PURPOSE Lymphopenia in patients with glioblastoma (GBM) is related to treatment as well as disease progression. This retrospective study investigated the prevalence, influencing factors, recoverability, and clinical significance of lymphopenia in GBM patients treated with concomitant chemoradiotherapy (CCRT).

PATIENTS AND METHODS A total of 219 patients with newly diagnosed GBM who had received at least 3 cycles of adjuvant temozolomide (TMZ) followed by CCRT with TMZ were enrolled. Serial data on complete blood cell counts, including differential cell counts, were collected just before a new phase and before every treatment cycle of the regimen. Relationships between white blood cell (WBC) variable changes and treatment modalities as well as survival were analyzed. Lymphopenia was classified using the definition of the Common Terminology Criteria for Adverse Events version 5.0.

RESULTS A total of 92 patients (42.0%) showed decreased levels of lymphocytes (< 1500/µL) at baseline. The WBC count, absolute neutrophil count, lymphocyte count, and neutrophil-to-lymphocyte ratio were all significantly decreased after RT/TMZ treatment and did not recover during the adjuvant TMZ period. However, these metrics all began to recover 3 months after the last TMZ cycle, except for the lymphocyte count. The proportion of lymphopenia patients (< 1500 lymphocytes/µL) increased to 74.8% after RT/TMZ and remained steady at approximately 71.5% (range 63.7-75.3%) throughout the management period. Moreover, the number of patients with grade 3 lymphopenia (< 500 lymphocytes/µL) also increased significantly after treatment to reach 2.9% (from 0.9% at baseline). Statistically, 75.7% of lymphopenia patients were predicted to recover in a median time of 240.3 days (95% confidence interval ± 104.7 days) after TMZ withdrawal. There were no dose-dependent relationships between RT or TMZ and lymphopenia. Grade 3 (< 500 lymphocytes/µL) lymphopenia measured at 1 month after RT/TMZ predicted significantly reduced survival (13.0 months vs. 19.5 months, p = 0.011).

CONCLUSION Lymphopenia is a frequent event during GBM disease progression and treatment. Treatment-related lymphopenia is profound and prolonged and can be used as a prognostic factor for GBM patients.