Comprehensive genomic profiling in Chinese patients with lung squamous cell carcinoma.

8540 Background: Lung squamous cell carcinoma (LUSC) is a major histological subtype of non-small cell lung cancer (NSCLC) and accounts for 30% of NSCLC. Previous studies had revealed the genomic characterization of LUSC in Western patients (pts). However, the comprehensive genomic features of LUSC in Chinese pts have not been well understood. Methods: Deep sequencing targeting 450 cancer genes was performed on FFPE and matching blood samples collected from 311 LUSC pts. Genomic alterations (GAs) including single nucleotide variations, short and long insertions and deletions, copy number variations, and gene rearrangements were analyzed. Tumor mutational burden (TMB) was measured by an algorithm developed in-house. Results: The median age of LUSC pts was 63 years old (range 57-68.5), of which 88% were male. The most frequently mutated genes were TP53 (88%), PIK3CA (34%), CDKN2A (33%), SOX2 (26%), LRP1B (22%), KLHL6 (21%), KMT2D (19%), PRKCI (19%), NFE2L2 (18%) and MAP3K13 (17%). Interestingly the mutation rates of PIK3CA (p = 1.93e-05) and CDKN2A (p = 2.48e-05) were significantly higher than that in TCGA cohort. Genomic alterations in eight druggable genes recommended by the NCCN guideline occurred in 32% of pts, and alterations to PI3K/mTOR signaling pathway related genes occurred in 52% of pts. One patient with PIK3CA amplification achieved stable disease for eight months after everolimus treatment. Moreover, variants in the homologous recombination (HR) pathway were identified in 17% of pts. The median TMB of LUSC pts was 10.8 Muts/MB (range 6.9-14.5 Muts/MB) which was higher than Western populations [PMID: 28420421]. The 1st Quartile (TMB-L), median and 3rd Quartile (TMB-H) TMB value was 6.9, 10.8 and 14.5 Muts/Mb respectively. Comparing with the TMB-L group, frequencies of CDKN2A (39% vs 19%, p= 0.005), LRP1B (45% vs 8%, p< 0.001) and KMT2D (27% vs 8%, p= 0.002) were higher in TMB-H group. Conclusions: In summary, we characterized the genomic alteration profile of Chinese LUSC pts. Consistent with previous reports, high mutation rates of TP53, PIK3CA and CDKN2A are the most important genomic features of LUSC. However, the proportion of PIK3CA and CDKN2A mutations in Chinese LUSC pts is higher than that of Western populations. In addition, we also found targetable pathways (including PI3K/mTOR) along with gene related variations and high TMB in many pts, providing potential targeted therapy and immunotherapy options for LUSC pts.