Unique genomic profiles obtained from cerebrospinal fluid cell-free DNA of non-small cell lung cancer patients with leptomeningeal metastases

New Breakthroughs in the Diagnosis of Leptomeningeal Carcinomatosis: A Review of Liquid Biopsies of Cerebrospinal Fluid

Leptomeningeal carcinomatosis represents a terminal stage and is a devastating complication of cancer. Despite its high incidence, current diagnostic methods fail to accurately detect this condition in a timely manner. This failure to diagnose leads to the refusal of treatment and the absence of clinical trials, hampering the development of new therapy strategies. The use of liquid biopsy is revolutionizing the field of diagnostic oncology. The dynamic and non-invasive detection of tumor markers has enormous potential in cancer diagnostics and treatment. Leptomeningeal carcinomatosis is a condition where invasive tissue biopsy is not part of the routine diagnostic analysis, making liquid biopsy an essential diagnostic tool. Several elements in cerebrospinal fluid (CSF) have been investigated as potential targets of liquid biopsy, including free circulating tumor cells, free circulating nucleic acids, proteins, exosomes, and even non-tumor cells as part of the dynamic tumor microenvironment. This review aims to summarize current breakthroughs in the research on liquid biopsy, including the latest breakthroughs in the identification of tumor cells and nucleic acids, and give an overview of future directions in the diagnosis of leptomeningeal carcinomatosis.

The coming of age of liquid biopsy in neuro-oncology

The clinical role of liquid biopsy in oncology is growing significantly. In gliomas and other brain tumours, targeted sequencing of cell-free DNA (cfDNA) from CSF may help differential diagnosis when surgery is not recommended and be more representative of tumour heterogeneity than surgical specimens, unveiling targetable genetic alterations. Given the invasive nature of lumbar puncture to obtain CSF, the quantitative analysis of cfDNA in plasma is a lively option for patient follow-up. Confounding factors may be represented by cfDNA variations due to concomitant pathologies (inflammatory diseases, seizures) or clonal haematopoiesis. Pilot studies suggest that methylome analysis of cfDNA from plasma and temporary opening of the blood-brain barrier by ultrasound have the potential to overcome some of these limitations. Together with this, an increased understanding of mechanisms modulating the shedding of cfDNA by the tumour may help to decrypt the meaning of cfDNA kinetics in blood or CSF.

Leptomeningeal metastasis from solid tumours: EANO-ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up

•This Clinical Practice Guideline provides recommendations for managing leptomeningeal metastases from solid tumours. •The guideline covers clinical, imaging and cytological diagnosis, staging and risk assessment, treatment and follow-up. •A treatment and management algorithm is provided. •The author panel encompasses a multidisciplinary group of experts from different institutions and countries in Europe. •Recommendations are based on available scientific data and the authors’ collective expert opinion.

Leptomeningeal Metastases in Melanoma Patients: An Update on and Future Perspectives for Diagnosis and Treatment

Leptomeningeal disease (LMD) is a devastating complication of cancer with a particularly poor prognosis. Among solid tumours, malignant melanoma (MM) has one of the highest rates of metastasis to the leptomeninges, with approximately 10-15% of patients with advanced disease developing LMD. Tumour cells that metastasise to the brain have unique properties that allow them to cross the blood-brain barrier, evade the immune system, and survive in the brain microenvironment. Metastatic colonisation is achieved through dynamic communication between metastatic cells and the tumour microenvironment, resulting in a tumour-permissive milieu. Despite advances in treatment options, the incidence of LMD appears to be increasing and current treatment modalities have a limited impact on survival. This review provides an overview of the biology of LMD, diagnosis and current treatment approaches for MM patients with LMD, and an overview of ongoing clinical trials. Despite the still limited efficacy of current therapies, there is hope that emerging treatments will improve the outcomes for patients with LMD.

Cerebrospinal fluid: A unique source of circulating tumor DNA with broad clinical applications

Malignancies involving the central nervous system present unique challenges for diagnosis and monitoring due to the difficulties and risks of direct biopsies and the low specificity and/or sensitivity of other techniques for assessment. In recent years, liquid biopsy of the cerebrospinal fluid (CSF) has emerged as a convenient alternative that combines minimal invasiveness with the ability to detect disease-defining or therapeutically actionable genetic alterations from circulating tumor DNA (ctDNA). Since CSF can be obtained by lumbar puncture, or an established ventricular access device at multiple time points, ctDNA analysis enables initial molecular characterization and longitudinal monitoring throughout a patient's disease course, promoting optimization of treatment regimens. This review outlines some of the key aspects of ctDNA from CSF as a highly suitable approach for clinical assessment, the benefits and drawbacks, testing methods, as well as potential future advancements in this field. We anticipate wider adoption of this practice as technologies and pipelines improve and envisage significant improvements for cancer care.

