Correlation of tumor mutational burden, tumor microenvironment and alterations of driver genes in patients with NSCLC: A retrospective analysis.

Abstract

e20019 Background: To investigate the correlation of tumor mutational burden, tumor microenvironment and alterations of driver genes in tumor tissue of patients with NSCLC. Methods: 79 patients with confirmed NSCLC admitted from January 2018 to January 2019 were included. Tumor DNA was isolated from FFPE samples or fresh tissue samples. Mutation profiles were obtained by targeted deep sequencing of 620 selected genes. Tumor mutational burden (TMB) was defined as the number of non-synonymous mutations per 1Mbp and divided into tertiles. PD-L1 expression, CD8+ T cell and tumor infiltrating lymphocyte density were evaluated by immunohistochemical analysis. The correlation coefficient of TMB, tumor microenvironment and alterations of driver genes was calculated by chi-square test. Results: Median TMB of these patients is 6.915 Muts/Mbp (4.22-9.44 Muts/Mbp). Prevalence of PD-L1 expression is 28.0% (n = 7/25) at a tumor proportion score cutoff of at least 5% evaluated by Dako 28-8 PharmDx Assay kit and prevalence of CD8+ T cell density is 95.8% (n = 23/24). TP53 mutations are the most common alteration (n = 49/79, 62.0%), followed by EGFR alterations (n = 31/79, 39.2%), CDKN2A alterations (n = 11/79, 13.9%), KRAS mutations (n = 10/79, 12.7%), STK11 mutations (n = 5/79, 6.3%), ALK fusions (n = 4/79, 5.1%) and POLE mutations (n = 4/79, 5.1%). According to results of chi-square test, squamous cell carcinoma has higher TMB (p= 0.023) than adenocarcinoma. Metastatic NSCLC has higher PD-L1 expression (p= 0.049) than non-metastatic NSCLC. Furthermore, EGFR alterations are associated with lower TMB (p=0.020) and POLE mutations are associated with higher TMB (p= 0.015). There are no correlations among CD8+ T cell density, tumor infiltrating lymphocyte density and other variants. Conclusions: Our study highlights the correlation of tumor mutational burden, tumor microenvironment and alterations of driver genes in patients with NSCLC. This result may be the reference of anti-PD-1 therapy.