Circulating Tumor DNA Reflects Tumor Metabolism Rather Than Tumor Burden in Chemotherapy-Naive Patients with Advanced Non-Small Cell Lung Cancer: 18F-FDG PET/CT Study

Circulating Tumor DNA in Head and Neck Squamous Cell Carcinoma: Association with Metabolic Tumor Burden Determined with FDG-PET/CT

BACKGROUND

The detection of circulating tumor DNA (ctDNA) with next-generation sequencing (NGS) in venous blood is a promising tool for the genomic profiling of head and neck squamous cell carcinoma (HNSCC). The association between ctDNA findings and metabolic tumor burden detected with FDG-PET/CT imaging is of particular interest for developing prognostic and predictive algorithms in HNSCC.

METHODS

Twenty-six prospectively enrolled HNSCC patients were eligible for further analysis. All patients underwent tumor tissue and venous liquid biopsy sampling and FDG-PET/CT before definitive oncologic treatment. An NGS-based commercial panel was used for a genomic analysis of the samples.

RESULTS

Maximum variant allele frequency (VAF) in blood correlated positively with whole-body (WB) metabolic tumor volume (MTV) and total lesion glycolysis (TLG) (r = 0.510, p = 0.008 and r = 0.584, p = 0.002, respectively). A positive liquid biopsy was associated with high WB-TLG using VAF ≥ 1.00% or ≥5.00% as a cut-off value (p = 0.006 or p = 0.003, respectively). Additionally, ctDNA detection was associated with WB-TLG when only concordant variants detected in both ctDNA and tissue samples were considered.

CONCLUSIONS

A high metabolic tumor burden based on FDG imaging is associated with a positive liquid biopsy and high maximum VAF. Our findings suggest a complementary role of metabolic and genomic signatures in the pre-treatment evaluation of HNSCC.

Associations between detectable circulating tumor DNA and tumor glucose uptake measured by 18F-FDG PET/CT in early-stage non-small cell lung cancer

BACKGROUND

The low level of circulating tumor DNA (ctDNA) in the blood is a well-known challenge for the application of liquid biopsies in early-stage non-small cell lung cancer (NSCLC) management. Studies of metastatic NSCLC indicate that ctDNA levels are associated with tumor metabolic activity as measured by ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET/CT). This study investigated this association in NSCLC patients considered for potentially curative treatment and explored whether the two methods provide independent prognostic information.

METHOD

Patients with stage I-III NSCLC who had routinely undergone an ¹⁸F-FDG PET/CT scan and exploratory ctDNA analyses were included. Tumor glucose uptake was measured by maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) from the ¹⁸F-FDG PET/CT scans. ctDNA detectability and quantity, using variant allele frequency, were estimated by tumor-informed ctDNA analyses.

RESULTS

In total, 63 patients (median age 70 years, 60% women, and 90% adenocarcinoma) were included. The tumor glucose uptake (SUVmax, MTV, and TLG) was significantly higher in patients with detectable ctDNA (n = 19, p < 0.001). The ctDNA quantity correlated with MTV (Spearman's ρ = 0.53, p = 0.021) and TLG (Spearman's ρ = 0.56, p = 0.013) but not with SUVmax (Spearman's ρ = 0.034, p = 0.15). ctDNA detection was associated with shorter OS independent of MTV (HR: 2.70, 95% CI: 1.07-6.82, p = 0.035) and TLG (HR: 2.63, 95% CI: 1.06-6.51, p = 0.036). Patients with high tumor glucose uptake and detectable ctDNA had shorter overall survival and progression-free survival than those without detectable ctDNA, though these associations were not statistically significant (p > 0.05).

CONCLUSION

There was a positive correlation between plasma ctDNA quantity and MTV and TLG in early-stage NSCLC patients. Despite the correlation, the results indicated that ctDNA detection was a negative prognostic factor independent of MTV and TLG.

Fluorometric Quantification of Total Cell-Free DNA as a Prognostic Biomarker in Non-Small-Cell Lung Cancer Patients Treated with Immune Checkpoint Blockade

The present study aimed to investigate the potential of basal cell-free fluorometric DNA (cfDNA) quantification as a prognostic biomarker in advanced non-small cell lung cancer (NSCLC) patients treated with an Immune Checkpoint Blockade (ICB). A discovery and validation cohort of 61 and 31 advanced lung cancer patients treated with ICB were included in this study. Quantification of cfDNA concentration was performed before the start of the treatment and patients were followed up for a median of 34 (30-40) months. The prognostic predicted value of cfDNA was evaluated based on ROC, and Cox regression was conducted via univariate and multivariate analyses to estimate the hazard ratio. We observed that a cfDNA cut-off of 0.55 ng/µL before the ICB determines the overall survival of patients with a log rank p-value of 3.3 × 10^-4. That represents median survivals of 3.8 vs. 17.5 months. Similar results were obtained in the validation cohort being the log rank p-value 3.8 × 10^-2 with median survivals of 5.9 vs. 24.3. The univariate and multivariate analysis revealed that the cut-off of 0.55 ng/µL before ICB treatment was an independent predictive factor and was significantly associated with a better survival outcome. High cfDNA concentrations identify patients with advanced NSCLC who do not benefit from the ICB. The determination of cfDNA is a simple test that could select a group of patients in whom new therapeutic strategies are needed.

Overall survival with circulating tumor DNA-guided therapy in advanced non-small-cell lung cancer

Circulating tumor DNA (ctDNA) sequencing guides therapy decisions but has been studied mostly in small cohorts without sufficient follow-up to determine its influence on overall survival. We prospectively followed an international cohort of 1,127 patients with non-small-cell lung cancer and ctDNA-guided therapy. ctDNA detection was associated with shorter survival (hazard ratio (HR), 2.05; 95% confidence interval (CI), 1.74-2.42; P < 0.001) independently of clinicopathologic features and metabolic tumor volume. Among the 722 (64%) patients with detectable ctDNA, 255 (23%) matched to targeted therapy by ctDNA sequencing had longer survival than those not treated with targeted therapy (HR, 0.63; 95% CI, 0.52-0.76; P < 0.001). Genomic alterations in ctDNA not detected by time-matched tissue sequencing were found in 25% of the patients. These ctDNA-only alterations disproportionately featured subclonal drivers of resistance, including RICTOR and PIK3CA alterations, and were associated with short survival. Minimally invasive ctDNA profiling can identify heterogeneous drivers not captured in tissue sequencing and expand community access to life-prolonging therapy.