Early Detection of Leptomeningeal Metastases Among Patients Undergoing Spinal Stereotactic Radiosurgery

Purpose

The management of patients with advanced solid malignancies increasingly uses stereotactic body radiation therapy (SBRT). Advanced cancer patients are at risk for developing leptomeningeal metastasis (LM), a fatal complication of metastatic cancer. Cerebrospinal fluid (CSF) is routinely collected during computed tomography (CT) myelography for spinal SBRT planning, offering an opportunity for early LM detection by CSF cytology in the absence of radiographic LM or LM symptoms (subclinical LM). This study tested the hypothesis that early detection of tumor cells in CSF in patients undergoing spine SBRT portends a similarly poor prognosis compared with clinically overt LM.

Methods and Materials

We retrospectively analyzed clinical records for 495 patients with metastatic solid tumors who underwent CT myelography for spinal SBRT planning at a single institution from 2014 to 2019.

Results

Among patients planned for SBRT, 51 (10.3%) developed LM. Eight patients (1.6%) had subclinical LM. Median survival with LM was similar between patients with subclinical versus clinically evident LM (3.6 vs 3.0 months, P = .30). Patients harboring both parenchymal brain metastases and LM (29/51) demonstrated shorter survival than those with LM alone (2.4 vs 7.1 months, P = .02).

Conclusions

LM remains a fatal complication of metastatic cancer. Subclinical LM detected by CSF cytology in spine SBRT patients has a similarly poor prognosis compared with standardly detected LM and warrants consideration of central nervous system-directed therapies. As aggressive local therapies are increasingly used for metastatic patients, more sensitive CSF evaluation may further identify patients with subclinical LM and should be evaluated prospectively.

Meta-analysis of commonly mutated genes in leptomeningeal carcinomatosis

Background

Leptomeningeal carcinomatosis (LMC) is a rare type of cancer that settles at the meninges through metastasis of non-small cell lung cancer (NSCLC), breast cancer and melanoma. The molecular mechanism underlying LMC is not known, therefore molecular studies investigating the development of LMC are needed. Here, we aimed to identify commonly mutated genes in LMC caused by NSCLC, breast cancer, and melanoma using an in-slico approach and their interactions using integrated bioinformatic approaches/tools in this meta-analysis.

Methods

We conducted a meta-analysis using information from 16 studies that included different sequencing techniques of patients with LMC caused by three different primary cancers: breast cancer, NSCLC, and melanoma. All studies that assessed mutation information from patients with LMC were searched in PubMed, from their inception to February, 16 2022. Studies that performed NGS on LMC patients with NSCLC, breast cancer, or melanoma were included, while studies that did not apply NGS to CSF samples, did not provide information on altered genes, were reviews, editorials, or conference abstracts, or whose main goal was the detection of malignancies were all excluded. We identified commonly mutated genes in all three types of cancer. Next, we constructed a protein-protein interaction network, then performed pathway enrichment analysis. We searched National Institutes of Health (NIH) and Drug-Gene Interaction Database (DGIdb) to find candidate drugs.

Results

We found that TP53, PTEN, PIK3CA, IL7R, and KMT2D genes were commonly mutated genes in all three types of cancer via our meta-analysis that consisted out of 16 studies. Our pathway enrichment analysis showed that all five genes were primarily associated with regulation of cell communication and signaling, and cell proliferation. Other enriched pathways included regulation of apoptotic processes of leukocytes and fibroblasts, macroautophagy and growth. According to our drug search we found candidate drugs; Everolimus, Bevacizumab and Temozolomide, which interact with these five genes.

Conclusion

In conclusion, a total of 96 mutated genes in LMC were investigated via meta-analysis. Our findings suggested vital roles of TP53, PTEN, PIK3CA, KMT2D, and IL7R, which can provide insight into the molecular basis of LMC development and paving the door to the development of new targeted medicine and will encourage molecular biologists to seek biological evidence.

Genomic Instability in Cerebrospinal Fluid Cell-Free DNA Predicts Poor Prognosis in Solid Tumor Patients with Meningeal Metastasis

Simple Summary

We established a genomic instability score using unfiltered sequencing data from meningeal metastasis (MM) cell-free circulating tumor DNA (ctDNA) samples and found that substantial genomic instability (GI) was present in cerebrospinal fluid ctDNA rather than plasma ctDNA, implying that MM lesions have a significantly increased GI status compared to primary tumors or extracranial metastatic lesions, which may suggest tumor clonal evolution. We also found that high GI status was an independent poor prognostic factor in lung adenocarcinoma MM patients, including meningeal metastasis-free survival (MFS) and overall survival (OS). Considering that genomically unstable tumors are more sensitive to PARP inhibitors, targeting GI alone or in combination with conventional therapy may be a promising treatment strategy for solid tumor patients with MM.

