Clinical Characteristics And Genomics In Leptomeningeal Metastasis Of Gastric Cancer

Leptomeningeal metastasis(LM)refers to metastasis caused by malignant tumor cells infiltrating from distant solid tumor into pia mater and arachnoid.It is a rare complication of central nervous system metastasis of solid tumor.The incidence of meningeal metastasis in cancer patients is about5-8%.The most common primary causes of meningeal metastases are lung cancer,melanoma,and breast cancer.gastric cancer leptomeningeal metastasis(GCLM)is very rare,only 0.16-0.69% of gastric cancer patients develop GCLM,and patients with gastric cancer leptomeningeal metastasis have poor prognosis of 1.5 months.Circulating tumor DNA(ctDNA)is a piece of DNA that is actively secreted by tumor cells or released into the circulatory system during apoptosis or necrosis of tumor cells.It is circulating in the human blood and body fluids.In meningeal metastasis,intracranial molecular markers in meningeal metastasis patients are usually difficult to enter the blood circulation due to the presence of blood brain barrier(BBB),and cerebrospinal fluid is in direct contact with meningeal metastasis tumor cells.CSF samples can more truly reflect LM mutations than blood samples.In recent years,there have been many studies on ctDNA in cerebrospinal fluid of patients with LM of lung cancer and breast cancer,and studies have shown that CSFctDNA can reveal the unique genetic characteristics of LM.Multiple copy number variation in cerebrospinal fluid with LM of lung cancer is more than that in plasma and tissue,and increased copy number of MET is the most common.Ultra low throughput whole genome sequencing ctDNA assay shows potential in the diagnosis of leptomeningeal metastases in breast cancer.CSFctDNA also predicts patient survival: Survival after metastasis in patients with ohtinib treated non-small cell lung cancer with leptomeningeal metastases was higher in patients with EGFR exon 19 deletion than in patients with EGFR exon 21 L858 R mutation.The survival of T790 M CSF genotype positive patients after LM was significantly longer than that of T790 M CSF genotype negative patients.At present,there are few reports on LM of gastric cancer,most of which are case reports,and the clinical characteristics of meningeal metastasis of gastric cancer and the clinical application of cerebrospinal fluid circulating tumor DNA(ctDNA)in GCLM are insufficient.Based on this,15 patients diagnosed with gastric cancer LM from the Second Hospital of Hebei Medical University from July 2016 to November 2020 were collected in this experiment.The age,gender,clinical symptoms and signs,whether meningeal metastasis was found in other sites,cerebrospinal fluid analysis,imaging examination,treatment plan and survival time were summarized and analyzed.In addition,we performed ctDNA genomics analysis and survival analysis of clinical features and genomic outcomes for paired tumor tissue samples,cerebrospinal fluid samples,and plasma samples.Part One Clinical features of leptomeningeal metastasis in gastric cancerObjective: To summarize the clinical features of leptomeningeal metastasis in gastric cancer.Methods: From July 2016 to November 2020,15 patients diagnosed with gastric cancer leptomeningeal metastasis were collected from the Second Hospital of Hebei Medical University.The age,gender,clinical symptoms and signs,whether meningeal metastasis was found in other sites,cerebrospinal fluid analysis,imaging examination,treatment plan and survival time were summarized and analyzed.Results: A total of 15 gastric cancer patients with leptomeningeal metastasis were included in this study,most of whom were male,and the median age at diagnosis of meningeal metastasis was 60 years old.Headache,nausea and vomiting were the most common symptoms,and neck resistance was present in 14 patients(93.3%).Tumor cells could be detected by cerebrospinal fluid cytology in all patients.Enhanced head MRI scan was performed in 8patients,and leptomeningeal enhancement was observed in 4 patients.Among the 15 patients with GCLM,10 patients received intrathecal chemotherapy only,2 patients received intrathecal chemotherapy combined with systemic chemotherapy,1 patient received intrathecal chemotherapy combined with chemotherapy and radiotherapy,and 1 patient received intrathecal chemotherapy combined with Ommaya capsule placement to relieve hypercranial pressure.Conclusions: Leptoeningeal metastasis of gastric cancer is more common in middle-aged and old men,and the histopathology