Radiation-related lymphopenia as a new prognostic factor in limited-stage small cell lung cancer.

The purpose of this study was to investigate whether the minimum absolute lymphocyte count during radiotherapy (min ALC) and the absolute lymphocyte count 1 month after radiotherapy (post ALC) could predict clinical outcome in limited-stage small cell lung cancer (LS-SCLC) patients. We analyzed 73 LS-SCLC patients treated with chemotherapy and radiotherapy; we collected data on the min ALC from 62 patients and on the post ALC from 60 patients. Both min ALC and post ALC were statistically significant predictors of overall survival in multivariate analysis (hazard ratio [95 % confidence interval] 2.67 [1.06-6.75], P = 0.038 and 2.62 [1.19-5.74], P = 0.016, respectively). The median overall survival of the patients with min ALC ≤297 and >297 cells/μL was 12.2 and 35.3 months, respectively (P < 0.001). Patients with post ALC ≤698 and >698 cells/μL had an overall survival of 19.3 and 46.9 months, respectively (P = 0.001). The median overall survival of the lymphopenia (min ALC ≤ 297 cells/μL or post ALC ≤ 698 cells/μL) and the non-lymphopenia group (min ALC > 297 cells/μL and post ALC > 698 cells/μL) was 19.0 and 131.7 months, respectively, while the median progression survival was 8.1 and 16.6 months, respectively (P < 0.001 and P = 0.001). Radiation-related lymphopenia could predict poor survival in LS-SCLC. Its prognostic role should be evaluated in further prospective studies.