Circulating Tumor DNA as a Prognostic Determinant in Small Cell Lung Cancer Patients Receiving Atezolizumab

Applied models and molecular characteristics of small cell lung cancer

Small cell lung cancer (SCLC) is a highly aggressive type of cancer frequently diagnosed with metastatic spread, rendering it surgically unresectable for the majority of patients. Although initial responses to platinum-based therapies are often observed, SCLC invariably relapses within months, frequently developing drug-resistance ultimately contributing to short overall survival rates. Recently, SCLC research aimed to elucidate the dynamic changes in the genetic and epigenetic landscape. These have revealed distinct subtypes of SCLC, each characterized by unique molecular signatures. The recent understanding of the molecular heterogeneity of SCLC has opened up potential avenues for precision medicine, enabling the development of targeted therapeutic strategies. In this review, we delve into the applied models and computational approaches that have been instrumental in the identification of promising drug candidates. We also explore the emerging molecular diagnostic tools that hold the potential to transform clinical practice and patient care.

Small-Cell Lung Cancer: Is Liquid Biopsy a New Tool Able to Predict the Efficacy of Immunotherapy?

Small-cell lung cancer (SCLC) cases represent approximately 15% of all lung cancer cases, remaining a recalcitrant malignancy with poor survival and few treatment options. In the last few years, the addition of immunotherapy to chemotherapy improved clinical outcomes compared to chemotherapy alone, resulting in the current standard of care for SCLC. However, the advantage of immunotherapy only applies to a few SCLC patients, and predictive biomarkers selection are lacking for SCLC. In particular, due to some features of SCLC, such as high heterogeneity, elevated cell plasticity, and low-quality tissue samples, SCLC biopsies cannot be used as biomarkers. Therefore, the characterization of the tumor and, subsequently, the selection of an appropriate therapeutic combination may benefit greatly from liquid biopsy. Soluble factors, circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and extracellular vesicles (EVs) are now useful tools in the characterization of SCLC. This review summarizes the most recent data on biomarkers detectable with liquid biopsy, emphasizing their role in supporting tumor detection and their potential role in SCLC treatment choice.

Tissue and circulating biomarkers of benefit to immunotherapy in extensive-stage small cell lung cancer patients

Extensive stage-Small-Cell Lung Cancer (ES-SCLC) is an aggressive cancer with dismal prognosis. The addition of immune-checkpoint inhibitors (ICIs) to platinum-based chemotherapy have been consistently demonstrated to improve outcomes and survival, becoming the new standard in first - line treatment of ES-SCLC patients. However, despite positive results reported in the pivotal trials, longer benefit appears evident only for a selected group of patients. Several predictive biomarkers have been studied so far but the prospective identification of patients more likely to experience better outcome seems to be challenging in SCLC. Indeed, classical immune predictive biomarkers as PD-L1 and tumor mutational burden (TMB) seem not to correlate with outcomes. Recently, a new molecular classification of SCLC based on differential expression of genes associated with specific clinical behaviors and therapeutic vulnerability have been presented suggesting a new field to be investigated. Despite the achievements, these studies focused mainly on inter-tumoral heterogeneity, limiting the exploration of intra-tumoral heterogeneity and cell to cell interactions. New analysis methods are ongoing in order to explore subtypes plasticity. Analysis on single biopsies cannot catch the whole genomic profile and dynamic change of disease over time and during treatment. Moreover, the availability of tissue for translational research is limited due to the low proportion of patients undergoing surgery. In this context, liquid biopsy is a promising tool to detect reliable predictive biomarkers. Here, we reviewed the current available data on predictive role of tissue and liquid biomarkers in ES-SCLC patients receiving ICIs. We assessed latest results in terms of predictive and prognostic value of gene expression profiling in SCLC. Finally, we explored the role of liquid biopsy as a tool to monitor SCLC patients over time.

Predictive biomarkers for immunotherapy response in extensive-stage SCLC

BACKGROUND

Small cell lung cancer (SCLC) accounts for about 13-15% of all lung cancers, and about 70% of SCLC patients have developed extensive-stage small cell lung cancer (ES-SCLC) at the time of diagnosis because of its highgrade malignancy, easy invasion, and metastasis. In recent years, immunotherapy combined with chemotherapy has become the standard first-line treatment for ES-SCLC. However, SCLC is a relatively immune-cold lung cancer subtype with a limited number of beneficiaries and a short benefit period. Therefore, the use of biomarkers to identify populations with significant benefits from immunotherapy will help improve the efficacy and survival benefits of immunotherapy. However, predictive biomarkers suitable for clinical practice have not been established in the field of SCLC.