Abstract

Genomic instability (GI), which leads to the accumulation of DNA loss, gain, and rearrangement, is a hallmark of many cancers such as lung cancer, breast cancer, and colon cancer. However, the clinical significance of GI has not been systematically studied in the meningeal metastasis (MM) of solid tumors. Here, we collected both cerebrospinal fluid (CSF) and plasma samples from 56 solid tumor MM patients and isolated cell-free ctDNA to investigate the GI status using a next-generation sequencing-based comprehensive genomic profiling of 543 cancer-related genes. According to the unfiltered heterozygous mutation data-derived GI score, we found that 37 (66.1%) cases of CSF and 3 cases (6%) of plasma had a high GI status, which was further validated by low-depth whole-genome sequencing analysis. It is demonstrated that a high GI status in CSF was associated with poor prognosis, high intracranial pressure, and low Karnofsky performance status scores. More notably, a high GI status was an independent poor prognostic factor of poor MM-free survival and overall survival in lung adenocarcinoma MM patients. Furthermore, high occurrences of the co-mutation of TP53/EGFR, TP53/RB1, TP53/ERBB2, and TP53/KMT2C were found in MM patients with a high GI status. In summary, the GI status in CSF ctDNA might be a valuable prognostic indicator in solid tumor patients with MM.

Circulating tumour DNA - looking beyond the blood

Over the past decade, various liquid biopsy techniques have emerged as viable alternatives to the analysis of traditional tissue biopsy samples. Such surrogate 'biopsies' offer numerous advantages, including the relative ease of obtaining serial samples and overcoming the issues of interpreting one or more small tissue samples that might not reflect the entire tumour burden. To date, the majority of research in the area of liquid biopsies has focused on blood-based biomarkers, predominantly using plasma-derived circulating tumour DNA (ctDNA). However, ctDNA can also be obtained from various non-blood sources and these might offer unique advantages over plasma ctDNA. In this Review, we discuss advances in the analysis of ctDNA from non-blood sources, focusing on urine, cerebrospinal fluid, and pleural or peritoneal fluid, but also consider other sources of ctDNA. We discuss how these alternative sources can have a distinct yet complementary role to that of blood ctDNA analysis and consider various technical aspects of non-blood ctDNA assay development. We also reflect on the settings in which non-blood ctDNA can offer distinct advantages over plasma ctDNA and explore some of the challenges associated with translating these alternative assays from academia into clinical use.

Sequencing of cerebrospinal fluid in non-small-cell lung cancer patients with leptomeningeal metastasis: A systematic review

Leptomeningeal metastasis (LM) refers to the dissemination of malignant cells in the subarachnoid space, pia, and arachnoid mater and is a severe condition associated with metastatic solid tumors. The most common solid tumor that develops into LM is lung cancer and the incidence increased in patients with advanced non-small-cell lung cancer (NSCLC) with targetable mutations. However, tissue biopsy of LM is inaccessible, leading to the paucity of genomic profiles of LM to guide targeted treatments and explore biological mechanisms. In recent years, liquid biopsy is considered a minimally invasive and dynamic method to trace the genomic alterations of cancer cells and some studies started to perform sequencing of cerebrospinal fluid (CSF) in patients with LM to reveal the targeted mutations and genomic profiles. In this review, we focused on studies performed sequencing of CSF in NSCLC patients with LM and summarized the sequencing results and their commonality. As the only way to reveal the genomic landscapes of LM, our review provided evidence that sequencing of CSF is a promising management method in LM patients to dynamically guide target therapy and monitor intracranial tumor response. Furthermore, it reveals a unique genomic profile of LM including driver genes, drug-resistant mutations, and a number of copy number variations. Sequencing of CSF in LM patients seems to provide more comprehensive genomic information than we expected and the biological significance behind the genomic alternations needs further study.

Challenges and Advances in Diagnosis and Treatment of Leptomeningeal Disease (LMD)

Leptomeningeal disease (LMD) is a devastating category of CNS metastasis with a very poor prognosis and limited treatment options. With maximal aggressive therapy, survival times remain short and, without treatment, prognosis is measured in weeks. Both LMD diagnosis and treatment are challenging topics within neuro-oncology. In this review, we discuss the advances in LMD diagnosis with a focus on the role of circulating tumor DNA (ctDNA) and discuss the role of targeted and immunotherapy in LMD treatment.

Systematic review and meta-analysis of lung cancer brain metastasis and primary tumor receptor expression discordance

BACKGROUND

Treatment paradigms for metastatic non-small cell lung cancer are increasingly based on biomarker-driven therapies, with the most common alteration being mutation in the epidermal growth factor receptor (EGFR). Change in expression of such biomarkers could have a profound impact on the choice and efficacy of a selected targeted therapeutic, and hence the objective of this study was to analyze discordance in EGFR status in patients with lung cancer brain metastasis (LCBM).

METHODS

Using PRISMA guidelines, a systematic review was performed of series in the Medline database of biopsied or resected LCBM published before May, 2020. Key words included "lung cancer" and "brain metastasis" combined with "epidermal growth factor receptor/EGFR," and "receptor conversion/discordance or concordance." Weighted random effects models were used to calculate pooled estimates.

