LM were much more frequent in patients with NSCLC harboring EGFR mutations. EGFR TKIs were the optimal treatment for LM, and active treatment with WBRT did not prolong OS for EGFR-mutated patients.

Introduction: Leptomeningeal metastases (LMs) indicated a poor prognosis in NSCLC. LMs were more frequent in driver gene-mutated patients, and cerebrospinal fluid (CSF) cell-free DNA has shown unique genetic profiles of LM in EGFR-mutated LM. However, studies in patients with ALK receptor tyrosine kinase gene (ALK)-rearranged NSCLC with LMs are scarce. Methods: Patients with lung cancer with ALK rearrangement were screened from September 2011 to February 2018 at our institute. CSF and paired plasma were tested by next-generation sequencing. Results: LMs were diagnosed in 30 (10.3%) of 291 patients with ALK-rearranged lung cancer. A total of 11 paired CSF and plasma samples tested by next-generation sequencing were analyzed. Driver genes were detected in 81.8% of the CSF samples (9 of 11) and 45.5% of the plasma samples (5 of 11) (p ¼ 0.183). The maximum allelic fractions were all higher in CSF than in plasma (p ¼ 0.009). ALK and tumor protein p53 gene (TP53) were the two most frequently mutated genes in CSF. Gatekeeper gene ALK G1202R and C1156F mutations were identified in CSF after resistance to alectinib. Multiple copy number variants were mainly found in CSF, including in EGFR, cyclin D1 gene (CCND1), fibroblast growth factor 3 gene (FGF3), and fibroblast growth factor 4 gene (FGF4). Also found were v-myc avian myelocytomatosis viral oncogene homolog gene (MYC) copy number gains and TP53 and cyclin dependent kinase inhibitor 2A gene (CDKN2A) copy number deletions. Brigatinib seemed to be effective in controlling LM. One case showed that CSF could be used to monitor disease development of LM and longitudinally monitor tumor response. Conclusion: Liquid biopsy of CSF is more sensitive than liquid biopsy of plasma to detect targetable alterations, characterizing resistance mechanisms on progression and monitoring tumor response in patients with ALK-rearranged NSCLC with LM. Thus, CSF might be promising as a medium of liquid biopsy in LM.

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Key Points Question What is the association of molecular alterations in cerebrospinal fluid with clinical outcomes of patients with a diagnosis of lung adenocarcinoma and central nervous system metastases? Findings In this cohort study of 94 patients, next-generation sequencing of cerebrospinal fluid showed that 5 molecular subtypes were associated with survival; the molecular subtype with abundant genetic alterations was associated with the shortest survival and increased risk of death. Specifically, EGFR variants coaltered with CDK4 , CDK6 , MYC , and MET were associated with poor outcomes. Meaning Based on genetic profiling in cerebrospinal fluid, this population experienced heterogenous survival outcomes, and some specific molecular alterations were associated with prognosis; therefore, as liquid biopsy is performed of central nervous system metastases, cerebrospinal fluid may facilitate risk stratifying central nervous system metastases into appropriate outcomes.

The DNR order-signing rate has been increasing annually among terminal patients with lung cancer in China. DNR orders, all of which were signed by surrogates, were more likely to be accepted by patients with slowly deteriorating disease and longer OS. More effort should be taken to help patients and medical professionals establish a sensible understanding of EOL care, including DNR orders, at earlier points during the disease course.

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9022 Background: In current clinical setting, NSCLC patients harboring specific driver mutation were usually treated guiding by prior profiling of the primary tumor when developed to brain metastasis. Some studies have shown that circulating tumor DNA (ctDNA) derived from cerebrospinal fluid (CSF) can reveal unique genomic alterations present in brain malignancies. We assessed CSF as a liquid biopsy media and compared to matched plasma. Methods: We performed capture-based ultra deep sequencing on ctDNA derived from matched CSF, plasma of 40 non-small cell lung cancer (NSCLC) patients with suspected leptomeningeal carcinomatosis (LC) using a panel consisting of 168 genes. Results: Among the 40 suspected LC cases, 35 were confirmed to have LC, ctDNA in CSF from the 5 non-LC cases are all undetectable. Circulating tumor DNA was detected in 93.8% of CSF and 66.7% of plasma. We compared mutation profiles and identified 86 and 46 SNVs from CSF and plasma, respectively, with 42 SNVs overlapping. Furthermore, ctDNA from CSF revealed many copy number variations (CNVs) that were not detected from plasma (189 CNVs vs. 3 CNVs). The average maximum allelic fraction (AF) of CSF ctDNA is significantly higher than in plasma (56.7% vs. 4.4% p < 10^-6). Twenty-eight patients were pre-treated with EGFR-TKIs and developed subsequent resistance. EGFR T790M and MET amplification were detected in 21% and 39% in CSF, respectively, showing a unique resistance profile among leptomeningeal metastases patients compared to the general population. Interestingly, 60% of CSF samples harbor TP53 loss of heterozygosity, only 11% of which were detected in the matched plasma samples. Such heterogeneity may reflect unique biological themes for brain metastatic tumor sub-clones. Furthermore, 26 patients received molecular targeted therapy based on the results from CSF, and 23 reported alleviation of symptoms at subsequent evaluations. Conclusions: Collectively, our data reveal that ctDNA derived from CSF provides a unique and more comprehensive characterization of genomic alterations of leptomeningeal carcinomatosis than plasma, supporting the importance of CSF as a liquid biopsy media.