PURPOSE

In order to find the predictive biomarkers of immunotherapy for ES-SCLC, we summarized the research progress of traditional biomarkers, such as programmed cell death ligand 1 (PD-L1) and tumor mutation burden (TMB), and summarizes the research of potential biomarkers associated with prognosis, such as molecular subtypes, special gene expression, expression of major histocompatibility complex (MHC) I and II classes, tumor immune microenvironment (TIME), and circulating tumor DNA (ctDNA) .We aim to provide new insights on biomarkers.

CONCLUSION

The exploration of biomarkers for immunotherapy of SCLC is still very difficult, and it is clear that conventional predictive biomarkers are not suitable for SCLC. At present, the molecular subtypes defined from transcription factors may have some guiding significance, which still needs to be confirmed by prospective clinical studies. In addition, the ctDNA positivity rate of SCLC is higher than that of other tumor types, which can also solve the dilemma of the difficulty of obtaining specimens of SCLC tissues. And the dynamic change of ctDNA also has great potential to predict the curative effect of SCLC, which is worth further clinical exploration.

A meta-analysis of circulating tumor DNA as a survival indicator in small cell lung cancer patients

A high level of circulating tumor DNA (ctDNA) has been linked to poor survival in patients with certain solid tumors. In spite of this, it is still unclear whether ctDNA is associated with poor survival in small cell lung cancer (SCLC). To investigate the above association, we conducted a systematic review and meta-analysis. PubMed, Web of Science, Cochrane's Library, and Embase were searched for relevant cohort studies from the inception of the databases to November 28, 2022. Data collection, literature search, and statistical analysis were carried out independently by two authors. To account for heterogeneity, we used a random-effects model. In this meta-analysis, 391 patients with SCLC were identified, and the data were pooled from nine observational studies and followed for 11.4 to 25.0 months. A high ctDNA was associated with worse overall survival (OS, risk ratio [RR] 2.50, 95% confidence interval [CI]1.85 to 3.38, p < 0.001; I2 = 25%) and progression-free survival (PFS, RR 2.33, 95% CI 1.48 to 3.64, p < 0.001, I2 = 42%). Subgroup analyses retrieved consistent results in prospective and retrospective studies, in studies with ctDNA measured with polymerase chain reaction or next-generation sequencing, and in studies analyzed with univariate or multivariate regression models. Studies suggest that ctDNA may be an important factor in predicting poor OS and PFS in SCLC patients.

ctDNA response after pembrolizumab in non-small cell lung cancer: phase 2 adaptive trial results

Circulating tumor DNA (ctDNA) has shown promise in capturing primary resistance to immunotherapy. BR.36 is a multi-center, randomized, ctDNA-directed, phase 2 trial of molecular response-adaptive immuno-chemotherapy for patients with lung cancer. In the first of two independent stages, 50 patients with advanced non-small cell lung cancer received pembrolizumab as standard of care. The primary objectives of stage 1 were to ascertain ctDNA response and determine optimal timing and concordance with radiologic Response Evaluation Criteria in Solid Tumors (RECIST) response. Secondary endpoints included the evaluation of time to ctDNA response and correlation with progression-free and overall survival. Maximal mutant allele fraction clearance at the third cycle of pembrolizumab signified molecular response (mR). The trial met its primary endpoint, with a sensitivity of ctDNA response for RECIST response of 82% (90% confidence interval (CI): 52-97%) and a specificity of 75% (90% CI: 56.5-88.5%). Median time to ctDNA response was 2.1 months (90% CI: 1.5-2.6), and patients with mR attained longer progression-free survival (5.03 months versus 2.6 months) and overall survival (not reached versus 7.23 months). These findings are incorporated into the ctDNA-driven interventional molecular response-adaptive second stage of the BR.36 trial in which patients at risk of progression are randomized to treatment intensification or continuation of therapy. ClinicalTrials.gov ID: NCT04093167 .