Circulating Tumor DNA Allele Fraction: A Candidate Biological Signal for Multicancer Early Detection Tests to Assess the Clinical Significance of Cancers

Current imaging-based cancer screening approaches provide useful but limited prognostic information. Complementary to existing screening tests, cell-free DNA-based multicancer early detection (MCED) tests account for cancer biology [manifested through circulating tumor allele fraction (cTAF)], which could inform prognosis and help assess the cancer's clinical significance. This review discusses the factors affecting circulating tumor DNA (ctDNA) levels and cTAF, and their correlation with the cancer's clinical significance. Furthermore, it discusses the influence of cTAF on MCED test performance, which could help inform prognosis. Clinically significant cancers show higher ctDNA levels quantified by cTAF than indolent phenotype cancers within each stage. This is because more frequent mitosis and cell death combined with increased trafficking of cell-free DNA into circulation leads to greater vascularization and depth of tumor invasion. cTAF has been correlated with biomarkers for cancer aggressiveness and overall survival; cancers with lower cTAF had better survival when compared with cancers as determined by the higher cTAF and Surveillance, Epidemiology, and End Results-based survival for that cancer type at each stage. MCED-detected cancers in case-control studies had comparable survival to Surveillance, Epidemiology, and End Results-based survival at each stage. Because many MCED tests use ctDNA as an analyte, cTAF could provide a common metric to compare performance. The prognostic value of cTAF may allow MCED tests to preferentially detect clinically significant cancers at early stages when outcomes are favorable and this may avoid overdiagnosis.

Combination of Circulating Tumour DNA and 18F-FDG PET/CT for Precision Monitoring of Therapy Response in Patients With Advanced Non-small Cell Lung Cancer: A Prospective Study

BACKGROUND/AIM

Circulating tumour DNA (ctDNA) represents an emerging biomarker in non-small cell lung cancer (NSCLC). We focused on the combination of ctDNA and positron emission tomography/computed tomography (PET/CT) in the follow-up monitoring of advanced-stage NSCLC patients treated with chemotherapy.

PATIENTS AND METHODS

Eighty-four patients were enrolled in this study. ¹⁸F-fluorodeoxyglucose PET/CT and ctDNA assessments were performed at baseline and after two cycles of chemotherapy (follow-up).

RESULTS

There was a correlation of ctDNA with metabolic tumour volume (MTV), total lesion glycolysis (TLG), and iodine concentration (IC) at baseline (p=0.001, p=0.001, p=0.003) and at follow-up (p=0.006, p=0.002, p=0.001). The objective response was associated with follow-up ctDNA (p<0.001) and the change of all PET/CT parameters. ROC analyses showed that the combination of follow-up ctDNA with changes in SUVmax is very promising for the estimation of objective response and progression-free survival.

CONCLUSION

The combination of ctDNA assessment with PET/CT is a promising approach for the follow-up monitoring of therapy response and prognosis estimation of advanced-stage NSCLC patients.

Blood, Toil, and Taxoteres: Biological Determinates of Treatment-Induce ctDNA Dynamics for Interpreting Tumor Response

Collection and analysis of circulating tumor DNA (ctDNA) is one of the few methods of liquid biopsy that measures generalizable and tumor specific molecules, and is one of the most promising approaches in assessing the effectiveness of cancer care. Clinical assays that utilize ctDNA are commercially available for the identification of actionable mutations prior to treatment and to assess minimal residual disease after treatment. There is currently no clinical ctDNA assay specifically intended to monitor disease response during treatment, partially due to the complex challenge of understanding the biological sources of ctDNA and the underlying principles that govern its release. Although studies have shown pre- and post-treatment ctDNA levels can be prognostic, there is evidence that early, on-treatment changes in ctDNA levels are more accurate in predicting response. Yet, these results also vary widely among cohorts, cancer type, and treatment, likely due to the driving biology of tumor cell proliferation, cell death, and ctDNA clearance kinetics. To realize the full potential of ctDNA monitoring in cancer care, we may need to reorient our thinking toward the fundamental biological underpinnings of ctDNA release and dissemination from merely seeking convenient clinical correlates.

Size distribution of cell-free DNA in oncology

Tumor-specific, circulating cell-free DNA (cfDNA) in liquid biopsy test is a novel promising biomarker in the advancement of cancer management, including early diagnosis, screening, prognosis, identification of actionable targets, and serial tumor monitoring. The specific size pattern of DNA fragments derived from cancer cells is observed to differ from that of cfDNA fragments shed by non-cancer cells. Research into the physiological and biological properties of cfDNA reveals the molecular signature carried by each cfDNA fragments, which can reflect their tissue origins, as well as the mutational profiles with significant genetic alterations. Understanding the fragmentation and size distribution of cfDNA might be a valuable hotspot in liquid biopsy research, with the potential to drive innovation in oncology.

The Role of the Immune Metabolic Prognostic Index in Patients with Non-Small Cell Lung Cancer (NSCLC) in Radiological Progression during Treatment with Nivolumab

Simple Summary

Identifying reliable prognostic biomarkers of progression in the early phases of treatment is crucial in patients undergoing immune checkpoints inhibitors (ICI) administration for advanced non-small cell lung cancer (NSCLC). With this aim, in this study we combined the prognostic power of the degree of systemic inflammation (depicted by peripheral inflammation indexes), the quantification of the metabolically active tumor burden (estimated using 18F-fluorodeoxyglucose positron emission tomography/computed tomography) as well as their combination in NSCLC patients receiving immune checkpoints inhibitors. This combined approach could be used to improve the risk stratification and the subsequent clinical management in NSCLC patients treated with immune checkpoints inhibitors.

