Circulating tumor cells in advanced non-small cell lung cancer patients are associated with worse tumor response to checkpoint inhibitors

The impact of platelets on the metastatic potential of tumour cells

In cancer, activation of platelets by tumor cells is critical to disease progression. Development of precise antiplatelet targeting may improve outcomes from anticancer therapy. Alongside a distinct shift in functionality such as pro-metastatic and pro-coagulant properties, platelet production is often accelerated significantly early in carcinogenesis and the cancer-associated thrombocytosis increases the risk of metastasis formation and thromboembolic events. Tumor-activated platelets facilitate the proliferation of migrating tumor cells and shield them from immune surveillance and physical stress during circulation. Additionally, platelet-tumor cell interactions promote tumor cell intravasation, intravascular arrest, and extravasation through a repertoire of adhesion molecules, growth factors and angiogenic factors. Particularly, the presence of circulating tumor cell (CTC) clusters in association with platelets is a negative prognostic indicator. The contribution of platelets to the metastatic process is an area of intense investigation and this review provides an overview of the advances in understanding platelet-tumor cell interactions and their contribution to disease progression. Also, we review the potential of targeting platelets to interfere with the metastatic process.

[Research Progress on Predictive Biomarkers of Immunotherapy Efficacy in Non-small Cell Lung Cancer]

Lung cancer is one of the most common malignant tumors in the world, of which non-small cell lung cancer (NSCLC) is the majority. The emergence of immune checkpoint inhibitors (ICIs) has greatly changed the treatment strategy of NSCLC and improved the prognosis of patients. However, in reality, only a small number of patients can achieve long-term benefit. Therefore, the identification of reliable predictive biomarkers is essential for the selection of treatment modalities. With the development of molecular biology and genome sequencing technology in recent years, as well as the in-depth understanding of tumor and its host immune microenvironment, research on biomarkers has emerged in an endless stream. This review focuses on the predictive biomarkers of immunotherapy efficacy in NSCLC, in order to provide some guidance for precision immunotherapy.
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The detection of circulating tumor cells indicates poor therapeutic efficacy and prognosis in patients with nonsmall cell lung cancer: A systematic review and meta-analysis

OBJECTIVE

The efficacy and prognostic value of circulating tumor cells (CTCs) in nonsmall cell lung cancer (NSCLC) are controversial based on the existing research. This systematic review and meta-analysis evaluated the significance of CTCs in NSCLC therapy monitoring and prognosis prediction, supporting their potential as clinical biomarkers.

METHODS

We conducted a comprehensive search of PubMed, Embase, Web of Science, The Cochrane Library, WanFang Data, CNKI, and VIP through September 20, 2023. Inclusion criteria were cohort studies involving NSCLC patients, focusing on peripheral blood CTCs, and assessing outcomes such as pre- and posttreatment CTC rates or levels, progression-free survival (PFS), and overall survival (OS). Two reviewers independently extracted the data and assessed risk of bias using the Newcastle-Ottawa Scale. We utilized Review Manager 5.4.1 for meta-analysis, calculating pooled odds ratios (ORs) for dichotomous outcomes, mean differences for continuous variables and hazard ratios (HRs) for survival data, applying fixed- or random-effects models based on heterogeneity assessed by the I2 statistic. This study was registered in PROSPERO (No. CRD42023450035).

RESULTS

Twenty-two eligible studies with a total of 1674 NSCLC patients were included. Meta-analysis results showed that the CTCs-positive rate (OR = 0.59, 95% CI 0.45 to 0.77, p = 0.0001) and CTCs count (mean difference = -3.10, 95% CI -5.52 to -0.69, p = 0.01) were significantly decreased after antitumor treatment. Compared with the CTCs nonreduced group, the CTC-reduced group showed better PFS (HR = 1.71, 95% CI 1.35 to 2.17, p < 0.00001) and OS (HR = 1.50, 95% CI 1.21 to 1.86, p = 0.0003) after treatment. PFS and OS in CTC-positive groups were lower than those in the CTCs-negative group pretreatment (HR = 2.49, 95% CI 1.78 to 3.47, p < 0.00001; HR = 1.80, 95% CI 1.29 to 2.52, p = 0.0006) and posttreatment (HR = 3.36, 95% CI 2.12 to 5.33, p < 0.00001; HR = 3.31, 95% CI 1.75 to 6.27, p = 0.0002).

CONCLUSIONS

CTCs can be used as a biomarker to monitor NSCLC efficacy, predict prognosis and guide follow-up treatment.

Liquid biopsy for human cancer: cancer screening, monitoring, and treatment

Currently, tumor treatment modalities such as immunotherapy and targeted therapy have more stringent requirements for obtaining tumor growth information and require more accurate and easy-to-operate tumor information detection methods. Compared with traditional tissue biopsy, liquid biopsy is a novel, minimally invasive, real-time detection tool for detecting information directly or indirectly released by tumors in human body fluids, which is more suitable for the requirements of new tumor treatment modalities. Liquid biopsy has not been widely used in clinical practice, and there are fewer reviews of related clinical applications. This review summarizes the clinical applications of liquid biopsy components (e.g., circulating tumor cells, circulating tumor DNA, extracellular vesicles, etc.) in tumorigenesis and progression. This includes the development process and detection techniques of liquid biopsies, early screening of tumors, tumor growth detection, and guiding therapeutic strategies (liquid biopsy-based personalized medicine and prediction of treatment response). Finally, the current challenges and future directions for clinical applications of liquid biopsy are proposed. In sum, this review will inspire more researchers to use liquid biopsy technology to promote the realization of individualized therapy, improve the efficacy of tumor therapy, and provide better therapeutic options for tumor patients.

Longitudinal tracking of circulating rare events in the liquid biopsy of stage III-IV non-small cell lung cancer patients

In the United States, lung cancer is the second most common type of cancer with non-small cell lung cancer (NSCLC) encompassing around 85% of total lung cancer cases. Late-stage patients with metastatic disease have worsening prognosis, highlighting the importance of longitudinal disease monitoring. Liquid biopsy (LBx) represents a way for physicians to non-invasively track tumor analytes, such as circulating tumor cells (CTCs), and understand tumor progression in real-time through analyzing longitudinal blood samples. CTCs have been shown to be effective predictive biomarkers in measuring treatment efficacy and survival outcomes. We used the third-generation High-Definition Single Cell Assay (HDSCA3.0) workflow to analyze circulating rare events longitudinally during treatment in a cohort of 10 late-stage NSCLC patients, identifying rare events including circulating cancer cells (i.e., CTCs), and oncosomes. Here, we show (1) that there is a cancer specific LBx profile, (2) there is considerable heterogeneity of rare cells and oncosomes, and (3) that LBx data elements correlated with patient survival outcomes. Additional studies are warranted to understand the biological significance of the rare events detected, and the clinical potential of the LBx to monitor and predict response to treatment in NSCLC patient care.

External Quality Assessment on Molecular Tumor Profiling with Circulating Tumor DNA-Based Methodologies Routinely Used in Clinical Pathology within the COIN Consortium

BACKGROUND

Identification of tumor-derived variants in circulating tumor DNA (ctDNA) has potential as a sensitive and reliable surrogate for tumor tissue-based routine diagnostic testing. However, variations in pre(analytical) procedures affect the efficiency of ctDNA recovery. Here, an external quality assessment (EQA) was performed to determine the performance of ctDNA mutation detection work flows that are used in current diagnostic settings across laboratories within the Dutch COIN consortium (ctDNA on the road to implementation in The Netherlands).

METHODS

Aliquots of 3 high-volume diagnostic leukapheresis (DLA) plasma samples and 3 artificial reference plasma samples with predetermined mutations were distributed among 16 Dutch laboratories. Participating laboratories were requested to perform ctDNA analysis for BRAF exon 15, EGFR exon 18-21, and KRAS exon 2-3 using their regular circulating cell-free DNA (ccfDNA) analysis work flow. Laboratories were assessed based on adherence to the study protocol, overall detection rate, and overall genotyping performance.