RESULTS

We identified 501 patients from 19 full-text articles for inclusion in this study. All patients underwent biopsy or resection of at least one intracranial lesion to compare to the primary tumor. On primary/LCBM comparison, the weighted pooled estimate for overall EGFR receptor discordance was 10% (95% CI 5-17%). The weighted effects model estimated a gain of an EGFR mutation in a brain metastases in patients with negative primary tumors was 7% (95% CI 4-12%). Alternatively, the weighted effects model estimate of loss of an EGFR mutation in patients with detected mutations in the primary tumor was also 7% (95% CI 4-10%). KRAS testing was also performed on both primary tumors and LCBM in a subset of 148 patients. The weighted effects estimate of KRAS-mutation discordance among LCBM compared to primary tumors was 13% (95% CI 5-27%). The weighted effects estimated of KRAS gain and loss in LCBM was 10% (95% CI 6-18%) and 8% (95% CI 4-15%), respectively. Meta-regression analysis did not find any association with any factors that could be associated with discordances.

CONCLUSIONS

EGFR and KRAS mutation status discordance between primary tumor and LCBM occurs in approximately 10% and 13% of patients, respectively. Evaluation of LCBM receptor status is key to biomarker-driven targeted therapy for intracranial disease and awareness of subtype switching is critical for those patients treated with systemic therapy alone for intracranial disease.

Advances in the diagnosis, evaluation, and management of leptomeningeal disease

Leptomeningeal metastasis (LM) is a devastating complication of cancer with variable clinical presentation and limited benefit from existing treatment options. In this review, we discuss advances in LM diagnostics and therapeutics with the potential to reverse this grim course. Emerging cerebrospinal fluid circulating tumor cell and cell-free tumor DNA analysis technologies will improve diagnosis of LM, while providing crucial genetic information, capturing tumor heterogeneity, and quantifying disease burden. Circulating tumor cells and cell-free tumor DNA have utility as biomarkers to track disease progression and treatment response. Treatment options for LM include ventriculoperitoneal shunting for symptomatic relief, radiation therapy including whole-brain radiation and focal radiation for bulky leptomeningeal involvement, and systemic and intrathecal medical therapies, including targeted and immunotherapies based on tumor mutational profiling. While existing treatments for LM have limited efficacy, recent advances in liquid biopsy together with increasing availability of targeted treatments will lead to rational multimodal individualized treatments and improved patient outcomes.

Genomic comparison between cerebrospinal fluid and primary tumor revealed the genetic events associated with brain metastasis in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is most common pathological type of lung cancer. LUAD with brain metastases (BMs) usually have poor prognosis. To identify the potential genetic factors associated with BM, a genomic comparison for BM cerebrospinal fluid (CSF) and primary lung tumor samples obtained from 1082 early- and late-stage LUAD patients was performed. We found that single nucleotide variation (SNV) of EGFR was highly enriched in CSF (87% of samples). Compared with the other primary lung tissues, copy number gain of EGFR (27%), CDK4 (11%), PMS2 (11%), MET (10%), IL7R (8%), RICTOR (7%), FLT4 (5%), and FGFR4 (4%), and copy number loss of CDKN2A (28%) and CDKN2B (18%) were remarkably more frequent in CSF samples. CSF had significantly lower tumor mutation burden (TMB) level but more abundant copy number variant. It was also found that the relationships among co-occurrent and mutually exclusive genes were dynamically changing with LUAD development. Additionally, CSF (97% of samples) harbored more abundant targeted drugs related driver and fusion genes. The signature 15 associated with defective DNA mismatch repair (dMMR) was only identified in the CSF group. Cancer associated pathway analysis further revealed that ErbB (95%) and cell cycle (84%) were unique pathways in CSF samples. The tumor evolution analysis showed that CSF carried significantly fewer clusters, but subclonal proportion of EGFR was remarkably increased with tumor progression. Collectively, CSF sequencing showed unique genomic characteristics and the intense copy number instability associated with cell cycle disorder and dMMR might be the crucial genetic factors in BM of LUAD.

Cell-free DNA from bile outperformed plasma as a potential alternative to tissue biopsy in biliary tract cancer

BACKGROUND

Biliary tract cancers (BTCs) are rare and highly heterogenous malignant neoplasms. Because obtaining BTC tissues is challenging, the purpose of this study was to explore the potential roles of bile as a liquid biopsy medium in patients with BTC.

PATIENTS AND METHODS

Sixty-nine consecutive patients with suspected BTC were prospectively enrolled in this study. Capture-based targeted sequencing was performed on tumor tissues, whole blood cells, plasma, and bile samples using a large panel consisting of 520 cancer-related genes.

RESULTS

Of the 28 patients enrolled in this cohort, tumor tissues were available in eight patients, and plasma and bile were available in 28 patients. Somatic mutations were detected in 100% (8/8), 71.4% (20/28), and 53.6% (15/28) of samples comprising tumor tissue DNA, bile cell-free DNA (cfDNA), and plasma cfDNA, respectively. Bile cfDNA showed a significantly higher maximum allele frequency than plasma cfDNA (P = 0.0032). There were 56.2% of somatic single-nucleotide variant (SNVs)/insertions and deletions (indels) shared between bile and plasma cfDNA. When considering the genetic profiles of tumor tissues as the gold standard, the by-variant sensitivity and positive predictive value for SNVs/indels in bile cfDNA positive for somatic mutations were both 95.5%. The overall concordance for SNVs/indels in bile was significantly higher than that in plasma (99.1% versus 78.3%, P < 0.0001). Moreover, the sensitivity of CA 19-9 combined with bile cfDNA achieved 96.4% in BTC diagnosis.

