CD8+ Tumour-Infiltrating Lymphocytes and Tumour Microenvironment Immune Types as Biomarkers for Immunotherapy in Sinonasal Intestinal-Type Adenocarcinoma

Background. Intestinal-type adenocarcinoma (ITAC) is a rare tumour occurring in the ethmoid sinus. Recent years have brought advances in endoscopic surgery and precision radiotherapy; however, five-year overall survival has not improved and remains at 35-80%, depending on tumour stage and histology. Therefore, there is a need for new therapeutic options. Methods. We evaluated CD8(+)tumour-infiltrating lymphocytes (TILs) and tumour microenvironment immune type (TMIT, combining CD8(+)TILs and PD-L1) as predictive biomarkers for immunotherapy in a series of 133 ITAC. All results were correlated to clinical and follow-up data. Results. The presence of intratumoural CD8(+)TILs was low in 57% of cases and high in 8% of cases. Tumoural PD-L1 positivity was observed in 26% of cases. CD8(+)TILs and TMIT correlated with the histological subtype of ITAC and with better overall survival. The presence of stromal PD-L1-positive macrophages was related to intratumoural CD8(+)TILs. PD-L1 expression on tumour cells or macrophages did not show prognostic value. Conclusions. TMIT classification did not have additional prognostic value over CD8(+)TILs alone. The modest percentage of CD8(high)/PD-L1(pos)cases indicates that ITAC is a lowly immunogenic tumour type. Nevertheless, a proportion of ITAC, especially the papillary and colonic subtypes, could benefit from therapy with immune checkpoint inhibitors.