LAUSR

Small cell lung cancer (SCLC) accounts for 15% of all lung cancers and belongs to the family of pulmonary neuroendocrine tumors. This tumor subgroup additionally includes large-cell neuroendocrine carcinomas (LCNEC) and pulmonary carcinoids (PCA), which occur in 3% and 2% of all lung cancer patients, respectively. Carcinoids are usually clinically benign, whereas SCLC and LCNEC are characterized as high-grade malignant tumors. Clinical and histologic studies have suggested similarities between SCLC and LCNECs: Both lung tumor subtypes are associated with heavy smoking and reveal an aggressive tumor growth resulting in a poor overall survival. We have performed comprehensive and multilevel genomic profiling on SCLC and LCNECs, including genome, exome, and transcriptome sequencing. SCLC and LCNEC tumors reveal high mutation rates with an average of 9.5 and 8.6 mutations per megabase, respectively. Our sequencing studies have shown that SCLC tumors are characterized by bi-allelic inactivation of TP53 and RB1 in almost 100% of the cases. LCNECs, on the other hand, are composed of two mutually exclusive subgroups, which we categorized as “type I LCNECs” and “type II LCNECs.” Type I LCNECs harbor TP53 and STK11 or KEAP1 alterations. Despite sharing genomic alterations with lung adenocarcinomas and squamous cell carcinomas, type I LCNECs exhibit a high neuroendocrine profile with close similarity to SCLC tumors. Type II LCNECs harbor loss of TP53 and RB1, thus showing genetic resemblance to SCLC. However, these tumors were revealed to be different from the majority of SCLC with reduced levels of neuroendocrine markers, an upregulated immune signaling profile, and high activity of the NOTCH pathway. Conclusively, our studies show marked biologic differences between high-grade neuroendocrine lung tumors and we emphasize the precise distinction of LCNEC subgroups from SCLC. Citation Format: Julie George. The genomic landscape of SCLC and other neuroendocrine lung tumors [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr IA28.