Microenvironment in head and neck cancer to identify biomarkers of response to therapy

748 Figure 2 Immune infiltration based on primary tumor location Increase in immune infiltrate in primary tumors as distance from liver increases. P-values determined by Jonckheere-Terpstra Test with FDR corrections Abstract 748 Figure 3 CD14 and CD163 Correlate with OS A+C) Kaplan Meier Curve of OS for (A) CD14 (Median OS: 20 vs. 90 months, log-rank p-value <0.01) and (C) CD163 (Median OS: 15 vs. 32 months, log-rank p-value<0.01). B+D) Multivariate Cox Hazard Models. Assumptions of Cox Hazard Model were checked with Schoenfeld residual values, significance level <0.01748 Figure 3 CD14 and CD163 Correlate with OS A+C) Kaplan Meier Curve of OS for (A) CD14 (Median OS: 20 vs. 90 months, log-rank p-value <0.01) and (C) CD163 (Median OS: 15 vs. 32 months, log-rank p-value<0.01). B+D) Multivariate Cox Hazard Models. Assumptions of Cox Hazard Model were checked with Schoenfeld residual values, significance level <0.01 Conclusions The TIME of CC varies significantly by primary tumor location and between primary and metastatic lesions. D-ECC has a favorable immune profile compared to ICC and H-ECC, with a better milieu for antigen presentation including increased mesothelin and less suppressive macrophages, which may support better response to checkpoint blockade. The data supported the hypothesis that higher densities of intra-tumoral M2 macrophages and myeloid cells correlated with worse OS, even after controlling for clinical variables, suggesting that these cell populations may represent promising immunotherapeutic targets in CC. http://dx.doi.org/10.1136/jitc-2020-SITC2020.0748 749 SPATIAL PROFILING OF THE TUMOUR MICROENVIRONMENT IN HEAD AND NECK CANCER TO IDENTIFY BIOMARKERS OF RESPONSE TO THERAPY Arutha Kulasinghe*. Queensland University of Technology, Kelvin Grove, Australia Background Immune checkpoint inhibitors (ICI) have shown durable and long-term benefits in a subset of head and neck squamous cell carcinoma (HNSCC) patients. To identify patient-responders from non-responders, biomarkers are needed which are predictive of outcome to ICI therapy. Cues in the tumour microenvironment (TME) have been informative in understanding the tumour-immune contexture. Methods In this study, the NanoString GemoMxTM Digital Spatial Profiling (DSP) technology was used to determine the immune marker and compartment specific measurements in a cohort of HNSCC tumours from patients receiving ICI therapy. Results Our data revealed that markers involved with immune cell infiltration (CD8 T-cells) were not predictive of outcome to ICI therapy. Rather, a number of immune cell types (CD4, CD68, CD45, CD44, CD66b) were found to correlate with progressive disease. Conclusions This study, to our knowledge, represents the first spatial analysis of HNSCC tumours. Ethics Approval The study was approved by the Queensland University of Technology Ethics Board. http://dx.doi.org/10.1136/jitc-2020-SITC2020.0749 750 MALAT1 LNCRNA CONTROLS METASTATIC REACTIVATION OF DORMANT BREAST CANCER BY IMMUNE EVASION Dhiraj Kumar*, Sreeharsha Gurrapu, Hyunho Han, Yan Wang, Seongyeon Bae, Hong Chen, Chang-Jiun Wu, Filippo Giancotti. The University of Texas MD Anderson Cancer Center,