Lymphocytopenia and survival after whole‐brain radiotherapy in patients with small‐cell lung cancer

BACKGROUND: To investigate whether whole‐brain radiotherapy (WBRT) decreases lymphocyte counts and evaluate the impact of treatment‐related lymphopenia on survival in patients with brain metastasis. METHODS: Medical records from 60 small‐cell lung cancer patients treated with WBRT from January 2010 to December 2018 were included in the study. Total lymphocyte count (TLC) was obtained pre and post treatment (within 1 month). We performed linear and logistic regression analyses to identify predictors of lymphopenia. The association between lymphopenia and survival was analyzed using Cox regression analysis. RESULTS: Thirty‐nine patients (65%) developed treatment‐related lymphopenia. The median TLC decrease was −374 cells/μL (interquartile range −50 to −722, p < 0.001). Baseline lymphocyte count was a significant predictor of TLC difference and percentage change in TLC. Logistic regression analysis found male sex (odds ratio [OR] 0.11, 95% confidence interval [CI] 0.00–0.79, p = 0.033) and higher baseline lymphocyte count (OR 0.91, 95% CI 0.82–0.99, p = 0.005) were associated with a lower risk of developing ≥grade 2 treatment‐related lymphopenia. Cox regression analysis showed that age at brain metastasis (hazard ratio [HR] 1.03, 95% CI 1.01–1.05, p = 0.013), ≥grade 2 treatment‐related lymphopenia, and percentage change in TLC (per 10%, HR 0.94, 95% CI 0.89–0.99, p = 0.032) were prognostic factors of survival. CONCLUSIONS: WBRT decreases TLC and the magnitude of treatment‐related lymphopenia is an independent predictor of survival in small‐cell lung cancer patients.