To identify prognostic factors and investigate patient survival after whole-brain radiotherapy (WBRT) for initial brain metastases arising from non-small cell lung cancer (NSCLC).

Patients diagnosed with NSCLC between 1 January 2010 and 30 September 2019, and who received WBRT upon first developing a brain metastasis, were investigated. Overall survival was determined as related to age, sex, duration between initial examination and brain metastasis detection, stage at the first examination, presence of metastases outside the brain, blood analysis findings, brain metastasis symptoms, radiotherapy dose and completion, imaging findings, therapeutic course of chemotherapy and/or radiation therapy, histological type, and gene mutation status.

Thirty-one consecutive patients (20 men and 11 women) with a mean age of 63·8 years and median survival of 129 days were included. Multivariate analysis with stepwise testing was performed to investigate differences in survival according to gene mutation status, lactate dehydrogenase (LDH) level, irradiation dose, WBRT completion and Stage status. Of these, a statistically significant difference in survival was observed in patients with gene mutation status (hazard ratio: 0·31, 95% CI: 0·11–0·86, p = 0·025), LDH levels <230 vs. ≥230 IU/L (hazard ratio: 4·08, 95% CI: 1·45–11·5, p < 0·01) received 30 Gy, 30 Gy/10 fractions to 35 Gy/14 fractions, and 37·5 Gy/15 fractions (hazard ratio: 0·26, 95% CI: 0·09–0·71, p < 0·01), and stage IV versus non-stage IV (hazard ratio: 0·13, 95 CI:0·02–0·64, p < 0·01)

Gene mutation, LDH, radiation dose and Stage are prognostic factors for patients with initial brain metastases who are treated with WBRT.