cfDNA Sequencing Research Articles

Liquid biopsy-based prediction of clinical benefit from immune checkpoint inhibitors in advanced biliary tract cancer.

e16179 Background: Immune checkpoint inhibitors (ICIs) show promising efficacy as first-line therapy for advanced biliary tract cancer (aBTC), but validated predictive biomarkers are lacking. Here, we identified liquid biopsy-based biomarkers and developed a prediction model. Methods: aBTC patients who received ICIs-based combination therapy as the first-line treatment were prospectively enrolled in this study (NCT06074029). Plasma samples were collected before the first and second immunotherapy infusion to perform cell-free DNA (cfDNA) sequencing of 1021 genes. Circulating tumor DNA (ctDNA) concentration was calculated by multiplying the mean variant allele frequency by the cfDNA concentration and ctDNA fold change was calculated by dividing on-treatment ctDNA concentration by the pre-treatment ctDNA concentration. Tumor mutation burden (TMB) was normalized using the cfDNA concentration. In addition, RNA was extracted from peripheral blood mononuclear cells to profile the leukocyte transcriptome using whole transcriptome sequencing, and the relative proportions of immune cells in leukocytes was deconvoluted using CIBERSORT algorithm. Log-rank and univariate Cox regression were used to evaluate the relationship between features and progression-free survival (PFS). Results: 37 patients were enrolled, with 62.2% having intrahepatic cholangiocarcinoma. The median age was 61 years and 54.1% of patients were females. The median PFS was 4.4 months. Variables related to PFS with the log-rank p value smaller than 0.05 (Table) were entered into a multivariate Cox regression using a stepwise approach for final variable selection. As a result, ctDNA fold change, KRAS mutation, and resting memory CD4 T cell level were used to construct a COX regression model to predict clinical benefit from ICIs. The model predicting 6-month PFS demonstrated an AUC of 0.909 (95% CI, 0.795-1.024). Internal validation, performed through a bootstrap analysis with 100 iterations, yielded an optimism-adjusted AUC estimate of 0.859. Conclusions: Our preliminary results support the excellent performance of this liquid biopsy-based multivariable model to early predict durable benefit from ICIs in aBTC. A large sample size and verifying this model with internal and external data are warranted. Clinical trial information: NCT06074029 . [Table: see text]

High-dose almonertinib in treatment-naïve EGFR-mutated NSCLC with CNS metastases: Efficacy and biomarker analysis.

2007 Background: Central nervous system (CNS) metastases is inevitable for epidermal growth factor receptor (EGFR)mutant non-small cell lung cancer (NSCLC). The pre-specified analysis of the FLAURA and other phase III studies has unveiled encouraging results in patients with CNS metastasis. Nevertheless, the availability of limited biomarkers poses a challenge for the early prediction of clinical effects. Methods: We launched a prospective, open-label, single-arm clinical trial across multiple centers (ACHIEVE). Participants, all diagnosed with EGFR-mutated NSCLC with CNS metastases, received first line treatment with high dose Almonertinib through once-daily oral administration, with each dose being 165 mg. The primary endpoints focused on progression free survival (PFS). Concurrently, we gathered baseline and end-of-first-cycle plasma samples, subjecting them to a comprehensive 520 gene-based sequencing analysis. Results: A total of 63 patients were selected and enrolled between Jul 6,2021 and Aug 31,2022. The median follow-up time, until Nov 30,2023, was 538 days. The confirmed Overall Response Rate (ORR) was 88.9% (56/63), while 42.9% (27/63) of patients progressed, with a median PFS of 17.71 months (11.96-NE). Moreover, a notable 88.9% (56/63) of intracranial lesions achieved either a Complete Response (CR) in 21 cases (33.3%) or a Partial Response (PR) in 35 cases (55.6%). To guide and enhance clinical strategy selection, we conducted a comprehensive biomarker evaluation using cell-free DNA (cfDNA) sequencing. Of the 60 baseline plasmas that passed quality control, 81.7% (46/60) were identified as having at least one somatic mutation (ctDNA+). No significant differences were observed between ctDNA+ and ctDNA- groups in terms of ORR (p = 0.33), intracranial ORR (p = 0.499), PFS (p = 0.363, HR = 1.75), and intracranial PFS (p = 0.562, HR = 1.56). Furthermore, we developed a novel algorithm named MedSR (Median Short cfDNA fragment Ratio) based on cfDNA fragment distribution patterns to quantify ctDNA amount. Notably, higher baseline MedSR values (above the median) predicted significantly poorer PFS (p = 0.001, HR = 0.22) and intracranial PFS (p = 0.067, HR = 0.35), demonstrating superior efficacy compared to traditional cfDNA biomarkers like maxAF. On Cycle 2, those achieving ctDNA clearance in C2D1, regardless of their ctDNA status on baseline, exhibited significantly improved PFS (p < 0.001, HR = 4.63) and intracranial PFS (p = 0.001, HR = 5.71). Conclusions: High dose Almonertinib exhibited promising efficacy and maintained tolerable safety as a first-line therapy in EGFR-mutated NSCLC with CNS metastases. The novel MedSR score demonstrated potential value in predicting the efficacy of TKI treatment. Clinical trial information: NCT04808752 .

High-sensitive multi-cancers early detection for 8 cancer types by cell-free DNA targeted methylation sequencing: A retrospective cohort study.

