(P08) Retrospective Comparison of Gammaknife Radiosurgery and Hypofractionated Radiotherapy as Treatment Options for Intracranial Metastases Measuring 4cc or Larger

Abstract

For patients with 1-3 metastatic brain lesions, cranial radiotherapy options include GammaKnife Radiosurgery (GKS) and hypofractionated radiotherapy (HFRT). For lesions measuring 4cc or larger, there is a lack of data regarding efficacy between these two options. We performed a retrospective review to assess various outcomes in such patients treated with GKS or HFRT. We assessed prospectively collected patients treated with GKS or HFRT at our institution for intracranial metastases greater than or equal to 4cc. Patients treated with GKS were collected from 2008-2017 where HFRT patients were collected 2015-2017. Information collected included age, performance status, primary malignancy site, lesion volume, dates of intervention, relapse at treated intracranial site, and last follow-up or death. There were 146 patients, a total of 166 lesions treated. Twenty four (14%) underwent HFRT versus 148 (86%) treated with GKS. The median age of patients was 61 years (range: 39-87 years). Outcomes assessed were local recurrence, distant intracranial failure, and overall survival. Median follow-up times were 6.2 months for GKS and 3.0 months for HFRT. The patient characteristics were well balanced with regard to performance status, age, and primary malignancy. The most common primary site was lung in both arms, comprising 63% overall (GKS: 66%, HFRT: 50%, p=0.29). Median tumor volume was 7.8cc (range: 4.0-92.7). Metastases treated with HFRT were larger (mean volume: 24.5cc versus 9.6cc for HFRT and GKS respectively; p=0.0022). There was no significant difference in local recurrence between the two arms (HFRT: 14.9%, GKS: 25.0%; p=0.23). Median survival significantly favored GKS (HFRT: 3.0 months, GKS: 10.2 months; p<0.01). Percent of distant intracranial failures were significantly higher in patients treated with GKS (HFRT: 4.2%, GKS: 25.7%; p=0.02). We did not find any difference in local recurrence between HFRT versus GKS for brain metastases over 4cc. However, our data resulted in improved survival in patients treated with GKS, despite patients in GKS arm developing more distant intracranial failures. This may be due to effective salvage treatments (GKS or surgical resection) available and shorter follow-up times in HFRT arm. HFRT seems to be as effective as GKS with regard to local control and can be used safely for poor performance status patients or when GKS is not available. Further studies are necessary to verify the effectiveness of HFRT for large, metastatic brain lesions.