Abstract

An emerging clinical need is represented by identifying reliable biomarkers able to discriminate between responders and non-responders among patients showing imaging progression during the administration of immune checkpoints inhibitors for advanced non-small cell lung cancer (NSCLC). In the present study, we analyzed the prognostic power of peripheral-blood systemic inflammation indexes and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in this clinical setting. In 45 patients showing radiological progression (defined as RECIST 1.1 progressive disease) during Nivolumab administration, the following lab and imaging parameters were collected: neutrophil-to-lymphocyte ratio (NLR), derived-NLR (dNLR), lymphocyte-to-monocyte ratio (LMR), platelets-to-lymphocyte ratio (PLR), systemic inflammation index (SII), maximum standardized uptake value, metabolic tumor volume (MTV), and total lesion glycolysis (TLG). MTV and SII independently predicted OS. Their combination in the immune metabolic prognostic index (IMPI) allowed the identification of patients who might benefit from immunotherapy continuation, despite radiological progression. The combination of FDG PET/CT volumetric data with SII also approximates the immune-metabolic response with respect to baseline, providing additional independent prognostic insights. In conclusion, the degree of systemic inflammation, the quantification of the metabolically active tumor burden, and their combination might disclose the radiological progression in NSCLC patients receiving Nivolumab.

Cell-free DNA concentration and fragment size fraction correlate with FDG PET/CT-derived parameters in NSCLC patients

PURPOSE

The aim of our study was to investigate the correlation between cfDNA concentration and fragment size fraction with FDG PET/CT- and CT-derived parameters in untreated NSCLC patient.

METHODS

Fifty-three patients diagnosed of locally advanced or metastatic NSCLC who had undergone FDG PET/CT, CT and cfDNA analysis prior to any treatment were included in this retrospective study. CfDNA concentration was measured by fluorometry and fragment size fractions were determined by microchip electrophoresis. [¹⁸F]F-FDG PET/CT was performed and standardised uptake values (SUV), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were calculated for primary, extrapulmonary and total disease. CT scans were evaluated according to RECIST 1.1 criteria.

RESULTS

CfDNA concentration showed a positive correlation with extrapulmonary MTV (r² = 0.36, P = 0.009), and extrapulmonary TLG (r² = 0.35, P = 0.009) and their whole-body (wb) ratios. Higher concentrations of total cfDNA were found in patients with liver lesions. Short fragments of cfDNA (100-250 bp) showed a positive correlation with extrapulmonary MTV (r² = 0.49, P = 0.0005) and extrapulmonary TLG (r² = 0.39, P = 0.006) and their respective wb ratios, and a negative correlation with SUVmean (r² = -0.31, P = 0.03) and SUVmean/SUVmax ratio (r² = -0.34, P = 0.02). A higher fraction of short cfDNA fragments was found in patients with liver and pleural lesions.

CONCLUSIONS

This study supports the hypothesis that cfDNA concentration and short cfDNA fragment size fraction reflect the tumour burden as well as metabolic activity in advanced NSCLC patients. This suggests their suitability as complementary tests for a more accurate diagnosis of tumour metabolic behaviour and to allow personalised therapies.

18F-FDG PET/CT and circulating tumor cells in treatment-naive patients with non-small-cell lung cancer

PURPOSE

This study retrospectively investigated the clinical utility of 2-deoxy-18F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) and circulating tumor cells (CTCs) in the diagnosis and prognosis of treatment-naive patients with non-small-cell lung cancer (NSCLC).

METHODS

The blood samples of treatment-naive patients with NSCLC were collected for CTCs detection, and the tumor metabolic parameters of ¹⁸F-FDG PET/CT, including maximum standard uptake value (SUVmax), metabolic tumor volume of primary lesion (MTV-P) and combination of primary lesion and metastases (MTV-C), and total lesion glycolysis of primary lesion (TLG-P) and combination of primary lesion and metastases (TLG-C), were analyzed. Age, sex, smoking, serum tumor markers, tumor size, location, TNM stage, and genetic mutations were also reviewed. Moreover, progression-free survival (PFS) and overall survival (OS) of these patients were analyzed.

RESULTS

A total of 309 patients with NSCLC (200 men, 109 women; mean age: 61 ± 9 years) were enrolled in this study, including 217 patients with adenocarcinoma and 92 with squamous cell carcinoma. Of the 309 cases, 11 were misdiagnosed with benign diseases by ¹⁸F-FDG PET/CT. CTCs positivity was detected in 234 cases. The sensitivity of ¹⁸F-FDG PET/CT and CTCs in NSCLC were 96.4% and 75.7%, respectively. SUVmax, MTV-P, TLG-P, MTV-C, TLG-C, tumor size, and serum CYFRA211 levels were significantly higher in CTCs positive group than negative group; and advanced TNM stage, squamous cell carcinoma, and EGFR wild type presented higher CTCs positivity. Multivariate logistic regression analysis revealed that SUVmax was significantly associated with CTCs positivity. Multivariate cox regression analysis showed that TLG-P, TLG-C, and CTCs were independent predictors of PFS in patients with NSCLC, and TLG-C and CTCs were independent predictors of OS.

CONCLUSIONS

¹⁸F-FDG PET/CT was superior to CTCs in the diagnosis of treatment-naive patients with NSCLC. The levels of CTCs in the peripheral blood were associated with tumor glucose metabolism in NSCLC. Metabolic parameters of ¹⁸F-FDG PET/CT and CTCs could separately predict the outcomes of treatment-naive patients with NSCLC.

Genotype-Specific Differences in Circulating Tumor DNA Levels in Advanced NSCLC

INTRODUCTION

Plasma-based circulating tumor DNA (ctDNA) is an established biomarker for molecular profiling with emerging applications in disease monitoring in multiple tumor types, including, NSCLC. However, determinants of ctDNA shedding and correlation with tumor burden are incompletely understood, particularly in advanced-stage disease.

METHODS

We retrospectively analyzed ctDNA-based and tissue-based genomic data and imaging from 144 patients with NSCLC. Tumor burden was quantified with computed tomography (CT) and brain magnetic resonance imaging for the overall cohort and 18F-fludeoxyglucose positron emission tomography-CT in a subset of patients.

