Metastases occur in approximately 40% of cancer patients, increase in frequency with prolonged survival from the primary disease, and represent a poor prognostic factor. Metastatic disease to the brain occurs in 15–28% of all cancer patients.169,170 Brain metastases usually occur in supratentorial watershed areas, but gastrointestinal and genitourinary carcinomas tend to metastasize to the posterior fossa.171 Lung and breast carcinomas are the most common primary tumors that spread to the brain (see Figure 10).171,172 Other primary tumors that progress to involve the central nervous system include gastrointestinal cancers, pelvic cancers, melanoma, and renal cell carcinomas.
Figure 10. Metastatic lung adenocarcinoma. 200x . Photomicrograph of sheets of highly pleomorphic malignant cells with epithelial characteristics. Note focal glandular formation (arrow).
Brain metastasis may be discovered serendipitously in an asymptomatic patient, or it may present as signs and symptoms of anatomic mass effect, intracranial hemorrhage, or seizures.154 Headaches are the most common presenting symptom, but epilepsy is also a common presentation, observed in 15–25% of patients.27 In one study, 17% of patients with brain tumors and epilepsy had metastatic disease after further evaluation. Most lesions were located in the centroparietal cortex.173
A patient presenting with a brain metastasis has a 1-month expected survival with no treatment, about 2 months with corticosteroids, and 3 to 6 months with whole-brain radiation.174–177 Patchell and colleagues found that patients with single brain metastases who had surgical resection followed by radiotherapy had fewer recurrences of cancer in the brain than similar patients treated with surgery alone. The likelihood of death from neurologic causes also decreased, but there was no significant increase in the duration of functional independence.178
In another study, comparing a group with surgical resection and radiation therapy with a group that had only brain biopsy and radiation, the group with surgical resection had a better survival, 40 weeks versus 15 weeks.185
Long-term survival greater than 10 years has been reported in a small subset of patients with metastatic non–small-cell lung carcinoma who were treated with surgical resection and radiation.
Stereotactic radiosurgery is another treatment modality that has gained popularity in recent years. Patients who respond best to this treatment are those with controlled systemic disease and non-melanoma primary histology. Such patients have a median survival of 39 weeks.79
Multiple metastases occur in 66% of patients. Some benefit from radiation therapy, but most are treated medically with corticosteroids and antiepileptic drugs. The overall prognosis for this subset of patients is poor, with survival ranging from 2 to 6 months.
Patients with metastatic brain disease and epilepsy are a treatment challenge. Selection of treatment must take into account not only seizures and other neurologic dysfunction, but also the systemic disease and the potential morbidities and mortality associated with treatment.
Reviewed and revised March 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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