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The application of genomic profiling assays using plasma circulating tumor DNA (ctDNA) is rapidly evolving in the management of patients with advanced solid tumors. Diverse plasma ctDNA technologies in both commercial and academic laboratories are in routine or emerging use. The increasing integration of such testing to inform treatment decision making by oncology clinicians has complexities and challenges but holds significant potential to substantially improve patient outcomes. In this review, the authors discuss the current role of plasma ctDNA assays in oncology care and provide an overview of ongoing research that may inform real‐world clinical applications in the near future.

Plasma cell‐free DNA (cfDNA) analysis to track estrogen receptor 1 (ESR1) mutations is highly beneficial for the identification of tumor molecular dynamics and the improvement of personalized treatments for patients with metastatic breast cancer (MBC). Plasma‐cfDNA is, up to now, the most frequent liquid biopsy analyte used to evaluate ESR1 mutational status. Circulating tumor cell (CTC) enumeration and molecular characterization analysis provides important clinical information in patients with MBC. In this study, we investigated whether analysis of CTCs and circulating tumor DNA (ctDNA) provide similar or complementary information for the analysis of ESR1 mutations. We analyzed both plasma‐cfDNA (n = 90) and paired CTC‐derived genomic DNA (gDNA; n = 42) from 90 MBC patients for seven ESR1 mutations. Eight out of 90 (8.9%) plasma‐cfDNA samples tested using the ddPLEX Mutation Detection Assay (Bio‐Rad, Hercules, CA, USA), were found positive for one ESR1 mutation, whereas 11/42 (26.2%) CTC‐derived gDNA samples were found positive for at least one ESR1 mutation. Direct comparison of paired samples (n = 42) revealed that the ESR1 mutation rate was higher in CTC‐derived gDNA (11/42, 26.2%) than in plasma‐cfDNA (6/42, 14.3%) samples. Our results, using this highly sensitive ddPLEX assay, reveal a higher percentage of mutations in CTC‐derived gDNAs than in paired ctDNA in patients with MBC. CTC‐derived gDNA analysis should be further evaluated as an important and complementary tool to ctDNA for identifying patients with ESR1 mutations and for guiding individualized therapy. Analysis of ESR1 mutations in plasma cell‐free DNA (cfDNA) is highly important for the selection of treatment in patients with breast cancer. Using multiplex‐ddPCR and identical blood draws, we investigated whether circulating tumor cells (CTCs) and cfDNA provide similar or complementary information for ESR1 mutations. Our results indicate a higher detection rate for ESR1 mutations in CTCs than in paired cfDNA.

Purpose The enucleation rate for retinoblastoma has dropped from over 95% to under 10% in the past 10 years as a result of improvements in therapy. This reduces access to tumor tissue for molecular profiling, especially in unilateral retinoblastoma, and hinders the confirmation of somatic RB1 mutations necessary for genetic counseling. Plasma cell‐free DNA (cfDNA) has provided a platform for noninvasive molecular profiling in cancer, but its applicability in low tumor burden retinoblastoma has not been shown. We analyzed cfDNA collected from 10 patients with available tumor tissue to determine whether sufficient tumorderived cfDNA is shed in plasma from retinoblastoma tumors to enable noninvasive RB1 mutation detection. Methods Tumor tissue was collected from eye enucleations in 10 patients diagnosed with advanced intra‐ocular unilateral retinoblastoma, three of which went on to develop metastatic disease. Tumor RB1 mutation status was determined using an FDA‐cleared tumor sequencing assay, MSK‐IMPACT. Plasma samples were collected before eye enucleation and analyzed with a customized panel targeting all exons of RB1. Results Tumor‐guided genotyping detected 10 of the 13 expected somatic RB1 mutations in plasma cfDNA in 8 of 10 patients (average variant allele frequency 3.78%). Without referring to RB1 status in the tumor, de novo mutation calling identified 7 of the 13 expected RB1 mutations (in 6 of 10 patients) with high confidence. Conclusion Plasma cfDNA can detect somatic RB1 mutations in patients with unilateral retinoblastoma. Since intraocular biopsies are avoided in these patients because of concern about spreading tumor, cfDNA can potentially offer a noninvasive platform to guide clinical decisions about treatment, follow‐up schemes, and risk of metastasis. The improved treatment strategy for retinoblastoma has led to increased ocular survival and less availability of tissue for molecular profiling. This study demonstrates that the identification of RB1 mutations by plasma cell‐free DNA and its absence in the buffy coat can conclusively determine whether or not the patient has a somatic RB1 mutation driving the disease.