RESULTS

There was a moderate but statistically significant correlation between ctDNA variant allele frequency and multiple imaging measures of tumor burden such as CT volume (rho = 0.34, p ≤ 0.0001) and metabolic tumor volume (rho = 0.36, p = 0.003). This correlation was strongest in KRAS-mutant tumors (rho = 0.56, p ≤ 0.001), followed by TP53 mutants (rho = 0.43, p ≤ 0.0001), and weakest in EGFR-mutated (EGFR+) tumors (rho = 0.24, p = 0.077). EGFR+ tumors with EGFR copy number gain had significantly higher variant allele frequency than EGFR+ without copy number gain (p ≤ 0.00001). In multivariable analysis, TP53 and EGFR mutations, visceral metastasis, and tumor burden were independent predictors of increased ctDNA shedding.

CONCLUSIONS

Levels of detectable ctDNA were affected not only by tumor burden but also by tumor genotype. The genotype-specific differences observed may be due to variations in DNA shedding and cellular turnover. These findings have implications for the emerging use of ctDNA in NSCLC disease monitoring and early detection.

Imaging Biomarkers of Tumour Proliferation and Invasion for Personalised Lung Cancer Therapy

Personalised treatment in oncology has seen great developments over the last decade, due to both technological advances and more in-depth knowledge of radiobiological processes occurring in tumours. Lung cancer therapy is no exception, as new molecular targets have been identified to further increase treatment specificity and sensitivity. Yet, tumour resistance to treatment is still one of the main reasons for treatment failure. This is due to a number of factors, among which tumour proliferation, the presence of cancer stem cells and the metastatic potential of the primary tumour are key features that require better controlling to further improve cancer management in general, and lung cancer treatment in particular. Imaging biomarkers play a key role in the identification of biological particularities within tumours and therefore are an important component of treatment personalisation in radiotherapy. Imaging techniques such as PET, SPECT, MRI that employ tumour-specific biomarkers already play a critical role in patient stratification towards individualized treatment. The aim of the current paper is to describe the radiobiological challenges of lung cancer treatment in relation to the latest imaging biomarkers that can aid in the identification of hostile cellular features for further treatment adaptation and tailoring to the individual patient’s needs.

Liquid biopsy for cancer management: a revolutionary but still limited new tool for precision medicine

The term liquid biopsy is used in contraposition to the traditional "solid" tissue biopsy. In the oncology field it has opened a new plethora of clinical opportunities as tumor-derived material is shedded into the different biofluids from where it can be isolated and analyzed. Common biofluids include blood, urine, saliva, cerebrospinal fluid (CSF), pleural effusion or bile. Starting from these biological specimens several analytes can be isolated, among which we will review the most widely used: circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), circulating tumor RNA (ctRNA), proteins, metabolites, and exosomes. Regarding the nature of the biomarkers it will depend on the analyte, the type of tumor and the clinical application of the liquid biopsy and it includes, somatic point mutations, deletions, amplifications, gene-fusions, DNA-methylated marks, tumor-specific miRNAs, proteins or metabolites. Here we review the characteristics of the analytes and the methodologies used for their isolation. We also describe the applications of the liquid biopsy in the management of patients with cancer, from the early detection of cancers to treatment guidance in patients with advanced tumors. Finally, we also discuss some current limitations and still open questions.

18F-FDG PET/CT total lesion glycolysis is associated with circulating tumor cell counts in patients with stage I to IIIA non-small cell lung cancer

Background

In non-small cell lung cancer (NSCLC), ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) uptake determined by PET and presence of circulating tumor cells (CTCs) in the peripheral blood independently predict outcomes. For ¹⁸F-FDG PET/CT staging interpretation, standardized uptake values (SUV_max/avg) are routinely used in clinical reporting. The goal was to investigate whether ¹⁸F-FDG uptake measured by SUV_max/avg, but also measures of metabolic tumor volume (MTV) and total lesion glycolysis (TLG) (MTV × SUV_avg), are associated with CTCs.

Methods

Prospectively, 7.5 mL blood was drawn from NSCLC patients at the time of staging 18F-FDG PET/CT and from healthy control subjects. CTCs were identified by immunofluorescent staining (CK8/18/19^pos/EpCAM^pos/CD45^neg/DAPI^pos nucleus). ¹⁸F-FDG PET/CTs were analyzed for SUV_max, SUV_avg, MTV, and TLG.

Results

In 16 NSCLC patients with stage I–IIIA, MTV and TLG, in contrast to SUV_max and SUV_avg, were positively associated with CTCs (linear regression analysis). No CTCs were detectable in 20 healthy control subjects.

Conclusions

This pilot study demonstrates that ¹⁸F-FDG PET/CT TLG correlates with CTCs in NSCLC patients without distant metastases. TLG might be a more appropriate marker for hematogenous micrometastatic potential than SUVs.

The Utility of Liquid Biopsies in Radiation Oncology

The use of therapeutic radiation is primarily guided by clinicopathologic factors and medical imaging, whereas molecular biomarkers currently play a comparatively minor role in most settings. Liquid biopsies provide a rich source of noninvasive tumor-specific biomarkers and are amenable to repeated and noninvasive assessment. Here, we review the current status of liquid biopsies and their potential impact on the field of radiation oncology. We focus on established and emerging approaches to analyze circulating tumor DNA and circulating tumor cells from peripheral blood. These promising classes of biomarkers could have an outsized impact on cancer management by meaningfully stratifying patients into risk groups, tracking radiation therapy efficacy during and after treatment, and identifying patients with radiosensitive or radioresistant disease. Finally, we highlight opportunities for future investigation including the need for prospective interventional studies employing liquid biopsies to guide the management of radiation therapy-treated patients.

