Introduction: Early-stage lung adenocarcinoma (LUAD) manifesting as subsolid nodules (SSNs) exhibit more favorable prognosis than solid nodules (SNs). However, the genomic underpinnings behind their indolent tumor behavior remain largely unexplained.
Methods: We identified patients with stage I invasive LUAD who underwent complete surgical resection and broad-panel next-generation sequencing (NGS). Comparative genomic profiling was then performed by radiological subtype (SSNs vs. SNs) regarding the general genomic features, driver genes, oncogenic pathways, therapeutic actionability, and evolutionary trajectory.
Results: In total, 177 SSN-LUADs and 133 SN-LUADs were included. Compared with SNs, SSN-LUADs possessed lower somatic mutation count (P < 0.001), genomic alteration count (P = 0.002), and intra-tumor heterogeneity (P = 0.006). In terms of driver genes, SSNs harbored more EGFR mutation (77% vs. 62%), but had lower frequencies of genes such as TP53, ARID1A, PIK3CA, CDKN2A, and BRAF (FDR q < 0.1). Besides, RBM10 mutation was independently associated with SSN-LUADs in multivariate analysis (P = 0.033). Three oncogenic pathways (p53, cell cycle, PI3K) were altered with statistical significance in SNs, while only RNA splicing/processing pathway was significantly altered in SSNs (FDR q < 0.1). Also, SSNs had significantly lower number of pathway alterations (P < 0.001). Finally, SSNs and SNs showed distinct evolutionary trajectories regarding somatic mutations during early-stage LUAD progression.
Conclusions: This study performed the first direct comparative genomic profiling in pathologic stage I invasive LUAD by radiological subtype, highlighting a less complex genomic architecture of SSNs, which might be the molecular interpretation of their indolent tumor behavior.
Keywords: Lung adenocarcinoma; Next-generation sequencing; Radiological subtype; Subsolid nodule; Tumor genomic profiling.
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