ANTI-TUMOUR TREATMENTThe management of brain metastases
Introduction
There are two types of brain tumours. Primary brain tumours arise from cells native to the central nervous system (CNS) and originate in the brain itself. Metastatic brain tumours begin growth in tissues outside the CNS and then spread secondarily to involve the brain. Of the two, brain metastases are the most common and outnumber primary brain tumours by at least 10 to 1. Metastases to the brain occur in over 170,000 patients per year in the USA (1) and are an extremely common complication of systemic cancer.
During the past 15 years, significant advances have been made in the diagnosis and treatment of brain metastases. Although the development of brain metastases still usually indicates a poor overall prognosis for the patient, it is now possible to reverse most of the symptoms of brain metastases and significantly improve a patient’s quality and length of life.
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Frequency
Brain metastases occur in 20 to 40% of cancer patients [1], [2], [3]. This number may increase in the future as the ability to detect small tumours with magnetic resonance imaging (MRI) improves. The frequency of brain metastases may also be rising due to the longer survival of cancer patients in general. The histological type of primary tumour is strongly associated with the frequency and pattern of intracranial spread (Table 1).
Method of spread and distribution
Most tumour cells reach the brain by haematogenous spread, usually through the arterial circulation. Most commonly, the metastasis originates in the lung from either a primary lung cancer or from a metastasis to the lung. Within the brain, metastases are most commonly found in the area directly beneath the grey/white junction [4], [5]. This is due to a change in the size of blood vessels at that point; the narrowed vessels act as a trap for emboli. Brain metastases tend to be more common at the
Clinical presentation
Brain metastases may be detected at the same time the primary is diagnosed (synchronous presentation) or in over 80% of cases, the brain metastases develop after the primary is diagnosed (metachronous presentation). Metastases to the brain are usually symptomatic, and more than two-thirds of patients with brain metastases have some neurological symptoms during the course of their illness [2], [8]. Headache is a common presenting symptom, is more common with multiple metastases or with posterior
Diagnosis
The best diagnostic test for brain metastases is contrast enhanced MRI [6], [9]. If the clinical history is typical and lesions are multiple, usually there is little doubt surrounding the diagnosis. However, it is important that metastases be distinguished carefully from primary brain tumours (benign or malignant), abscesses, cerebral infarction, and haemorrhages. One study (10) has shown that the false positive rate, even when using contrast MRI for the diagnosis of single brain metastases, is
Treatment
The optimum therapy of brain metastases is still evolving. Corticosteroids, radiotherapy, surgical therapy, and radiosurgery all have an established place in management. In addition, chemotherapy is useful in some patients. There are several things to be considered when determining the best treatment for each patient, including the extent of systemic disease, neurological status at diagnosis and the number and site of metastases.
Regardless of treatment, brain metastases are associated with a
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