Circulating Tumor Cells and Metabolic Parameters in NSCLC Patients Treated with Checkpoint Inhibitors

Circulating tumor cells (CTC) count and characterization have been associated with poor prognosis in recent studies. Our aim was to examine CTC count and its association with metabolic parameters and clinical outcomes in non-small cell lung carcinoma (NSCLC) patients treated with immune checkpoint inhibitors (ICI). For this prospective study, data from 35 patients (23 males, 12 females) were collected and analyzed. All patients underwent an 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) scan and CTC detection through Isolation by Size of Tumor/Trophoblastic Cells (ISET) from peripheral blood samples obtained at baseline and 8 weeks after ICI initiation. Association of CTC count with clinical and metabolic characteristics was studied. Progression-free survival (PFS) and overall survival (OS) were analyzed using the Kaplan–Meier method and the log-rank test. Median follow-up was 13.2 months (range of 4.9–21.6). CTC were identified in 16 out of 35 patients (45.7%) at baseline and 10 out of 24 patients at 8 weeks (41.7%). Mean CTC numbers before and after 8 weeks were 15 ± 28 and 11 ± 19, respectively. Prior to ICI, the mean CTC number was significantly higher in treatment-naïve patients (34 ± 39 vs. 9 ± 21, p = 0.004). CTC count variation (ΔCTC) was significantly associated with tumor metabolic response set by European Organization for Research and Treatment of Cancer (EORTC) criteria (p = 0.033). At the first restaging, patients with a high tumor burden, that is, metabolic tumor volume (MTV) and total lesion glycolysis (TLG), had a higher CTC count (p = 0.009). The combination of mean CTC and median MTV at 8 weeks was associated with PFS (p < 0.001) and OS (p = 0.024). Multivariate analysis identified CTC count at 8 weeks as an independent predictor for PFS and OS, whereas ΔMTV and maximum standardized uptake value variation (ΔSUVmax) was predictive for PFS and OS, respectively. Our study confirmed that CTC number is modulated by previous treatments and correlates with metabolic response during ICI. Moreover, elevated CTC count, along with metabolic parameters, were found to be prognostic factors for PFS and OS.

Pathophysiology of ctDNA Release into the Circulation and Its Characteristics: What Is Important for Clinical Applications

The clinical implications of being able to accurately detect tumor-derived DNA in the circulation, termed circulating tumor DNA (ctDNA), could be enormous. Already, a plethora of clinical applications is under validation that include detection of minimal residual disease and predicting recurrence, monitoring response and resistance to treatment, identifying targets for therapies, and early detection. ctDNA is only a fraction of the total cell-free DNA (cfDNA) which confounds its detection and sometimes conceals its properties. To use ctDNA as a cancer biomarker with confidence, we need to understand its nature. Its characteristics, including size, half-life, and amount, are critical for the development of tests for its detection and discrimination from the rest of the cfDNA. Technological advances have enabled the detection and quantification of individual fragments of cfDNA, which is pivotal for clinical applications. Understanding the causes, the source of and the mechanisms of release of ctDNA are important for the interpretation of test results. Despite the many advances in understanding the nature and biology of ctDNA, we do not yet have a clear appreciation of the processes that govern its presence and levels in the circulation. ctDNA is not detectable in the blood of every cancer patient, and there is not a directly proportional relationship to tumor type, size, or stage. It is not clear if the lack of correlation with these specific clinical parameters is strictly due to technical or biological challenges. Better understanding of the pathophysiology of ctDNA is therefore important for the improvement of clinical applications and interpretation of their results.

Liquid biopsy in the clinical management of bladder cancer: current status and future developments

Introduction: The use of liquid biopsy on the blood from solid malignancies provides a convenient way of detecting actionable mutations, monitoring treatment response, detecting early recurrence and prognosticating outcomes. The aim of this review is to discuss the current status and future direction of serum biomarkers in the clinical management of urinary bladder cancer.Areas covered: This review provides an overview of blood liquid biopsy and bladder cancer using methods of circulating tumors cells, circulating RNA, serum metabolites and cell-free DNA. Recent clinical studies and advances in methodology are emphasized. We performed a literature search using PMC/PubMed with keywords including 'liquid biopsy', 'circulating tumor DNA', 'cell-free DNA', 'biomarkers', 'bladder cancer' 'precision medicine'. Additional articles were obtained from the cited references of key articles. An emphasis was placed on recent studies published since 2018.Expert opinion: Liquid biopsies represent a potential biomarker using cell-free DNA, metabolomic profiles of altered cellular metabolism, circulating cancer cells and RNA. Despite displaying tremendous clinical promise, the current status of the blood liquid biopsies has not reached fruition. However, future investigations should lead the evolution of liquid biomarker into clinical utility for the management of bladder cancer.

Cell-free tumour DNA testing for early detection of cancer - a potential future tool

In recent years, detection of cell-free tumour DNA (ctDNA) or liquid biopsy has emerged as an attractive noninvasive methodology to detect cancer-specific genetic aberrations in plasma, and numerous studies have reported on the feasibility of ctDNA in advanced cancer. In particular, ctDNA assays can capture a more 'global' portrait of tumour heterogeneity, monitor therapy response, and lead to early detection of resistance mutations. More recently, ctDNA analysis has also been proposed as a promising future tool for detection of early cancer and/or cancer screening. As the average proportion of mutated DNA in plasma is very low (0.4% even in advanced cancer), exceedingly sensitive techniques need to be developed. In addition, as tumours are genetically heterogeneous, any screening test needs to assay multiple genetic targets in order to increase the chances of detection. Further research on the genetic progression from normal to cancer cells and their release of ctDNA is imperative in order to avoid overtreating benign/indolent lesions, causing more harm than good by early diagnosis. More knowledge on the sources and elimination of cell-free DNA will enable better interpretation in older individuals and those with comorbidities. In addition, as white blood cells are the major source of cell-free DNA in plasma, it is important to distinguish acquired mutations in leukocytes (benign clonal haematopoiesis) from an upcoming haematological malignancy or other cancer. In conclusion, although many studies report encouraging results, further technical development and larger studies are warranted before applying ctDNA analysis for early cancer detection in the clinic.