3043 Background: Early screening effectively reduces mortality associated with cancer. Currently, most cancers lack effective screening paradigms. We developed blood-based multi-cancers early detection (MCED) and cancer signal origin (CSO) approaches in 8 types of cancers including esophageal, stomach, colorectal, pancreatic, liver, lung, breast and ovarian cancer. Methods: DNA methylation data generated based on GM-seq by public and internal whole genome methylation data. Based on these data, a panel of 155,362 CpG sites spanning the 2.0M genome was constructed and validated. We enrolled a case-control cohort of 746 participants (522 cancers, 224 non-cancers) for MCED model development. cell-free DNA (cfDNA) was isolated from 10 ml peripheral blood from each participant. A targeted methylation sequencing of cfDNA in plasma baseline was established using 224 non-cancers blood samples for 8 types of cancers. Finally, we developed a MCED model named AMBER for distinguishing cancer from non-cancer individuals. Results: DNA methylation data were from 8 types of cancers (cancer tissues: n=812, adjacent/normal tissues: n=416, cancer peripheral bloods: n=624, normal peripheral bloods: n=503) in internal and Infinium Human Methylation 450K array (cancer tissues: n=5000+, adjacent/normal tissues: n=1000+) from public data. 224 non-cancer individuals (healthy: n=196, cancer benign: n=28, male: female, 54.3%: 45.7%) were collected as control, while 522 cancer patients (male: female, 50.0%: 50.0%, stage I 26.9%, II 21.1%) from esophageal (n=56, stage I: n=10), stomach (n=47, stage I: n=11), colorectal (n=72, stage I: n=16), pancreatic (n=64, stage I: n=16), liver (n=69, stage I: n=22), lung (n=103, stage I: n=46), breast (n=41) and ovarian cancer (n=70, stage I: n=17). AMBER showed 99.1% specificity and total sensitivity 77.2% (95% confidence interval (CI): 73.4% to 80.7%). Of them, 56.8% (95% CI: 48.2% to 65.2%) of all stage I cases were detected, 70.6% (95% CI: 61.2% to 79.0%) for stage II, 84.5% (95% CI: 77.6% to 89.9%) for stage III, and 96.7% (95% CI: 91.8% to 99.1%) for stage IV. Strikingly, for stage I cancers, the sensitivity of esophageal, stomach, colorectal, pancreatic, liver, lung and ovarian cancer were 80.0%, 63.6%, 43.8%, 62.5%, 86.4%, 30.4% and 82.4% respectively. The sensitivity of esophageal, stomach, colorectal, pancreatic, liver, lung, breast and ovarian cancer reached 91.1%, 76.6%, 75.0%, 78.1%, 94.2%, 55.3%, 65.9% and 90.0%. For CSO model, the accuracy of TPO1 and TPO2 was 78.9% (95% CI: 74.6% to 82.8%) and 89.1% (95% CI: 85.6% to 92.0%). Conclusions: Our MCED tests demonstrated superior performance in detecting 8 types of cancers, especially early cancer screening, by utilizing cfDNA methylation information. It suggests the model can complement lack of multi-cancers early detection.

Systematic biases in reference-based plasma cell-free DNA fragmentomic profiling

Plasma cell-free DNA (cfDNA) fragmentation patterns are emerging directions in cancer liquid biopsy with high translational significance. Conventionally, the cfDNA sequencing reads are aligned to a reference genome to extract their fragmentomic features. In this study, through cfDNA fragmentomics profiling using different reference genomes on the same datasets in parallel, we report systematic biases in such conventional reference-based approaches. The biases in cfDNA fragmentomic features vary among races in a sample-dependent manner and therefore might adversely affect the performances of cancer diagnosis assays across multiple clinical centers. In addition, to circumvent the analytical biases, we develop Freefly, a reference-free approach for cfDNA fragmentomics profiling. Freefly runs ∼60-fold faster than the conventional reference-based approach while generating highly consistent results. Moreover, cfDNA fragmentomic features reported by Freefly can be directly used for cancer diagnosis. Hence, Freefly possesses translational merit toward the rapid and unbiased measurement of cfDNA fragmentomics.

Effects of blood-processing protocols on cell-free DNA fragmentomics in plasma: Comparisons of one- and two-step centrifugations

BackgroundCell-free DNA (cfDNA) fragmentomic characteristics are promising analytes with abundant physiological signals for non-invasive disease diagnosis and monitoring. Previous studies on plasma cfDNA fragmentomics commonly employed a two-step centrifugation process for removing cell debris, involving a low-speed centrifugation followed by a high-speed centrifugation. However, the effects of centrifugation conditions on the analysis of cfDNA fragmentome remain uncertain. MethodsWe collected blood samples from 10 healthy individuals and divided each sample into two aliquots for plasma preparation with one- and two-step centrifugation processes. We performed whole genome sequencing (WGS) of the plasma cfDNA in the two groups and comprehensively compared the cfDNA fragmentomic features. Additionally, we reanalyzed the fragmentomic features of cfDNA from 16 healthy individuals and 16 COVID-19 patients, processed through one- and two-step centrifugation in our previous study, to investigate the impact of centrifugation on disease signals. ResultsOur results showed that there were no significant differences observed in the characteristics of nuclear cfDNA, including size, motif diversity score (MDS) of end motifs, and genome distribution, between plasma samples treated with one- and two-step centrifugation. The cfDNA size shortening in COVID-19 patients was observed in plasma samples with one- and two-step centrifugation methods. However, we observed a significantly higher relative abundance and longer size of cell-free mitochondrial DNA (mtDNA) in the one-step samples compared to the two-step samples. This difference in mtDNA caused by the one- and two-step centrifugation methods surpasses the pathological difference between COVID-19 patients and healthy individuals. ConclusionsOur findings indicate that one-step low-speed centrifugation is a simple and potentially suitable method for analyzing nuclear cfDNA fragmentation characteristics. These results offer valuable guidance for cfDNA research in various clinical scenarios.

