Integrated molecular analysis of NSCLC brain metastasis tissue and multimodal ctDNA reveals distinct signatures of patient outcomes

While recent therapeutic advances have extended the survival of patients with non-small cell lung cancer (NSCLC), overcoming metastatic progression in the CNS remains a significant challenge. Some patients with NSCLC may require concurrent management of CNS and extracranial metastases, while others develop isolated brain metastasis or leptomeningeal disease. These heterogenous clinical outcomes are difficult to predict and diagnose for early intervention with current surveillance modalities. Herein, we comprehensively analyzed gene mutations, copy number variations, and DNA methylation of NSCLC brain metastasis tissue collected at the time of craniotomy, combined with ctDNA sequencing of paired plasma and CSF liquid biopsies. We confirmed a high concordance between the molecular features of brain metastasis tissue with ctDNA from CSF which were largely distinct from ctDNA alterations in paired plasma samples. Plasma ctDNA tumor fraction and ctDNA hypermethylation were most significantly associated with extracranial metastasis and overall survival. Alternatively, we identified specific hypermethylated DNA loci in brain metastasis tissue and CSF ctDNA as significant correlates of brain metastasis progression and risk of leptomeningeal disease. Our findings support the utility of integrating ctDNA testing from CSF and plasma, while revealing distinct epigenetic features and biomarkers of brain metastasis or leptomeningeal disease.