Prognostic Relevance of Circulating Tumor Cells and Circulating Cell-Free DNA Association in Metastatic Non-Small Cell Lung Cancer Treated with Nivolumab

The treatment of advanced non-small cell lung cancer (NSCLC) has been revolutionized by immune checkpoint inhibitors (ICIs). The identification of prognostic and predictive factors in ICIs-treated patients is presently challenging. Circulating tumor cells (CTCs) and cell-free DNA (cfDNA) were evaluated in 89 previously treated NSCLC patients receiving nivolumab. Blood samples were collected before therapy and at the first and second radiological response assessments. CTCs were isolated by a filtration-based method. cfDNA was extracted from plasma and estimated by quantitative PCR. Patients with baseline CTC number and cfDNA below their median values (2 and 836.5 ng from 3 mL of blood and plasma, respectively) survived significantly longer than those with higher values (p = 0.05 and p = 0.04, respectively). The two biomarkers were then used separately and jointly as time-dependent covariates in a regression model confirming their prognostic role. Additionally, a four-fold risk of death for the subgroup presenting both circulating biomarkers above the median values was observed (p < 0.001). No significant differences were found between circulating biomarkers and best response. However, progressing patients with concomitant lower CTCs and cfDNA performed clinically well (p = 0.007), suggesting that jointed CTCs and cfDNA might help discriminate a low-risk population which might benefit from continuing ICIs beyond progression.

Clinical implications of circulating cell-free DNA quantification and metabolic tumor burden in advanced non-small cell lung cancer

OBJECTIVES

This study unravels the significance of cell-free DNA (cfDNA) quantification as a promising measure of the biological behavior/aggressiveness of tumors. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) measured by positron emission tomography/computed tomography scan enable a precise assessment of metabolic tumor burden. However, their clinical implications in identifying patients who need more aggressive treatment in advanced non-small cell lung cancer (NSCLC) are not fully understood.

MATERIALS AND METHODS

In the current prospective trial, we analyzed 101 newly diagnosed advanced NSCLC (stage III-IV) patients with measurable baseline MTV, TLG, and cfDNA quantification. The best cut-offs for cfDNA levels, MTV, and TLG to predict progression-free survival and overall survival were determined using X-tile analysis.

RESULTS

There were significant positive correlations between cfDNA and MTV (r = 0.488, p <  0.001) and between cfDNA and TLG (r = 0.554, p <  0.001). High-cfDNA levels and high-MTV/TLG negatively correlated with overall survival (OS) (all p <  0.001). Patients with high-MTV showed similar median OS irrespective of their cfDNA levels (low-cfDNA vs. high-cfDNA=9.2 vs 6.6 months; p >  0.05). However, patients with low-MTV and low-cfDNA levels showed longer OS than those with low-MTV and high-cfDNA levels (low-cfDNA vs. high-cfDNA=49.3 vs 11.5 months; p <  0.001). The patient group with low-TLG also showed similar trends. The cfDNA level was an independent prognostic factor for OS by Cox-proportional hazard analysis.

CONCLUSION

Although the patients with high metabolic tumor burden had a poor prognosis, regardless of the biological behavior/aggressiveness of the tumor, patients with low metabolic tumor burden and high cfDNA levels showed a poor prognosis. Taken together, this study indicates a stronger prognostic value of baseline cfDNA levels in identifying patients with advanced NSCLC and personalizing their treatment strategies for better survival.

Development, validation, and comparison of gene analysis methods for detecting EGFR mutation from non-small cell lung cancer patients-derived circulating free DNA

The feasibility and required sensitivity of circulating free DNA (cfDNA)-based detection methods in second-line epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) treatment are not well elucidated. We examined T790M and other activating mutations of EGFR by cfDNA to assess the clinical usability. In 45 non-small cell lung cancer (NSCLC) patients harboring activating EGFR mutations, cfDNAs were prepared from the plasma samples. EGFR mutations in cfDNA were detected using highly sensitive methods and originally developed assays and these results were compared to tissue-based definitive diagnoses. The specificity of each cfDNA-based method ranged 96–100% whereas the sensitivity ranged 56–67%, indicating its low pseudo-positive rate. In EGFR-TKI failure cohort, 41–46% samples were positive for T790M by each cfDNA-based method, which was comparable to re-biopsy tissue-based T790M positive rates in literature. The concordance of the results for each EGFR mutation ranged from 83–95%. In eight patients, the results of the cfDNA-based assays and re-biopsy-derived tissue-based test were compared. The observed overall agreement ranged in 50–63% in T790M, and in 63–100% in activating EGFR mutations. In this study, we have newly developed three types of assay which have enough sensitivity to detect cfDNA. We also detected T790M in 44% of patients who failed prior EGFR-TKI treatment, indicating that cfDNA-based assay has clinical relevance for detecting acquired mutations of EGFR.

Life and death of circulating cell-free DNA

Tumor-specific, circulating cell-free DNA in liquid biopsies is a promising source of biomarkers for minimally invasive serial monitoring of treatment responses in cancer management. We will review the current understanding of the origin of circulating cell-free DNA and different forms of DNA release (including various types of cell death and active secretion processes) and clearance routes. The dynamics of extracellular DNA in blood during therapy and the role of circulating DNA in pathophysiological processes (tumor-associated inflammation, NETosis, and pre-metastatic niche development) provide insights into the mechanisms that contribute to tumor development and metastases formation. Better knowledge of circulating tumor-specific cell-free DNA could facilitate the development of new therapeutic and diagnostic options for cancer management.

The interplay of circulating tumor DNA and chromatin modification, therapeutic resistance, and metastasis

Peripheral circulating free DNA (cfDNA) is DNA that is detected in plasma or serum fluid with a cell-free status. For cancer patients, cfDNA not only originates from apoptotic cells but also from necrotic tumor cells and disseminated tumor cells that have escaped into the blood during epithelial-mesenchymal transition. Additionally, cfDNA derived from tumors, also known as circulating tumor DNA (ctDNA), carries tumor-associated genetic and epigenetic changes in cancer patients, which makes ctDNA a potential biomarker for the early diagnosis of tumors, monitory and therapeutic evaluations, and prognostic assessments, among others, for various kinds of cancer. Moreover, analyses of cfDNA chromatin modifications can reflect the heterogeneity of tumors and have potential for predicting tumor drug resistance.