RESULTS

A broad range of preanalytical conditions (e.g., plasma volume, elution volume, and extraction methods) and analytical methodologies (e.g., droplet digital PCR [ddPCR], small-panel PCR assays, and next-generation sequencing [NGS]) were used. Six laboratories (38%) had a performance score of >0.90; all other laboratories scored between 0.26 and 0.80. Although 13 laboratories (81%) reached a 100% overall detection rate, the therapeutically relevant EGFR p.(S752_I759del) (69%), EGFR p.(N771_H773dup) (50%), and KRAS p.(G12C) (48%) mutations were frequently not genotyped accurately.

CONCLUSIONS

Divergent (pre)analytical protocols could lead to discrepant clinical outcomes when using the same plasma samples. Standardization of (pre)analytical work flows can facilitate the implementation of reproducible liquid biopsy testing in the clinical routine.

Blood-based biomarkers in patients with non-small cell lung cancer treated with immune checkpoint blockade

The paradigm of non-small cell lung cancer (NSCLC) treatment has been profoundly influenced by the development of immune checkpoint inhibitors (ICI), but the range of clinical responses observed among patients poses significant challenges. To date, analyses of tumor biopsies are the only parameter used to guide prognosis to ICI therapy. Tumor biopsies, however, are often difficult to obtain and tissue-based biomarkers are limited by intratumoral heterogeneity and temporal variability. In response, there has been a growing emphasis on the development of "liquid biopsy"‒ derived biomarkers, which offer a minimally invasive means to dynamically monitor the immune status of NSCLC patients either before and/or during the course of treatment. Here we review studies in which multiple blood-based biomarkers encompassing circulating soluble analytes, immune cell subsets, circulating tumor DNA, blood-based tumor mutational burden, and circulating tumor cells have shown promising associations with the clinical response of NSCLC patients to ICI therapy. These investigations have unveiled compelling correlations between the peripheral immune status of patients both before and during ICI therapy and patient outcomes, which include response rates, progression-free survival, and overall survival. There is need for rigorous validation and standardization of these blood-based assays for broader clinical application. Integration of multiple blood-based biomarkers into comprehensive panels or algorithms also has the potential to enhance predictive accuracy. Further research aimed at longitudinal monitoring of circulating biomarkers is also crucial to comprehend immune dynamics and resistance mechanisms and should be used alongside tissue-based methods that interrogate the tumor microenvironment to guide treatment decisions and may inform on the development of novel therapeutic strategies. The data reviewed here reinforce the opportunity to refine patient stratification, optimize treatments, and improve outcomes not only in NSCLC but also in the wider spectrum of solid tumors undergoing immunotherapy.

Predictive biomarkers for immune-related adverse events in cancer patients treated with immune-checkpoint inhibitors

PURPOSE

The objective of this study was to identify potential predictors of immune-related adverse events (irAEs) in cancer patients receiving immune checkpoint inhibitor therapy among serum indexes, case data, and liquid biopsy results.

METHODS

We retrospectively analyzed 418 patients treated with anti-programmed cell death 1(PD-1)/PD-1 ligand (PD-L1) inhibitors from January 2018 to May 2022 in our cancer center. We identified factors that correlated with the occurrence of irAEs and evaluated associations between irAEs and anti-PD-1/PD-L1 inhibitor responses.

RESULTS

The incidence of irAEs was 42.1%, and pneumonitis (9.1%), thyroid toxicity (9.1%), cardiotoxicity (8.1%), and dermatologic toxicity (6.9%) were the four most common irAEs. Multivariate logistic analysis identified female sex, antibiotic use, higher post-treatment neutrophil-to-lymphocyte ratio (NLR), and higher baseline circulating tumor cell (CTC) level, as predictive biomarkers for the occurrence of irAEs. A lower baseline prognostic nutritional index (PNI), body mass index (BMI) ≥ 25 kg/m2, and higher post-treatment lactate dehydrogenase (LDH) level were predictive factors for more severe irAEs (higher severity grade). Patients without irAEs had better overall survival than those with irAEs. Specifically, pneumonitis and cardiotoxicity were found to be significant predictors of poor prognosis in the irAE subgroup with different organ-related irAEs. Low-dose steroid (dexamethasone 10 mg) treatment had no significant effect on outcomes.

CONCLUSIONS

Gender, antibiotic use, post-treatment NLR, and baseline CTC level are potential predictive biomarkers of irAEs, while baseline PNI, BMI, and post-treatment LDH may predict the severity of irAEs. The predictive effect of irAE occurrence on survival benefit may depend on the type of irAE.

A novel model for predicting prognosis and response to immunotherapy in nasopharyngeal carcinoma patients

Blood-based biomarkers of immune checkpoint inhibitors (ICIs) response in patients with nasopharyngeal carcinoma (NPC) are lacking, so it is necessary to identify biomarkers to select NPC patients who will benefit most or least from ICIs. The absolute values of lymphocyte subpopulations, biochemical indexes, and blood routine tests were determined before ICIs-based treatments in the training cohort (n = 130). Then, the least absolute shrinkage and selection operator (Lasso) Cox regression analysis was developed to construct a prediction model. The performances of the prediction model were compared to TNM stage, treatment, and Epstein-Barr virus (EBV) DNA using the concordance index (C-index). Progression-free survival (PFS) was estimated by Kaplan-Meier (K-M) survival curve. Other 63 patients were used for validation cohort. The novel model composed of histologic subtypes, CD19+ B cells, natural killer (NK) cells, regulatory T cells, red blood cells (RBC), AST/ALT ratio (SLR), apolipoprotein B (Apo B), and lactic dehydrogenase (LDH). The C-index of this model was 0.784 in the training cohort and 0.735 in the validation cohort. K-M survival curve showed patients with high-risk scores had shorter PFS compared to the low-risk groups. For predicting immune therapy responses, the receiver operating characteristic (ROC), decision curve analysis (DCA), net reclassifcation improvement index (NRI) and integrated discrimination improvement index (IDI) of this model showed better predictive ability compared to EBV DNA. In this study, we constructed a novel model for prognostic prediction and immunotherapeutic response prediction in NPC patients, which may provide clinical assistance in selecting those patients who are likely to gain long-lasting clinical benefits to anti-PD-1 therapy.

Circulating Tumour Cells in the Prediction of Bone Metastasis

Bone is the most common organ for the development of metastases in many primary tumours, including those of the breast, prostate and lung. In most cases, bone metastasis is incurable, and treatment is predominantly palliative. Much research has focused on the role of Circulating Tumour Cells (CTCs) in the mechanism of metastasis to the bone, and methods have been developed to isolate and count CTCs from peripheral blood. Several methods are currently being used in the study of CTCs, but only one, the CellSearchTM system has been approved by the United States Food and Drug Administration for clinical use. This review summarises the advantages and disadvantages, and outlines which clinical studies have used these methods. Studies have found that CTC numbers are predictive of bone metastasis in breast, prostate and lung cancer. Further work is required to incorporate information on CTCs into current staging systems to guide treatment in the prevention of tumour progression into bone.

Circulating tumour cells and PD-L1-positive small extracellular vesicles: the liquid biopsy combination for prognostic information in patients with metastatic non-small cell lung cancer

BACKGROUND

Circulating tumour cells (CTCs), circulating tumour DNA (ctDNA), and extracellular vesicles (EVs) are minimally invasive liquid biopsy biomarkers. This study investigated whether they predict prognosis, alone or in combination, in heterogenous unbiased non-small cell lung cancer (NSCLC) patients.

METHODS

Plasma samples of 54 advanced NSCLC patients from a prospective clinical trial. CtDNA mutations were identified using the UltraSEEK™ Lung Panel (MassARRAY® technology). PD-L1 expression was assessed in small EVs (sEVs) using an enzyme-linked immunosorbent assay.

