Clinical outcome of gamma knife (GK) radiotherapy for central nervous system (CNS) metastases from renal cell carcinoma (RCC).

Abstract

e15071 Background: Current treatment modalities for RCC CNS metastases include resection, GK and whole-brain radiotherapy. Existing series describing treatment outcomes include a mix of tumor types, and thus provide little insight into CNS metastasis response by tumor type. Although RCC has historically been considered radioresistant, GK is increasingly being applied to RCC CNS metastases. Methods: RCC pts with brain metastases treated with GK between 1996 and 2010 were retrospectively identified. Pt, GK and systemic therapy characteristics were recorded. Pts were followed radiographically at 30 days post GK and every 3-6 months thereafter with MRI scans. Local failure was defined as treated tumor progression after GK and distant failure was defined as new CNS metastases not in the GK field. Results: One hundred sixty-six patients were identified: 75% male, median age 60, 55% performance status 0, 21% received systemic therapy within 30 days of GK and 97% clear cell histology. Two hundred thirty-three GK procedures were performed on a total of 487 CNS lesions, most commonly in the frontal lobe (32%), parietal lobe (17%), cerebellum (12%), occipital lobe (11%) and temporal lobe (9%). The median interval from diagnosis of RCC to first GK was 20 months (range, 0.1-310). The majority of pts (65%) received a GK dose of 24 Gy with a mean of 1.8 targets per GK procedure. 76% of pts received 1 GK and 24% received multiple GK procedures. Considering all GK procedures, local control was 87%, with an additional 38% of patients having distant CNS failure. The median time to local or distant failure was 9.9 months (range, 5.9-12.9). Local control and failure-free interval of a second GK procedure was not different from the first GK procedure (p=.31, sign test). Potential predictors of CNS failure were examined, and only age >60 (p=.07) and number of targets > 2 (p=.09) approached significance. Prognostic variables, GK treatment characteristics or systemic targeted therapy within 30 days of GK did not predict for subsequent CNS relapse. Conclusions: GK is a common treatment modality for RCC CNS metastases, providing excellent local control and freedom from CNS relapse for several months.