Combining 18F-FDG PET/CT-Based Metabolically Active Tumor Volume and Circulating Cell-Free DNA Significantly Improves Outcome Prediction in Chemorefractory Metastatic Colorectal Cancer

Baseline whole-body metabolically active tumor volume (WB-MATV) measured by ¹⁸F-FDG PET/CT and circulating cell-free DNA (cfDNA) have been separately validated as predictors of overall and progression-free survival (OS/PFS) in chemorefractory metastatic colorectal cancer (mCRC) patients. This study assessed the correlation between WB-MATV and cfDNA, evaluating the added prognostic value of these in combination, along with clinical parameters. Methods: Of 141 mCRC patients included in a prospective multicenter trial, 132 were evaluable for OS/PFS. cfDNA was extracted from 3 mL of plasma and quantified using a fluorometer. All target lesions were delineated on ¹⁸F-FDG PET/CT, and their metabolic volumes were summed to obtain the WB-MATV. Results: Baseline WB-MATV and cfDNA were strongly correlated (r = 0.70; P < 0.001) but showed discordance in 23 of 132 (17%) patients. A multivariate analysis identified 3 independent negative predictors of PFS (high cfDNA, short time since diagnosis, and body mass index < 30) and 5 of OS (high cfDNA, high WB-MATV, body mass index < 30, poor performance status, and short time since diagnosis). Combining WB-MATV and cfDNA increased the overall prognostic value and allowed identification of a subgroup of patients with low cfDNA and high WB-MATV who were associated with intermediate survival (median OS of 8.1 for low-cfDNA/high-MATV patients vs. 12.7 mo for low-cfDNA/low-MATV patients; hazard ratio, 2.04; P = 0.02). Conclusion: This study confirms the added prognostic value of combined circulating cfDNA and PET-based WB-MATV in chemorefractory mCRC patients. The combination of these two biomarkers should provide a firm basis for risk stratification, both in clinical practice and in research trials.

Circulating Tumor Cell Detection in Lung Cancer: But to What End?

The understanding of the natural history and biology of lung cancer has been enhanced by studies into circulating tumor cells (CTCs). Fundamental and translational research, as well as clinical trials in the characterization and behavior of these cells, have constantly contributed to improving understanding within the domain of thoracic oncology. However, the use of these CTCs as prognostic and predictive biomarkers has not been adopted to the same extent as circulating free DNA (cf-DNA) in plasma, in the daily practice of thoracic oncologists. However, recent technological advances have firmly put the detection and characterization of CTCs in thoracic oncology back on the agenda, and have opened up perspectives for their routine clinical use. This review discusses the major advances of using CTCs in the domain of thoracic oncology, as well as the envisaged short- and long-term prospects.

Epithelial‑mesenchymal transition phenotype of circulating tumor cells is associated with distant metastasis in patients with NSCLC

Circulating tumor cells (CTCs) are closely associated with cancer metastasis in preclinical models and patients with cancer. However, to the best of the authors knowledge, it remains unknown which type of CTCs may serve the key role in cancer metastasis. The present study investigated the association between the epithelial‑mesenchymal transition (EMT) phenotype of CTCs from the peripheral blood and distant metastasis in patients with non‑small cell lung cancer (NSCLC). Expression of EMT markers in CTCs from a cohort of patients was detected using Canpatrol™ CTC assays. A total of 110 patients (85 patients with NSCLC and 25 patients with benign diseases) were recruited. Among the 110 patients, 88 (80.0%) were characterized as CTC positive with EMT markers. Receiver operating characteristic curves revealed that E+/M+ CTCs exhibited the highest area under the curve (AUC) value of 0.876 [95% confidence interval (CI), 0.805‑0.948; P<0.001) in distinguishing between patients with NSCLC and benign pulmonary diseases, and M+ CTCs had the highest AUC value of 0.723 (95% CI, 0.612‑0.833; P<0.001) in differentiating patients with NSCLC with distant metastasis from those with non‑distant metastasis. The results indicate the potential predictive value of distant metastasis of the EMT phenotype of CTCs in the peripheral blood of patients with NSCLC.

Clinical utility of tumor genomic profiling in patients with high plasma circulating tumor DNA burden or metabolically active tumors

BACKGROUND

This retrospective study was undertaken to determine if the plasma circulating tumor DNA (ctDNA) level and tumor biological features in patients with advanced solid tumors affected the detection of genomic alterations (GAs) by a plasma ctDNA assay.

METHOD

Cell-free DNA (cfDNA) extracted from frozen plasma (N = 35) or fresh whole blood (N = 90) samples were subjected to a 62-gene hybrid capture-based next-generation sequencing assay FoundationACT. Concordance was analyzed for 51 matched FoundationACT and FoundationOne (tissue) cases. The maximum somatic allele frequency (MSAF) was used to estimate the amount of tumor fraction of cfDNA in each sample. The detection of GAs was correlated with the amount of cfDNA, MSAF, total tumor anatomic burden (dimensional sum), and total tumor metabolic burden (SUVmax sum) of the largest ten tumor lesions on PET/CT scans.

RESULTS

FoundationACT detected GAs in 69 of 81 (85%) cases with MSAF > 0. Forty-two of 51 (82%) cases had ≥ 1 concordance GAs matched with FoundationOne, and 22 (52%) matched to the National Comprehensive Cancer Network (NCCN)-recommended molecular targets. FoundationACT also detected 8 unique molecular targets, which changed the therapy in 7 (88%) patients who did not have tumor rebiopsy or sufficient tumor DNA for genomic profiling assay. In all samples (N = 81), GAs were detected in plasma cfDNA from cancer patients with high MSAF quantity (P = 0.0006) or high tumor metabolic burden (P = 0.0006) regardless of cfDNA quantity (P = 0.2362).

CONCLUSION

This study supports the utility of using plasma-based genomic assays in cancer patients with high plasma MSAF level or high tumor metabolic burden.

