The primary objective of this study is to identify the degree of immunosuppression, measured by absolute lymphocyte count (ALC), in newly diagnosed glioblastoma (GBM) patients receiving concurrent temozolomide chemoradiation (CRT). Secondary objectives included associations between ALC, progression free survival (PFS), and overall survival (OS).

Standard GBM treatment includes radiotherapy, chemotherapy, and steroids; all of which can result in immunosuppression by decreasing ALC ^1,2 . Grossman et al. identified a relationship between low ALC and CD4 counts with low CD4 being associated with worse PFS and OS outcomes³.  There remains a lack of research addressing predictors of immunosuppression in patients with newly diagnosed with GBM.

We retrospectively reviewed 158 newly diagnosed GBM patients’ who underwent surgery followed by standard of care CRT. A multivariate proportional hazards Cox model was used to assess the association between the potential prognostic factors, PFS, and OS. We also analyzed the association between ALC and age, sex, MGMT methylation status, and extent of surgical resection. ALC was collected at the time of surgery, CRT start date, and two, four, six, and 10 weeks post CRT start date. 

Of the 158 patients collected, 92 were males, 47 had gross total resection of the tumor, 58 patients were younger than 65 years, and 47 (30%) were MGMT methylated. Patients with ALC lower than 300/mm³ had a median survival of 3.5 months compared to the 16 months in patients with ALC median higher than >300 (p=0.0007). ALC higher than 300/mm³ compared to PFS and OS showed an adjusted hazard ratio of 0.358 (p=0.006) and 0.297 (p=0.002), respectively. 

Our study concluded that ALC lower than 300/mm³ was associated with a significant decrease in PFS and OS in this dataset.