To evaluate plasma cell‐free DNA (cfDNA) as a promising biomarker for neuroblastoma (NB) tumor burden. Seventy‐nine eligible patients with newly diagnosed NB were recruited from Beijing Children's Hospital between April 2016 and April 2017. Additionally, from September 2011 to June 2017, 79 patients with stable NB were evaluated with a median follow‐up time of 21 months. Approximately 2 mL of peripheral blood was drawn upon enrollment, and plasma cfDNA levels were measured via quantitative polymerase chain reaction (qPCR). Total cfDNA analysis was performed using the long interspersed nuclear element 1 (LINE‐1) 79 bp fragment, and DNA integrity was calculated by the ratio of the LINE‐1 300 bp fragment to the LINE‐1 79 bp fragment. A total of 79 NB patients with a median age of 36 months comprised the group of newly diagnosed NB patients. The main primary tumor site was the retroperitoneal and adrenal region (81%). Three or more metastatic sites were found in 17.7% of patients. Stable NB patients older than 18 months comprised 98.7% of the stable NB patients. Neuron‐specific enolase (NSE), lactate dehydrogenase (LDH), and cfDNA levels were dramatically increased in the newly diagnosed NB patients and significantly different from those in the stable NB patients. Moreover, the concentration of cfDNA was much higher in patients with larger tumors. By analyzing the area under the receiver operator characteristic (ROC) curve (AUC), the areas of total cfDNA, NSE, and LDH levels were 0.953, 0.929, and 0.906, respectively. The sensitivity and specificity data clarified that the level of circulating cfDNA in plasma can be considered as a reliable biomarker for describing tumor load in NB. The plasma cfDNA concentration was as good as the levels of LDH and NSE to discriminate the tumor burden in children with NB. The concentration of plasma cell‐free DNA is significantly upregulated in newly diagnosed NB patients compared with stable NB. Consistent with the pattern of serum tumor markers in NB, plasma cell‐free DNA is significantly higher in high‐risk NB than low‐risk NB. Plasma cell‐free DNA can be served to detect minimal residual disease of NB and closely correlates to tumor burden.

Purpose Plasma cell-free DNA (cfDNA) variant analysis is commonly used in many cancer subtypes. Cell-free methylated DNA immunoprecipitation sequencing (cfMeDIP-seq) has shown high sensitivity for cancer detection. To date, studies have not compared the sensitivity of both methods in a single cancer subtype. Methods cfDNA from 40 metastatic RCC (mRCC) patients was subjected to targeted panel variant analysis. For 34 of 40, cfMeDIP-seq was also performed. A separate cohort of 38 mRCC patients were used in cfMeDIP-seq analysis to train an RCC classifier. Results cfDNA variant analysis detected 21 candidate variants in 11 of 40 mRCC patients (28%), after exclusion of 2 germline variants and 6 variants reflecting clonal hematopoiesis. Among 23 patients with parallel tumor sequencing, cfDNA analysis alone identified variants in 9 patients (39%), while cfDNA analysis focused on tumor sequencing variant findings improved the sensitivity to 52%. In 34 mRCC patients undergoing cfMeDIP-seq, cfDNA variant analysis identified variants in 7 (21%), while cfMeDIP-seq detected all mRCC cases (100% sensitivity) with 88% specificity in 34 control subjects. In 5 patients with cfDNA variants and serial samples, variant frequency correlated with response to therapy. Conclusion cfMeDIP-seq is significantly more sensitive for mRCC detection than cfDNA variant analysis. However, cfDNA variant analysis may be useful for monitoring response to therapy.