Small Cell Lung Carcinoma: Current Diagnosis, Biomarkers, and Treatment Options with Future Perspectives

Small cell lung cancer (SCLC) is an aggressive malignancy characterized by rapid proliferation, early dissemination, acquired therapy resistance, and poor prognosis. Early diagnosis of SCLC is crucial since most patients present with advanced/metastatic disease, limiting the potential for curative treatment. While SCLC exhibits initial responsiveness to chemotherapy and radiotherapy, treatment resistance commonly emerges, leading to a five-year overall survival rate of up to 10%. New effective biomarkers, early detection, and advancements in therapeutic strategies are crucial for improving survival rates and reducing the impact of this devastating disease. This review aims to comprehensively summarize current knowledge on diagnostic options, well-known and emerging biomarkers, and SCLC treatment strategies and discuss future perspectives on this aggressive malignancy.

Society for Immunotherapy of Cancer (SITC) consensus definitions for resistance to combinations of immune checkpoint inhibitors

Immunotherapy is the standard of care for several cancers and the field continues to advance at a rapid pace, with novel combinations leading to indications in an increasing number of disease settings. Durable responses and long-term survival with immunotherapy have been demonstrated in some patients, though lack of initial benefit and recurrence after extended disease control remain major hurdles for the field. Many new combination regimens are in development for patients whose disease progressed on initial immunotherapy. To guide clinical trial design and support analyses of emerging molecular and cellular data surrounding mechanisms of resistance, the Society for Immunotherapy of Cancer (SITC) previously generated consensus clinical definitions for resistance to single-agent anti-PD-1 immune checkpoint inhibitors (ICIs) in three distinct scenarios: primary resistance, secondary resistance, and progression after treatment discontinuation. An unmet need still exists, however, for definitions of resistance to ICI-based combinations, which represent an expanding frontier in the immunotherapy treatment landscape. In 2021, SITC convened a workshop including stakeholders from academia, industry, and government to develop consensus definitions for resistance to ICI-based combination regimens for improved outcome assessment, trial design and drug development. This manuscript reports the minimum drug exposure requirements and time frame for progression that define resistance in both the metastatic setting and the perioperative setting, as well as key caveats and areas for future research with ICI/ICI combinations. Definitions for resistance to ICIs in combination with chemotherapy and targeted therapy will be published in companion volumes to this paper.

Society for Immunotherapy of Cancer (SITC) consensus definitions for resistance to combinations of immune checkpoint inhibitors with chemotherapy

Although immunotherapy can offer profound clinical benefit for patients with a variety of difficult-to-treat cancers, many tumors either do not respond to upfront treatment with immune checkpoint inhibitors (ICIs) or progressive/recurrent disease occurs after an interval of initial control. Improved response rates have been demonstrated with the addition of ICIs to cytotoxic therapies, leading to approvals from the US Food and Drug Administration and regulatory agencies in other countries for ICI-chemotherapy combinations in a number of solid tumor indications, including breast, head and neck, gastric, and lung cancer. Designing trials for patients with tumors that do not respond or stop responding to treatment with immunotherapy combinations, however, is challenging without uniform definitions of resistance. Previously, the Society for Immunotherapy of Cancer (SITC) published consensus definitions for resistance to single-agent anti-programmed cell death protein 1 (PD-1). To provide guidance for clinical trial design and to support analyses of emerging molecular and cellular data surrounding mechanisms of resistance to ICI-based combinations, SITC convened a follow-up workshop in 2021 to develop consensus definitions for resistance to multiagent ICI combinations. This manuscript reports the consensus clinical definitions for combinations of ICIs and chemotherapies. Definitions for resistance to ICIs in combination with targeted therapies and with other ICIs will be published in companion volumes to this paper.

Plasma circulating tumor DNA profiling in patients with chemo-refractory germ cell tumors

OBJECTIVES

Molecular analysis of tumor tissues has been extensively analyzed in germ cell tumors. However, genetic analysis of plasma circulating tumor DNA has been limited. Our objective was to analyze genetic alterations in circulating tumor DNA as well as its impact on prognosis in patients with chemo-refractory germ cell tumors.

METHODS

We included 13 patients with chemo-refractory germ cell tumors who relapsed after second-line or higher previous chemotherapy and performed targeted sequencing of plasma cell-free DNA using an AVENIO Expanded kit.

RESULTS

Tumor-specific genetic alterations were identified in all patients. The most frequently mutated gene was TP53 (53.4%), followed by PTEN (23.1%), GNAS (15.4%) and MTOR (15.4%). Moreover, EGFR amplification (38.5%) and MET amplification (15.4%) were also identified. We defined two or more single nucleotide variants detected in plasma cell-free DNA as circulating tumor DNA-positive. Kaplan-Meier analysis revealed that overall survival was significantly shorter in circulating tumor DNA-positive patients than circulating tumor DNA negative-patients (median overall survival 3.13 vs. 8.73 months; p = 0.042).

