Stereotactic Radiosurgery in the Management of Brain Metastasis

Michael L. Smith, M.D.; John Y. K. Lee, M.D.

Disclosures

Neurosurg Focus. 2007;22(3) 

In This Article

Abstract and Introduction

Abstract

Metastatic disease to the brain occurs in a significant percentage of patients with cancer and can limit survival and worsen quality of life. Glucocorticoids and whole-brain radiation therapy (WBRT) have been the mainstay of intracranial treatments, while craniotomy for tumor resection has been the standard local therapy. In the last few years however, stereotactic radiosurgery (SRS) has emerged as an alternative form of local therapy. Studies completed over the past decade have helped to define the role of SRS. The authors review the evolution of the techniques used and the indications for SRS use to treat brain metastases. Stereotactic radiosurgery, compared with craniotomy, is a powerful local treatment modality especially useful for small, multiple, and deep metastases, and it is usually combined with WBRT for better regional control.

Introduction

Brain Metastasis is the most common intracranial tumor, with an estimated annual incidence of more than 100,000 cases.[44] In 20 to 40% of patients with cancer, metastatic lesions travel to the brain.[8,44] On the basis of historical studies, medical treatment with glucocorticoids alone yields a life expectancy of less than 3 months. The addition of WBRT improves survival to 3 to 6 months.[6,27] Aggressive local treatments such as resection and radiosurgery in combination with WBRT can achieve median survival times of 9 to 12 months in some patients.[2,40]

The RTOG has conducted multiple studies that have helped to delineate several predictive variables for patients with metastatic brain disease. Among the most important predictive factors is the general medical and oncological condition of a patient. Gaspar and colleagues[21] evaluated 1200 patients from previous RTOG studies and used RPA to identify three major variables predictive of outcome: patient age greater than or equal to 65 years, functional independence as defined by a KPS score greater than or equal to 70, and controlled compared with uncontrolled extracranial disease. The authors then stratified the patients into RPA Classes 1, 2, or 3 according to these variables. The single most important predictor of out come was functional status, and patients with KPS scores less than 70 (RPA Class 3) had the worst prognosis. Young and functionally independent patients with controlled extracranial disease (RPA Class 1) had the best prognosis ( Table 1 ).

Although RPA class is the most important predictor of survival, aggressive local therapy (such as resection) for metastatic foci in addition to regional therapy (WBRT) improves survival in selected patients.[35,40] In a surgical trial conducted at a single medical center in the United States, Patchell et al.[40] randomly assigned 48 patients with single brain metastases to two treatment groups and demonstrated a median survival of 40 weeks in the patients that underwent resection and WBRT compared with 15 weeks in patients who underwent WBRT alone. Similarly, Noordjik and coworkers[35] showed a statistically significant survival advantage in their European study of patients with single brain metastases who underwent resection. One study of 83 patients failed to prove a survival benefit in patients who underwent resection.[31] The lack of benefit in this last study has been attributed to the overwhelming influence of RPA class on survival, especially in terms of control of extracranial disease. Patient selection is crucial, therefore, to realizing benefit from aggressive local management of patients with brain metastasis.

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