RESULTS

At least one ctDNA mutation was detected in 37% of patients. Mutations were not correlated with overall survival (OS) (HR = 1.1, 95% CI = 0.55; 1.83, P = 0.980) and progression-free survival (PFS) (HR = 1.00, 95% CI = 0.57-1.76, P = 0.991). High PD-L1+ sEV concentration was correlated with OS (HR = 1.14, 95% CI = 1.03-1.26, P = 0.016), but not with PFS (HR = 1.08, 95% CI = 0.99-1.18, P = 0.095). The interaction analysis suggested that PD-L1+ sEV correlation with PFS changed in function of CTC presence/absence (P interaction = 0.036). The combination analysis highlighted worse prognosis for patients with CTCs and high PD-L1+ sEV concentration (HR = 7.65, 95% CI = 3.11-18.83, P < 0.001). The mutational statuses of ctDNA and tumour tissue were significantly correlated (P = 0.0001).

CONCLUSION

CTCs and high PD-L1+ sEV concentration correlated with PFS and OS, but not ctDNA mutations. Their combined analysis may help to identify patients with worse OS.

TRIAL REGISTRATION

NCT02866149, Registered 01 June 2015, https://clinicaltrials.gov/ct2/show/study/NCT02866149 .

Detection of lung cancer metastasis from blood using L-MISC nanosensor: Targeting circulating metastatic cues for improved diagnosis

Metastatic lung cancers are considered one of the most clinically significant malignancies, comprising about 40% of deaths caused by cancers. Detection of lung cancer metastasis prior to symptomatic relapse is critical for timely diagnosis and clinical management. The onset of cancer metastasis is indicated by the manifestation of tumor-shed signatures from the primary tumor in peripheral circulation. A subset of this population, characterized as the metastasis-initiating stem cells, are capable of invasion, tumor initiation, and propagation of metastasis at distant sites. In this study, we have developed a SERS-functionalised L-MISC (Lung-Metastasis Initiating Stem Cells) nanosensor to accurately capture the trace levels of metastatic signatures directly from patient blood. We investigated the signatures of cancer stem cell enriched heterogenous population of primary and metastatic lung cancer cells to establish a metastatic profile unique to lung cancer. Multivariate statistical analyses revealed statistically significant differences in the molecular profiles of healthy, primary, and metastatic cell populations. The single-cell sensitivity of L-MISC nanosensor enabled a label-free detection of MISCs with high sensitivity and specificity. By employing a robust machine learning model, our diagnostic methodology can accurately detect metastatic lung cancer from not more than 5 μl of blood. A pilot validation of our study was carried out using clinical samples for the prediction of metastatic lung cancers resulting in 100% diagnostic sensitivity. The L-MISC nanosensor is a potential tool for highly rapid, non-invasive, and accurate diagnosis of lung cancer metastasis.

Recent Progress in Enhanced Cancer Diagnosis, Prognosis, and Monitoring Using a Combined Analysis of the Number of Circulating Tumor Cells (CTCs) and Other Clinical Parameters

Analysis of circulating tumor cells (CTCs) holds promise to diagnose cancer or monitor its development. Among the methods, counting CTC numbers in blood samples could be the simplest way to implement it. Nevertheless, its clinical utility has not yet been fully accepted. The reasons could be due to the rarity and heterogeneity of CTCs in blood samples that could lead to misleading results from assays only based on single CTC counts. To address this issue, a feasible direction is to combine the CTC counts with other clinical data for analysis. Recent studies have demonstrated the use of this new strategy for early detection and prognosis evaluation of cancers, or even for the distinguishment of cancers with different stages. Overall, this approach could pave a new path to improve the technical problems in the clinical applications of CTC counting techniques. In this review, the information relevant to CTCs, including their characteristics, clinical use of CTC counting, and technologies for CTC enrichment, were first introduced. This was followed by discussing the challenges and new perspectives of CTC counting techniques for clinical applications. Finally, the advantages and the recent progress in combining CTC counts with other clinical parameters for clinical applications have been discussed.

Biomarkers for immunotherapy of hepatocellular carcinoma

Immune-checkpoint inhibitors (ICIs) are now widely used for the treatment of patients with advanced-stage hepatocellular carcinoma (HCC). Two different ICI-containing regimens, atezolizumab plus bevacizumab and tremelimumab plus durvalumab, are now approved standard-of-care first-line therapies in this setting. However, and despite substantial improvements in survival outcomes relative to sorafenib, most patients with advanced-stage HCC do not derive durable benefit from these regimens. Advances in genome sequencing including the use of single-cell RNA sequencing (both of tumour material and blood samples), as well as immune cell identification strategies and other techniques such as radiomics and analysis of the microbiota, have created considerable potential for the identification of novel predictive biomarkers enabling the accurate selection of patients who are most likely to derive benefit from ICIs. In this Review, we summarize data on the immunology of HCC and the outcomes in patients receiving ICIs for the treatment of this disease. We then provide an overview of current biomarker use and developments in the past 5 years, including gene signatures, circulating tumour cells, high-dimensional flow cytometry, single-cell RNA sequencing as well as approaches involving the microbiome, radiomics and clinical markers. Novel concepts for further biomarker development in HCC are then discussed including biomarker-driven trials, spatial transcriptomics and integrated 'big data' analysis approaches. These concepts all have the potential to better identify patients who are most likely to benefit from ICIs and to promote the development of new treatment approaches.

Polyphyllin VII induces CTC anoikis to inhibit lung cancer metastasis through EGFR pathway regulation

Circulating tumor cells (CTCs) are cells that detach from the primary tumor and enter the bloodstream, playing a crucial role in the metastasis of lung cancer. Unfortunately, there is currently a lack of drugs specifically designed to target CTCs and prevent tumor metastasis. In this study, we present evidence that polyphyllin VII, a potent anticancer compound, effectively inhibits the metastasis of lung cancer by inducing a process called anoikis in CTCs. We observed that polyphyllin VII had significant cytotoxicity and inhibited colony formation, migration, and invasion in both our newly established cell line CTC-TJH-01 and a commercial lung cancer cell line H1975. Furthermore, we found that polyphyllin VII induced anoikis and downregulated the TrkB and EGFR-MEK/ERK signaling pathways. Moreover, activation of TrkB protein did not reverse the inhibitory effect of polyphyllin VII on CTCs, while upregulation of EGFR protein effectively reversed it. Furthermore, our immunodeficient mouse models recapitulated that polyphyllin VII inhibited lung metastasis, which was associated with downregulation of the EGFR protein, and reduced the number of CTCs disseminated into the lungs by inducing anoikis. Together, these results suggest that polyphyllin VII may be a promising compound for the treatment of lung cancer metastasis by targeting CTCs.

Plasma extracellular vesicle long RNAs predict response to neoadjuvant immunotherapy and survival in patients with non-small cell lung cancer

Neoadjuvant immunotherapy has brought new hope for patients with non-small cell lung cancer (NSCLC). However, limited by the lack of clinically feasible markers, it is still difficult to select NSCLC patients who respond well and to predict patients' clinical outcomes before the treatment. Before the treatment, we isolated plasma extracellular vesicles (EVs) from three cohorts (discovery, training and validation) of 78 NSCLC patients treated with neoadjuvant immunotherapy. To identify differentially-expressed EV long RNAs (exLRs), we employed RNA-seq in the discovery cohort. And we subsequently used qRT-PCR to establish and validate the predictive signature in the other two cohorts. We have identified 8 candidate exLRs from 27 top-ranked exLRs differentially expressed between responders and non-responders, and tested their expression with qRT-PCR in the training cohort. We finally identified H3C2 (P = 0.029), MALAT1 (P = 0.043) and RPS3 (P = 0.0086) significantly expressed in responders for establishing the predictive signature. Integrated with PD-L1 expression, our signature performed well in predicting immunotherapeutic responses in the training (AUC=0.892) and validation cohorts (AUC=0.747). Furthermore, our signature was proven to be a predictor for favorable prognosis of patients treated with neoadjuvant immunotherapy, which demonstrates the feasibility of our signature in clinical practices (P = 0.048). Our results demonstrate that the exLR-based signature could accurately predict responses to neoadjuvant immunotherapy and prognosis in NSCLC patients.

