Brain metastasis may be detected during the initial screening that is performed after diagnosis of a primary cancer or through screening that is arranged if a patient begins to exhibit symptoms of brain metastasis.
Metastatic brain tumors are diagnosed based on a combination of neurological assessment and imaging studies. More than one imaging study may be used to diagnose the tumor. Magnetic resonance imaging (MRI) and computed tomography (CT) are the most commonly used techniques. Contrast dyes are used during a CT scan or MRI scan to help the physician see the location, size and number of the tumors as well as any pressure or impact on surrounding structures.
Magnetic resonance spectrometry is another technique that may be used to assess the brain metastasis. This technique is used to measure the chemical content in the brain. In addition, position emission tomography (PET) scans provide information about how the tumor uses glucose, which can help the physician tell which parts of the brain tissue are healthy, cancerous, dead or swollen. Full body PET scans can also be performed to detect the primary site of the cancer in cases where the brain metastasis was detected first.
Types of brain metastasis
Some examples of the different types of brain metastasis that arise are described below:
Metastatic lung tumor – This is the most common form of brain metastasis. The tumors are often found before or around the same time as the primary tumor is found in the lung.
Metastatic breast tumor – This is the second most common brain metastasis to occur and often develops a few years after the breast cancer is detected, although it is not unusual for these to develop up to ten years after the primary breast cancer was found. Breast metastasis tends to occur in younger and premenopausal women and is also more common in women with triple negative or HER2/neu positive breast cancer.
Metastatic melanoma – This is the second most common form of brain metastasis to occur in men. Two or more tumors usually develop, which are usually well supplied with blood vessels and tend to bleed.
Metastatic colorectal tumor – This is the third most common type of brain metastasis to occur in both men and women and a single tumor is often found.
The treatment of brain metastasis is usually focused on relieving symptoms and prolonging survival. In some cases, procedures such as open craniotomy, aggressive chemotherapy and radiosurgery may be attempted if a patient is young and fit.
Treatment is usually managed by several specialists including a neurosurgeon and a radiation oncologist. Some of the symptomatic therapies that may be administered include corticosteroids (such as dexamethasone) to prevent swelling in the brain and antiepileptic drugs (such as phenytoin) to prevent seizures.
Radiotherapy may be given in the form of whole-brain irradiation, radiosurgery or fractionated radiotherapy. Surgery is often used to remove single brain tumors or a limited number of brain tumors that are close to each other. This may be followed up with whole brain irradiation.
Chemotherapy is reserved for multiple brain metastases (four or more tumors) and may be combined with other therapies such as radiotherapy.
In cases where cancer has spread to the spine (spinal metastasis), treatment may include radiation therapy alone or in combination with surgery. Spinal metastasis is often seen in cancers of the breast, lung or prostate as well as in lymphoma cases.
Reviewed by Sally Robertson, BSc