Staged Stereotactic Radiosurgery for Large Brain Metastases: Local Control and Clinical Outcomes of a One-Two Punch

BACKGROUND: Treatment options are limited for large, unresectable brain metastases. OBJECTIVE: To report a single institution series of staged stereotactic radiosurgery (SRS) that allows for tumor response between treatments in order to optimize the therapeutic ratio. METHODS: Patients were treated with staged SRS separated by 1 mo with a median dose at first SRS of 15 Gy (range 10-21 Gy) and a median dose at second SRS of 14 Gy (range 10-18 Gy). Overall survival was evaluated using the Kaplan-Meier method. Cumulative incidences were estimated for neurological death, radiation necrosis, local failure (marginal or central), and distant brain failure. Absolute cumulative dose-volume histogram was created for each treated lesion. Logistic regression and competing risks regression were performed for each discrete dose received by a certain volume. RESULTS: Thirty-three patients with 39 lesions were treated with staged radiosurgery. Overall survival at 6 and 12 mo was 65.0% and 60.0%, respectively. Cumulative incidence of local failure at 6 and 12 mo was 3.2% and 13.3%, respectively. Of the patients who received staged therapy, 4 of 33 experienced local failure. Radiation necrosis was seen in 4 of 39 lesions. Two of 33 patients experienced a Radiation Therapy Oncology Group toxicity grade > 2 (2 patients had grade 4 toxicities). Dosimetric analysis revealed that dose (Gy) received by volume of brain (ie, V-Dose(Gy)) was associated with radiation necrosis, including the range V-44.5Gy to V-87.8Gy. CONCLUSION: Staged radiosurgery is a safe and effective option for large, unresectable brain metastases. Prospective studies are required to validate the findings in this study.