is found and the patient is not believed to have been previously diagnosed with cancer, the “primary site” (site of the primary cancer) needs to be discovered.

Cause of Condition

The primary cause of brain metastasis is the migration of the primary cancer cells from a different body part to the brain. Cancer cells veer away from the primary tumor and enter the bloodstream, using it as a vehicle to transport themselves to another section of the body and attach themselves to a different organ, in this case, the brain. Initially, the body’s immune system may attempt to destroy these rogue cells but if they are huge in number, the body may be overwhelmed and unable to cope. When these rogue cancer cells reach their destination, they may either lie dormant until activated at a later stage or rapidly enlarge causing a new, secondary cancer.

Certain cancers tend to send their cells to a specific organ based on the flow of blood and of their connection with the lymphatic system (which is another highway for spreading cancer cells). For instance, lung cancer usually metastasizes to the brain as breast cancer usually metastasizes to the bones.

Key Symptoms

The key symptoms that trigger a diagnosis of brain metastasis vary depending on where the tumor is located in the brain. These include:

  • Headaches – Headaches, which range from mild to severe, are often the first symptoms that indicate brain metastasis. Headaches may be caused by the tumor itself and may indicate increased intracranial pressure (ICP) caused by the swelling and compression of the brain due to the growing tumor. ICP may also lead to vomiting and disturbance of consciousness.

  • Nausea and vomiting

  • Alteration in consciousness – A brain tumor can affect how the brain functions. When one experiences a mild or radical change in personality or behavior, it usually means that the brain is impaired. For instance, a brain tumor in the frontal lobe can affect logical reasoning while a tumor in the parietal lobe can affect sensory perception.

  • Motor dysfunction – A tumor in the cerebellum often leads to motor problems, such as a problem with balance.

  • Seizures – Seizures occur when there is a disruption in the normal electrical activity of the brain. Nerve cells relay instructions from the brain to the rest of the body. When something happens, such as when a brain tumor impinges the nerves, the proper flow of instructions is affected and a partial or generalized seizure ensues.

Who to See and Types of Treatments Available

As mentioned, the discovery of brain metastasis can occur accidentally when a routine procedure uncovers a brain tumor.

However, when any of the symptoms mentioned above are experienced, further testing is needed to determine whether there is indeed brain metastasis, especially when there is no history of cancer or when the patient has cancer to begin with.

Brain metastasis is diagnosed through a number of imaging procedures like:

  • Computerized tomography (CT) – is often the first measure in determining the presence of brain tumors

  • Positron emission tomography (PET) – differentiates healthy tissue, cancer cells, diseased tissue and swelling

  • Magnetic Resonance Imaging (MRI) – gives a very clear picture of the brain using magnetic and radio waves and provide the exact location, size, and characteristics of the tumor.

Once a brain metastasis diagnosis is confirmed, the neuro-oncologist or neurosurgeon may recommend further testing, such as a biopsy. If the brain metastasis is discovered prior to the primary cancer site, then more lab work and further scans may be prescribed to locate the primary cancer site.

Brain metastasis can be treated in many different ways. Radiation therapy, chemotherapy, combined therapies, experimental therapies and integration therapy are all possible modes of treatment for this condition. Among them, radiation therapy is the preferred treatment protocol as some tumors are less resistant to chemotherapy. In most cases, a combination of surgical, radiation therapy and chemotherapy is required.

Surgery is another option for solitary metastases larger than 3cm and in non-eloquent areas of the brain (outside of speech or motor-related areas). However, surgery may not be an option if the tumor responds well to radiation, if there are multiple tumors and they’re in different sections of the brain and if they’re located in speech or motor-related areas.

The symptoms that were discussed earlier also have to be managed, especially when the headaches become too severe, the vomiting is becoming uncontrollable, or the seizures happen too often. Steroids may help in reducing the swelling that happens in the brain, thereby lessening the pressure on the brain and decreasing the incidence of headaches too. Anti-seizure drugs may be prescribed to curb the seizures.

References:

  • Perry MC. Approach to the patient with cancer. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 182.
  • National Cancer Institute
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