CONCLUSION

We demonstrated that bile cfDNA was superior to plasma cfDNA in the detection of tumor-related genomic alterations. Bile cfDNA as a minimally invasive liquid biopsy medium might be a supplemental approach to confirm BTC diagnosis.

Liquid biopsy from research to clinical practice: focus on non-small cell lung cancer

INTRODUCTION

In the current era of personalized medicine, liquid biopsy has acquired a relevant importance in patient management of advanced stage non-small cell lung cancer (NSCLC). As a matter of fact, liquid biopsy may supplant the problem of inadequate tissue for molecular testing. The term 'liquid biopsy' refers to a number of different biological fluids, but is most clearly associated with plasma-related platforms. It must be taken into account that pre-analytical processing and the selection of the appropriate technology according to the clinical context may condition the results obtained. In addition, novel clinical applications beyond the evaluation of the molecular status of predictive biomarkers are currently under investigation.

AREAS COVERED

This review summarizes the available evidence on pre-analytical issues and different clinical applications of liquid biopsies in NSCLC patients.

EXPERT OPINION

Liquid biopsy should be considered not only as a valid alternative but as complementary to tissue-based molecular approaches. Careful attention should be paid to the optimization and standardization of all phases of liquid biopsy samples management in order to determine a significant improvement in either sensitivity or specificity, while significant reducing the number of 'false negative' or 'false positive' molecular results.

The Liquid Biopsy for Lung Cancer: State of the Art, Limitations and Future Developments

Simple Summary

During the development and progression of lung tumors, processes such as necrosis and vascular invasion shed tumor cells or cellular components into various fluid compartments. Liquid biopsies consist of obtaining a bodily fluid, typically peripheral blood, in order to isolate and investigate these shed tumor constituents. Circulating tumor cells (CTCs) are one such constituent, which can be isolated from blood and can act as a diagnostic aid and provide valuable prognostic information. Liquid-based biopsies may also have a potential future role in lung cancer screening. Circulating tumor DNA (ctDNA) is found in small quantities in blood and, with the recent development of sensitive molecular and sequencing technologies, can be used to directly detect actionable genetic alterations or monitor for resistance mutations and guide clinical management. While potential benefits of liquid biopsies are promising, they are not without limitations. In this review, we summarize the current state and limitations of CTCs and ctDNA and possible future directions.

Abstract

Lung cancer is a leading cause of cancer-related deaths, contributing to 18.4% of cancer deaths globally. Treatment of non-small cell lung carcinoma has seen rapid progression with targeted therapies tailored to specific genetic drivers. However, identifying genetic alterations can be difficult due to lack of tissue, inaccessible tumors and the risk of complications for the patient with serial tissue sampling. The liquid biopsy provides a minimally invasive method which can obtain circulating biomarkers shed from the tumor and could be a safer alternative to tissue biopsy. While tissue biopsy remains the gold standard, liquid biopsies could be very beneficial where serial sampling is required, such as monitoring disease progression or development of resistance mutations to current targeted therapies. Liquid biopsies also have a potential role in identifying patients at risk of relapse post treatment and as a component of future lung cancer screening protocols. Rapid developments have led to multiple platforms for isolating circulating tumor cells (CTCs) and detecting circulating tumor DNA (ctDNA); however, standardization is lacking, especially in lung carcinoma. Additionally, clonal hematopoiesis of uncertain clinical significance must be taken into consideration in genetic sequencing, as it introduces the potential for false positives. Various biomarkers have been investigated in liquid biopsies; however, in this review, we will concentrate on the current use of ctDNA and CTCs, focusing on the clinical relevance, current and possible future applications and limitations of each.

Evaluating Infectious, Neoplastic, Immunological, and Degenerative Diseases of the Central Nervous System with Cerebrospinal Fluid-Based Next-Generation Sequencing