Circulating cell-free DNA (cfDNA) sequencing offers a minimally invasive approach for profiling tumor genomes, but detecting copy number alterations (CNAs) from cfDNA whole-exome sequencing (WES) remains technically challenging due to noise and guanine–cytosine (GC)-related bias. Building upon our previous study that characterized read count patterns in cfDNA WES data, we developed and evaluated an advanced pipeline for robust CNA detection in patients with advanced non-small cell lung cancer (NSCLC). Read count signals showed strong correlation with GC content, and applying locally estimated scatterplot smoothing (LOESS)-based GC bias correction effectively reduced false positives and improved CNA detection. The resulting cfDNA CNA profiles were reproducible within patients and showed strong concordance with The Cancer Genome Atlas (TCGA) tissue-level patterns for lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). These findings demonstrate that cfDNA WES, when combined with appropriate bias correction, can serve as a practical and minimally invasive alternative for genomic characterization of NSCLC.

Metagenomic next-generation sequencing (mNGS) of plasma cell-free DNA (cfDNA) shows promising application for complicated infections that cannot be resolved by conventional microbiological tests (CMTs). The criteria for cfDNA sequencing are currently in need of agreement and standardization. We performed a retrospective cohort observation of 653 patients who underwent plasma cfDNA mNGS, including 431 with suspected bloodstream infections (BSI) and 222 with other suspected systemic infections. Plasma mNGS and CMTs were performed simultaneously in clinical practice. The diagnostic efficacy of plasma mNGS and CMTs in the diagnosis of blood-borne and other systemic infections was evaluated using receiver operating characteristic (ROC) curves. The sensitivity and specificity of the two methods were analyzed based on the final clinical outcome as the gold standard. The mNGS test showed an overall positive rate of 72.3% (472/653) for detecting microorganisms in plasma cfDNA, with a range of 2 to 6 different microorganisms detected in 171 patient specimens. Patients with positive mNGS results were more immunocompromised and had a higher incidence of severe disease (P<0·05). The sensitivity of mNGS was higher for BSI (93·5%) and other systemic infections (83·6%) compared to CMTs (37·7% and 14·3%, respectively). The mNGS detected DNA from a total of 735 microorganisms, with the number of microbial DNA reads ranging from 3 to 57,969, and a higher number of reads being associated with clinical infections (P<0·05). Of the 472 patients with positive mNGS results, clinical management was positively affected in 203 (43%) cases. Negative mNGS results led to a modified clinical management regimen in 92 patients (14.1%). The study also developed a bacterial and fungal library for plasma mNGS and obtained comparisons of turnaround times and detailed processing procedures for rare pathogens. Our study evaluates the clinical use and analytic approaches of mNGS in predicting bloodstream and local infections in clinical practice. Our results suggest that mNGS has higher positive predictive values (PPVs) for BSI and systemic infections compared to CMTs, and can positively affect clinical management in a significant number of patients. The standardized whole-process management procedure for plasma mNGS developed in this study will ensure improved pre-screening probabilities and yield clinically valuable data.

