Abstract 6236: Low CD8 T cells predicts benefit from hypoxia-modifying therapy in bladder cancer
Authors: Smith Vicky , Mukherjee Debayan , Tsakiroglou Anna Maria , Baker Alexander , Mistry Hitesh , Choudhury Ananya , Hoskin Peter , Illidge Tim , West Catharine 
Published: June 2022

Abstract
Introduction: Hypoxia and an immunosuppressive tumor microenvironment (TME) are both independent negative prognostic factors that contribute to radiotherapy resistance in muscle-invasive bladder cancer (MIBC). Therefore, we sought to investigate the relationship between them and whether the immune TME can predict benefit from hypoxia-modifying therapy in the BCON trial that randomized MIBC patients to radiotherapy alone or with carbogen plus nicotinamide (CON).
Methods: Tissue microarrays of diagnostic biopsies from 116 MIBC patients from the BCON trial were stained using Akoya Opal࣪ multiplex immunohistochemistry (IHC) reagents (CD8, CD4, FOXP3, CD68, PDL1, DAPI). Following multispectral scanning the slides were spectrally unmixed using Inform and marker proportion quantified using HALO software as the percentage of the total cell count per sample. Hypoxia was assessed as the presence of CA9 protein using IHC (n=111) and by using transcriptomic data (n=80) previously acquired to determine an hypoxia score (HS). Relationships with overall (OS) and local progression-free (LPFS) survival were assessed using Cox proportional hazard models and Kaplan-Meier curves in R. Molecular subtypes were determined using the consensusMIBC package in R.
Results: Basal/squamous and stroma-rich vs other molecular subtypes had increased hypoxia scores and immune markers (CD8, CD4, CD68, PDL1). Tumors with CA9 present had significantly lower proportion of CD8 T cells (p=0.027), and CD4 T cells (p=0.01) but there were no significant differences for other immune markers or significant differences associated with HS. Only CD8 showed a relationship with survival and we found the relationship between log(HR) and CD8 to be non-linear, which led to placing patients within groups. Patients with a low vs high proportion of CD8 T cells had a significantly worse 2-year OS (n=116, p=0.003) and LPFS (n=116, p=0.02). CD8 proportion was also prognostic in patients receiving radiotherapy alone for OS (n=61; p=0.003) and LPFS (n=61; p=0.003). Patients with low CD8 T cells had improved OS when CON was given with radiotherapy (n=87; p=0.05), but those with high CD8 T cells derived no benefit (n=27; p=0.95). Prognostic significance of low CD8 T cells in the whole cohort remained after adjusting for clinicopathologic variables and hypoxia measured using CA9 (HR 0.32; 95% CI 0.18-0.57; p&lt;0.001) while hypoxia had borderline significance (HR=0.62; 95% CI 0.37-1.02; p=0.059).
Conclusions: Low proportion of CD8 T cells in the TME of MIBC patients has independent prognostic and predictive value. It can be used to identify patients likely to benefit from the addition of carbogen and nicotinamide to radiotherapy.
Citation Format: Vicky Smith, Debayan Mukherjee, Anna Maria Tsakiroglou, Alexander Baker, Hitesh Mistry, Ananya Choudhury, Peter Hoskin, Tim Illidge, Catharine West. Low CD8 T cells predicts benefit from hypoxia-modifying therapy in bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6236.