shows adenocarcinoma,some of which can be seen as sig-ring cell carcinoma.The gold standard for the diagnosis of leptomeningeal metastasis of gastric cancer is cerebrospinal fluid cytology,which is usually diagnosed as advanced gastric cancer with multiple organ metastases such as lymph nodes,bone and lung.Intrathecal chemotherapy is the main treatment after leptomeningeal metastasis of gastric cancer,which can be combined with chemotherapy and radiotherapy.Part Two Genomics in Leptomeningeal Metastasis of Gastric CancerObjective: To evaluate the difference of ctDNA types and quantities in different samples leptomeningeal metastasis in gastric cancer,and to determine the feasibility of CSF as a liquid biopsy object.Methods: Gene sequencing of cerebrospinal fluid,tumor tissue samples and blood samples using high-throughput sequencing,statistical statistics of ctDNA species in different samples,and pathway enrichment.Results: CSF had a higher mutant allele frequency,with more mutations and more copy number changes than blood and tumor tissue samples.Among the genetic alterations in CSF,MYC and CCNE1 are one of the most heavily mutated genes.More potential,and markers associated with lm progression were detected in CSF samples,including PREX2,IGF1 R,AR,SMARCB1 mutations compared than tumor samples,and these changes may be associated with the cell cycle pathway,RTK / RAS pathway,as well as the PI3 K pathway.Conclusions: CSF is promising as a new liquid biopsy medium to monitor the development of meningeal metastasis in gastric cancer.Part Three Survival analysis of leptomeningeal metastasis in gastric cancerObjective: To investigate the genomic and clinical characteristics related to survival in patients with gastric cancer with leptomeningeal metastasis.Methods: The mutant genes associated with leptomeningeal metastasis of gastric cancer were selected from the genomic results and the clinical characteristics,such as age,baseline KPS score,hemoglobin,nuclear magnetic manifestations,cranial pressure,protein level,intrathecal injection MTX dose,treatment regimen,cerebrospinal fluid cytological changes,and so on,for survival analysis.Results:1.Relationship between MYC and CCNE1 amplification and survival in tumor tissue and CSF samples: CSF CCNE1 amplification leads to worse OS performance.2.Molecular characteristics associated with survival of gastric cancer with leptomeningeal metastasis: mutations in primary tumors PTPN13 and ERBB2 are associated with significantly shortened PFS.PREX2 mutation,IGF1 R mutation,AR mutation,SMARCB1 deletion,SMAD4 deletion,and TGF-beta pathway aberration in CSF were associated with PFS.3.Clinical features associated with survival of gastric cancer with leptomeningeal metastasis: higher KPS,improved intracranial pressure,improved CSF cytology after treatment,and lower CSF relative ctDNA abundance were significantly associated with better PFS.Conclusions: Genetic mutations in primary tumor tissue and CSF and clinical features such as KPS,intracranial pressure and CSF cytology can predict the survival of patients.Part Four Dynamic monitoring of cerebrospinal fluid ctDNA with lept- omeningeal metastasis in gastric cancerObjective: To evaluate the changes of ctDNA in the diagnosis and treatment of gastric cancer patients with leptomeningeal metastasis.Methods: The diagnosis and treatment process of a patient with gastric cancer meningeal metastasis was described.Cerebrospinal fluid ctDNA was detected at three stages of diagnosis,remission and recurrence,and the changes of ctDNA of Cerebrospinal fluid in patients with gastric cancer leptomeningeal metastasis were determined at different stages of diagnosis and treatment.Results: A 58-year-old man was hospitalized for 22 days with headache,vomiting,dizziness,and weakness in his left leg.Leptomeningeal metastases were diagnosed by cerebrospinal fluid cytology and cranial MRI enhancement.The poorly differentiated adenocarcinoma of gastric antrum was found by examination,which was considered to be leptomeningeal metastases of gastric cancer.Intrathecal chemotherapy combined with radiotherapy and systemic chemotherapy were given,and the survival time after meningeal metastases was 12 months.The gene profile of ctDNA in CSF showed dynamic changes in driver genes,and allele frequencies of ctDNA in CSF were consistent with patient clinical assessments.Conclusions: Cerebrospinal fluid ctDNA monitoring has potential clinical value in the diagnosis and treatment of leptomeningeal metastasis of gastric cancer.