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

Stereotactic Radiosurgery for Brain Metastases

Because of the success of aggressive local control with resection for a single metastasis, neurosurgeons have pursued a complementary approach with the use of SRS to control single and multiple brain metastases. In a relatively short time, SRS has emerged as an important noninvasive option in the neurosurgical armamentarium against brain metastasis. Brain metastases are discrete and often semispherical, thus making attractive radiosurgical targets.

The largest and most influential study conducted to date in patients with brain metastasis treated with SRS comes from RTOG 95-08 by Andrews and colleagues.[2] This was a multiinstitutional clinical trial in which 333 patients were randomly assigned to two treatment groups. The patients in one group underwent both SRS and WBRT and those in the other group underwent WBRT alone. Study inclusion criteria were the presence of one to three brain metastases, patient age older than 17 years with no history of previous cranial irradiation, and a KPS score greater than 70. In contrast to the patients who participated in the studies of resection alone, patients with multiple brain metastases (one to three lesions) were eligible to participate. The primary end point was survival. Two major groups of patients benefitted from radiosurgery: those with a single metastasis (regardless of RPA class) and those in RPA Class 1 with up to three brain metastases. An intent-to-treat analysis was used to control for both known and unknown biases. It is important to note that 31 of 164 patients assigned to the SRS group did not actually undergo SRS, and 28 of 167 patients in the WBRT arm received salvage SRS. Hence, a "per protocol" analysis probably would have demonstrated an even greater survival advantage for the same groups. On the basis of this randomized trial, SRS has been established as an important tool in the local management of brain metastasis.

In an earlier randomized clinical trial, Kondziolka et al.[24] examined local control as the primary end point in their study of patients with multiple metastases. The authors compared local control in patients with two to four metastases who underwent either WBRT alone or WBRT and SRS. The study was stopped after 60% accrual because the interim analysis showed a dramatic advantage to adding SRS.[24] Median time to local failure was 6 months in patients who received WBRT alone and 36 months in patients who received both WBRT and SRS. Because the study was stopped early, the survival difference between the two groups was not statistically significant. Nevertheless, the authors demonstrated that SRS improves local control.

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