Clinical Study On Cerebrospinal Fluid Gene Detection In Patients With Brain (Leptomeningeal) Metastasis Of Lung Adenocarcinoma

Background: The patients with brain(leptomeningeal)metastasis of lung adenocarcinoma had poor prognosis,and the patients with EGFR mutations could benefit significantly from treatment with EGFR tyrosine kinase inhibitors(TKIs).Therefore,It was very important to identify the molecular characteristics of brain metastatic tumors for the development of treatment plans,but the current research data on the molecular characteristics of brain metastatic tumors and cerebrospinal fluid were still very limited.Objective: This subject mainly analyzed the clinical data of CSF gene detection in patients with lung adenocarcinoma with brain metastasis,and discussed the clinical value of CSF gene detection.(1).To identify the molecular characteristics of cerebrospinal fluid in patients with cerebral metastasis of lung adenocarcinoma;(2).To clarify the molecular characteristics and clinical significance of cerebrospinal fluid in patients with pulmonary adenocarcinoma with leptomeningeal metastasis;(3).To clarify the clinical significance of ctDNA changes in cerebrospinal fluid in the treatment of patients with leptomeningeal metastasis of lung adenocarcinoma.Subjects and methods:(1).The NGS results of brain metastatic tumor tissues,CSF circulating tumor DNA,plasma ctDNA and CTCs from 5 patients of lung adenocarcinoma with brain metastasis were analyzed;The NGS results of CSF circulating tumor DNA,plasma ctDNA and CTCs from 11 patients with leptomeningeal metastasis of lung adenocarcinoma and 10 patients with brain metastasis of lung adenocarcinoma were analyzed.(2).Collected the clinical datas of20 patients with leptomeningeal metastasis of lung adenocarcinoma.The NGS were used to carry out gene detection and comparative analysis of ctDNA in CSF and ctDNA in peripheral blood of patients with leptomeningeal metastasis of lung adenocarcinoma.Used subgroup analyzed the molecular characteristics of ctDNA in CSF and ctDNA in peripheral blood of lung adenocarcinoma with leptomeningeal metastasis.The test results were used to guide the clinical development of treatment plans,and the results of gene test were verified by efficacy evaluation.(3).CSF samples of 8 patients with leptomeningeal metastasis of lung adenocarcinoma who received EGFR-TKIs therapy were collected,and CSF routine,biochemical,cytological,tumor marker,and NGS method gene detection were performed.Results:(1).A total of 21 patients with brain(leptomeningeal)metastasis of lung adenocarcinoma were enrolled in this study,10 patients with brain parenchymal metastasis of lung adenocarcinoma and 11 patients with leptomeningeal metastasis of lung adenocarcinoma.(1).Gene testing of brain metastatic tumor tissue,CSF circulating tumor DNA,plasma ctDNA and CTCs was performed in 5 patients with lung adenocarcinoma with brain metastasis.The gene detection results of CSF and brain metastases in 5 patients suggested that the mutation status of EGFR and TP53 gene was consistent.CSF ctDNA has a unique gene spectrum.(2).The detection rates of ctDNA in CSF,ctDNA in plasma and CTCs in 21 patients with brain(leptomeningeal)metastasis of lung adenocarcinoma were 95.24%,66.67% and39.09%,respectively.The positive rates of EGFR gene mutation in CSF samples were significantly higher than that in peripheral blood(P< 0.05).(3).The positive rate of EGFR gene detection in cerebrospinal fluid samples of patients with leptomeningeal metastasis was significantly higher than that of patients with parenchymal metastasis(81.82% Vs 30%),and the difference was statistically significant(P =0.008).(2).A total of 20 patients with leptomeningeal metastasis of lung adenocarcinoma were enrolled in this study,4(20.0%)of whom were initially diagnosed with meningeal metastasis,and 16(80.0%)of whom were re-diagnosed with meningeal metastasis of lung adenocarcinoma.(1).All the 20 patients received gene testing in cerebrospinal fluid and blood samples,and the detection rate of classical mutation of EGFR gene was 45.0% and 20.0%,respectively.The detection rates of non-classical mutation and compound mutation were 45.0% and 10.0%,respectively.There was a statistically significant difference in EGFR positive rates between CSF and blood genetic tests(P < 0.001).(2).Among the 16 patients with rediagnosed leptomeningeal metastasis,7 patients adjusted the targeted drugs according to the results of CSF and blood gene tests,Objective response rate(ORR):85.71%,disease control rate(DCR): 100%.Among the 4 initially diagnosed patients with leptomeningeal metastasis,3 patients were given EGFR-TKIs therapy based on the positive result of the driver gene,ORR: 75.0%,DCR: 75.0%.(3).8 patients with leptomeningeal metastasis of lung adenocarcinoma were enrolled in this study.There were no significant difference in CSF cytology,routine,biochemistry and CEA before and after treatment.The mutations of EGFR to the same site were detected by cerebrospinal fluid gene test before and after treatment,and no drug-resistant mutations were found,but the detected abundance were significantly lower than that detected in the first tests,with statistically significant difference(P=0.016).Conclusion:(1).The CSF ctDNA has higher detection sensitivity and unique mutation spectrum of driver gene.CSF ctDNA can better represent the molecular state of intracranial lesions,especially in patients with leptomeningeal metastasis,The CFS ctDNA gene detection had important guiding significance for the treatment of patients with leptomeningeal metastasis.(2).The CSF specimens of patients with leptomeningeal metastasis of lung adenocarcinoma had a higher positive rate of EGFR gene mutations than peripheral blood specimens.CSF samples detected high percentage of uncommon EGFR mutations,It may suggested that the CSF of patients with leptomeningeal metastasis who have clinical progression during treatment with EGFR-TKIs had unique molecular characteristics.The progression of disease cannot be explained by the gene for drug resistance,EGFR uncommon mutations may cause insensitivity to drugs.The clinical significance of some uncommon mutations remains need further studied.(3).The CSF CEA value and the abundance of the mutated gene are decreased during treatment,but at a certain level,this may be one of the reasons to explain the disease progress slowly,and not just because of resistance gene sites.The CSF gene testing may be used to dynamically monitor the tumor load of leptomeningeal metastasis,and may be an indicator of the efficacy and prognosis of treatment with EGFR-TKIs.