81PHigher PD-L1 expression correlates with lymphocyte infiltration in early non-small cell lung cancer

Background: Patients with advanced NSCLC (Non-small cell lung cancer) benefit from ICIs (immune checkpoint inhibitors) as part of their treatment strategy. This benefit might also be observed in earlier stages. The aim of our work was to characterize the immune contexture of early NSCLC and assess the impact on outcome of immune biomarkers. Methods: Formalin-fixed paraffin embedded (FFPE) 1 mm cores from patients that underwent curative surgical treatment between 2006 and 2018 at Hospital del Mar (Barcelona, Spain), and did not received neoadjuvant therapy were included in a tissue microarray. PD-L1 expression as well as CD3, CD4, CD8, CD80 and CD103 were evaluated by immunohistochemistry. We report the percentage of positive cells for each marker from all nucleated cells. We evaluated the association between clinicopathological and molecular characteristics and immune biomarkers (Mann-Whitney, Kruskal-Wallis and Spearman correlation) and their impact on survival outcomes (Cox regression). Results: Samples from 195 patients were included (Adenocarcinomas n = 130, Squamous cell carcinoma n = 61, Other histology n = 4). In our cohort, 74.9% of the cases were males, predominantly smokers (87.2%). Tumor size was less or equal than 40mm in 72.3% of the cases. Stage I, II, III and IV tumors represent 44.6%, 25.1% and 26.7% of all cases included in our study, respectively. PD-L1 expression was <1%, 1 - <50% and ³50%, in 46.7%, 29.2% and 24.1% of the cases respectively. PD-L1 expression was positively correlated with higher percentage of CD4 (rho=0.195), CD8 (rho=0.3272), CD80 (rho=0.2152) and CD103 (rho=0.4237) (all p-values<0.05). CD103 expression was positively correlated with CD80 expression (rho=0.514; p < 0.001). A higher percentage of lymphocytes measured by CD3 expression in tumor tissue was correlated with better overall survival (p = 0.045; HR = 0.98 (0.96-0.99)) when adjusted by TNM 8thedition stage and adjuvant chemotherapy. No correlations with clinicopathological features were observed. Conclusions: Immune biomarker expression is highly heterogeneous in early NSCLC. Lymphocyte infiltration is associated with higher PD-L1 expression. Evaluation of immune biomarkers might better inform the choice of adjuvant treatment for NSCLC patients. Legal entity responsible for the study: The authors. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.