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.