Abstract PO5-14-05: Circulating tumor DNA fraction correlates with residual cancer burden post-neoadjuvant chemotherapy in triple negative breast cancer patients

Abstract Background: Pathologic response after preoperative/neoadjuvant chemotherapy is a continuum that can range from no residual cancer to extensive disease. Viable cancers can shed tumor DNA into the blood and we hypothesized that plasma ctDNA levels can reflect pathologic response as continuum. Patients and methods: Post-neoadjuvant plasma samples were obtained after completion of chemotherapy but before surgery from patients with stage I to III TNBC who received treatment with durvalumab concurrent with weekly nab-paclitaxel followed by dose dense doxorubicin/cyclophosphamide in a single arm neoadjuvant clinical trial (NCT02489448). Up to 3 mL of blood was collected into EDTA- and heparin- containing vacutainer tubes, and plasma cfDNA was extracted and twice purified in the lab at Predicine Inc. Pathologic response was quantified on a continuous scale using the Residual Cancer Burden (RCB) score, and also categorized as RCB-0 (complete pathologic response, n=21), -I (minimal residual cancer, n=7), -II (moderate residual cancer, n=13), and -III (extensive residual cancer, n=3). Median follow-up was 35 months (range 25-70 months). Tumor whole exome sequencing (WES) data was previously generated using HiSeq 4000 at the Yale Center for Genome Analysis (dbGaP: PRJNA558949). A personalized MRD panel of up to 60 personalized variants per patient was designed based on the tumor WES data, and ultra-deep next-generation sequencing (100,000X) of plasma cfDNA was performed using the PredicineBEACON assay for MRD detection by Predicine. CtDNA positivity (MRD) was defined as a weighted score equivalent to 2 or more tumor variants detected in the plasma. cfDNA tumor fraction was measured based on mutant allele fraction of observed variants. Adjusted tumor fraction could be confidently measured for 37 out of 44 patients that had enough confidently called personalized ctDNA variants. We compared tumor fraction versus RCB score as continuous variables, and also compared tumor fraction between RCB categories as ordinal variables. Invasive disease-free survival was examined by Kaplan-Meier analysis. Bioinformatic data analysis was performed using Graphpad Prism and R. Results: 44 of 48 plasma samples yielded successful cfDNA generation and sequencing. Six patients (13.6%) were MRD positive. Among these 6 cases, 3 had RCB-0 response (14.3% of RCB 0 cases), 1 had RCB II response (7.7% of RCB II cases), and 2 had RCB III response (66.7% of RCB III cases). The median cfDNA tumor fraction of patients with pathological complete response to treatment (pCR) was significantly lower than patients with residual disease (RD) (0.06% vs. 0.3%, p=0.02). There was a positive correlation between RCB scores and tumor fraction (r= 0.45, Spearman). Tumor fraction was more strongly correlated with later recurrence than a binary ctDNA positivity call. Tumor fraction was significantly higher in patients that later experienced local or metastatic recurrence (n=8) compared to those with no evidence of disease (n=29) (Wilcoxon test, p=0.02). Both ctDNA positive RCB III cases had metastatic recurrence while the remaining 4 ctDNA positive cases currently remain recurrence-free. Mutational genomic landscape of both tumor WES and plasma ctDNA samples identified hotspot mutations in 19 cancer-associated genes. Novel hot-spot mutations were observed in the plasma of two patients following treatment. TP53 mutations were highly prevalent in tissue and plasma, however no significant association of mutation of any gene with treatment response was detected. Conclusions: PredicineBeacon MRD assay was successfully performed on 3 mL plasma samples collected using from EDTA and heparin-containing tubes. Tumor fraction correlated with residual disease, RCB score and disease recurrence. Citation Format: Naing Lin Shan, Billie Gould, Kim Blenman, Julia Foldi, Pan Du, Frank Zhang, Myles Walsh, Lajos Pusztai. Circulating tumor DNA fraction correlates with residual cancer burden post-neoadjuvant chemotherapy in triple negative breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-14-05.

Abstract PO5-04-13: Liquid Biopsy Testing in a Greek Cohort of ER-positive, HER2-negative metastatic breast cancer patients

