Immune-related molecular characteristics of Chinese lung cancer patients with different types of ALK rearrangement.

e21144 Background: Anaplastic lymphoma kinase ( ALK) gene rearrangements are found in approximately 5% of non-small-cell lung cancer (NSCLC). Since ALK-TKIs have been developed for patients with ALK-positive advanced NSCLC, it remained 20%-30% non-responders, thus other treatment strategies would be explored to prolong overall survival. Previous studies have shown that ALK rearrangement can upregulate PD-L1 expression via signaling pathways such as ERK/AKT, and the high expression of PD-L1 negatively affects the efficacy of crizotinib and would be more suitable for immunotherapy. However, only a few immunotherapy clinical studies recruited tiny amounts of ALK rearrangement NSCLC, making it difficult to investigate the relationship between this oncogenic gene alteration and therapeutic effects. Herein, we described the immune-related molecular characteristics of ALK-rearranged patients in a large group of Chinese lung cancer, hoping to provide more precise treatment strategies. Methods: A total of 1410 lung cancer patients harboring ALK rearrangement were included in this analysis. Using wide NGS panel testing, we elucidated ALK gene fusions, intergenic region fusions ( ALK-IR) as well as other genomic alterations and TMB levels in each patients’ tumor specimen. PD-L1 expression level was evaluated by the tumor positive score (TPS). Results: Over two hundreds of types of ALK rearrangement were identified. The whole population was divided into six subgroups according to types of ALK rearrangements: 3'- ALK-only (71.1%), 5'-non- EML4-ALK-only (1.0%), multi- ALK fusion (14.2%), single ALK-IR (3.2%), multi-3'- ALK-IR (10.1%), and multi-5'- ALK-IR (0.5%). The overall PD-L1 expression level was high in ALK rearrangement lung cancer, of which the proportion of patients with TPS ≥ 50% was 19.5%, and the TPS ≥ 50% proportion in the single ALK-IR subgroup was the highest (28.6%) among all subgroups. We then evaluated the distribution of TMB levels and found the median TMB level was higher than 30% lung cancer. Of note, the single ALK-IR subgroup also present a trend of higher TMB level among all subgroups. We also observed more DNA damage response (DDR) gene mutations (median number: 2, range: 1-22) in the single ALK-IR subgroup. Somatic copy number amplifications (SCNAs) were detected in 195 (13.8%) ALK -rearranged lung cancer patients, and the proportion of SCNAs in each subgroup was similar. The most frequently high-level amplified genes were MYC (23.9%) and EGFR (10.9%). Furthermore, the 3'- ALK-only subgroup mainly occurred low-level SCNAs (68.5%), whereas the multi- ALK fusion and multi-3'- ALK-IR subgroups were more likely to harbor high and moderate level SCNAs. Conclusions: Our findings demonstrated that lung cancer with ALK-IR might have active immune microenvironment, indicating it’s a subset of ALK-rearranged patients who would benefit from immunotherapy.