CONCLUSION

Analysis of plasma circulating tumor DNA could detect genetic alterations in patients with chemo-refractory GCT. Moreover, detectable circulating tumor DNA in plasma was associated with poor prognosis in those patients. These results suggest that liquid biopsy using analysis of plasma circulating tumor DNA may be clinically useful for germ cell tumor patients.

Regulatory implications of ctDNA in immuno-oncology for solid tumors

In the era of precision oncology, use of circulating tumor DNA (ctDNA) is emerging as a minimally invasive approach for the diagnosis and management of patients with cancer and as an enrichment tool in clinical trials. In recent years, the US Food and Drug Administration has approved multiple ctDNA-based companion diagnostic assays for the safe and effective use of targeted therapies and ctDNA-based assays are also being developed for use with immuno-oncology-based therapies. For early-stage solid tumor cancers, ctDNA may be particularly important to detect molecular residual disease (MRD) to support early implementation of adjuvant or escalated therapy to prevent development of metastatic disease. Clinical trials are also increasingly using ctDNA MRD for patient selection and stratification, with an ultimate goal of improving trial efficiency through use of an enriched patient population. Standardization and harmonization of ctDNA assays and methodologies, along with further clinical validation of ctDNA as a prognostic and predictive biomarker, are necessary before ctDNA may be considered as an efficacy-response biomarker to support regulatory decision making.

Liquid biopsy approaches to capture tumor evolution and clinical outcomes during cancer immunotherapy

Circulating cell-free tumor DNA (ctDNA) can serve as a real-time biomarker of tumor burden and provide unique insights into the evolving molecular landscape of cancers under the selective pressure of immunotherapy. Tracking the landscape of genomic alterations detected in ctDNA may reveal the clonal architecture of the metastatic cascade and thus improve our understanding of the molecular wiring of therapeutic responses. While liquid biopsies may provide a rapid and accurate evaluation of tumor burden dynamics during immunotherapy, the complexity of antitumor immune responses is not fully captured through single-feature ctDNA analyses. This underscores a need for integrative studies modeling the tumor and the immune compartment to understand the kinetics of tumor clearance in association with the quality of antitumor immune responses. Clinical applications of ctDNA testing in patients treated with immune checkpoint inhibitors have shown both predictive and prognostic value through the detection of genomic biomarkers, such as tumor mutational burden and microsatellite instability, as well as allowing for real-time monitoring of circulating tumor burden and the assessment of early on-therapy responses. These efforts highlight the emerging role of liquid biopsies in selecting patients for cancer immunotherapy, monitoring therapeutic efficacy, determining the optimal duration of treatment and ultimately guiding treatment selection and sequencing. The clinical translation of liquid biopsies is propelled by the increasing number of ctDNA-directed interventional clinical trials in the immuno-oncology space, signifying a critical step towards implementation of liquid biopsies in precision immuno-oncology.

Dissecting Immunotherapy Strategies for Small Cell Lung Cancer: Antibodies, Ionizing Radiation and CAR-T

Small cell lung cancer (SCLC) is a highly aggressive malignancy that accounts for about 14% of all lung cancers. Platinum-based chemotherapy has been the only available treatment for a long time, until the introduction of immune checkpoint inhibitors (ICIs) recently changed first-line standard of care and shed light on the pivotal role of the immune system. Despite improved survival in a subset of patients, a lot of them still do not benefit from first-line chemo-immunotherapy, and several studies are investigating whether different combination strategies (with both systemic and local treatments, such as radiotherapy) may improve patient outcomes. Moreover, research of biomarkers that may be used to predict patients' outcomes is ongoing. In addition to ICIs, immunotherapy offers other different strategies, including naked monoclonal antibodies targeting tumor associated antigens, conjugated antibody, bispecific antibodies and cellular therapies. In this review, we summarize the main evidence available about the use of immunotherapy in SCLC, the rationale behind combination strategies and the studies that are currently ongoing in this setting, in order to give the reader a clear and complete view of this rapidly expanding topic.

