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.