Perioperative immunotherapy for esophageal squamous cell carcinoma: Now and future

Esophageal cancer (EC) ranks among the most prevalent malignant tumors affecting the digestive tract. Esophageal squamous cell carcinoma (ESCC) stands as the prevailing pathological subtype, encompassing approximately 90% of all EC patients. In clinical stage II-IVA locally advanced ESCC cases, the primary approach to treatment involves a combination of neoadjuvant therapy and surgical resection. Despite concerted efforts, the long-term outcomes for ESCC patients remain unsatisfactory, with dismal prognoses. However, recent years have witnessed remarkable strides in immunotherapy, particularly in the second- and first-line treatment of advanced or metastatic ESCC, with the development of monoclonal antibodies that inhibit programmed death 1 or programmed death ligand 1 demonstrating encouraging responses and perioperative clinical benefits for various malignancies, including ESCC. This comprehensive review aims to present the current landscape of perioperative immunotherapy for resectable ESCC, focusing specifically on the role of immune checkpoint inhibitors during the perioperative period. Additionally, the review will explore promising biomarkers and offer insights into future prospects.

Biomarkers for Immune Checkpoint Inhibitor Response in NSCLC: Current Developments and Applicability

Lung cancer has the highest mortality rate among all cancer types, resulting in over 1.8 million deaths annually. Immunotherapy utilizing immune checkpoint inhibitors (ICIs) has revolutionized the treatment of non-small cell lung cancer (NSCLC). ICIs, predominantly monoclonal antibodies, modulate co-stimulatory and co-inhibitory signals crucial for maintaining immune tolerance. Despite significant therapeutic advancements in NSCLC, patients still face challenges such as disease progression, recurrence, and high mortality rates. Therefore, there is a need for predictive biomarkers that can guide lung cancer treatment strategies. Currently, programmed death-ligand 1 (PD-L1) expression is the only established biomarker for predicting ICI response. However, its accuracy and robustness are not consistently reliable. This review provides an overview of potential biomarkers currently under development or in the validation stage that hold promise in improving the classification of responders and non-responders to ICI therapy in the near future.

Liquid Biopsy in NSCLC: An Investigation with Multiple Clinical Implications

Tissue biopsy is essential for NSCLC diagnosis and treatment management. Over the past decades, liquid biopsy has proven to be a powerful tool in clinical oncology, isolating tumor-derived entities from the blood. Liquid biopsy permits several advantages over tissue biopsy: it is non-invasive, and it should provide a better view of tumor heterogeneity, gene alterations, and clonal evolution. Consequentially, liquid biopsy has gained attention as a cancer biomarker tool, with growing clinical applications in NSCLC. In the era of precision medicine based on molecular typing, non-invasive genotyping methods became increasingly important due to the great number of oncogene drivers and the small tissue specimen often available. In our work, we comprehensively reviewed established and emerging applications of liquid biopsy in NSCLC. We made an excursus on laboratory analysis methods and the applications of liquid biopsy either in early or metastatic NSCLC disease settings. We deeply reviewed current data and future perspectives regarding screening, minimal residual disease, micrometastasis detection, and their implication in adjuvant and neoadjuvant therapy management. Moreover, we reviewed liquid biopsy diagnostic utility in the absence of tissue biopsy and its role in monitoring treatment response and emerging resistance in metastatic NSCLC treated with target therapy and immuno-therapy.

Clinical Significance of PD-L1 Status in Circulating Tumor Cells for Cancer Management during Immunotherapy

The approval of monoclonal antibodies against programmed death-ligand 1 (PD-L1) and programmed cell death protein (PD1) has changed the landscape of cancer treatment. To date, many immune checkpoint inhibitors (ICIs) have been approved by the FDA for the treatment of metastatic cancer as well as locally recurrent advanced cancer. However, immune-related adverse events (irAEs) of ICIs highlight the need for biomarker analysis with strong predictive value. Liquid biopsy is an important tool for clinical oncologists to monitor cancer patients and administer or change appropriate therapy. CTCs frequently express PD-L1, and this constitutes a clinically useful and non-invasive method to assess PD-L1 status in real-time. This review summarizes all the latest findings about the clinical significance of CTC for the management of cancer patients during the administration of immunotherapy and mainly focuses on the assessment of PD-L1 expression in CTCs.

Potential non-invasive biomarkers in tumor immune checkpoint inhibitor therapy: response and prognosis prediction

Immune checkpoint inhibitors (ICIs) have dramatically enhanced the treatment outcomes for diverse malignancies. Yet, only 15-60% of patients respond significantly. Therefore, accurate responder identification and timely ICI administration are critical issues in tumor ICI therapy. Recent rapid developments at the intersection of oncology, immunology, biology, and computer science have provided an abundance of predictive biomarkers for ICI efficacy. These biomarkers can be invasive or non-invasive, depending on the specific sample collection method. Compared with invasive markers, a host of non-invasive markers have been confirmed to have superior availability and accuracy in ICI efficacy prediction. Considering the outstanding advantages of dynamic monitoring of the immunotherapy response and the potential for widespread clinical application, we review the recent research in this field with the aim of contributing to the identification of patients who may derive the greatest benefit from ICI therapy.

Soluble biomarkers to predict clinical outcomes in non-small cell lung cancer treated by immune checkpoints inhibitors

Lung cancer remains the first cause of cancer-related death despite many therapeutic innovations, including immune checkpoint inhibitors (ICI). ICI are now well used in daily practice at late metastatic stages and locally advanced stages after a chemo-radiation. ICI are also emerging in the peri-operative context. However, all patients do not benefit from ICI and even suffer from additional immune side effects. A current challenge remains to identify patients eligible for ICI and benefiting from these drugs. Currently, the prediction of ICI response is only supported by Programmed death-ligand 1 (PD-L1) tumor expression with perfectible results and limitations inherent to tumor-biopsy specimen analysis. Here, we reviewed alternative markers based on liquid biopsy and focused on the most promising biomarkers to modify clinical practice, including non-tumoral blood cell count such as absolute neutrophil counts, platelet to lymphocyte ratio, neutrophil to lymphocyte ratio, and derived neutrophil to lymphocyte ratio. We also discussed soluble-derived immune checkpoint-related products such as sPD-L1, circulating tumor cells (detection, count, and marker expression), and circulating tumor DNA-related products. Finally, we explored perspectives for liquid biopsies in the immune landscape and discussed how they could be implemented into lung cancer management with a potential biological-driven decision.

Liquid biopsy on the horizon in immunotherapy of non-small cell lung cancer: current status, challenges, and perspectives

Non-small cell lung cancer (NSCLC) is one of the most threatening malignancies to human health and life. In most cases, patients with NSCLC are already at an advanced stage when they are diagnosed. In recent years, lung cancer has made great progress in precision therapy, but the efficacy of immunotherapy is unstable, and its response rate varies from patient to patient. Several biomarkers have been proposed to predict the outcomes of immunotherapy, such as programmed cell death-ligand 1 (PD-L1) expression and tumor mutational burden (TMB). Nevertheless, the detection assays are invasive and demanding on tumor tissue. To effectively predict the outcomes of immunotherapy, novel biomarkers are needed to improve the performance of conventional biomarkers. Liquid biopsy is to capture and detect circulating tumor cells (CTCs), circulating tumor DNA (ctDNA) and exosomes in body fluids, such as blood, saliva, urine, pleural fluid and cerebrospinal fluid as samples from patients, so as to make analysis and diagnosis of cancer and other diseases. The application of liquid biopsy provides a new possible solution, as it has several advantages such as non-invasive, real-time dynamic monitoring, and overcoming tumor heterogeneity. Liquid biopsy has shown predictive value in immunotherapy, significantly improving the precision treatment of lung cancer patients. Herein, we review the application of liquid biopsy in predicting the outcomes of immunotherapy in NSCLC patients, and discuss the challenges and future directions in this field.

Advances in liquid biopsy-based markers in NSCLC

Lung cancer is the second most-frequently occurring cancer and the leading cause of cancer-associated deaths worldwide. Non-small cell lung cancer (NSCLC), the most common type of lung cancer is often diagnosed in middle or advanced stages and have poor prognosis. Diagnosis of disease at an early stage is a key factor for improving prognosis and reducing mortality, whereas, the currently used diagnostic tools are not sufficiently sensitive for early-stage NSCLC. The emergence of liquid biopsy has ushered in a new era of diagnosis and management of cancers, including NSCLC, since analysis of circulating tumor-derived components, such as cell-free DNA (cfDNA), circulating tumor cells (CTCs), cell-free RNAs (cfRNAs), exosomes, tumor-educated platelets (TEPs), proteins, and metabolites in blood or other biofluids can enable early cancer detection, treatment selection, therapy monitoring and prognosis assessment. There have been great advances in liquid biopsy of NSCLC in the past few years. Hence, this chapter introduces the latest advances on the clinical application of cfDNA, CTCs, cfRNAs and exosomes, with a particular focus on their application as early markers in the diagnosis, treatment and prognosis of NSCLC.

