Immune checkpoint expression in HNSCC patients before and after definitive chemoradiotherapy

Abstract

Background: Primary platinum-based chemoradiotherapy (CRT) remains the treatment of choice for nonresectable squamous cell carcinoma of the head and neck (HNSCC). Immune-checkpoint modulators are used as palliative therapy and studied in combination with definitive CRT. However, the immunological changes by CRT need yet to be understood. Methods: A cohort consisting of 67 paired tissue biopsies (N = 134) of HNSCC patients before and after CRT was created. The expression of PD-1, PD-L1, and CD27 of tumor and immune cells by immunohistochemistry was evaluated. Results: PD-L1 expression on immune cells of non-responders was significantly lower before CRT (P =.008). CD27 was expressed only on immune cells and not on cancer cells. A significant lower CD27-expression score was observed following CRT (P =.019). Conclusions: Conventional CRT changes the expression of CD27 in the tumor microenvironment. Whether this is due to a loss of expression or a reduction of CD27+ cells must be evaluated in further analyses.