Mutational characteristics of bone metastasis of lung cancer

Roughly 30-40% of lung cancer (LC) patients develop bone metastasis during the course of disease. The genetic differences between primary LC and matched bone metastasis are not yet fully understood. A total of 40 LC patients with bone metastasis were collected and 450 targeted cancer-related genes were sequenced for genomic-alteration (GA) identification. Among the 40 LC patients, 33 had adenocarcinomas and 7 had squamous cell carcinomas. The metastatic sites of the 33 lung adenocarcinomas (LUADs) were the pelvis (6 patients), spine (16 patients), and limbs (11 patients). A total of 425 and 422 GAs were detected in the primary and metastatic lesions, respectively. The most common GAs were epidermal growth factor receptor (EGFR) mutations, which had mutation rates of 85.0% and 72.5% in the primary and metastatic lesions, respectively, and tumor protein 53 (TP53) mutations, which had mutation rates of 52.5% and 67.5% in the primary and metastatic lesions, respectively. Metastases to the pelvis and spine were most commonly accompanied by factor receptor substrate 2 (FRS2), cyclin-dependent kinase 4 (CDK4), and murine double minute 2 (MDM2) amplification, and cyclin-dependent kinase inhibitor 2A (CDKN2A) deletion. The concordance between primary lung squamous cell carcinoma (LUSC) and corresponding metastasis was significantly higher than that of primary LUAD and corresponding metastasis (P=0.033). Compared to limb and pelvis metastases, the shared mutation in spine metastasis was significantly lower (P=0.016 and P=0.023, respectively). In matched primary LUSCs and bone metastasis lesions, there was no significant difference in the distribution of the tumor mutational burden (TMB) (P=0.9). Conversely, a significant difference of the TMB distribution was detected in pairs of primary LUAD and corresponding bone metastasis lesions (P=0.021). The consistency of mutation patterns between primary LC lesions and matched bone metastases may vary in terms of metastatic sites, but is very high in general. There was a significant difference in the TMB between primary LUAD and matched bone metastatic lesions. Our findings contribute to molecular understandings of primary LC and matched bone metastatic lesions.