Stereotactic radiosurgery for brain metastases.

Worldwide, approximately 100,000 patients have undergone stereotactic radiosurgery for a variety of intracranial lesions, of which brain metastases represent the most common treatment indication. This article summarizes the major issues surrounding the management of brain metastases, and also analyzes 21 independent reports of Gamma Knife- or linear accelerator-based radiosurgery, representing over 1,700 patients and more than 2,700 lesions. Variable reporting in the studies precludes a definitive, rigorous analysis, but the composite data reveal an average local control rate of 83% and median survival of 9.6 months, both of which are comparable to results in recent surgical reports. The most important prognostic factors for survival appear to be fewer than three lesions, controlled extracranial disease, and Karnofsky performance score (KPS). The exact impact of dose has not been clarified, but a dose-response relationship, especially for > or = 18 Gy, is emerging. The role of whole-brain radiotherapy remains unresolved. It may enhance local control but does not convincingly improve survival and, in some series, is associated with an increased risk of late complications. Chronic steroid dependence and increased intracranial edema do not appear to be common problems. This is an opportune time for the completion of ongoing randomized trials to validate these observations.