The CCTG PA.7 phase II trial of gemcitabine and nab-paclitaxel with or without durvalumab and tremelimumab as initial therapy in metastatic pancreatic ductal adenocarcinoma

Immunotherapy-based monotherapy treatment in metastatic pancreatic ductal adenocarcinoma (mPDAC) has shown limited benefit outside of the mismatch repair deficiency setting, while safety and efficacy of combining dual-checkpoint inhibitor immunotherapy with chemotherapy remains uncertain. Here, we present results from the CCTG PA.7 study (NCT02879318), a randomized phase II trial comparing gemcitabine and nab-paclitaxel with and without immune checkpoint inhibitors durvalumab and tremelimumab in 180 patients with mPDAC. The primary endpoint was overall survival. Secondary endpoints included progression-free survival and objective response rate. Results of the trial were negative as combination immunotherapy did not improve survival among the unselected patient population (p = 0.72) and toxicity was limited to elevation of lymphocytes in the combination immunotherapy group (p = 0.02). Exploratory baseline circulating tumor DNA (ctDNA) sequencing revealed increased survival for patients with KRAS wildtype tumors in both the combination immunotherapy (p = 0.001) and chemotherapy (p = 0.004) groups. These data support the utility of ctDNA analysis in PDAC and the prognostic value of ctDNA-based KRAS mutation status.

Personalized treatment of extensive stage small cell lung cancer: A case report and literature review

A 50-year-old female patient presented with post-exercise dyspnea in September 2016, and was subsequently diagnosed with SCLC with multiple brain and spinal metastases. The first-line treatment was etoposide combined with cisplatin and synchronously performed radiotherapy for the brain and spinal cord metastases. She was treated with anlotinib after disease progression in December 2018 and continued to have clinical benefit for nearly 25 months. Unexpectedly, the patient can still benefit from further combination treatment with durvalumab after another disease progression in February 2021. Thus, it may be a potential option to use anlotinib along with immunotherapy after the anlotinib resistance in SCLC, but more clinical data are still needed to confirm it. Moreover, ctDNA dynamic monitoring was performed and reflected the outcome of the process of treatment.

Current and Future Clinical Applications of ctDNA in Immuno-Oncology

Testing peripheral blood for circulating tumor DNA (ctDNA) offers a minimally invasive opportunity to diagnose, characterize, and monitor the disease in individual cancer patients. ctDNA can reflect the actual tumor burden and specific genomic state of disease and thus might serve as a prognostic and predictive biomarker for immune checkpoint inhibitor (ICI) therapy. Recent studies in various cancer entities (e.g., melanoma, non-small cell lung cancer, colon cancer, and urothelial cancer) have shown that sequential ctDNA analyses allow for the identification of responders to ICI therapy, with a significant lead time to imaging. ctDNA assessment may also help distinguish pseudoprogression under ICI therapy from real progression. Developing dynamic changes in ctDNA concentrations as a potential surrogate endpoint of clinical efficacy in patients undergoing adjuvant immunotherapy is ongoing. Besides overall ctDNA burden, further ctDNA characterization can help uncover tumor-specific determinants (e.g., tumor mutational burden and microsatellite instability) of responses or resistance to immunotherapy. In future studies, standardized ctDNA assessments need to be included in interventional clinical trials across cancer entities to demonstrate the clinical utility of ctDNA as a biomarker for personalized cancer immunotherapy.

Carboplatin and nab-paclitaxel chemotherapy with or without atezolizumab as front-line management for treatment-naïve metastatic nonsquamous non-small cell lung cancer with PD-L1 staining: a retrospective study

Purpose

The aim of this retrospective review was to compare the efficacy and safety of the atezolizumab plus carboplatin and nab-paclitaxel regimen versus the carboplatin and nab-paclitaxel regimen as front-line management for treatment-naïve, metastatic nonsquamous programmed death-ligand 1 (PD-L1)-positive non-small cell lung cancer (NSCLC) in a selected population.

Methods

Consecutive patients with untreated, metastatic nonsquamous PD-L1-positive NSCLC who initially received the atezolizumab plus carboplatin and nab-paclitaxel (ACN) regimen or carboplatin and nab-paclitaxel (CN) regimen were retrospectively identified in two medical institutions from 2017 to 2020. The co-primary end points were overall survival (OS) and progression-free survival (PFS); secondary end point was the rate of key adverse events (AEs).

