All variables with prognostic significance in the univariate analysis were further entered into the multivariate Cox regression analysis, and the results showed that dynamic change of SII (P = 0.032), Lung-molGPA (P < 0.001), and thoracic radiation (P = 0.048) were independent indicators of brain radiotherapy outcomes in patients with BM arising from EGFR-mutant lung adenocarcinoma. The gene discussed is EGFR; the disease is lung adenocarcinoma.