Small-cell lung cancer (SCLC) has poor prognosis owing to the high risk of distant metastasis.

To identify the prognosticators of brain metastasis from SCLC treated by whole-brain radiotherapy.

We evaluated patients diagnosed with primary brain metastasis from SCLC between 1 January 2010 and 30 September 2019. Age, sex, disease stage at the first examination, time to the diagnosis of brain metastasis, state of other lesions at the diagnosis of brain metastasis, haematological parameters, neurologic symptoms, whole-brain radiotherapy dose, imaging findings of the brain metastasis (single or multiple), and chemotherapy and radiotherapy status were investigated for correlations with survival from the diagnosis of brain metastasis.

A total of 24 participants were evaluated. After radiotherapy, the median survival period was 118·5 (22–998) days, and 21 patients died during the follow-up period. Multivariate stepwise analysis of the four parameters of lactate dehydrogenase (LDH) level (within vs. above the reference value), platelet level (continuous variable), neurologic symptoms (with versus. without), and NSE (neuron-specific enolase) level (continuous variable) identified the following significant differences: neurologic symptoms were 3·81 (95% CI 1·07–13·5, p = 0·04), and NSE was 1·01 (95% CI 1·00–1·01, p = 0·04).

NSE and neurologic symptoms are prognosticators of brain metastasis from SCLC treated by whole-brain radiotherapy.