Results

In sum, 171 patients were retrospectively analysed, 47 of whom were excluded according to the criteria used in this study, leaving 124 patients (ACN: n = 60, median age 64 years [range 46–75]; CN: n = 64, 63 years [47–72]). The median duration of follow-up was 27 months [range 1–37]. At the final follow-up, the median OS was 19.9 months (95% confidence interval [CI], 16.3–22.5) in the ACN group vs. 14.8 months (95% CI 12.5–17.2) in the CN group (hazard ratio [HR] 0.51, 95% CI 0.33–0.77; p = 0.001). A marked distinction in the median PFS was seen (8.5 months [95% CI 6.7–9.4] in the ACN group vs. in the CN group [5.1 months [95% CI 3.6–6.8; HR 0.60; 95% CI 0.38–0.95; p = 0.005]). The rates of the key AEs (neutropenia and anaemia) were greater in the ACN group than in the CN group (all p < 0.05), but these AEs were manageable.

Conclusion

Among selected populations of individuals with treatment-naïve, metastatic nonsquamous PD-L1-positive NSCLC, atezolizumab combined with carboplatin and nab-paclitaxel chemotherapy might have encouraging anticancer activity, with a tolerable safety profile.

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.

Current state of the art and future perspectives with immunotherapy in the management of small cell lung cancer

INTRODUCTION

Small cell lung cancer (SCLC) is an aggressive tumor with a severe prognosis. At the time of diagnosis, most patients present with extensive-stage (ES) disease. For decades, platinum-based chemotherapy has been the only pillar of SCLC treatment, but now, the clinical management of this disease is rapidly evolving thanks to the introduction of immune checkpoint inhibitors (ICIs).

AREAS COVERED

In this review, we describe the most recent advances in the treatment of SCLC and discuss the emerging challenges associated with ICI treatments. Meaningful data were collected from the currently available literature on PubMed and in international oncology meetings.

EXPERT OPINION

Recently, meaningful improvements in outcomes of SCLC patients have been achieved with anti-PD-L1 atezolizumab or durvalumab combined with chemotherapy in first line. Results of studies evaluating the role of ICIs in limited-stage (LS) SCLC patients are awaited. Further efforts are required to better understand the role of immunotherapy in the treatment of SCLC and to identify patients most likely to benefit from this treatment strategy.

Liquid Biopsy for Small Cell Lung Cancer either De Novo or Transformed: Systematic Review of Different Applications and Meta-Analysis

BACKGROUND

The potential added value of liquid biopsy (LB) is not well determined in the case of small cell lung cancer (SCLC), an aggressive tumor that can occur either de novo or from the histologic transformation of non-small cell lung cancer (NSCLC).

METHODS

A systematic review of studies adopting LB in patients with SCLC have been performed to assess the clinical utility of circulating tumor DNA (ctDNA) or circulating tumor cells (CTCs).

RESULTS

After a screening of 728 records, 62 studies (32 evaluating CTCs, 27 ctDNA, and 3 both) met predetermined eligibility criteria. Only four studies evaluated LB in the diagnostic setting for SCLC, while its prognostic significance was evaluated in 38 studies and prominently supported by both ctDNA and CTCs. A meta-analysis of 11 studies as for CTCs enumeration showed an HR for overall survival of 2.63 (1.71-4.05), with a potential publication bias. The feasibility of tumor genomic profiling and the predictive role of LB in terms of response/resistance to chemotherapy was assessed in 11 and 24 studies, respectively, with greater consistency for those regarding ctDNA. Intriguingly, several case reports suggest that LB can indirectly capture the transition to SCLC in NSCLC treated with EGFR tyrosine kinase inhibitors.

CONCLUSIONS

While dedicated trials are needed, LB holds potential clinical roles in both de novo and transformed SCLC. CtDNA analysis appears the most valuable and practicable tool for both disease monitoring and genomic profiling.

Current status of ctDNA in precision oncology for hepatocellular carcinoma

The conventional method used to obtain a tumor biopsy for hepatocellular carcinoma (HCC) is invasive and does not evaluate dynamic cancer progression or assess tumor heterogeneity. It is thus imperative to create a novel non-invasive diagnostic technique for improvement in cancer screening, diagnosis, treatment selection, response assessment, and predicting prognosis for HCC. Circulating tumor DNA (ctDNA) is a non-invasive liquid biopsy method that reveals cancer-specific genetic and epigenetic aberrations. Owing to the development of technology in next-generation sequencing and PCR-based assays, the detection and quantification of ctDNA have greatly improved. In this publication, we provide an overview of current technologies used to detect ctDNA, the ctDNA markers utilized, and recent advances regarding the multiple clinical applications in the field of precision medicine for HCC.