Abstract AIM Endocrine therapy (ET) represents the first line treatment for patients with ER+, HER2- breast cancer, however disease progression is observed in many cases. PIK3CA and ESR1 are the most encountered mutated genes that have been associated with targeted molecular treatment, as well as with resistance to Endocrine Therapy. Liquid biopsy is a non-invasive procedure, that can provide “real-time” monitoring of disease progression and response to treatment. The aim of this study is to determine the mutation rate of ESR1 and PIK3CA genes in a selected cohort of 200 Greek breast cancer patients, using liquid biopsies and NGS technology. PATIENTS AND METHODS Liquid biopsies were collected from 200 ER-positive, HER2-negative metastatic breast cancer patients who have received at least one previous line of endocrine treatment. cfDNA was extracted using the QIAamp Circulating Nucleic Acid Kit (Qiagen). Library preparation was performed using Oncomine™ Breast cfDNA Research Assay (Thermofisher Scientific) and sequencing was carried out using Ion GeneStudio™ S5 System (Thermofisher Scientific). Ion Torrent Oncomine Knowledgebase Reporter was used in sequence analysis and interpretation of Copy number variations, SNPs, and indels. RESULTS Preliminary data of the first 49 examined samples demonstrated the prevalence of ESR1 and PIK3CA mutations in 20.4% (10/49) and 38.7% (19/49) of the cases respectively. The most frequently mutated codon in the ESR1 gene is the Y537, while in the PIK3CA gene, the H1047 codon is mainly altered. ESR1 and PIK3CA genes were co-mutated in 10.2% of the cases. Mutations in KRAS (6.1%) and TP53 (24%) were also detected. CONCLUSION More than 20% of the ER-positive, HER2-negative breast cancer patients with metastatic disease are eligible for targeted treatment with elacestrant. In addition, the high prevalence of mutations detected in our cohort indicates that liquid biopsy NGS panel testing can be used to monitor treatment response, track the development of resistance, and identify emerging genetic alterations that may guide treatment adjustments or the selection of alternative targeted therapies in breast cancer patients. REFERENCES Demir Cetinkaya B, Biray Avci C. Molecular perspective on targeted therapy in breast cancer: a review of current status. Med Oncol. 2022 Jul 14;39(10):149. doi: 10.1007/s12032-022-01749-1. PMID: 35834030; PMCID: PMC9281252. Liao H, Huang W, Pei W, Li H. Detection of ESR1 Mutations Based on Liquid Biopsy in Estrogen Receptor-Positive Metastatic Breast Cancer: Clinical Impacts and Prospects. Front Oncol. 2020 Dec 15;10:587671. doi: 10.3389/fonc.2020.587671. PMID: 33384956; PMCID: PMC7770162. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-elacestrant-er-positive-her2-negative-esr1-mutated-advanced-or-metastatic-breast-cancer Citation Format: Nikolaos Tsoulos, Angeliki Meintani, Georgios Kapetsis, Chrysiis Chatzigiannidou-Florou, Aikaterini Tsantikidi, Stella Maxouri, Eleni Thanou, Kalliopi Aggelaina, Vasiliki Metaxa-Mariatou, Georgios Tsaousis, Ioannis Natsiopoulos, Vasileios Venizelos, Christos Markopoulos, Flora Zagouri, Eleftherios Kampletsas, Eirini Karyda, Dimitrios Tryfonopoulos, Konstantinos Papazisis, Dimitrios Ziogas, Ilias Athanasiadis, Eirini Papadopoulou, Georgios Nasioulas. Liquid Biopsy Testing in a Greek Cohort of ER-positive, HER2-negative metastatic breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-04-13.

Application value of metagenomic next-generation sequencing in hematological patients with high-risk febrile neutropenia.

Metagenomic next-generation sequencing (mNGS) is a novel non-invasive and comprehensive technique for etiological diagnosis of infectious diseases. However, its practical significance has been seldom reported in the context of hematological patients with high-risk febrile neutropenia, a unique patient group characterized by neutropenia and compromised immune responses. This retrospective study evaluated the results of plasma cfDNA sequencing in 164 hematological patients with high-risk febrile neutropenia. We assessed the diagnostic efficacy and clinical impact of mNGS, comparing it with conventional microbiological tests. mNGS identified 68 different pathogens in 111 patients, whereas conventional methods detected only 17 pathogen types in 36 patients. mNGS exhibited a significantly higher positive detection rate than conventional methods (67.7% vs. 22.0%, P < 0.001). This improvement was consistent across bacterial (30.5% vs. 9.1%), fungal (19.5% vs. 4.3%), and viral (37.2% vs. 9.1%) infections (P < 0.001 for all comparisons). The anti-infective treatment strategies were adjusted for 51.2% (84/164) of the patients based on the mNGS results. mNGS of plasma cfDNA offers substantial promise for the early detection of pathogens and the timely optimization of anti-infective therapies in hematological patients with high-risk febrile neutropenia.

Targeted Linked-Read Sequencing for Direct Haplotype Phasing of Parental GJB2/SLC26A4 Alleles: A Universal and Dependable Noninvasive Prenatal Diagnosis Method Applied to Autosomal Recessive Nonsyndromic Hearing Loss in At-Risk Families

Noninvasive prenatal diagnosis (NIPD) for autosomal recessive nonsyndromic hearing loss (ARNSHL) has been rarely reported until recent years. Additionally, the existing method can not be used for challenging genome loci (eg, copy number variations, deletions, inversions, or gene recombinants) or on families without proband genotype. This study assessed the performance of relative haplotype dosage analysis (RHDO)-based NIPD for identifying fetal genotyping in pregnancies at risk of ARNSHL. Fifty couples carrying pathogenic variants associated with ARNSHL in either GJB2 or SLC26A4 were recruited. The RHDO-based targeted linked-read sequencing combined with whole gene coverage probes was used to genotype the fetal cell-free DNA of 49 families who met the quality control standard. Fetal amniocyte samples were genotyped using invasive prenatal diagnosis (IPD) to assess the performance of NIPD. The NIPD results showed 100% (49/49) concordance with those obtained through IPD. Two families with copy number variation and recombination were also successfully identified. Sufficient specific informative single-nucleotide polymorphisms for haplotyping, as well as the fetal cell-free DNA concentration and sequencing depth, are prerequisites for RHDO-based NIPD. This method has the merits of covering the entire genes of GJB2 and SLC26A4, qualifying for copy number variation and recombination analysis with remarkable sensitivity and specificity. Therefore, it has clinical potential as an alternative to traditional IPD for ARNSHL.

Molecular phenotyping of small cell lung cancer using targeted cfDNA profiling of transcriptional regulatory regions.

