Correlative Analyses Between Immune Markers, Tumor Hypoxia And Outcomes Of Head-And-Neck Cancer Patients Undergoing Chemoradiation: Results From A Prospective Trial

Abstract

Tumor-infiltrating lymphocytes (TILs) influence the response of patients with head-and-neck squamous cell carcinomas (HNSCCs) to chemoradiation and are modulated by the tumor microenvironment and tumor-associated hypoxia. This analysis aimed to assess the prognostic value of TILs and their association with the dynamic tumor hypoxia during chemoradiation in a prospective trial of HNSCC patients. 49 patients with locally advanced HNSCCs were enrolled in this prospective trial prior to undergoing definitive chemoradiation. Patients received tumor biopsies and [18F]-FDG-PET imaging at baseline and [18F]-FMISO hypoxia PET at baseline and in weeks 2 and 5 into treatment. Total lymphocytes, CD3-, CD4-, CD8-positive lymphocytes and expression of PD-1 and PD-L1 were quantified by immunohistochemistry in tumoral and stromal areas of the biopsies and correlated with the tissue hypoxia markers HIF1α, CAIX, CD34 and the longitudinal hypoxia PET/CT data. Potential correlations of immune markers with locoregional control and patient survival were assessed. Patients with high TIL numbers demonstrated increased locoregional control (p = 0.007) and progression-free survival (p = 0.003) compared to patients with lower levels in the biopsies. High numbers of CD3-positive T lymphocytes correlated with improved progression-free (p = 0.018) and overall survival (p = 0.037). In contrast, there was a trend towards impaired progression-free survival for high numbers of CD4-positive regulatory T lymphocytes (p = 0.091), while neither CD8-positive cytotoxic T lymphocytes nor PD-1 or PD-L1 expression correlated with patient outcomes. High levels of TILs were linked to an increased density of CD34-positive microvessels, but not increased levels of hypoxia markers HIF1α or CAIX. No significant correlations could be observed between TILs and dynamic hypoxia PET imaging parameters. In contrast, high expression of intratumoral and stromal PD-1 was associated with low initial tumor hypoxia levels (p = 0.023 for intratumoral PD-1, p = 0.004 for stromal PD-1) as well as a further decrease in the PET hypoxia signal between treatment initiation and week 5 (p = 0.033 for intratumoral PD-1, p = 0.001 for stromal PD-1). In this trial, infiltration of CD3-positive, but not CD4-positive or CD8-positive lymphocytes correlated with an improved locoregional control and increased survival of HNSCC patients after chemoradiation. While no clear associations were found between lymphocyte counts and tumor hypoxia, tumoral PD-1 expression was linked to low initial hypoxia levels and further reductions during treatment. The interplay between tumor hypoxia and tumor-associated immune patterns warrants further investigations to predict treatment response of HNSCC patients.