Blood biomarker analysis to differentiate between pseudo-progression and true disease progression in post-treatment glioblastoma.

Abstract

e13501 Background: Current standard treatment for patients with glioblastoma (GBM) includes glucocorticoid therapy, temozolomide (TMZ), and radiation (RT) which may result in lymphotoxic and immunosuppressive effects. MRI use is currently unreliable in differentiating true from pseudo-progression pathology. Recent studies have suggested that total lymphocyte count (TLC) and CD4 cell count are associated with clinical outcomes. Our objective was to investigate whether TLC or CD4 may help to differentiate treatment effect (pesudoprogression) from tumor progression. Methods: Patients were eligible for this retrospective study if they had 1) GBM diagnosed between February 2010 and July 2015, 2) series of cell counts and clinical follow-ups monitored at Washington University, and 3) tumor progression documented by MRI and pathology. The data were analyzed using descriptive statistics, chi-square tests, Kaplan-Meier survival curves, and progression-free survival. Results: A total of 728 charts were reviewed, of which 45adults met eligibility criteria. The median age and KPS scores were 58 years and 80, respectively. MGMT was detected in 33% of patients and 69% of patients had undergone a gross total resection. Median TLC at baseline was 1700 cells/mm3 (range 400-3100). After the completion of RT/TMZ, TLC dropped 41% to a median of 1000 cells/mm3 (range 200-2900). Median TLC was 1000 cells/mm3 (range 300-2900) at the first MRI documented progression. Patients underwent surgery for this MRI documented progression. Pathology revealed that 62% of patients had true tumor progression, 33% had mixed treatment effect and residual tumor, and 4% had necrosis. The median time from diagnosis to progression was 15 months. There were no statistically significant differences in overall survival or progression free survival found in patients with higher vs lower TLC at baseline, completion of RT/TMZ, and time of progression. Conclusions: These preliminary results do not indicate that TLC level in GBM patients can differentiate between true disease progression and pseudo-progression. A larger sample size that includes patients with CD4 data is needed to confirm these results.