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

BackgroundAssess clinical outcomes of focal radiotherapy (RT) in patients with limited brain metastasis (LBM) with whole brain RT (WBRT) avoidance. MethodsPatients 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. ResultsOne hundred and sixty-six patients were managed with median follow-up of 13months and median overall survival of 15months (95% confidence interval (CI) 10.8-19.2). Eighty-three patients had central nervous system (CNS) relapse with median progression-free survival of 11months (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 12months. 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. ConclusionFocal 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.