Timing of Brain Radiation Therapy Impacts Outcomes in Patients with 
Non-small Cell Lung Cancer Who Develop Brain Metastases

Background and objective Radiotherapy combined with chemotherapy or molecular targeted therapy remains the standard of treatment for brain metastases from non-small cell lung cancer (NSCLC). The aim of this study is to determine if the deferral of brain radiotherapy impacts patient outcomes. Methods Between May 2003 and December 2015, a total of 198 patients with brain metastases from NSCLC who received both brain radiotherapy and systemic therapy (chemotherapy or targeted therapy) were identified. The rate of grade 3-4 adverse reactions related to chemotherapy and radiotherapy had no significant difference between two groups. 127 patients received concurrent brain radiotherapy and systemic therapy, and 71 patients received deferred brain radiotherapy after at least two cycles of chemotherapy or targeted therapy. Disease specific-graded prognostic assessment was similar in early radiotherapy group and deferred radiotherapy group. Results Median overall survival (OS) was longer in early radiotherapy group compared to deferred radiotherapy group (17.9 months vs 12.6 months; P=0.038). Progression free survival (PFS) was also improved in patients receiving early radiotherapy compared to those receiving deferred radiotherapy (4.0 months vs 3.0 months; P<0.01). Receiving tyrosine kinase inhibitor (TKI) therapy after the diagnosis of brain metastases as any line therapy improved the OS (20.0 months vs 10.7 months; P