Brain metastasis

A brain metastasis is a cancer that has metastasized (spread) to the brain from another location in the body. Brain metastases are the most common cause of intracranial mass lesions, and up to 45% of cancer patients eventually develop brain metastases during the course of their illness, with 98,000 to 170,000 new cases diagnosed each year in the US. As primary cancer treatments such as surgery, radiation therapy and chemotherapy have become more effective in the past few decades, people with cancer are fortunately living longer and longer after initial treatment than ever before. However, brain metastases still occur in many patients months or even years after their original cancer treatment. Brain metastases have a poor prognosis for cure, but modern treatments are allowing patients to live months and sometimes years after the diagnosis.

Most common sources of brain metastases

Micrograph showing metastatic colorectal carcinoma. HPS stain.

The most common source of brain metastases in one case series of 2,700 patients undergoing treatment at Sloan Kettering hospital were:

• Lung cancer, 48%
• Breast cancer, 15%
• Melanoma, 9%
• Genitourinary tract cancers, 11%
• Osteosarcoma, 10%
• Neuroblastoma, 5%
• Head and neck cancer, 6%
• Lymphoma, 1%
• Gastrointestinal cancers, especially colorectal and pancreatic carcinoma, 3%

Symptoms

Often, patients have no obvious symptoms that their cancer has spread to the brain. What happens is they come to the doctor for a follow-up visit and the cancer is found on a scan.

Brain metastases can cause a wide variety of symptoms, many of which are also present in minor, more common conditions. They include:

• Vertigo
• New onset headaches
• Cognitive, personality, and behavioral changes.
• Nausea and vomiting
• Memory loss
• Increased intracranial pressure
• Paraesthias
• Visual changes
• Bells palsy
• Ataxia
• Seizure

Treatment

Treatment for brain metastases is primarily palliative, with the goals of therapy being reduction of symptoms and prolongation of life. However, in some patients, particularly younger, healthier patients, aggressive therapy with open craniotomy and maximal excision, aggressive chemotherapy, and radiosurgical intervention (gamma knife radiosurgery) [sentence fragment].

Symptomatic care

Symptomatic care should be given to all patients with brain metastases, as brain metastases often result in severe, debilitating symptoms. In patients with brain metastases, treament consists mainly of:

• Corticosteroids - Corticosteroid therapy is essential for all patients with brain metastases, as it prevents development of cerebral edema (swelling of the brain tissue), as well as treating other neurological symptoms such as headache, cognitive dysfunction, and emesis. Dexamethasone is the corticosteroid of choice.
• Anticonvulsants - Anticonvulsants should be used in all of the 30-40% of patients with brain metastases who experience seizures, as there is a risk of status epilepticus and death, as is the case with other patients with possibly severe seizure types (particularly generalized tonic- clonic, or grand mal, seizures, where the entire brain, not just one local focus or lobe, is pathologically affected). Phenytoin is the most commonly used drug in this setting, but valproic acid and other anticonvulsants could also be used; newer anticonvulsants generally have the advantage of fewer toxic side effects.

Radiotherapy

Radiotherapy plays a critical role in the treatment of brain metastases, and includes whole-brain irradiation, fractionated radiotherapy, and radiosurgery. For decades, whole brain irradiation has been advocated for patients with multiple lesions, a life expectancy of less than three months, or a low Karnofsky performance score, and it does appear at least somewhat effective. However, it often causes severe side effects, including radiation necrosis, dementia, leukoencephalopathy, headache, partial to complete hair loss, nausea, headache, and otitis media. In children the treatment may cause mental retardation, psychiatric disturbances, and other neuropsychiatric effects. Patients are encouraged to talk to their radiation oncologists to weigh the risks and the benefits of some types of whole brain radiation.

Surgery

Brain metastases are often managed surgically, with maximum surgical resection followed by whole-brain irradiation delivering superior survival compared to whole brain irradiation alone. Therefore, in patients with one metastatic brain lesion, limited, absent, or controlled systemic disease, a life expectancy of at least 3 months, and good performance status.

Chemotherapy

Chemotherapy is rarely used for the treatment of brain metastases, as chemotheraputic agents penetrate the blood brain barrier poorly. However, some cancers such as lymphoma,small cell lung carcinoma and breast cancer are very chemosensitive and chemotherapy may be used to treat extracranial sites of metastatic disease in these cancers. Intrathecal chemotherapy is an experimental but promising treatment for brain metastases that involves an intralumbar injection of a chemotheraputic drug into the cerebrospinal fluid. However, it is not approved by the FDA for the treatment of brain metastases.

Prognosis

The prognosis for brain metastases is variable. It depends on the type of primary cancer, the age of the patient, the absence or presence of extracranial metastases, and the number of metastatic sites in the brain. For all patients combined, median survival is only 2.3 months. However, in some patients, such as those with no extracranial metastases, those who are younger than 65, and those with a single site of metastasis in the brain only, prognosis is much better, with median survival rates of up to 13.5 months.

See also

• Neoplasm
• Metastasis
• Cancer
• Brain tumor