Tumor-Infiltrating Lymphocytes (Tils) and Pd-L1 Expression in Non- Small Cell Lung Cancer Brain Metastases (Bm) and Matched Primary Tumors (Pt)

Abstract

Aim: To investigate TIL infiltration and the PD1/PD-L1 axis inNSCLC BM.Methods: We performed immunohistochemistry for CD3, CD8,CD45RO, PD1 and PDL1 in 73 NSCLC BM specimens and 25/73 (34%)matched PT specimens of 73 patients (46/73 63%) male; 27/73(37%) female; 15/73 (21%) squamous histology; 58/73 (79%) nonsquamous histology).Results: BM and PT both showed accumulationof TILs in the tumor stroma, perivascular area and at the tumorborder to the surrounding parenchyma. Strong, membranous PDL1expression was observed in 25/46 (52%; 12/46 (26%) expressionin >5% of tumor cells) BM and in 8/25 (32%; 3/25 (12%)expression in >5% of tumor cells) matched PT. Accentuation ofPDL1+ tumor cells at the tumor border and in regions with highTIL density was evident in BM and PT. Significant correlation ofinfiltration density between BM and matched PT was observed forCD3+ TILs (p = 0.002) and CD8+ TILs (p = 0.003). Denseinfiltration with CD3 + , CD8+ CD45R0+ and PD1+ TILs was morefrequently observed in PT than in BM, while PD-L1 expression wasmore frequently observed in BM than in PT. No correlation ofsurvival from diagnosis of BM and TIL infiltration or PDL1expression was observed (p > 0.05).Conclusions: (1) NSCLC BMcontain considerable TILS infiltrates and show high PD-L1expression. (2) The composition of the immune response differbetween tumor sites with BM showing less dense TIL infiltrationbut more PD-L1 expression than PT. Our data may be relevant forclinical trials with immune checkpoint inhibitors in NSCLCBM.Disclosure: All authors have declared no conflicts ofinterest.