Gamma Knife surgery for metastatic brain tumors

Abstract

The authors compared results of Gamma Knife surgery (GKS) for brain metastases obtained at 2 institutions in Japan. They analyzed a consecutive series of 2390 patients with brain metastases who underwent GKS from 1998 through 2005 in 2 institutes (1,181 patients in Chiba; 1,209 in Mito). In the 2 facilities, 1 neurosurgeon each was responsible for diagnosis, patient selection, GKS procedures, and follow-up (T.S. in Chiba, M.Y. in Mito). Even if tumor numbers exceeded 4, all visible lesions were irradiated with a total skull integral dose (TSID) of <or= 10-12 J. No prophylactic whole-brain radiotherapy (WBRT) was applied. If new distant lesions were detected, salvage GKS was appropriately performed. The distributions of patient and treatment factors did not differ between institutes. The most common primary tumors were lung cancer (1,572 patients), followed by gastrointestinal tract (316), breast (211), kidney (113), and other cancers (159). The median survival periods were 7.7 months in Chiba and 7.0 months in Mito (p = 0.0635). The significant poor prognostic factors for overall survival were active extracranial disease status, male sex, and low initial Karnofsky Performance Scale score on multivariate analysis (all p < 0.0001). The neurological survival rates at 1 year were 86.6% in Chiba and 84.2% in Mito (p = 0.3310). This 2-institute study demonstrated no significant institutional differences in any of the treatment result items. Gamma Knife surgery for brain metastases without prophylactic WBRT prevents neurological death and allows a patient to maintain good brain condition. However, there is 1 important patient selection criterion: regardless of how many tumors there are, all lesions can be irradiated with a TSID of <or=12 J.