RT-39 * CONTROL OF BRAIN METASTASES FROM RADIORESISTANT TUMORS TREATED BY GAMMA KNIFE RADIOSURGERY

Abstract

BACKGROUND: Renal cell carcinoma, sarcoma, and melanoma are considered to be “radioresistant” tumor histologies. Brain metastases (BM) from these tumors are unlikely to be controlled using the relatively low doses used in whole brain radiotherapy (WBRT). This study was designed to analyze the efficacy of Gamma Knife Radiosurgery (GKRS) on local control of BM from radioresistant primary tumors. METHODS: We reviewed all patients who received GKRS for BM at Columbia University Medical Center between January 2009 and April 2014. All patients were treated using the Gamma Knife Perfexion System. Dosimetric data was collected from treatment plans and metastases were categorized as radioresistant or not. Response was assessed by reviewing follow-up brain imaging studies and classified according to the Response Evaluation Criteria in Solid Tumors. Local control was calculated using the Kaplan-Meier method. RESULTS: In total, 373 tumors were analyzed. Of these, 49 (13.1%) originated from radioresistant cancers. Median follow up was 6 months in the radioresistant cohort and 5 months in the non-radioresistant cohort. The overall local control rate in the radioresistant cohort was 89.8% and 90.1% in the non-radioresistant cohort. Local control of radioresistant tumors at 6-, 12-, and 18- months was 97.2%, 91.5%, and 69.7%, respectively. Local control of non-radioresistant tumors at 6-, 12-, and 18- months was 94.2%, 83.0%, and 79.6%, respectively. Univariate and multivariate analyses demonstrated that radioresistance status of the primary tumor had no significant effect on local control with hazard ratios of 1.0 (p = 1.0, 95% CI: 0.388-2.576) and 0.954 (p = 0.926, 95% CI: 0.349-2.603) respectively. CONCLUSIONS: There was no significant difference in local control of BM from radioresistant and non-radioresistant primary tumors treated with GKRS. Both cohorts showed excellent response and local control, suggesting that GKRS upfront or in addition to WBRT may be an appropriate strategy in the treatment of BM from radioresistant cancers.