We report an approach for cancer phenotyping based on targeted sequencing of cell-free DNA (cfDNA) for small cell lung cancer (SCLC). In SCLC, differential activation of transcription factors (TFs), such as ASCL1, NEUROD1, POU2F3, and REST defines molecular subtypes. We designed a targeted capture panel that identifies chromatin organization signatures at 1535 TF binding sites and 13,240 gene transcription start sites and detects exonic mutations in 842 genes. Sequencing of cfDNA from SCLC patient-derived xenograft models captured TF activity and gene expression and revealed individual highly informative loci. Prediction models of ASCL1 and NEUROD1 activity using informative loci achieved areas under the receiver operating characteristic curve (AUCs) from 0.84 to 0.88 in patients with SCLC. As non-SCLC (NSCLC) often transforms to SCLC following targeted therapy, we applied our framework to distinguish NSCLC from SCLC and achieved an AUC of 0.99. Our approach shows promising utility for SCLC subtyping and transformation monitoring, with potential applicability to diverse tumor types.

Abstract 6562: Comprehensive liquid biopsy: Multi-analyte evaluation of cellular and plasma components of blood in prostate cancer from a single blood collection tube

Abstract Background Liquid biopsy samples offer a non-invasive method for investigating drug targets and biomarkers in solid tumors. In this study, we describe a comprehensive liquid biopsy analysis of whole blood to identify circulating tumor cells (CTCs), large extracellular vesicles and CTC fragments, and CTC-white blood cell hybrids; quantify protein biomarker expression on CTCs; perform targeted mutation profiling on CTCs and cell-free DNA (cfDNA) from plasma; and analyze protein expression on white blood cells (WBCs) from a single 7.5 mL blood sample. This array of tests was applied to blood samples from patients with Stage IV prostate cancer to demonstrate clinical feasibility. Methods A novel dual biomarker CTC assay was developed to measure protein expression of PSMA and ARv7 on CTCs from stage IV prostate cancer patients. Nucleated cells from clinical samples were processed to microscope slides using AccuCyte®, an unbiased, density-based separation method that also allows for plasma collection for downstream analysis. Slides were fixed and stained with antibodies to cytokeratin, EpCAM, and CD45 to detect CTCs and exclude WBCs, and with PSMA and ARv7 to evaluate protein biomarker expression on identified CTCs. The slides were imaged with the CyteFinder® automated immunofluorescence scanning microscope that identifies CTCs for confirmation by trained reviewers and quantitatively measures protein mean fluorescence intensity (MFI) on any cells detected on the slides (CTCs, CTC-WBC hybrids, large extracellular vesicles and CTC fragments and WBCs). Individual CTCs and control pools of WBCs from clinical samples with at least 4 CTCs were picked using CytePicker®, a needle-based system used to isolate single cells. cfDNA was isolated from plasma removed during the AccuCyte® process using a QIAamp MinElute ccfDNA kit. Picked CTCs, WBC pools, and isolated ctDNA were sequenced using the OncoZoom Cancer HotSpot panel from Paragon Genomics. Results Nine progressing Stage IV prostate cancer patient blood samples were stained with a novel PSMA/ARv7 dual biomarker assay. CTCs were identified in all clinical samples (median 4, range 1 - 384). PSMA positivity in clinical samples ranged from 0% to 75%, and ARv7 positivity ranged from 33% to 100%, and. Additional analysis using QuPath was performed to determine PSMA/ARv7 protein expression on WBCs and CTC fragments. ctDNA analysis from 5 individual samples was compared to sequencing results from individual CTCs from the same samples. Conclusions Using a single 7.5 mL blood liquid biopsy, we can measure protein expression on enumerated CTCs and quantify these same protein biomarkers on WBCs and CTC fragments/oncosomes, determine the genetic makeup of the tumor through the sequencing of cfDNA, and monitor genetic mutations in intact CTCs in circulation. Citation Format: Jon Ladd, Erin Bayer, Brock Bartels, Arista Tischner, Rachel Ponting, Eric Kaldjian, Arturo Ramirez. Comprehensive liquid biopsy: Multi-analyte evaluation of cellular and plasma components of blood in prostate cancer from a single blood collection tube [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6562.

Abstract 3448: A novel liquid biopsy lung cancer detection method using a coverage and fragment end motif machine learning analysis

Abstract Lung cancer remains the leading cause of cancer death in the United States. One reason for this high mortality is that &amp;gt;40% of cases are diagnosed at a late stage, where the 5-year survival rate is low. Liquid biopsy molecular testing has transformed lung cancer care through the identification of driver mutations when tissue is inaccessible. It also has promise as a tool in early detection and diagnosis, thereby reducing mortality. The existing paradigm for lung cancer screening and diagnosis includes low dose CT (LDCT) scans and tissue biopsy. LDCT scans yield a visualization of lung abnormalities. However, many of these abnormalities are difficult to characterize and next steps are often unclear to physicians. One option is to continue to monitor the patient, which may risk a delay in cancer treatment. Up to 15% of all individuals who are put on a monitoring regime will ultimately be diagnosed with lung cancer. A second option is to biopsy the nodule, which risks unnecessary invasive procedures and expenses to patients. 42-62% of indeterminate nodules detected by LDCT are found to be benign after biopsy. Furthermore, 15% of transthoracic needle biopsies result in complications. Genece Health aims to decrease uncertainty in cancer diagnosis and improve patient outcomes through a minimally invasive liquid biopsy assay that detects the presence of lung cancer. The technology utilizes a proprietary algorithm that leverages machine learning models to detect lung cancer signals in low-pass whole genome sequencing (LP-WGS) of patient cfDNA isolated from plasma. To establish assay performance, 50 clinical lung cancer samples from a commercial biobank, and 100 presumed normal samples were collected in Streck cfDNA BCT Devices. Following cfDNA extraction from plasma, LP-WGS was performed. Sequencing data was then processed to generate fragment end-motif and size (FEMS) and fragment coverage data that was input into Genece Health’s proprietary machine learning classifier to generate a final cancer prediction score. In addition, a limit of detection was determined using three late-stage lung cancer samples, with tumor fractions estimated using whole exome sequencing and ichorCNA scores. Our results show &amp;gt;80% specificity, &amp;gt;90% sensitivity, and a limit of detection of &amp;lt;1% tumor fraction. Through this testing, we demonstrate the assay’s ability to detect lung cancer across various lung cancer stages, including early stage disease, and histologies. Genece has developed a highly sensitive and specific lung cancer detection liquid biopsy assay. We present this assay as a cost-effective approach to discriminate between benign and malignant nodules identified by LDCT. In addition, this assay has the potential to be applied across the cancer care continuum. For example, future work will involve characterizing the assay’s ability to be applied in early cancer screening. Citation Format: Bryan Leatham, Michael Salmans, Molly Smith, Mengchi Wang, Andrew Carson, Kristin Fathe, Byung In Lee. A novel liquid biopsy lung cancer detection method using a coverage and fragment end motif machine learning analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3448.

