Abstract 4105: CD8 positive tumor infiltrated lymphocytes as prognostic factor in sinonasal squamous cell carcinoma

Abstract

Abstract Introduction Sinonasal squamous cell carcinoma (SNSCC) patients have a poor survival rate and treatment options are limited. We evaluated CD8-positive tumor-infiltrated lymphocytes (TILs) in 57 SNSCC and the relation to PD-L1 expression. Furthermore, we analyzed PD-L1 mutations and CMTM6 expression in relation to enhanced ability to inhibit TILs. Our aim was to identify patients that may benefit from therapy with immune checkpoint inhibitors. Experimental Procedures Four tissue microarray blocks were constructed including three 1 mm cores from different areas of 57 SNSCC. Each block also contained normal mucosa samples as controls. The presence of CD8+ TILs, tumoral PD-L1 and CMTM6 expression was evaluated by immunohistochemistry. The stainings were evaluated by 3 independent observers and results were correlated to clinico-pathological characteristics and follow-up data. Co-localization of CD8+ TILs and PD-L1+ cells was performed in 2-μm-thick FFPE sections by immunofluorescence. Exon 6 of the PD-L1 gene, which encodes the DTSSK motif, was amplified by PCR and products were sequenced by Sanger sequencing. Results High level presence of intratumoral CD8+ TILs occurred in 11/57 (19%), low level in 39/57 (69%) and absence in 7/57 (12%) cases. Five-year disease-specific survival (DSS) was 34% of cases with intratumoral CD8+ versus 71% in cases CD8- (P=0.03). Five-year DSS was 0%, 24% and 43% in high level, low level and absence of intratumoral CD8+ TILs, respectively (p=0.006). PD-L1 expression was observed in 26/57 (46%) of cases and did not correlate with clinico-pathological parameters or DSS. All patients with high intratumoral CD8+ expression were PD-L1 positive and 75% of patients with strong PD-L1 staining showed high intratumoral CD8+ expression. All intratumoral CD8+/PD-L1+/- patients died of disease before 5 years compared to 24% CD8-/PD-L1- and 48% CD8-/PD-L1+ patients who survived up to 5 years (P=0.003). Tumors CD8+/PD-L1+/- had a significant worse DSS than CD8-/PD-L1+/- cases (p=0.015). No mutations were found in the DTSSK domain of PD-L1 and CMTM6 showed expression in 43/57 (75%) of patients while 17 of those 43 (40%) were also PD-L1+. Conclusion Our data showed that SNSCC are immunogenic tumors with up to 88% of cases harboring some level of CD8+ TILs. The presence of intratumoral CD8+ TILs was correlated to worse survival, as has been observed previously in other tumor types. We also found 46% of tumors to express PD-L1. Together these results indicate that SNSCC patients could benefit from immunotherapy releasing the PD-1/PD-L1 immune checkpoint and reactivating the already present cytotoxic CD8+ TILs to exercise their antitumor activity. Pembrolizumab and nivolumab have already received FDA approval for clinical application in recurrent or metastatic HNSCC and may also be considered for treatment of recurrent SNSCC. Citation Format: ROCIO GARCIA-MARIN, CRISTINA RIOBELLO, VIRGINIA N. CABAL, LAURA SUAREZ-FERNANDEZ, SARA REDA, FERNANDO LOPEZ, JOSE L LLORENTE, MARIO HERMSEN. CD8 positive tumor infiltrated lymphocytes as prognostic factor in sinonasal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4105.