Molecular basis and clinical application of targeted therapy in oncology

Targeted therapy and precision oncology aim to improve efficacy and minimize side effects by targeting specific molecules involved in cancer growth and spread. With the advancements in genomics, proteomics, and transcriptomics with the accessible modalities such as next-generation sequencing, circulating tumor cells, and tumor Deoxyribonucleic Acid (DNA), more number of patients are being offered the targeted therapy in form of monoclonal antibodies and various intracellular targets, specific for their tumor. The harnessing of host immunity against the cancer cells by utilizing immune-oncology agents and chimeric antigen receptor T-cell therapy has further revolutionized the management of various cancers. These agents, however, have the challenge of managing the adverse effects that are peculiar to the class of drugs and very different from the conventional chemotherapy. This review article discusses the molecular basis, diagnostics, and use of targeted therapy in oncology.

Comparison of the tumor immune microenvironment and checkpoint blockade biomarkers between stage III and IV non-small cell lung cancer

BACKGROUND

Adjuvant immune checkpoint blockade (ICB) following chemoradiotherapy and adding ICB to chemotherapy have been key advances for stages III-IV non-small cell lung cancer (NSCLC) treatment. However, known biomarkers like PD-L1 are not consistently indicative of ICB response. Other markers within the tumor immune microenvironment (TIME) may better reflect ICB response and/or resistance mechanisms, but an understanding of how TIMEs differ between stage III and IV NSCLC has not been explored.

METHODS

Real-world data from unresectable, stage III-IV, non-squamous, pretreatment NSCLCs (stage III n = 106, stage IV n = 285) were retrospectively analyzed. PD-L1 immunohistochemistry (IHC) was compared to CD274 gene expression. Then, differential gene expression levels, pathway enrichment, and immune infiltrate between stages were calculated from whole-transcriptome RNA-seq. Analyses were stratified by EGFR status.

RESULTS

PD-L1 IHC and CD274 expression in tumor cells were highly correlated (n = 295, P < 2.2e-16, ⍴ = 0.74). CTLA4 expression was significantly increased in stage III tumors (P = 1.32e-04), while no differences were observed for other ICB-related genes. Metabolic pathway activity was significantly enriched in stage IV tumors (P = 0.004), whereas several immune-related KEGG pathways were enriched in stage III. Stage IV tumors had significantly increased macrophage infiltration (P = 0.0214), and stage III tumors had a significantly higher proportion of CD4 + T cells (P = 0.017). CD4 + T cells were also relatively more abundant in EGFR-mutant tumors vs. wild-type (P = 0.0081).

CONCLUSION

Directly comparing the TIMEs of stage III and IV NSCLC, these results carry implications for further studies of ICB response in non-resectable stage III NSCLC and guide further research of prognostic biomarkers and therapeutic targets.

Liquid Biopsy and Immuno-Oncology for Advanced Nonsmall Cell Lung Cancer

BACKGROUND

In the last decade, immune checkpoint inhibitors have revolutionized the treatment of metastatic nonsmall cell lung cancer without oncogenic addiction. Currently, programmed death ligand 1 (PD-L1) status, assessed in tissue biopsy samples, is the only test for guiding the prescription of these therapies in clinical practice. However, obtaining tumor tissue from patients with lung cancer is not always feasible and PD-L1 positivity is not a guarantee of immunotherapy efficacy. In this context, liquid biopsy, represented by several circulating biomarkers that reflect the tumor characteristics, is emerging as an interesting alternative approach.

CONTENT

We describe the main blood biomarkers evaluated in patients with metastatic nonsmall cell lung cancer before/during immune checkpoint inhibitor treatment, with a focus on circulating cell-free DNA, circulating tumor DNA (ctDNA), blood tumor mutational burden, and circulating tumor cells (CTCs).

SUMMARY

Monitoring of ctDNA and CTCs during immunotherapy may be a promising tool to help clinicians in therapeutic decision-making.

Diagnosis, Monitoring, and Prognosis of Liquid Biopsy in Cancer Immunotherapy

Liquid biopsy (LB), as a minimally invasive method of gleaning insight into the dynamics of diseases through a patient fluid sample, represents an interesting tool that can advise in disease monitoring, treatment selection, early diagnosis, evaluation of the response, and prognosis. Cancer immunotherapy is a breakthrough in cancer treatment, which is now recognized as the "fourth pillar" of cancer treatment, after surgery, chemotherapy, and radiotherapy. Liquid biopsy offers a different befalling for beneath invasive diagnosis, real-time accommodating monitoring, and analysis options, involving the isolation of circulating biomarkers, such as cell-free DNA (cfDNA), circulating tumor cells (CTCs), exosomes, and microRNAs (miRNAs). The biomarkers herein have great potential to allow the realization of liquid biopsy for predicting the immunotherapy response and precision medicine. Liquid biopsy offers an alternative, less invasive approach to select cancer patients who would benefit from immunotherapy and to monitor patients during their disease course. This review focuses on the use of liquid biopsy in the immunotherapy treatment of patients with cancer. In this review, we addressed the different promising liquid biopsy-based biomarkers in cancer patients that enable the selection of patients who benefit from immunotherapy and the monitoring of patients during this therapy.

Immunotherapy with radiotherapy fails to improve prognosis of patients with stage IV non-small cell lung cancer: a retrospective cohort analysis of the THUNDER-2 study

Background

Radiotherapy (RT) may enhance the systemic antitumor reaction to immunotherapy (IT). Currently, the effect of RT in stage IV non-small cell lung cancer (NSCLC) patients treated with IT is uncertain. This study aimed to confirm the role of RT in these patients.

Methods

We enrolled 120 stage IV NSCLC patients who had been treated with IT and had received external beam radiation therapy (EBRT) or radioactive particle implantation (RPI) at 3 oncology centers in Shandong province between 2019 and 2021. We assessed relevant clinical factors and regular follow-up was conducted via electronic medical records and telephone. The primary endpoint was overall survival (OS). Different combination models in various populations were compared by generating Kaplan-Meier curves and Cox regression analysis.

Results

The OS for the overall population was 5 months (range, 0-31 months) and the overall survival rate was 47.5%. Patients receiving IT with RPI had the least favorable prognostic trend (median survival: 2 months) compared to those receiving IT without RT (median survival: 9 months) and IT with EBRT (median survival: 10 months), but this difference was not significant (P=0.148). In subgroup analysis, patients treated with IT with RPI appeared to have a worse prognosis in some specific cohorts, such as males [hazard ratio (HR) =2.433, P=0.031], non-squamous carcinoma histologies (HR =2.680, P=0.034), patients with oligometastases (HR =7.967, P=0.024), patients with liver metastases (HR =10.808, P=0.011) or brain metastases (HR =20.087, P=0.005), and those with Eastern Cooperative Oncology Group (ECOG) performance score ≥2 (HR =2.769, P=0.043). Multivariate Cox analysis of total population revealed that ECOG score and IT stage were the independent prognostic factors. IT combined with EBRT did not have a significant survival benefit in all subgroups. Concurrent IT with RT and first-line and second-line IT combined with RT trended toward improved long-term prognosis.

Conclusions

While the robustness of the present conclusions is limited by relatively small sample size and retrospective nature of this research, the addition of EBRT or RPI to IT did not significantly improve patients' OS in stage IV NSCLC. Early combination IT after RT may benefit patients with long-term survival.