Cerebrospinal fluid (CSF) is a clear and paucicellular fluid that circulates within the ventricular system and the subarachnoid space of the central nervous system (CNS), and diverse CNS disorders can impact its composition, volume, and flow. As conventional CSF testing suffers from suboptimal sensitivity, this review aimed to evaluate the role of next-generation sequencing (NGS) in the work-up of infectious, neoplastic, neuroimmunological, and neurodegenerative CNS diseases. Metagenomic NGS showed improved sensitivity—compared to traditional methods—to detect bacterial, viral, parasitic, and fungal infections, while the overall performance was maximized in some studies when all diagnostic modalities were used. In patients with primary CNS cancer, NGS findings in the CSF were largely concordant with the molecular signatures derived from tissue-based molecular analysis; of interest, additional mutations were identified in the CSF in some glioma studies, reflecting intratumoral heterogeneity. In patients with metastasis to the CNS, NGS facilitated diagnosis, prognosis, therapeutic management, and monitoring, exhibiting higher sensitivity than neuroimaging, cytology, and plasma-based molecular analysis. Although evidence is still rudimentary, NGS could enhance the diagnosis and pathogenetic understanding of multiple sclerosis in addition to Alzheimer and Parkinson disease. To conclude, NGS has shown potential to aid the research, facilitate the diagnostic approach, and improve the management outcomes of all the aforementioned CNS diseases. However, to establish its role in clinical practice, the clinical validity and utility of each NGS protocol should be determined. Lastly, as most evidence has been derived from small and retrospective studies, results from randomized control trials could be of significant value.

Current and future trends in non-small cell lung cancer biomarker testing: The American experience

Biomarker testing in patients with advanced stage non-small cell lung cancer provides essential information that can be used to select the most appropriate therapy. The regular updates of guideline recommendations reflect the growing number of biomarkers that must be assessed, and as such signal the shift from single-gene assays to more comprehensive genomic profiling using next-generation sequencing modalities. Cytology and small biopsy specimens have proven to be more than adequate substrates for these types of ancillary molecular testing; however, other alternative testing substrates are beginning to emerge. These include so-called liquid biopsies as well the supernatant fluid from cytology specimens, both of which have demonstrated promise for use in the clinical realm. This review will briefly cover the current state of non-small cell lung cancer biomarker testing in the United States, with a focus on these novel nonconventional substrates that are increasingly being incorporated into testing paradigms.

The Underlying Biology and Therapeutic Vulnerabilities of Leptomeningeal Metastases in Adult Solid Cancers

Metastasis to the central nervous system occurs in approximately 20% of patients with advanced solid cancers such as lung cancer, breast cancer, and melanoma. While central nervous system metastases most commonly form in the brain parenchyma, metastatic cancer cells may also reside in the subarachnoid space surrounding the brain and spinal cord to form tumors called leptomeningeal metastases. Leptomeningeal metastasis involves cancer cells that reach the subarachnoid space and proliferate in the cerebrospinal fluid compartment within the leptomeninges, a sequela associated with a myriad of symptoms and poor prognosis. Cancer cells exposed to cerebrospinal fluid in the leptomeninges must contend with a unique microenvironment from those that establish within the brain or other organs. Leptomeningeal lesions provide a formidable clinical challenge due to their often-diffuse infiltration within the subarachnoid space. The molecular mechanisms that promote the establishment of leptomeningeal metastases have begun to be elucidated, demonstrating that it is a biological entity distinct from parenchymal brain metastases and is associated with specific molecular drivers. In this review, we outline the current state of knowledge pertaining to the diagnosis, treatment, and molecular underpinnings of leptomeningeal metastasis.

Cell-free DNA from cerebrospinal fluid can be used to detect the EGFR mutation status of lung adenocarcinoma patients with central nervous system metastasis

Background

EGFR tyrosine kinase inhibitors (TKIs) have revolutionized the therapeutic approach for EGFR mutated patients. However, acquired resistance to EGFR-TKI therapy is unavoidable. Repeat biopsy cannot be used, and peripheral blood detection shows a low positive rate in cases of brain-only disease progression.

Methods

Droplet digital polymerase chain reaction (PCR) (ddPCR) was performed on the plasma and cerebrospinal fluid (CSF) samples of 79 lung adenocarcinoma (LUAD) patients with EGFR mutations and central nervous system (CNS) metastasis. The differences in the EGFR mutation status between the paired plasma and CSF samples were assessed, and the role of CSF testing as a predictor of overall survival was evaluated.

Results

The CSF of patients with neurological symptoms, EGFR-TKI treatment, or leptomeningeal metastasis (LM) had a significantly higher positive rate of EGFR mutation compared to the plasma samples (P=0.001, P=0.035, P=0.019, respectively). Moreover, EGFR mutation status in CSF was consistent with neurological symptoms and LM (kappa =0.455, P<0.001; kappa =0.508, P<0.001; respectively). For the patients with brain metastasis, EGFR mutation-positive rate in CSF samples was lower than that in plasma samples (28.3% vs. 64.2%, P<0.001), while the patients with LM had the opposite result (84.6% vs. 38.5%, P=0.004). Moreover, patients with EGFR mutation in their CSF experienced worse survival [hazard ratio (HR) =2.93, 95% confidence interval (CI): 1.45–5.92; P=0.003, P _adjust <0.0001].

Conclusions

The EGFR mutation status of CSF was different from that of plasma and is correlated with patient prognosis. CSF could be helpful in detecting the EGFR mutation status of patients, particularly in cases of LM.