Tumor fraction in cell-free DNA as a biomarker in prostate cancer

BACKGROUND

Tumor content in circulating cell-free DNA (cfDNA) is a promising biomarker, but longitudinal dynamics of tumor-derived and non-tumor-derived cfDNA through multiple courses of therapy have not been well described.

METHODS

CfDNA from 663 plasma samples from 140 patients with castration-resistant prostate cancer (CRPC) was subject to sparse whole genome sequencing. Tumor fraction (TFx) estimated using the computational tool ichorCNA was correlated with clinical features and responses to therapy.

RESULTS

TFx associated with the number of bone metastases (median TFx = 0.014 with no bone metastases, 0.047 with 1-3 bone metastases, 0.190 for 4+ bone metastases; P < 0.0001) and with visceral metastases (P < 0.0001). In multivariable analysis, TFx remained associated with metastasis location (P = 0.042); TFx was positively correlated with alkaline phosphatase (P = 0.0227) and negatively correlated with hemoglobin (Hgb) (P < 0.001), but it was not correlated with prostate specific antigen (PSA) (P = 0.75). Tumor-derived and non-tumor-derived cfDNA track together and do not increase with generalized tissue damage from chemotherapy or radiation at the time scales examined. All new treatments that led to ≥30% PSA decline at 6 weeks were associated with TFx decline when baseline TFx was >7%; however, TFx in patients being subsequently maintained on secondary hormonal therapy was quite dynamic.

CONCLUSION

TFx correlates with clinical features associated with overall survival in CRPC, and TFx decline is a promising biomarker for initial therapeutic response.

TRIAL REGISTRATION

Dana-Farber/Harvard Cancer Center (DF/HCC) protocol no. 18-135.

FUNDING

Wong Family Award in Translational Oncology, Dana Farber Cancer Institute Medical Oncology grant, Gerstner Family Foundation, Janssen Pharmaceuticals Inc., and Koch Institute Support (core) grant P30-CA14051 from the National Cancer Institute (NCI).

Circulating tumor DNA detectable in early- and late-stage colorectal cancer patients

Characterization, diagnosis, and treatment of colorectal cancers (CRC) is difficult due to limited biopsy information, impracticality of repeated biopsies, and cancer biomarker fallibility. Circulating tumor DNA (ctDNA) has recently been investigated as a non-invasive way to gain representative gene mutations in tumors, in addition to monitoring disease progression and response to treatment. We analyzed ctDNA mutations and concentrations in 47 early- and late-stage CRC patients using a targetted sequencing approach using a panel that covers 50 cancer-related genes. ctDNA mutations in 37 genes were identified in 93.6% of the patients (n=47). The results showed that TP53, PIK3CA, APC, and EGFR were the most frequently mutated genes. Stage IV patients had significantly higher ctDNA concentration than Stage I patients, and increased ctDNA concentration correlated with increased tumor size. Additionally, ctDNA detection was found to be a greater predictor of disease when compared with five known commonly used tumor biomarkers. The present study supports the use of ctDNA as a liquid biopsy to gain clinical tumor information that may facilitate early diagnosis and treatment and improve CRC patient prognosis.

In Vitro Cell-free DNA Quantification: A Novel Method to Accurately Quantify Cell Survival after Irradiation

Circulating tumor DNA (ctDNA) analysis has been shown to aid in both the detection of cancer and evaluation of somatic mutations in tumors. CtDNA concentration in plasma increases in proportion to tumor volume and/or metabolic activity and growth; however, this principle has yet to be applied to cell culture. We hypothesized that cell line-specific cell-free DNA (cfDNA) can be used to measure cell viability and cell survival in cell culture. Clonogenic assays on non-small cell lung cancer (NSCLC) cell lines H322, A549 and H322 were exposed to radiation doses of 0, 4 and 8 Gy. Prior to colony fixation and counting, cfDNA was extracted and quantified from cell culture media. The correlation between cell line-specific cfDNA and number of colonies grown on culture plates was examined. An H1299:A549 coculture model was used to evaluate the differential release of cell line-specific cfDNA. The results of this work indicate a strong correlation between CfDNA quantification from cell culture media and clonogenic survival at all radiation doses and in all cell lines tested (R² range = 0.77-0.99). Cell survival curves derived from cfDNA were virtually indistinguishable from matched traditional clonogenic survival data ( P > 0.05; no significant difference exists between clonogenic curves). CfDNA quantification also accurately estimates colony count in a two-cell-line coculture model. In conclusion, cell-free DNA quantification from cell culture media can be used to measure cell survival, and appears suitable for development in a high-throughput clonogenic assay and radiosensitizer screening platform.

Proof of concept: prognostic value of the plasmatic concentration of circulating cell free DNA in desmoid tumors using ddPCR

Since desmoid tumors (DT) exhibit an unpredictable clinical course, with stabilization and/or spontaneous regression, an initial "wait-and-see" policy is the new standard of care-thus, the actual challenge is to identify early factors of progression. We present a method of detection of CTNNB1 mutations using a targeted digital droplet PCR (ddPCR) on cell-free DNA (cfDNA) extracted from blood samples of 31 DT patients. Furthermore, we analyzed the correlation between DT evolution and plasmatic concentration of total and mutated cfDNA at the time of diagnosis. Circulating copies of CTNNB1 mutants (ctDNA) were detected in the plasma of 6 patients (33%) but their concentration was not correlated with evolution of the tumor. Concentration of total cfDNA was higher in the plasma of patients with progressive desmoids (p = 0,0009). Using a threshold <900 copies/mL of plasma to detect indolent desmoid and a threshold >1375, it was possible to predict desmoid evolution for 65% of patients by measuring the quantity of circulating DNA in their plasma as early as the time of diagnosis. Albeit showing that the detection of CTNNB1 mutants is possible in the plasma of patients harboring a desmoid tumor, the results of this preliminary study raise the hypothesis that most of the circulating DNA detected in their plasma is derived from non-neoplastic cells, most likely normal neighboring tissues being actively invaded. Our results open the perspective of using cfDNA as a biomarker to predict prognosis at the time of diagnosis and assess tumor dynamics to optimize the treatment strategy.