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 radiosurgery. 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 age ranged from 28 to 75 years (median 58 years) and the female/male ratio was 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 follow up was 12 months (range 1-23 months) and the median survival was 46 weeks. Six-month and 1-year survival rates were 63% and 39%, respectively. Karnofsky Performance Scale score, tumor volume, and presence of extracranial disease were statistically significant prognostic factors (p < 0.05)for survival in multivariate analysis. Number of lesions, patient age, and adjuvant whole-brain radiation therapy were not statistically significant. Ninety-one of 121 lesions with follow-up images were included in the local control analysis. The 1-year actuarial local control rate was 48%. In multivariate analysis smaller volume was associated with better control (p = 0.0043), and, control period of renal cell carcinoma was shorter than that of the other tumor types (p = 0.0070). Conclusions. Karnofsky Performance Scale score, tumor volume, controlled primary cancer, and absence of extracranial metastases were associated with longer survival in the present study. For local control, tumor volume was a statistically significant factor.