Gamma knife radiosurgery for brain metastases: prognostic factors for survival and local control

Object. The authors conducted an analysis of prognostic factors for patient survival and local control of brain metastases after gamma knife radiosurg ery. Methods. In the survival analysis, 53 consecutive patients with 121 lesions treated in the last 2 years were examined. Common primary sites were lung (26 patients), kidney (seven), breast (three), and colon (three). Patient a ge ranged from 28 to 75 years (median 58 years) and the female/male ratio w as 1:0.9. The median tumor volume was 2.1 cm(3) (range 0.02-45.5cm(3)) and the average prescription dose was 15.4 Gy to the 50% isodose. The median fo llow up was 12 months (range 1-23 months) and the median survival was 46 we eks. Six-month and 1-year survival rates were 63% and 39%, respectively. Karnofs ky Performance Scale score, tumor volume, and presence of extracranial dise ase were statistically significant prognostic factors (p < 0.05)for surviva l in multivariate analysis. Number of lesions, patient age, and adjuvant wh ole-brain radiation therapy were not statistically significant. Ninety-one of 121 lesions with follow-up images were included in the local control ana lysis. The 1-year actuarial local control rate was 48%. In multivariate ana lysis smaller volume was associated with better control (p = 0.0043), and, control period of renal cell carcinoma was shorter than that of the other t umor types (p = 0.0070). Conclusions. Karnofsky Performance Scale score, tumor volume, controlled pr imary cancer, and absence of extracranial metastases were associated with l onger survival in the present study. For local control, tumor volume was a statistically significant factor.