Frameless Fractionated Gamma Knife Radiosurgery with ICON™ for Large Metastatic Brain Tumors

BACKGROUND: Recently, a new generation of gamma knife radiosurgery (GKRS) equipped with a frameless immobilization system has encouraged the use of fractionated GKRS as an increasingly favorable treatment option. We investigated the preliminary outcome of efficacy and toxicity associated with frameless fractionated gamma knife radiosurgery (FF GKRS) for the treatment of large metastatic brain tumors. METHODS: Fifteen patients with 17 lesions were treated using FF GKRS and included in this study, because of the large tumor size of more than 10 cm(3). FF GKRS was performed based on a thermoplastic mask system for 3 to 5 consecutive days. RESULTS: The mean duration of clinical follow-up was 12 months (range, 4–24), and the local control rate was 100%. Tumor volume decreased in 13 lesions (76.5%), and remained stable in 4 lesions (23.5%). One patient was classified as new lesion development because of the occurrence of leptomeningeal seeding regardless of the tumor volume change. Compared with the initial volume at the time of FF GKRS, tumor volume change at the last follow-up was 62.32% ± 29.80%. Cumulative survival rate at 12 months was 93.3% ± 6.4%. One patient died during the follow-up period because of the progression of the primary disease. No patient showed radiation necrosis on the follow-up images. CONCLUSION: Daily FF GKRS by gamma knife ICON™ revealed satisfactory tumor control rate and low morbidity, despite the short follow-up period. Further prospective studies and a longer follow-up of a large cohort of patients diagnosed with brain metastases are required to elucidate the effect of FF GKRS in brain metastases.