Stereotactic Radiosurgery Alone for Limited Brain Metastases: are We Ready for Prime Time?

Whole brain radiotherapy (WBRT) has traditionally been the standard treatment for brain metastases [1]. More recently, patients with limited brain metastases are being offered stereotactic radiosurgery (SRS), with or without WBRT, in an attempt to improve survival and functional outcomes. A recent editorial has suggested that the sun is setting on WBRT and SRS is rising to be the standard of care [2]. This editorial summarizes the data from individual international randomized trials and a meta-analysis regarding the role of SRS in patients with limited brain metastases, and will focus on its role as a definitive therapy. For patients with limited brain metastases, definitive local therapy in addition to WBRT has been demonstrated to improve local control and overall survival compared with WBRT alone [3–5]. In the Radiation Therapy Oncology Group (RTOG) 9508 trial, patients with 1–3 new brain metastases were randomized to WBRT alone or WBRT plus SRS. A survival advantage was observed in patients with a single brain metastasis who were treated with WBRT plus SRS [5]. Furthermore, the addition of SRS resulted in significant improvements in local tumor control, Karnofsky Performance Status (KPS) and reducing steroid dependency and did not increase acute or late toxicities [5]. Reinforcement of the importance of local control for brain metastasis patients was provided by two Phase III trials comparing WBRT with or without surgical resection in patients with solitary metastases [3,4]. In these studies, both local control and survival were improved by more aggressive local therapy. Interestingly and importantly, a trial comparing resection with or without WBRT showed no survival advantage to the addition of WBRT, even though decreased distant brain failures were observed [6]. This result likely reflects both the efficacy of SRS and WBRT as salvage therapies and the competing risk of extracranial disease