Prognostic Significance of Immune Cell Infiltration in Muscle Invasive Bladder Cancer Treated with Definitive Chemoradiation: A Secondary Analysis of RTOG 0524 and 0712
Chemoradiation therapy (CRT) is a treatment for muscle invasive bladder cancer (MIBC). Using a novel transcriptomic profiling panel, we validated prognostic immune biomarkers for response to CRT on 70 pre-treatment tumor samples from NRG/RTOG 0524 and 0712, two prospective trials of MIBC. Disease-free survival (DFS) and overall survival (OS) was estimated by Kaplan-Meier method and stratified by genes correlated with immune cell proportions and activation.  Cox proportional hazards models were used to assess group differences. Sample clustering based on gene expression profiles driven by immune cell proportions demonstrated cluster 2 with a high percentage of immune cell content with significantly longer DFS (Hazard Ratio (HR): 0.53 (95% CI: 0.26 – 1.10), p=0.071) and OS (HR: 0.48 (95% CI: 0.24 – 0.97), p=0.040) than cluster 1 with a low percentage of immune cell content.  Higher expression of T cell infiltration genes (CD8A and ICOS ) showed longer DFS (HR: 0.40 (95% CI: 0.21 – 0.75), p=0.005) and OS (HR: 0.49 (95% CI: 0.25 – 0.94), p=0.033). Higher expression of interferon gamma signaling (IDO1) also showed longer DFS (HR: 0.44 (95% CI: 0.24 – 0.88), p=0.021) and OS (HR: 0.49 (95% CI: 0.24 – 0.99), p=0.048). These findings have treatment implications that should be validated in CRT MIBC trials particularly those that integrate immunotherapy. Overall design: To validate the prognostic value of T cell infiltration and IGS gene signatures in MIBC treated with CRT using a novel next-generation RNA-sequencing (NGS) profiling platform (Cofactor ImmunoPrism assay) that requires as little as 20 ng input RNA utilizing samples from two prospective trials of CRT in MIBC (NRG/RTOG 0524 (4) and 0712 (5)).Samples from the NRG biobank were profiled with the Cofactor Genomics ImmunoPrism assay, a CAP-CLIA certified NGS platform to quantify TME immune cell populations and activation using novel deconvolution algorithms from bulk tumor RNA .Using 64 differentially expressed genes associated with total immune cell proportions we identified high and low total immune cell proportions.