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

背景与目的

肺癌脑膜转移病死率极高。循环肿瘤DNA（circulating tumor DNA, ctDNA）已被证实含有肿瘤的基因组改变信息，并已被用于监测肿瘤的进展和对治疗的响应。对于存在脑膜转移瘤的患者，由于血脑屏障等因素的存在，外周血ctDNA不能反映脑部病灶的信息，此时脑脊液ctDNA作为检测样本能更好地体现颅内肿瘤的基因状态，指导临床对颅内病灶的靶向治疗。本研究旨在探究脑脊液ctNDA用于监测非小细胞肺癌（non-small cell lung cancer, NSCLC）脑膜转移的可行性以及脑脊液ctDNA检测对NSCLC脑膜转移的临床价值。

方法

入组NSCLC脑膜转移患者21例，通过二代基因测序技术对患者的脑脊液及外周血样本进行基因检测，并进行脑脊液细胞学病理学检测和头颅核磁共振增强检查。

结果

入组21例患者脑脊液中均检测到ctDNA。脑脊液ctDNA检测的灵敏性在脑膜转移诊断方面优于细胞学（P < 0.001）。脑脊液的基因突变检出率及基因突变丰度均高于血浆（P < 0.001）。脑脊液具有独特的基因谱。6例动态检测的患者中，脑脊液中ctDNA丰度变化均同时或早于临床疾病变化出现，可及时揭示耐药机制和监测复发趋势。

结论

脑脊液ctDNA检出率高于细胞学及影像学；脑脊液ctDNA检测可展现脑膜转移病灶特有的突变图谱；脑脊液ctDNA动态监测对肺癌患者临床疗效具有提示意义。

Central nervous system metastases and oligoprogression during treatment with tyrosine kinase inhibitors in oncogene-addicted non-small cell lung cancer: how to treat and when?

Up to 70% of non-small cell lung cancer (NSCLC) patients develop central nervous system (CNS) metastases during the course of their disease, especially those with oncogenic drivers treated with a first-generation tyrosine kinase inhibitor (TKI), because of the relatively poor CNS penetration. CNS metastases are associated with a negative impact on quality of life and survival. As, with the introduction of newer generation TKIs, the survival rates are increasing in this particular population, treatment and/or prevention of CNS metastases becomes even more relevant and the TKI with the best CNS efficacy should be selected. Unfortunately, CNS efficacy data in clinical trials are not fully comparable. Furthermore, oligoprogression to the brain without extracranial progression regularly occurs in the oncogenic driver population and both local therapy and switch of systemic therapy are possible treatment options. However, the best order of systemic and local therapy is still not precisely known. In this narrative review, we will summarize incidence and treatment of CNS metastases in oncogene driven NSCLC, including the optimal treatment of CNS oligometastatic disease (synchronous as well as oligoprogressive).

Standardizing a volume benchmark for cerebrospinal fluids for optimal diagnostic accuracy

INTRODUCTION

Cerebral spinal fluid (CSF) cytomorphologic analysis remains the gold standard in the evaluation of malignant leptomeningeal involvement. However, collection of optimal volumes for adequate cytomorphologic evaluation is not standardized. Our study investigated optimal CSF volumes that result in a significant diagnostic result.

METHODS

A total of 4114 samples were retrospectively identified from 2014 to 2018, and 2557 samples had concurrent flow cytometry (FC) study. Each specimen was grouped as unsatisfactory, negative, atypical, or positive. Positive samples were grouped as either solid tumors, leukemia, or lymphoma by the type of malignancy detected. Demographic data as well as CSF source was recorded. Specimens with FC were separated by detection on cytology and/or FC. A t-test and ANOVA test were used to compare the average volumes for each group.

RESULTS

Average volumes for negative, atypical, and positive samples are 7.48 mL (95% CI: 7.33, 7.63), 7.97 mL (95% CI: 7.37, 8.57), and 8.44 mL (95% CI: 7.46, 9.43), respectively. Average volumes for solid tumors, leukemia, and lymphoma positive samples are 12.0 mL (95% CI: 9.11, 14.89), 6.73 mL (95% CI: 5.94, 7.53), and 8.44 mL (95% CI: 6.78, 10.09). For cases with FC, the volumes are 10.11 mL (95% CI: 9.28, 10.96), 7.28 mL (95% CI: 6.87, 7.70), and 6.86 mL (95% CI: 6.25, 7.49) for positive cytology only, positive cytology/FC, and negative for both, respectively.

CONCLUSIONS

Our results suggest that higher volumes produce better results for analysis. We recommend an optimal volume of 8.44 mL for cytologic work-up of malignancies. However, optimal volumes may differ based upon malignancy type and utilization of flow cytometry.

Management of leptomeningeal carcinomatosis and challenges of trial design

PURPOSE OF REVIEW

Highlight recent data in lung and breast cancer leptomeningeal disease and address clinical trials that are open for patients.

RECENT FINDINGS

Patients with lung and breast cancer leptomeningeal disease have survival outcomes of less than 1 year, despite advances in treatment strategy. Efforts to develop liquid biopsy biomarkers of disease progression from cerebrospinal fluid and plasma are underway. There are over 10 clinical trials open for patients with leptomeningeal disease, half of which use immunotherapy.

