Focal radiation therapy for limited brain metastases is associated with high rates of local control and low subsequent whole brain radiation therapy

Abstract

BACKGROUND: Assess clinical outcomes of focal radiotherapy (RT) in patients with limited brain metastasis (LBM) with whole brain RT (WBRT) avoidance. METHODS: Patients diagnosed with LBM were entered into a database between January 2010 and February 2017. Patients were recommended WBRT avoidance with focal therapy and three-monthly magnetic resonance imaging. The primary endpoint was overall survival. Secondary endpoints included progression-free survival, initial-site failure (ISF), distant brain relapse (DBF), leptomeningeal disease and rate of WBRT. Analysis involved Kaplan-Meier survival estimate with log-rank tests and Cox-regression analysis. RESULTS: One hundred and sixty-six patients were managed with median follow-up of 13 months and median overall survival of 15 months (95% confidence interval (CI) 10.8-19.2). Eighty-three patients had central nervous system (CNS) relapse with median progression-free survival of 11 months (95% CI 6.7-15.3), of which most failures were DBF (83.1%) with 27 ISF (32.5%). Of the ISFs, 12 (43%) had surgery alone, six had chemotherapy alone and nine received RT. Surgery or chemotherapy alone compared with RT had a significantly higher incidence of ISF with a hazard ratio of 4.96 (P < 0.0001, 95% CI 2.10-11.83) and 6.54 (P = 0.001, 95% CI 2.26-18.87), respectively. WBRT was utilized in only 24 patients, with 83% patients free of WBRT at 12 months. On univariate analysis, number of metastases (P = 0.04), symptomatic extracranial disease (P = 0.04) and early CNS relapse within 6 months (P < 0.01) had worse survival. No grade 3-4 toxicity events were noted in 129 patients undergoing RT. CONCLUSION: Focal RT has a low rate of ISF with low toxicity in patients with LBMs. CNS progression was mainly DBF with low rates of salvage WBRT.