Abstract 5762: Genomic correlates of response to immune checkpoint blockade in Epstein-Barr virus-associated pulmonary lymphoepithelioma-like carcinoma

Abstract Introduction: Pulmonary lymphoepithelioma-like carcinoma (PLELC) is a rare and distinct subtype of non-small cell lung cancer (NSCLC). The use of immune checkpoint inhibitors (ICIs) for advanced PLELC and tumor genomic features underlying varied treatment responses remains poorly investigated. Methods: The study involved 33 PLELC patients with clinically annotated outcomes to ICIs. Targeted sequencing covering 520 cancer related genes were performed in 22 patients to identify single nucleotide variations (SNVs), copy number variations (CNVs), tumor mutation burden (TMB) and microsatellite instability. Mutation profiles of PLELC were compared with other NSCLC subtypes including lung adenocarcinoma (LUAD) and squamous cell lung carcinoma (LUSC) as well as EBV (Epstein-Barr virus) positive nasopharyngeal carcinoma (NPC) in public databases. Associations between PLELC mutation profiles and treatment responses to ICIs were analyzed. An external dataset of ICI-treated melanoma was used in further analysis of B2M. Results: The objective response rate (ORR), disease control rate (DCR), durable clinical benefit (DCB) rate, and median PFS was 18.2%, 60.6%, 45.5%, and 4.5 months respectively. Genetic alterations were frequently identified in B2M (9 of 22, 41%), CDKN1B (7 of 22, 32%), TP53 (6 of 22, 27%), SGK1 (5 of 22, 23%), NFKBIA (4 of 22, 18%) and TNFAIP3 (4 of 22, 18%). CNVs were comprehensively presented in PLELC while SVNs were less common. In our study, 8 of 9 tumors with B2M mutations and all tumors with CDKN1B, SGK1, TNFAIP3 mutations harbored copy number amplifications. Mutation profiles of PLELC were largely different from those of LUAD and LUSC but were similar to NPC. The median TMB was 2.99 mutations/Mb. All tumors were microsatellite stable (MSS). Patients with higher TMB showed improved DCR (p=0.029), PFS (p=0.056) and overall survival (p=0.038) than those with lower TMB. Patients with lower baseline plasma EBV DNA level also had longer PFS (p<0.001). The presence of B2M amplifications was significant associated with higher TMB level (p=0.022). The PFS of 7 patients with high TMB and amplified B2M were significantly longer than that of other patients (p=0.046). In the external dataset, higher expression of B2M was associated with better ICI responses for melanoma (p<0.05). Pathways involving anti-tumor immune responses such as NK cell-mediated cytotoxicity, antigen processing and presentation were correlated with high B2M expression while Wnt, TGF-beta and MAPK pathways that define poor response to ICI were correlated with low B2M expression. Conclusion: Our study observed comprehensive CNVs in PLELC patients which is a unique molecular feature compared with other NSCLC subtypes and EBV-positive NPC. Higher TMB level and amplifications of B2M in PLELC patients may be used as potential biomarkers to indicate better treatment responses to ICIs. Citation Format: Li-na He, Xuanye Zhang, Xinze Lv, Yuxi Zhou, Min Li, Ting Hou, Wenjie Sun, Li Zhang, ShaoDong Hong. Genomic correlates of response to immune checkpoint blockade in Epstein-Barr virus-associated pulmonary lymphoepithelioma-like carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5762.