Abstract 967: Clinical applicability of targeted panel sequencing in liquid biopsies for disease diagnosis and monitoring of patients with pediatric solid tumors

Abstract Liquid biopsy assays based on sequence analysis of cell-free DNA (cfDNA) have the potential to transform patient care. We recently validated a liquid biopsy platform, LBSeq4Kids, for patients with retinoblastoma, brain tumors and solid tumors using low pass whole genome sequencing (LP-WGS) of cfDNA from aqueous humor (AH), cerebrospinal fluid (CSF), and plasma (PL) to detect Copy Number Alterations (CNAs) in circulating tumor DNA (ctDNA). Herein, we present phase 2, a high-depth comprehensive Next-Generation Sequencing (NGS) panel using cfDNA that allows us to detect SNV’s, indels and gene fusions in clinically relevant genes for pediatric solid and brain tumors. Seventy-four cfDNA specimens have been analyzed to date, using plasma from 43 patients with solid tumors, CSF from 25 patients with brain tumors and AH from six patients with ocular tumors including retinoblastoma. cfDNA was extracted at diagnosis, during therapy, at remission and/or relapse. Sequencing libraries were constructed with the xGen Prism DNA Library Prep Kit using 5ng of cfDNA. For the detection of recurrent mutations and fusions we designed a custom panel using a hybridization-based capture method (Twist Bioscience) that included full coverage of the exons of 136 genes harboring recurrent mutations and selected introns for five genes with recurrent rearrangement breakpoints including BRAF, EWSR1, SYT, FOXO1 and NTRK1. Hybridized libraries were paired-end sequenced (Illumina NextSeq 500) at an average 1000x collapsed coverage. Mutations identified in cfDNA were compared with those in the primary or metastatic tumors profiled with our OncoKids® NGS panel. A total of 35/43 (81%) plasma specimens were positive for either an SNV, deletion or fusion with the most common events being a somatic missense variant in TP53 (13/35, 37%) or translocation involving EWSR1 (9/35, 26%). A total of 16/25 (64%) CSF specimens were positive for SNVs and fusions, most often involving KIAA1549::BRAF (7/25, 28%) in low grade gliomas. A germline variant in RB1 was detectable in two AH specimens from the left and right eye of a patient with bilateral retinoblastoma while plasma from a patient with metastatic retinoblastoma demonstrated clinically relevant variants in RB1 and DICER1. Serial cfDNA profiling revealed a clinically reported TP53 c.746G&amp;gt;C missense variant in the plasma of a patient with osteosarcoma at multiple timepoints through the disease course, with evidence for relapse prior to standard imaging. These data suggest that clinical implementation of a second version of LBSeq4Kids that combines CNA and mutation analysis allows for diagnosis, residual disease detection and risk stratification for pediatric patients with diverse tumor types, regardless of histologic grade, with a variety of pediatric solid and brain tumors. Citation Format: Eirini Christodoulou, Venkata Yellapantula, Katrina O'Halloran, Liya Xu, Jesse L. Berry, Fariba Navid, Dejerianne Ostrow, Jaclyn A. Biegel. Clinical applicability of targeted panel sequencing in liquid biopsies for disease diagnosis and monitoring of patients with pediatric solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 967.

Abstract 5014: Analytical validation of a complete system for detection and characterization of genomic aberrations in circulating tumor DNA

