Baseline tumor genomic and gut microbiota association with clinical outcomes in newly diagnosed glioblastoma (GBM) treated with atezolizumab in combination with temozolomide (TMZ) and radiation.

2006 Background: Checkpoint inhibitor (CPI) therapy has demonstrated overall limited efficacy in the treatment of GBM. Sixty newly diagnosed GBM patients unselected for MGMT status underwent treatment with concurrent atezolizumab with radiation therapy and TMZ followed by adjuvant atezolizumab and TMZ (NCT03174197). Clinical data has been reported previously. Methods: Genomic (WES with somatic mutation and SCNA determination N = total 42 samples, 33 baseline, 9 TP-2), transcriptomic (RNA seq N = total 72 samples, 54 baseline, 18 TP-2), and metagenomic sequencing of fecal samples (N = total 45 samples, 26 pre samples, 13 post RT samples, six 6m samples) analyses were conducted on pre-treatment samples. Findings were correlated with clinical outcome including OS and PFS. Twenty of the 60 patients underwent re-resection for suspected recurrent disease of which nine patients had WES and RNA seq performed successfully on paired pre and post treatment samples. Results: Somatic mutation, copy number and ploidy profiles were consistent with known aberrations in GBM. An unsupervised molecular network-based stratification of pre-treatment tumor mutations resulted in patients being grouped in 3 clusters with survival difference. Patients with GBM harboring an EGFR aberrancy were associated with a relatively worse mOS following treatment compared to patients with tumors enriched with PTEN alterations, while patients with IDH1 mutations had the longest mOS. Gene set enrichment analysis of gene expression in tumors from patients ( < mOS vs ≥mOS) identified genes associated with lymphocyte activation and immune response in patients with longer survival (p < 0.01) Unsupervised hierarchical clustering of bacterial taxa demonstrated two distinct clusters with significant difference by OS. Survival analysis and Analysis of Compositions of Microbiomes with Bias Correction (ANCOM-BC) revealed distinct taxa associated with OS ( Ruminococcus spp.) and response to treatment ( Eubacterium spp.), respectively. Conclusions: In this small CPI-treated GBM cohort, WES, SCNA and RNA seq identified pre-treatment tumor features that separated patients by survival. The fecal microbiome observations in our GBM cohort warrants further investigation. Clinical trial information: NCT03174197.