Background Neoadjuvant chemoimmunotherapy does not benefit all non-small cell lung cancer (NSCLC) patients, and reliable biomarkers are urgently needed. We conducted this prospective phase II trial of neoadjuvant chemoimmunotherapy to explore the role of cell-free DNA (cfDNA) features in pathological response assessment. Methods Totally, 100 patients with stage IIB-IIIB NSCLC were enrolled and treated with neoadjuvant toripalimab plus chemotherapy for at least 2 cycles. Targeted methylation panel sequencing and whole methylome sequencing were conducted on 195 cfDNA samples collected from 60 patients before each treatment cycle (C0, C1) and before surgery (BS), with subsequent calculations of methylation fragment ratio (MFR) and chromosome aneuploid of featured fragment (CAFF) scores, respectively. The correlations between MFR or CAFF and pathological response were evaluated. Results Finally, 83 patients underwent surgery, and 54 (65.1%) patients achieved major pathological response (MPR), including 38 (45.8%) with complete pathological response (pCR). The median MFR and CAFF scores in both the MPR and non-MPR groups significantly decreased after the first cycle, and the MPR group maintained low levels before surgery ( P  < 0.001). According to pre-defined cut-off values, the MFR and CAFF scores were recategorized as low or high status. Patients with low MFR status at BS (74.5% vs. 11.1%, P  < 0.001) or low CAFF status at C1 (73.9% vs. 36.4%, P  = 0.031) and BS (76.2% vs. 38.9%, P  = 0.008) were more likely to achieve MPR than those with high status. Three dynamic patterns were identified: C0 low, C0 high/C1 low, and C0 high/C1 high. These patterns were further divided by BS low or high status, which indicated distinctive MPR rate (C0 low: BS low vs. high 78.9% vs 0%; C0 high/C1 low: BS low vs. high 73.9% vs. 25%; C0 high/C1 high: BS low vs. high 83.3% vs. 0%). An integrative model was constructed by incorporating immune parameters (PD-L1 and CD8 + CD28- T lymphocytes) and cfDNA features (MFR and CAFF) at C1 and BS, achieving an AUC of 0.86 (95% CI 0.80–0.92). Conclusions Dynamic monitoring of cfDNA methylation has potential to predict pathological response of neoadjuvant chemoimmunotherapy in NSCLC. Trial registration RENAISSANCE study, NCT04606303, initiated on October 27, 2020.

Background Children affected by infectious diseases may not always have a detectable infectious etiology. Diagnostic uncertainty can lead to prolonged hospitalizations, inappropriately broad or extended courses of antibiotics, invasive diagnostic procedures, and difficulty predicting the clinical course and outcome. Cell-free plasma next-generation sequencing (cfNGS) can identify viral, bacterial, and fungal infections by detecting pathogen DNA in peripheral blood. This testing modality offers the ability to test for many organisms at once in a shotgun metagenomic approach with a rapid turnaround time. We sought to compare the results of cfNGS to conventional diagnostic test results and describe the impact of cfNGS on clinical care in a diverse pediatric population at a large academic children’s hospital. Methods We performed a retrospective chart review of hospitalized subjects at a tertiary pediatric hospital to determine the diagnostic yield of cfNGS and its impact on clinical care. Results We describe the clinical application of results from 142 cfNGS tests in the management of 110 subjects over an 8-month study period. In comparison to conventional testing as a reference standard, cfNGS was found to have a positive percent agreement of 89.6% and negative percent agreement of 52.3%. Furthermore, 32.4% of cfNGS results were directly applied to make a clinical change in management. Conclusions We demonstrate the clinically utility of cfNGS in the management of acutely ill children. Future studies, both retrospective and prospective, are needed to clarify the optimal indications for testing.

This study aimed to evaluate the clinical performance of plasma cell-free DNA (cfDNA) next-generation sequencing (NGS) for pathogen detection in patients with sepsis. A total of 43 pairs of blood and plasma samples form 33 blood culture-positive patients were used as testing samples in metagenomic NGS (mNGS) and NGS of 16S ribosomal RNA gene amplicons (16S rRNA NGS). The results of routine tests, including microbial culture, complete blood count, and biochemical tests, were collected from electronic medical records. Using blood as an mNGS testing sample, the proportion of host DNA was 99.9%, with only three bacteria and no fungi detected. When using plasma in mNGS, the proportion of host DNA was approximately 97%, with 84 bacteria and two fungi detected. Notably, 16S rRNA NGS detected 15 and 16 bacteria in 43 pairs of blood and plasma samples, respectively. Blood culture detected 49 bacteria (23 gram-negative bacilli and 26 gram-positive cocci) and four fungi, with 14 bacteria considered contaminants by clinical microbiologists. For all blood cultures, plasma cfDNA mNGS detected 78.26% (19/23) gram-negative rods, 17% (2/12) gram-positive cocci, and no fungi. Compared to blood cultures, the sensitivity and specificity of plasma cfDNA mNGS for detecting bacteria and fungi were 62.07% and 57.14%, respectively. Compared to blood, plasma is more suitable for the detection of bloodstream infections using mNGS and is less affected by host DNA. The positive detection rate of plasma cfDNA mNGS for bloodstream infections caused by gram-negative bacteria was higher than that caused by gram-positive cocci.