P2.03-32 Metastatic Lymph Nodes as High Immunogenicity Media for Perioperative Immunotherapy in Locally Advanced NSCLC

Abstract

Perioperative chemotherapy showed limited survival benefit and increased toxicities while neoadjuvant immunotherapy achieved great success in early phase trials. Both inter/intra-tumoral heterogeneity (ITH) between primary lesion and metastatic lymph nodes (mLNs), and rationale of superior efficacy for immunotherapy remained poorly explored in locally advanced non-small cell lung cancer (NSCLC). We retrospectively collected 6 locally advanced lung adenocarcinoma (LUAD) patients. 15 tissue samples were performed multi-region whole exosome sequencing and TCR repertoire analysis as well as 18 matched metastatic lymph nodes (mLNs). 290 somatic mutations in average were identified in primary LUAD (PL) and 441.6 for mLNs. Tumor mutation burden as well as tumor neoantigen burden was significant higher in mLNs than in primary LUAD (median value, 6.6mut/Mb vs. 3.4mut/Mb, P=0.0376; 229.5 neo counts vs. 165 neo counts, P=0.0287). Increased transversion ratio was found in mLNs compared to primary lesions. The genomic concordance between primary lesions and mLNs was 58.4%±12.5% and 33.3% for EGFR-mutation. 87 copy number variants were detected in 14 samples with 3q, 8q and X chromosome as frequently mutated cytobands. Small cell lung cancer functional pathway was enriched in mLNs exclusively. Both expression of PD-L1 and CD8 revealed high level (median value 20% and 40%) and consistence (5/6, 83.3%) between primary and metastatsis lesions. TCR clonality was 17.2% and 9.1% for primary and metastasis lesions, respectively with higher T cell diversity and intra-tumoral heterogeneity of TCR found in mLNs. Extensive genomic and TCR ITH was found between primary LUAD and mLNs which may lead to mixed response to perioperative treatment. mLNs may serve as a better immunogenicity media for perioperative immunotherapy suggesting a potential adjuvant modality of immunotherapy performing lymph nodes sampling during surgery. Results of an initiated single cell sequencing program including paired samples were pending to further provide insights of diverse immune-microenvironment.