Post-Chemoradiation Lymphopenia and Baseline Eosinophil Counts as Prognostic Markers in Glioblastoma

Purpose To evaluate whether post-treatment lymphopenia and white-cell differentials predict overall survival (OS) in glioblastoma (GBM). Methods We retrospectively analyzed 93 GBM patients treated with standard surgery, radiotherapy (60 Gy in 30 fractions), and temozolomide. Clinical data (age, Karnofsky performance status, extent of resection, MGMT methylation, corticosteroid use, dose metrics) and hematologic indices (absolute lymphocyte count (ALC), neutrophil-to-lymphocyte ratio (NLR), absolute eosinophil (AEC) and basophil counts, etc.) were collected at baseline and up to 3 months post-chemoradiation. Results Median OS in our cohort was 24.7 months (95% CI, 20.8–35.0). On univariate analysis, ALC < 0.75 ×10³/µL at 3 months was associated with shorter OS (HR 1.88; p  = 0.042), and higher AEC correlated with improved OS at baseline (HR 0.71; p  = 0.022) and at 1–2 months (HR 0.44 and 0.57; p  = 0.046 and 0.016). In the combined multivariable model—controlling for age, extent of resection, MGMT status, steroid usage and dose metrics—baseline AEC remained independently prognostic (aHR 0.57; p  = 0.016), whereas the association for 3-month ALC < 0.75 ×10³/µL attenuated (aHR 1.27; p  = 0.49). Conclusions Baseline eosinophils were independently associated with improved survival, while post-treatment lymphopenia was adverse only on univariate analysis. Such findings highlight the importance of host immunity and baseline eosinophils as a potential prognostic marker of OS in GBM and warrant larger, prospective studies on lymphocyte-sparing treatment strategies and prognostic marker validation.