Gamma knife surgery for brain metastases: indications for and limitations of a local treatment protocol.

Abstract

The purpose of this retrospective study was to evaluate results of a local treatment protocol using gamma knife surgery (GKS) for brain metastases without upfront whole brain radiation therapy (WBRT). Results for 521 consecutive patients satisfying the following 3 criteria were analysed: 1) a maximum of 3 tumours with a diameter of 25 mm or more; 2) no prior WBRT; 3) no surgically in accessible large (>30 mm) tumours. Large tumours were surgically removed and all smaller lesions were treated by GKS without up front WBRT. New lesions, detected with follow-up MRI, were appropriately treated with repeat GKS. Overall survival (OS), neurological survival (NS), qualitative survival (QS) and new lesion-free survival (NLFS) curves were calculated and the prognostic values of covariates were obtained. OS and NS were compared according to tumour number. In total, 1023 separate sessions were required to treat 4562 lesions. The primary organs were lung in 369 patients, gastro-intestinal tract in 70, breast in 33, urinary tract in 24, and others/unknown in 25. The median OS period was 9.0 months. On multivariate analysis, the significant prognostic factors for OS were found to be extracranial disease (risk factor: active), Karnofsky performance status (KPS) score (<70) and gender (male). NS and QS at one year were 85.6% and 73.0%, respectively. The only significantly poor prognostic factor for NS was carcinomatous meningitis. NLFS at 6 months was 68.9%. For both OS and NS, the differences between a few (</=3) and many (4-10) brain lesions were not significant (OS: p=0.3128, NS: p=0.5509). Patients with numerous (>10) tumours had a significantly poorer prognosis than those with </=10. Our protocol, aggressively applying GKS, provides excellent results in selected patients with </=10 brain lesions and no carcinomatous meningitis.