New strategy for antimetastatic treatment of lung cancer: a hypothesis based on circulating tumour cells

Metastasis is the primary cause of death in lung cancer patients. However, until now, effective drugs and intervention strategies for treating lung cancer metastasis have been lacking. This hypothesis focuses on circulating tumour cells (CTCs) to develop a new antimetastatic therapeutic strategy for lung cancer. Here, we outline the role of CTCs in tumour metastasis and their functional effects during the treatment of lung cancer patients. Additionally, we hypothesized the possibility of CTCs as a novel biomarker and therapeutic target in preventing and treating metastasis in patients with early-stage lung cancer. We hope that the realization of this hypothesis will improve the overall survival of lung cancer.

Extracellular vesicle-based checkpoint regulation and immune state in cancer

Tumor cells exploit several mechanisms for hijacking an immunosuppressive tumor ecosystem in order to evade immune surveillance and to progress toward metastasis. Equipment of extracellular vesicles (EVs) with checkpoints is an example of cancer control over anti-tumor responses from immune system. Programmed death-ligand 1 (PD-L1) is a checkpoint highly expressed in a tumor at progressive stage. Interactions between PD-L1 with its receptor programmed death-1 receptor (PD-1) expressed on T cells will block the effector function of CD8⁺ T cells, known as one of the most important defensive cells against cancer. Evaluation of circulatory exosomal PD-L1 can be a prognostic biomarker in tumor diagnosis and responses to the immune checkpoint inhibitor (ICI) therapy, and can be considered as a tool in clinical practice for exploiting personalized therapy. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is also a checkpoint that its engagement with CD80/CD86 expressed on antigen-presenting cells (APCs), such as dendritic cells (DCs) hamper the priming phase of CD4⁺ and CD8⁺ T cells. Harvesting EVs from tumor and their modification with desired anti-checkpoint antibodies can be a promising strategy in cancer immunotherapy. The aim of this review is to discuss about EV roles in checkpoint regulation, cancer diagnosis and ICI responses, and to survey possible application of such vesicles in cancer immunotherapy.

PD-L1/pS6 in Circulating Tumor Cells (CTCs) during Osimertinib Treatment in Patients with Non-Small Cell Lung Cancer (NSCLC)

The PD-1/PD-L1 axis provides CTCs an escape route from the immune system. Phosphorylation of the ribosomal protein S6 is implicated in the same pathway, following mTOR activation. The aim of the study was to investigate the expression of PD-L1 and pS6 in CTCs from NSCLC patients under Osimertinib treatment at a single cell level. CTCs were isolated using ISET from NSCLC patients’ blood [37 at baseline, 25 after the 1st cycle, and 23 at the end of treatment (EOT)]. Staining was performed using immunofluorescence. Cytokeratin-positive (CK+) CTCs were detected in 62% of patients. CK+PD-L1+CD45− and CK+pS6+ phenotypes were detected in 38% and 41% of the patients at baseline, in 28% and 32% after 1st cycle, and in 30% and 35% at EOT, respectively. Spearman’s analysis revealed statistically significant correlations between PD-L1 and pS6 phenotypes at all time points. Survival analysis revealed that CK+pS6+ (p = 0.003) and CKlowpS6+ (p = 0.021) phenotypes after 1st cycle were related to significantly decreased one-year progression-free survival (PFS12m) and PFS, respectively. CK+PD-L1+CD45−phenotype at baseline and after 1st cycle showed a trend for decreased PFS12m. Increased expression of PD-L1/pS6 in CTCs of Osimertinib-treated NSCLC patients implies the activation of the corresponding pathway, which is potentially associated with poor clinical outcomes.

Prognostic value of integrating circulating tumour cells and cell-free DNA in non-small cell lung cancer

Background

Non-small cell lung cancer (NSCLC) often presents at an incurable stage, and majority of patients will be considered for palliative treatment at some point in their disease. Despite recent advances, the prognosis remains poor, with a median overall survival of 12–18 months. Liquid biopsy-based biomarkers have emerged as potential candidates for predicting prognosis and response to therapy in NSCLC patients. This pilot study evaluated whether combining circulating tumour cells and clusters (CTCs) and cell-free DNA (cfDNA) can predict progression-free survival (PFS) in NSCLC patients.

Methods

CTC and cfDNA/ctDNA from advanced stage NSCLC patients were measured at study entry (T⁰) and 3-months post-treatment (T¹). CTCs were enriched using a spiral microfluidic chip and characterised by immunofluorescence. ctDNA was assessed using an UltraSEEK® Lung Panel. Kaplan-Meier plots were generated to investigate the contribution of the presence of CTC/CTC clusters and cfDNA for PFS. Cox proportional hazards analysis compared time to progression versus CTC/CTC cluster counts and cfDNA levels.

Results

Single CTCs were found in 14 out of 25 patients, while CTC clusters were found in 8 out of the 25 patients at T⁰. At T¹, CTCs were found in 7 out of 18 patients, and CTC clusters in 1 out of the 18 patients. At T⁰, CTC presence and the combination of CTC cluster counts with cfDNA levels were associated with shorter PFS, p = 0.0261, p = 0.0022, respectively.

Conclusions

Combining CTC cluster counts and cfDNA levels could improve PFS assessment in NSCLC patients. Our results encourage further investigation on the combined effect of CTC/cfDNA as a prognostic biomarker in a large cohort of advanced stage NSCLC patients.

Current status and future perspectives of immune checkpoint inhibitors in extensive-stage small cell lung cancer

Small-cell lung cancer (SCLC) is a type of neuroendocrine neoplasms with high aggressiveness and poor prognosis. Chemotherapy has been the standard first-line therapy for SCLC over the past several decades. In recent years, results of randomized phase III CASPIAN and IMpower-133 trials indicated that the combination of immune checkpoint inhibitors (ICIs) with platinum-etoposide chemotherapy improved the overall survival (OS) of patients with extensive stage small-cell lung cancer (ES-SCLC), which has transformed the treatment model for ES-SCLC. ICIs combined with chemotherapy has become the new first-line standard treatment of ES-SCLC with the latest research results from CASPIAN and ASTRUM-005 studies. This review summarizes the recent progress of ICIs in the treatment of ES-SCLC and expounds the mode and efficacy of immunotherapy for ES-SCLC. Future research focused on exploring basic SCLC biology and identifying novel predictive biomarkers in response to ICIs in ES-SCLC is essential. Double-ICIs treatment strategies, bispecific antibodies, and ICIs combined with other therapies, such as chemotherapy, radiotherapy, and targeted therapy, represent a new modality and show great promise for the treatment of ES-SCLC, which should achieve greater therapeutic effects through multiple synergistic mechanisms.

Blood Biomarkers of Response to Immune Checkpoint Inhibitors in Non-Small Cell Lung Cancer

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment landscape of non-small cell lung cancer (NSCLC), either used in monotherapy or in combination with chemotherapy. While some patients achieve durable responses, some will not get benefit from this treatment. Early identification of non- responder patients could avoid unnecessary treatment, potentially serious immune-related adverse events and reduce treatment costs. PD-L1 expression using immunohistochemistry is the only approved biomarker for the selection of patients that can benefit from immunotherapy. However, application of PD-L1 as a biomarker of treatment efficacy shows many deficiencies probably due to the complexity of the tumor microenvironment and the technical limitations of the samples. Thus, there is an urgent need to find other biomarkers, ideally blood biomarkers to help us to identify different subgroups of patients in a minimal invasive way. In this review, we summarize the emerging blood-based markers that could help to predict the response to ICIs in NSCLC.

Challenges and the Evolving Landscape of Assessing Blood-Based PD-L1 Expression as a Biomarker for Anti-PD-(L)1 Immunotherapy

While promising, PD-L1 expression on tumor tissues as assessed by immunohistochemistry has been shown to be an imperfect biomarker that only applies to a limited number of cancers, whereas many patients with PD-L1-negative tumors still respond to anti-PD-(L)1 immunotherapy. Recent studies using patient blood samples to assess immunotherapeutic responsiveness suggests a promising approach to the identification of novel and/or improved biomarkers for anti-PD-(L)1 immunotherapy. In this review, we discuss the advances in our evolving understanding of the regulation and function of PD-L1 expression, which is the foundation for developing blood-based PD-L1 as a biomarker for anti-PD-(L)1 immunotherapy. We further discuss current knowledge and clinical study results for biomarker identification using PD-L1 expression on tumor and immune cells, exosomes, and soluble forms of PD-L1 in the peripheral blood. Finally, we discuss key challenges for the successful development of the potential use of blood-based PD-L1 as a biomarker for anti-PD-(L)1 immunotherapy.

