TP53 or CDKN2A/B covariation in ALK/RET/ROS1-rearranged NSCLC is associated with a high TMB, tumor immunosuppressive microenvironment and poor prognosis.

INTRODUCTION: ALK-rearranged lung adenocarcinomas with TP53 mutations have more unstable genomic features, poorer ALK-TKI efficacy and a worse prognosis than ALK-rearranged lung adenocarcinomas with wild-type TP53. Here, we examine the gene variations that co-occur with ALK/RET/ROS1 rearrangements in NSCLC and the corresponding tumor immune microenvironment, as well as their association with prognosis.

METHODS: A total of 155 patients with ALK/RET/ROS1 fusions were included retrospectively. Tumor genome mutation analysis was performed by next-generation sequencing. PD-L1 expression and tumor-infiltrating lymphocytes were assessed by multiplex immunohistochemistry. The correlations among gene covariation, the tumor immune microenvironment, and clinicopathological characteristics were analyzed.

RESULTS: Among the 155 patients, concomitant TP53 mutation appeared most frequently (31%), followed by CDKN2A/B copy number loss (15%). The ALK/RET/ROS1 fusion and TP53 or CDKN2A/B covariation group had more males and patients with stage IV disease (p < 0.001, p = 0.0066). Patients with TP53 or CDKN2A/B co-occurrence had higher tumor mutation burdens and more neoantigens (p < 0.001, p = 0.0032). PD-L1 expression was higher in the tumor areas of the TP53 or CDKN2A/B co-occurring group (p = 0.00038). However, the levels of CD8+ , CD8+ PD1- , and CD8+ PD-L1- TILs were lower in the tumor areas of this group (p = 0.043, p = 0.029, p = 0.025). In the TCGA NSCLC cohorts, the top 2 mutated genes were CDKN2A/B (24%) and TP53 (16%). The TP53 or CDKN2A/B co-occurring group had higher tumor mutation burdens and shorter OS (p < 0.001, p < 0.001).

CONCLUSIONS: Patients with co-occurring TP53/CDKN2A/B variations and ALK/RET/ROS1 rearrangements are associated with high TMB, more neoantigens, an immunosuppressive microenvironment and a worse prognosis.