[Clinical Value of Cerebrospinal Fluid ctDNA in Patients with Non-small Cell Lung Cancer Meningeal Metastasis]

Abstract

Background: The mortality rate of lung cancer meningeal metastasis is extremely high. Circulating tumor DNA (ctDNA) has been confirmed to be contain the genomic alterations present in tumors and has been used to monitor tumor progression and response to treatments. Due to the presence of blood-brain barrier and other factors, peripheral blood ctDNA cannot reflect the information of brain lesions for patients with meningeal metastases. However, cerebrospinal fluid ctDNA as a test sample can better reflect the genetic status of intracranial tumors and guide clinical targeted treatment of intracranial lesions. This study explored the feasibility of cerebrospinal fluid ctNDA for evaluating non-small cell lung cancer (NSCLC) meningeal metastasis and the potential clinical value of cerebrospinal fluid ctDNA detection in NSCLC meningeal metastasis.

Methods: A total of 21 patients with NSCLC meningeal metastasis were included. Tumor genomic variation was performed on the cerebrospinal fluid and peripheral blood samples of patients by second-generation gene sequencing technology. The situation was examined, and pathological evaluation of cerebrospinal fluid cytology and head magnetic resonance imaging (MRI) enhanced examination were performed.

Results: ctDNA was detected in the cerebrospinal fluid of 21 patients. The sensitivity of cerebrospinal fluid ctDNA detection was superior to cytology in the diagnosis of meningeal metastasis (P<0.001). The detection rate and gene mutation abundance of cerebrospinal fluid were higher than plasma (P<0.001). Cerebro-spinal fluid had a unique genetic profile. In 6 patients with dynamic detection, changes of ctDNA allele fraction occurred at the same time or earlier than clinical disease changes, which could timely monitor drug resistance mechanism and relapse trend.

Conclusions: The detection rate of ctDNA in cerebrospinal fluid is higher than that in cytology and imaging. The detection of ctDNA in cerebrospinal fluid can reveal the specific mutation map of meningeal metastasis lesions. The dynamic monitoring of ctDNA in cerebrospinal fluid has hint significance for clinical response of lung cancer patients.

Keywords: Circulating tumor DNA; Lung neoplasms; Meningeal metastasis; Response evaluation.

图 1

患者肺组织基因突变谱。5例患者（P1、P6、P9、P14、P20）既往有肺组织留存，进行基因检测，检测率最高为EGFR（80%）及TP53（60%）突变，还可检测到ALK、RB1等基因突变。 Gene mutation spectrum of patients' lung tissues. Five patients (P1, P6, P9, P14, P20) had performed genetic testing of lung tissue. The highest detection frequencies were EGFR (80%) and TP53 (60%) mutations. ALK, RB1 and other gene mutations can also be detected.

图 2

脑脊液与血浆基因突变丰度对比。对21例匹配的的脑脊液及血浆样本进行基因检测，脑脊液检测率大大高于血浆（P < 0.001）。突变丰度：在该位点所有的等位基因中，突变的等位基因的占比（相对野生型等位基因）。 Comparison of allele fraction between cerebrospinal fluid and plasma. Genetic testing of 21 matched cerebrospinal fluid and plasma samples, the detection rate of cerebrospinal fluid is much higher than that of plasma (P < 0.001). CSF: cerebrospinal fluid. Mutation abundance: the proportion of mutant alleles (relative to wild-type alleles) among all alleles at this locus. AF: alleles frequency.

图 3

患者P1动态监测丰度结果。患者P1治疗过程中一直保持病情稳定，脑脊液中EGFR及TP53的突变丰度未出现显著的波动。 Dynamic monitoring results of patient P1. The patient's condition remained stable during the treatment of P1, and the mutation abundance of EGFR and TP53 in cerebrospinal fluid did not fluctuate much. ctDNA: circulating tumor DNA; SD: stable disease.

图 4

患者P4动态监测丰度结果。患者P4 ctDNA丰度保持稳定，脑脊液EGFR基因突变丰度均在上升后落回原来的水平，虽然有波动但并无明显的上升趋势。 Dynamic monitoring results of patient P4. The abundance of ctDNA in P4 remained stable, and the abundance of cerebrospinal fluid EGFR gene mutations fell back to the original level after rising. Although there was fluctuation, there was no obvious upward trend.

图 5

患者P13动态监测丰度结果。患者P13 ctDNA一直保持稳定，脑脊液EGFR基因突变丰度均在上升后落回原来的水平并再次上升，虽然有波动但并无明显的上升趋势。 Dynamic monitoring results of patient P13. The ctDNA of P13 has remained stable, and the abundance of cerebrospinal fluid EGFR gene mutations have fallen back to their original levels and increased again after rising. Although there is fluctuation, there is no obvious upward trend.

图 6

患者P2动态监测丰度结果。A：患者P2使用奥西替尼后病情得到有效控制，其脑脊液由首次检测突变丰度下降；而在第4次复查时，患者临床症状加重，脑脊液EGFR突变丰度上升。B：患者P2 MRI图像：2019-4-18箭头指示局部未见异常强化；2019-9-4出现结节样脑膜强化；2019-11-3显示强化范围扩大。C：患者P2 MRI图像：2019-4-18箭头指示局部未见异常强化；2019-9-4出现片状脑膜强化；2019-11-3显示脑膜强化较前相仿。 Dynamic monitoring results of patient P2. A: The patient's condition was effectively controlled after taking Osimertinib in P2, and the abundance of his cerebrospinal fluid decreased from the first detection of the mutation; while at the fourth review, the patient's clinical symptoms worsened and the abundance of cerebrospinal fluid EGFR mutation increased. B: MRI image of patient P2: The arrow indicates that there is no abnormal enhancement in the area on April 18, 2019; Nodular meningeal enhancement appears on September 4, 2019; On November 3, 2019, the scope of enhancement is enlarged. C: MRI image of patient P2: The arrow indicates that there is no abnormal enhancement in the area on April 18, 2019; Sheet-like meningeal enhancement appears on September 4, 2019. On November 3, 2019, the meningeal enhancement is similar to before.

图 7

患者P3动态监测丰度结果。患者P3在第3次复查时脑脊液EGFR基因突变丰度升高，3个月后患者再次进行复查，脑脊液基因突变丰度与第3次结果相比并无明显变化。 Dynamic monitoring results of patient P3. The P3 patient's cerebrospinal fluid EGFR gene mutation abundance increased at the third review, and the patient was reexamined three months later. The cerebrospinal fluid gene mutation abundance did not change significantly from the third result.

图 8

患者P20动态监测丰度结果。患者P20在确诊1个月后复查，脑脊液ctDNA丰度上升。 Dynamic monitoring results of patient P20. P20 was reexamined one month after diagnosis, and the abundance of ctDNA in cerebrospinal fluid increased.