Clinical Applications of Circulating Tumour Cells and Circulating Tumour DNA in Non-Small Cell Lung Cancer-An Update

Despite efforts to improve earlier diagnosis of non-small cell lung cancer (NSCLC), most patients present with advanced stage disease, which is often associated with poor survival outcomes with only 15% surviving for 5 years from their diagnosis. Tumour tissue biopsy is the current mainstream for cancer diagnosis and prognosis in many parts of the world. However, due to tumour heterogeneity and accessibility issues, liquid biopsy is emerging as a game changer for both cancer diagnosis and prognosis. Liquid biopsy is the analysis of tumour-derived biomarkers in body fluids, which has remarkable advantages over the use of traditional tumour biopsy. Circulating tumour cells (CTCs) and circulating tumour DNA (ctDNA) are two main derivatives of liquid biopsy. CTC enumeration and molecular analysis enable monitoring of cancer progression, recurrence, and treatment response earlier than traditional biopsy through a minimally invasive liquid biopsy approach. CTC-derived ex-vivo cultures are essential to understanding CTC biology and their role in metastasis, provide a means for personalized drug testing, and guide treatment selection. Just like CTCs, ctDNA provides opportunity for screening, monitoring, treatment evaluation, and disease surveillance. We present an updated review highlighting the prognostic and therapeutic significance of CTCs and ctDNA in NSCLC.

Navigate Towards the Immunotherapy Era: Value of Immune Checkpoint Inhibitors in Non-Small Cell Lung Cancer Patients With Brain Metastases

Brain metastases (BMs) in non-small-cell lung cancer (NSCLC) patients are associated with significant morbidity and poor prognosis. Immune checkpoint inhibitors (ICIs) have resulted in a paradigm shift in the management of advanced NSCLC. However, the value of ICIs in NSCLC patients with BMs remains unclear because patients with BMs are routinely excluded in numerous prospective trials on ICIs. Here, starting from the mechanisms of ICIs for BMs, we will reveal the value of ICIs by reviewing the efficacy and adverse effects of ICIs monotherapy as well as promising combination strategies, such as combinations with chemotherapy, radiotherapy, and anti-angiogenic drugs, etc. In addition, the methods of patient selection and response assessment will be summarized to assist clinical practice and further studies.

Predictive biomarkers for response to immune checkpoint inhibition

Immune checkpoint inhibitors have transformed the prognosis and treatment paradigm of many cancer types, through the potential for durable responses. However, the majority of patients still do not benefit. Response to checkpoint inhibition is determined by dynamic host, tumour and tumour microenvironment factors that display spatial and temporal variability, but our understanding of these interactions is incomplete. Through investigating biomarkers of resistance and response, opportunities arise to discover new therapeutic targets and shape personalised treatment strategies. Here we review approved and emerging biomarkers of response to immune checkpoint inhibitors, in particular the recent rapid progress in host and tumour genomics. It is unlikely that a single biomarker will precisely predict response, but multivariate multiomic markers may provide a balanced assessment of these factors and more accurately identify patients who will benefit. Further efforts are required to translate these groundbreaking discoveries into novel therapeutics and biomarker driven clinical trials, to provide durable treatment response to a greater population of patients.

Recent advances in lung cancer genomics: Application in targeted therapy

Genomic characterization of lung cancer has not only improved our understanding of disease biology and carcinogenesis but also revealed several therapeutic opportunities. Targeting tumor dependencies on specific genomic alterations (oncogene addiction) has accelerated the therapeutic developments and significantly improved the outcomes even in advanced stage of disease. Identification of genomic alterations predicting response to specific targeted treatment is the key to success for this "personalized treatment" approach. Availability of multiple choices of therapeutic options for specific genomic alterations highlight the importance of optimum sequencing of drugs. Multiplex gene testing has become mandatory in view of constantly increasing number of therapeutic targets and effective treatment options. Influence of genomic characteristics on response to immunotherapy further makes comprehensive genomic profiling necessary before therapeutic decision making. A comprehensive elucidation of resistance mechanisms and directed treatments have made the continuum of care possible and transformed this deadly disease into a chronic condition. Liquid biopsy-based approach has made the dynamic monitoring of disease possible and enabled treatment optimizations accordingly. Current lung cancer management is the perfect example of "precision-medicine" in clinical oncology.

Leukapheresis increases circulating tumour cell yield in non-small cell lung cancer, counts related to tumour response and survival

BACKGROUND

Circulating tumour cells (CTCs) can be used to monitor cancer longitudinally, but their use in non-small cell lung cancer (NSCLC) is limited due to low numbers in the peripheral blood. Through diagnostic leukapheresis (DLA) CTCs can be obtained from larger blood volumes.

METHODS

Patients with all stages of NSCLC were selected. One total body blood volume was screened by DLA before and after treatment. Peripheral blood was drawn pre- and post DLA for CTC enumeration by CellSearch. CTCs were detected in the DLA product (volume equalling 2 × 10⁸ leucocytes) and after leucocyte depletion (RosetteSep, 9 mL DLA product). Single-cell, whole-genome sequencing was performed on isolated CTCs.

RESULTS

Fifty-six patients were included. Before treatment, CTCs were more often detected in DLA (32/55, 58%) than in the peripheral blood (pre-DLA: 18/55, 33%; post DLA: 13/55, 23%, both at p < 0.01). CTCs per 7.5 mL DLA product were median 9.2 times (interquartile range = 5.6-24.0) higher than CTCs in 7.5 mL blood. RosetteSEP did not significantly improve CTC detection (pretreatment: 34/55, 62%, post treatment: 16/34, 47%) and CTCs per mL even decreased compared to DLA (p = 0.04).. Patients with advanced-stage disease with DLA-CTC after treatment showed fewer tumour responses and shorter progression-free survival (PFS) than those without DLA-CTC (median PFS, 2.0 vs 12.0 months, p < 0.01). DLA-CTC persistence after treatment was independent of clinical factors associated with shorter PFS (hazard ratio (HR) = 5.8, 95% confidence interval (CI), 1.4-35.5, p = 0.02). All evaluable CTCs showed aneuploidy.

CONCLUSIONS

DLA detected nine times more CTCs than in the peripheral blood. The sustained presence of CTCs in DLA after treatment was associated with therapy failure and shortened PFS.

TRIAL REGISTRATION

The study was approved by the Medical Ethical Committee (NL55754.042.15) and was registered in the Dutch trial register (NL5423).

Circulating tumor cells: biology and clinical significance

Circulating tumor cells (CTCs) are tumor cells that have sloughed off the primary tumor and extravasate into and circulate in the blood. Understanding of the metastatic cascade of CTCs has tremendous potential for the identification of targets against cancer metastasis. Detecting these very rare CTCs among the massive blood cells is challenging. However, emerging technologies for CTCs detection have profoundly contributed to deepening investigation into the biology of CTCs and have facilitated their clinical application. Current technologies for the detection of CTCs are summarized herein, together with their advantages and disadvantages. The detection of CTCs is usually dependent on molecular markers, with the epithelial cell adhesion molecule being the most widely used, although molecular markers vary between different types of cancer. Properties associated with epithelial-to-mesenchymal transition and stemness have been identified in CTCs, indicating their increased metastatic capacity. Only a small proportion of CTCs can survive and eventually initiate metastases, suggesting that an interaction and modulation between CTCs and the hostile blood microenvironment is essential for CTC metastasis. Single-cell sequencing of CTCs has been extensively investigated, and has enabled researchers to reveal the genome and transcriptome of CTCs. Herein, we also review the clinical applications of CTCs, especially for monitoring response to cancer treatment and in evaluating prognosis. Hence, CTCs have and will continue to contribute to providing significant insights into metastatic processes and will open new avenues for useful clinical applications.

