Feasibility and safety of cavity-directed stereotactic radiosurgery for brain metastases at a high-volume medical center

OBJECTIVE: Our objective was to report safety and efficacy of stereotactic radiosurgery (SRS) to the surgical bed following resection of brain metastases. METHODS: Eighty-seven consecutive patients who underwent cavity-directed SRS to the operative bed for the treatment of brain metastases between 2002 and 2010 were evaluated. SRS required a gadolinium-enhanced, high-resolution, T1-weighted magnetic resonance imaging for tumor targeting and delivered a median dose of 18 Gy (14-22 Gy) prescribed to encompass the entire resection cavity. Whole brain irradiation was reserved for salvage. Patients were followed every 3 months with clinical examination and magnetic resonance imaging. Overall survival, local and regional recurrence, and factors affecting these outcomes were evaluated using Kaplan-Meier and log-rank analyses. RESULTS: The median imaging follow-up was 7.1 months, with >40% of patients having imaging for ≥1 year. Local control at 1 and 2 years was 82% and 75%, respectively. Cavity recurrence was more common with a tumor diameter >3 cm (P < .020) or resection cavity volume >14 mL (P < .050). One-year local control for tumors <2 cm, 2 cm to 3 cm, and >3 cm were 100%, 86%, and 72%, respectively. Neither subtotal resection nor target margins >2 mm to 3 mm affected local control. The median overall survival was 14.3 months with actuarial 5-year survival of 20%. Actuarial regional central nervous system recurrence was 44% at 1 year. On univariate analysis, only the presence of extracranial disease was associated with survival (P < .001) and central nervous system failure (P < .030). CONCLUSIONS: Excellent local control is achievable with cavity-directed SRS in well-selected patients, particularly for lesions with diameter <3 cm and resection cavity volumes <14 mL. Long-term survival is possible for select patients.