Abstract
Radiosurgery has recently provided an alternative to conventional therapy for the treatment of brain metastases. This non-invasive technique delivers a single large fraction of ionizing radiation to a well-defined small intracranial target as brain metastases. After a computerized tomography (CT) with stereotactic frame in place for tumor localization, a dosimetric study was performed. The sharp dose gradient of radiation reduces the dose to the surrounding normal structures at a minimal level (> 10%). The prescribed dose at the periphery of the lesion varies from 8 to 27 Gy with a combined whole brain irradiation and from 20 to 35 Gy without any irradiation. Radiosurgery has been reported to be highly efficacious with a local control rate of 86% (not increased size without local recurrence). Brain metastases from melanoma and renal carcinoma are usually resistant to conventional irradiation and are highly sensitive with this technique. The morbidity is very low with a symptomatic edema rate of 5-10% at 2 years, resolved with corticosteroids. A radiation necrosis has been reported in less than 5% of cases. The patients with a good performance status, without any extracranial metastasis and with a solitary brain metastases have presented the best survival rate. New brain metastases have occurred in 20 to 30% of the cases during the follow-up. Eleven to 25% of patients died from their intracranial disease and the others from the extracranial evolution of the cancer. The median survival was still poor, ranging from 8 to 12 months. Radiosurgery is a good choice for surgically inaccessible and recurrent tumors. It represents an alternative to the neurosurgery with or without whole brain irradiation, taking into account different prognostic factors and morbidity rate. The local control and the survival rates without neurologic symptom should be considered the major endpoints of different ongoing randomized studies for evaluating the role of the radiosurgery.
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