PD-L1 expression on circulating tumor cells and platelets in patients with metastatic breast cancer

Background

Immune checkpoint inhibition is effective in several cancers. Expression of programmed death-ligand 1 (PD-L1) on circulating tumor or immune effector cells could provide insights into selection of patients for immune checkpoint inhibition.

Methods

Whole blood was collected at serial timepoints from metastatic breast cancer patients and healthy donors for circulating tumor cell (CTC) and platelet PD-L1 analysis with a phycoerythrin-labeled anti-human PD-L1 monoclonal antibody (Biolegend clone 29E.2A3) using the CellSearch^® assay. CTC PD-L1 was considered positive if detected on at least 1% of the cells; platelet PD-L1 was considered positive if ≥100 platelets per CellSearch frame expressed PD-L1.

Results

A total of 207 specimens from 124 metastatic breast cancer patients were collected. 52/124 (42%) samples at timepoint-1 (at or close to time of progressive disease) had ≥5 CTC/7.5ml whole blood. Of those, 21 (40%) had positive CTC PD-L1. In addition, platelet PD-L1 expression was observed in 35/124 (28%) at timepoint-1. Platelet PD-L1 was not detected in more than 70 specimens from 12 healthy donors. Platelet PD-L1 was associated with ≥5 CTC/7.5ml whole blood (p = 0.0002), less likely in patients with higher red blood cell counts (OR = 0.72, p<0.001) and a history of smoking tobacco (OR = 0.76, p<0.001). Platelet PD-L1 staining was not associated with tumor marker status, recent procedures or treatments, platelet-affecting drugs, or CTC PD-L1 expression.

Conclusion

PD-L1 expression was found in metastatic breast cancer patients on both CTC and platelets in an independent fashion. Inter-patient platelet PD-L1 expression was highly heterogeneous suggesting that it is a biological event associated with cancer in some but not all patients. Taken together, our data suggest that CTC and platelet PD-L1 expression could play a role in predicting which patients should receive immune checkpoint inhibition and as a pharmacodynamics biomarker during treatment.

Circulating Tumour Cells (CTCs) in NSCLC: From Prognosis to Therapy Design

Designing optimal (neo)adjuvant therapy is a crucial aspect of the treatment of non-small-cell lung carcinoma (NSCLC). Standard methods of chemotherapy, radiotherapy, and immunotherapy represent effective strategies for treatment. However, in some cases with high metastatic activity and high levels of circulating tumour cells (CTCs), the efficacy of standard treatment methods is insufficient and results in treatment failure and reduced patient survival. CTCs are seen not only as an isolated phenomenon but also a key inherent part of the formation of metastasis and a key factor in cancer death. This review discusses the impact of NSCLC therapy strategies based on a meta-analysis of clinical studies. In addition, possible therapeutic strategies for repression when standard methods fail, such as the administration of low-toxicity natural anticancer agents targeting these phenomena (curcumin and flavonoids), are also discussed. These strategies are presented in the context of key mechanisms of tumour biology with a strong influence on CTC spread and metastasis (mechanisms related to tumour-associated and -infiltrating cells, epithelial–mesenchymal transition, and migration of cancer cells).

Circulating tumor DNA as a biomarker for monitoring early treatment responses of patients with advanced lung adenocarcinoma receiving immune checkpoint inhibitors

Immunotherapy for metastasized non-small-cell lung cancer (NSCLC) can show long-lasting clinical responses. Selection of patients based on programmed death-ligand 1 (PD-L1) expression shows limited predictive value for durable clinical benefit (DCB). We investigated whether early treatment effects as measured by a change in circulating tumor DNA (ctDNA) level is a proxy of early tumor response to immunotherapy according to response evaluation criteria in solid tumors v1.1 criteria, progression-free survival (PFS), DCB, and overall survival (OS). To this aim, blood tubes were collected from advanced-stage lung adenocarcinoma patients (n = 100) receiving immune checkpoint inhibitors (ICI) at baseline (t0 ) and prior to first treatment evaluation (4-6 weeks; t1 ). Nontargetable (driver) mutations detected in the pretreatment tumor biopsy were used to quantify tumor-specific ctDNA levels using droplet digital PCR. We found that changes in ctDNA levels were strongly associated with tumor response. A > 30% decrease in ctDNA at t1 correlated with a longer PFS and OS. In total, 80% of patients with a DCB of ≥ 26 weeks displayed a > 30% decrease in ctDNA levels. For patients with a PD-L1 tumor proportion score of ≥ 1%, decreasing ctDNA levels were associated with a higher frequency a DCB (80%) and a prolonged median PFS (85 weeks) and OS (101 weeks) compared with patients with no decrease in ctDNA (34%; 11 and 39 weeks, respectively). This study shows that monitoring of ctDNA dynamics is an easy-to-use and promising tool for assessing PFS, DCB, and OS for ICI-treated NSCLC patients.

Liquid Biopsy-Based Biosensors for MRD Detection and Treatment Monitoring in Non-Small Cell Lung Cancer (NSCLC)

Globally, non-small cell lung cancer (NSCLC) is the leading cause of cancer deaths. Despite advancements in chemotherapy and targeted therapies, the 5-year survival rate has remained at 16% for the past forty years. Minimal residual disease (MRD) is described as the existence of either isolated tumour cells or circulating tumour cells in biological liquid of patients after removal of the primary tumour without any clinical signs of cancer. Recently, liquid biopsy has been promising as a non-invasive method of disease monitoring and treatment guidelines as an MRD marker. Liquid biopsy could be used to detect and assess earlier stages of NSCLC, post-treatment MRD, resistance to targeted therapies, immune checkpoint inhibitors (ICIs) and tumour mutational burden. MRD surveillance has been proposed as a potential marker for lung cancer relapse. Principally, biosensors provide the quantitative analysis of various materials by converting biological functions into quantifiable signals. Biosensors are usually operated to detect antibodies, enzymes, DNA, RNA, extracellular vesicles (EVs) and whole cells. Here, we present a category of biosensors based on the signal transduction method for identifying biosensor-based biomarkers in liquid biopsy specimens to monitor lung cancer treatment.

Tumour burden and efficacy of immune-checkpoint inhibitors

Accumulating evidence suggests that a high tumour burden has a negative effect on anticancer immunity. The concept of tumour burden, simply defined as the total amount of cancer in the body, in contrast to molecular tumour burden, is often poorly understood by the wider medical community; nonetheless, a possible role exists in defining the optimal treatment strategy for many patients. Historically, tumour burden has been assessed using imaging. In particular, CT scans have been used to evaluate both the number and size of metastases as well as the number of organs involved. These methods are now often complemented by metabolic tumour burden, measured using the more recently developed 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (FDG)-PET/CT. Serum-based biomarkers, such as lactate dehydrogenase, can also reflect tumour burden and are often also correlated with a poor response to immune-checkpoint inhibitors. Other circulating markers (such as circulating free tumour DNA and/or circulating tumour cells) are also attracting research interest as surrogate markers of tumour burden. In this Review, we summarize evidence supporting the utility of tumour burden as a biomarker to guide the use of immune-checkpoint inhibitors. We also describe data and provide perspective on the various tools used for tumour burden assessment, with a particular emphasis on future therapeutic strategies that might address the issue of inferior outcomes among patients with cancer with a high tumour burden.

Peripheral Blood-Based Biomarkers for Immune Checkpoint Inhibitors

As cancer immunotherapy using immune checkpoint inhibitors (ICIs) is rapidly evolving in clinical practice, it is necessary to identify biomarkers that will allow the selection of cancer patients who will benefit most or least from ICIs and to longitudinally monitor patients' immune responses during treatment. Various peripheral blood-based immune biomarkers are being identified with recent advances in high-throughput multiplexed analytical technologies. The identification of these biomarkers, which can be easily detected in blood samples using non-invasive and repeatable methods, will contribute to overcoming the limitations of previously used tissue-based biomarkers. Here, we discuss the potential of circulating immune cells, soluble immune and inflammatory molecules, circulating tumor cells and DNA, exosomes, and the blood-based tumor mutational burden, as biomarkers for the prediction of immune responses and clinical benefit from ICI treatment in patients with advanced cancer.