Abstract Cell-free DNA (cfDNA) fragments are readily detected at a low concentration in the human blood stream. In healthy patients cfDNA is primarily derived from apoptosis of hematopoietic cells. In cancer patients circulating DNA derived from tumor cells (ctDNA) undergoing apoptosis, shedding, and necrosis contribute to total cfDNA. Next generation sequencing (NGS) of cfDNA isolated from patient plasma can be used to fully characterize cancer driven changes in the tumor DNA including the relative contribution of cfDNA, single nucleotide variants (SNVs), small insertions and deletions (Indels), larger deletions, regions of amplified DNA, and structural rearrangements. Frontage has developed a complete lab system for analysis of circulating cfDNA including automated sample extraction, preparation and sequencing of libraries targeting exon sequences of 293 oncology-related genes, and a bioinformatic reporting system. The Frontage sample extraction process uses a post-extraction size selection step to remove high molecular weight DNA derived from lysed blood cells in the plasma sample to increase the sensitivity of detection of ctDNA. The NGS platform couples hybridization-based selection of genomic DNA fragments derived from protein-coding exons with deep sequencing to ~4,000X gross coverage on the NextSeq 2000. The bioinformatic pipeline integrates unique molecular barcode-based generation of consensus reads for each template molecule, somatic variant calling with GATK Mutect2 and FreeBayes, and removal of false positive variants by comparison to a 60 samples healthy patient data set. Analytical validation was performed for each component of the system. For verification of the sample extraction process, cfDNA was extracted in duplicate from four lots of pooled K2 EDTA plasma of healthy patients as well as individual K2 EDTA plasma of colorectal cancer (CRC) patients in four independent extraction runs. The mean yields of cfDNA from healthy samples ranged from 2.3 - 4.2 nanograms per ml plasma and all 32 of the isolated cfDNA aliquots from healthy patient plasma showed a prominent peak around 167 nt with minimal contamination from high molecular weight DNA. For validation of the NGS and bioinformatics platform a set of 8 different reference cfDNAs were processed through four independent runs of library preparation, sequencing, and analysis. For each of the validation runs, greater than 97% of 208 SNVs and Indels with expected allele frequencies (AF) between 2-3% were detected by the platform with higher levels of accuracy for variants at above 3% AF. Two or less false positive variants per run were detected out of 278,000 nucleotides of verified non-mutated sequence that overlapped with the 293 gene panel. Four known DNA amplification events were detected in each of the validation runs. Data from characterization of CRC and other clinical samples with the system will be presented. Citation Format: Ericca Stamper, Weiming Shen, Aman Pruthi, Casey Nagel, Marcin Piechota, Katarzyna Tomala, Qi Wei, David Willoughby. Analytical validation of a complete system for detection and characterization of genomic aberrations in circulating tumor DNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5014.

Abstract 965: Urine cell-free DNA multi-omics combining copy number analysis with fragmentomics to detect minimal residual disease in bladder cancer patients

Abstract Background: Standard-of-care for patients with localized muscle-invasive bladder cancer (BC) is neoadjuvant chemotherapy followed by radical cystectomy (RC). Bladder-sparing treatments are limited by our current inability to sensitively detect minimal residual disease (MRD). Here, we analyzed urine, a noninvasive and proximal biofluid, from patients with bladder cancer and utilized an approach that incorporates copy number-derived tumor fraction as well as fragmentomics to sensitively detect MRD and predict pathologic complete response (pCR). Methods: We acquired urine preoperatively from 51 BC patients (80% muscle-invasive) on the day of standard-of-care RC, and after neoadjuvant chemotherapy in 57% of patients. We performed whole genome sequencing (WGS) of urine cfDNA (median depth: 10X) from all 51 BC patients and 13 healthy adults. Tumor fraction level based on genome-wide copy number alterations was estimated using ichorCNA. We inferred fragment size and genomic coverage of urine cfDNA using Picard Tools. Then, we computed the short-to-long (S/L) fragment ratio for genomic bins in each sample. The S/L ratio per bin was derived by partitioning the genome into 100 kb bins and evaluating the ratio of GC-corrected short fragments (50-150 bp) to long fragments (151-250 bp) within each bin. A normalized genome-wide S/L score was calculated by averaging across all bins. Results: In our cohort of 51 BC patients, 45% of patients achieved pCR (n = 23) while 55% had residual disease detected in their surgical sample (no pCR; n = 28). Patients with no pCR had significantly higher copy number-derived tumor fractions in urine compared to patients with pCR (median 10.6% vs 1.9%, p = 0.0002) and healthy adults (n = 12) (median 10.6% vs 1.8%, p = 0.003). Tumor fraction achieved an AUC of 0.89 for classification of No pCR from pCR with sensitivity of 82% and specificity of 92%. Presumed cancer-free patients (healthy and pCR) had significantly longer urine cfDNA median fragment sizes than patients with no pCR (median 177 bp vs 156 bp, p = 0.002). Presumed cancer-free patients (healthy and pCR) also had significantly lower S/L ratio scores than no pCR patients (mean .98 vs 1.5, p = 0.007). The top 100 bins with maximally differential S/L ratio between these two patient groups were enriched for genes involved in KEGG pathways implicated in cancer and immune signaling (autophagy, transcriptional misregulation in cancer, Th1 differentiation) indicating biological relevance. Conclusion: Copy number alteration-derived tumor fraction inference combined with fragmentomic analysis of urine cell-free DNA can enable sensitive detection of MRD to predict pCR and reveal potentially onco-relevant pathways. Citation Format: Arpit Panda, Irfan Alahi, Pradeep S. Chauhan, John Sheng, Nathan Colon, Cayce Nawaf, Alexander Shiang, Peter K. Harris, Faridi Qaium, Eric H. Kim, Melissa A. Reimers, Woodson Smelser, Zachary L. Smith, Aadel A. Chaudhuri. Urine cell-free DNA multi-omics combining copy number analysis with fragmentomics to detect minimal residual disease in bladder cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 965.

