Background: In the treatment of brain metastases using a stereotactically modified linear accelerator it could be shown that a single dose between 15 and 25 Gy leads to partial or complete remission of so-called radioresistant metastases from melanoma and hypernephroma. Radiosurgery of brain metastases then started in centers all over the world, however, experiences with brain metastases of renal cell carcinoma are yet limited. The aim of this analysis is therefore to present the treatment results of radiosurgery of brain metastases. Furthermore, in this paper prognostic subgroups shall be defined, in order to establish guidelines for an optimal therapy strategy.
Materials and methods: Radiosurgery means stereotactically guided high-precision irradiation methods by extremely focussing ionizing radiation within the target volume as a single dose application. The characteristic steep dose decrease allows the selective destruction of small intracranial lesions, while the surrounding brain tissue is optimally protected. Two methods, Gamma Knife and stereotactic modified linear accelerator are clinically available.
Results: In larger studies from different groups all over the world, local tumor control rates from 85% to 95%, recurrence rates from 6% to 15% and side effects between 3% and 15% have been attained, independent of the system used. Prognostic factors, like volume of metastases < 10 ml, applied dose > 18 Gy, one or two metastases, absence of extracranial metastases, good patient performance with a Karnofsky score > 70%, primary treatment and more than one year between primary diagnosis and brain metastases showed a trend toward improved survival. Depending on the prognostic factors the median survival after radiosurgery ranged from 6 to 12 months. Retrospective comparison of radiosurgery and surgical series suggest that both modalities attain similar results. The dose can be applied with an accuracy of 0.3 mm.
Discussion: Based on these experiences, brain metastases can be treated by radiosurgery, primarily in patients with one or two metastases or in combination with whole brain irradiation as a boost in patients with more than two metastases. Furthermore with radiosurgery a new treatment modality exists to re-irradiate patients who have been failed after surgery or whole brain irradiation.