Genetic landscape and PD-L1 expression of Chinese patients with small cell lung cancer.

Abstract

e21099 Background: Small cell lung cancer (SCLC) is a highly aggressive carcinoma of the lung. Whereas, precise treatment options for SCLC are limited. Genomic profiling would be essential to understand drug resistance related mechanism. So far, little is known about an in-depth molecular characterization for SCLC in Chinese patients. Here we described the mutational landscape and programmed cell death-1 (PD-L1) expression profile in Chinese patients with SCLC by next-generation sequencing (NGS) assay. Methods: Chinese patients with SCLC were included in this study. Genomic profiling of DNA was performed on formalin-fixed paraffin-embedded tumor samples and matched blood through a NGS with 381 cancer-related genes panel. PD-L1 expression status of tumor tissue was determined by immunohistochemistry. Results: In total, 115 patients with SCLC were included in the present study. We identified 2,948 mutations, spanning 434 genes, with TP53, RB1 and LRP1B being the most frequently mutated genes, occurring in 109(94.78%), 88(76.52%) and 48(41.74%) of SCLC patients, respectively. For somatic single nucleotide variant (SNV), TP53 (108/115, 93.91%), RB1 (82/115, 71.30%) and LRP1B (43/115, 37.39%) were frequently mutated, which exhibited the similar mutation frequencies with TCGA database. To be noted, 79 (68.70%) SCLC patients harbored both RB1 and TP53 mutations, which was comparable with TCGA data (84/110, 76.36%). Germline SNV spectrum varied significantly compare with somatic SNV. BLM, MSH2 and VEGFA were the most frequently germline mutated genes. In our dataset, the tumor mutation burden (TMB) of 108 patients, PD-L1 expression status of 95 patients and microsatellite stabilities/instabilities (MSS/MSI) status of 112 patients were also analyzed. The median TMB was 10.61/MB. The positive rate of PD-L1 expression was 12.63%. All patients were MSS. Conclusions: Our study revealed the genetic landscape and PD-L1 expression of SCLC. The data may provide the support on immunotherapy and targeted therapy research.