SUMMARY

Consortium-based, multicenter clinical trials for patients with leptomeningeal disease are urgently needed to expand the treatment armamentarium.

Circulating Tumor DNA Analysis for Patients with Oncogene-Addicted NSCLC With Isolated Central Nervous System Progression

INTRODUCTION

In patients with oncogene-addicted NSCLC and isolated central nervous system progression (iCNS), tissue biopsy is challenging, and the clinical utility of plasma liquid biopsy (i.e., circulating tumor DNA [ctDNA]) is unknown.

METHODS

Patients with advanced NSCLC with known baseline genomic alteration (GA) (EGFR, ALK, BRAF, KRAS, HER2, ROS1, MET, PIK3CA, STK11, TP53) on tissue were divided into three groups on the basis of their disease progression pattern: iCNS, extra-CNS only (noCNS), or both (cCNS). All patients with available plasma ctDNA were included and were analyzed by next-generation sequencing InVisionFirst-Lung. ctDNA was considered positive if at least one GA was detected. Cell-free tumor DNA was analyzed in cerebrospinal fluid when available.

RESULTS

Out of 517 patients screened, 247 were included: 54 had iCNS, 99 had noCNS, and 94 had cCNS progressive disease (64, 128, and 110 ctDNA samples, respectively). CtDNA was positive in 52% iCNS versus 84% in noCNS and 92% in cCNS (p < 0.00001), with lower detection of driver (37% versus 77% and 73%, respectively) and resistance alterations (6% versus 45% and 44%). Patients with iCNS and positive ctDNA were more at risk of extra-CNS progression (32% versus 7%, p = 0.026). In 12 patients with iCNS, ctDNA was positive in six (50%) plasma and in 10 (83%) paired cerebrospinal fluid (p = 0.193).

CONCLUSIONS

Although tagged amplicon-based next-generation sequencing has high detection rates of GA in plasma ctDNA in patients with NSCLC with extra-CNS disease, detection rate of GAs (52%) is lower in the subset of patients with iCNS disease. Complementary tests such as cerebrospinal fluid cell-free DNA may be useful. Further evidence would be beneficial to understand the genomic landscape in patients with NSCLC and iCNS.

Radiographic appearance of leptomeningeal disease in patients with EGFR-mutated non-small-cell lung carcinoma treated with tyrosine kinase inhibitors: a case series

EGFR is frequently mutated in non-small-cell lung carcinomas (NSCLCs). Clinically available tyrosine kinase inhibitors (TKIs) are effective in treating EGFR-mutant NSCLC. In this case series, we present five patients with TKI-treated EGFR-mutated NSCLC who developed leptomeningeal disease (LMD) lacking characteristic imaging findings. All five patients received TKIs prior to development of cytology-confirmed LMD. Clinical signs of LMD preceded radiographic evidence by 2–12 months. T790M, the most common resistance mutation to first-generation EGFR inhibitors, was identified in four cases. These cases illustrate that in patients with EGFR-mutant NSCLC, TKIs may effectively control LMD, creating a lag between onset of symptoms and observation of radiographic findings.

Activity of EGFR Tyrosine Kinase Inhibitors in NSCLC With Refractory Leptomeningeal Metastases

INTRODUCTION

Leptomeningeal metastases (LMs) are associated with dismal prognosis in NSCLC. Optimal management remains unknown in patients with EGFR-mutated NSCLC after initial tyrosine kinase inhibitor (TKI) failure.

METHODS

We conducted a multicenter retrospective study including patients with EGFR-mutated NSCLC and LM. TKI failure was defined as diagnosis of LM on TKI, or progression of known LM on TKI.

RESULTS

Ninety-two patients were included, median age of 60 years, predominantly female (68%), never-smokers (74%). EGFR mutations included L858R (45%), exon 19 deletions (28%), or other mutations (14%). Median time to LM diagnosis was 18.5 months after initial diagnosis of advanced NSCLC. LM was diagnosed after a median of 2 (range: 0-9) systemic therapies. Median overall survival from LM diagnosis was 6.1 months (95% confidence interval [CI]: 4.2-7.6 months). Among 87 patients with TKI failure, patients rechallenged with TKI (n = 50) had a median LM overall survival of 7.6 months (95% CI: 5.7-10.9) compared to 4.2 months (95% CI: 1.6-6.7) in patients without further therapy. Overall, 60% of patients rechallenged with TKI experienced clinical benefit (clinical response or stable disease >2 months), and 23% were treatment failure-free at 6 months. Clinical benefit was reported in 11 of 20 (55%) patients treated with erlotinib after afatinib or gefitinib. Strategies based on increasing dose intensity (n = 17) yielded clinical benefit in 59% of patients. All four patients who received osimertinib after first- and second-generation TKI experienced clinical benefit.

CONCLUSIONS

TKI rechallenge strategies, including dosing intensification, may improve clinical outcomes of patients with LM from EGFR-mutated NSCLC after initial TKI failure.