Abstract 981: Robustness of fragmentation-based cell-free DNA approaches to clonal hematopoiesis

Abstract INTRODUCTION: Clonal hematopoiesis (CH) is the result of the clonal expansion of hematopoietic stem cells which acquire and pass on somatically gained mutations, including SNVs as well as arm level losses and gains, defined here as mosaic deletions and amplifications (mDAs). The proportion of blood cells in circulation containing CH alterations increases with age and environmental exposures such as smoking, leading to a higher prevalence in many high-risk cancer screening populations. CH remains a major confounder for mutation-based liquid biopsy tests evaluating circulating cell-free DNA (cfDNA), since these assays are unable to discriminate between mutations originating from the tumor as opposed to CH. While the impact of CH mutations on fragmentation-based methods of detecting ctDNA appears to be limited, the effect of mDAs has not yet been explored. METHODS: To assess the impact of mDAs on screening efforts using whole genome sequencing (WGS) of cfDNA, we performed copy number analyses on cfDNA from plasma collected from 895 individuals consisting of high-risk individuals meeting the USPSTF guidelines for annual lung cancer screening using low-dose computed tomography. From a subset of 203 available donors (157 without cancer and 46 with lung cancer), matched genomic DNA from white blood cells (WBCs) were extracted from the isolated buffy coat and WGS was performed to evaluate whether ploidy in cfDNA plasma is derived from WBCs. Genome-wide fragmentation features (short to long ratios and fragment size densities), coverage-based statistics, and copy number (CN) statistics adjusting for mDAs were calculated (CNadj). Machine learning models to calculate the probability of cancer based on these features were then derived. RESULTS: 3.8% (95% CI 0.9%-6.8%) of individuals without cancer had an mDA in their WBCs that were also observed in the plasma (p &amp;lt; 0.01, permutation test). Fragmentation features were not different in regions with mDAs in individuals without cancer (p = 0.619; permutation test) but were altered in regions of tumor-derived chromosomal changes in patients with cancer (p &amp;lt; 0.01; permutation test). Coverage-based statistics were impacted by mDAs (p &amp;lt; 0.01; Wilcoxon test). Machine learning models fit with CNadj showed improved performance over CN. However, machine learning models fit with fragmentation features compensated for this difference overall showing robustness to mDAs (p = 0.45; bootstrap) demonstrating the robustness of cfDNA fragmentomes for detecting lung cancer. CONCLUSIONS: While coverage-based statistics of WGS analyses of cfDNA may be affected by mDAs, fragmentation-based approaches relying on cfDNA fragment length are robust to effects of CH. CNadj is an improved statistic for detecting tumor-derived chromosomal copy number changes in cfDNA, providing increased specificity by conditioning on fragment size distributions. Citation Format: Stephen Cristiano, Bahar Alipanahi, Jamie E. Medina, Lorenzo Rinaldi, Nicholas Dracopoli, Robert B. Scharpf, Alessandro Leal, Victor E. Velculescu, Jennifer Tom. Robustness of fragmentation-based cell-free DNA approaches to clonal hematopoiesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 981.

Abstract 2294: Monitoring glioma treatment response through longitudinal analysis of cell-free DNA in cerebrospinal fluid: Insights from a comprehensive study using next-generation sequencing

Abstract Background: Assessing treatment response in gliomas with high fidelity remains challenging. Cell-free DNA (cfDNA) is increasingly recognized as a liquid biomarker in plasma and cerebrospinal fluid (CSF), showing promise in optimizing therapeutic regimens for various cancers. While CSF has been explored as a source of cfDNA for gliomas, understanding the dynamics of cfDNA abundance and sequencing changes during treatment and recurrence is essential. Leveraging our biobank of longitudinal CSF specimens obtained through CSF access devices, we aimed to determine the potential utility of CSF cfDNA as a monitoring tool for treatment response in glioma patients. Materials and methods: Longitudinal CSF specimens were collected through Ommaya reservoirs (NCT04692337) or ventriculoperitoneal shunts (NCT04692324) from patients with brain tumors, including gliomas. cfDNA was extracted from 1-5 mL of CSF based on available sample volumes and quantified using Qubit. Next-Generation sequencing using PredicineCARE or PredicineSCORE low-pass whole genome sequencing (LPWGS) was performed based on the available cfDNA. Results: CSF collected before versus after resection showed an increase in quantified cfDNA (2.97x, range: 1.58-5.26x), indicating the impact of increased parenchymal disruption and closer contact with CSF. Subsequently, CSF cfDNA decreased during chemoradiation and adjuvant treatment and increased at recurrence, even in patients co-enrolled in immunotherapy trials for IL-7 agonists and pembrolizumab. Notably, copy number burden (CNB) increased at recurrence in three patients with known disease progression and decreased throughout immunotherapy treatment in one patient despite concerns of pseudoprogression. In a patient with a hypermutated glioblastoma, CSF cfDNA revealed over 59 genomic alterations, including MAP2K1, KIT, and PDGFRA. Another patient with a progressing EGFR-amplified GBM showed over 200 new variants in the final sample, with EGFR copy number increasing from 2 to over 30. Conclusion: Analysis of cfDNA throughout a patient’s disease course, encompassing resection and treatment with standard-of-care and experimental therapies, may aid in disease monitoring and treatment response. Further evaluation in a larger patient cohort is needed to determine the sensitivity of changes in mutations, CNB, and cfDNA quantity for glioma disease burden. Citation Format: Riviere-Cazaux Cecile, Xiaoxi Dong, Chao Dai, Wei Mo, Pan Du, Shidong Jia, Terence Burns. Monitoring glioma treatment response through longitudinal analysis of cell-free DNA in cerebrospinal fluid: Insights from a comprehensive study using next-generation sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2294.

Abstract 6079: Comparison of FIT and cell-free DNA analyses for detection of individuals with colorectal cancer in population based screening

Abstract Background The fecal immunochemical test (FIT) is widely used in population based colorectal cancer (CRC) screening programs. Recently, circulating cell-free DNA (cfDNA) analyses have emerged as a new avenue for early cancer detection. The performance of cfDNA methods in comparison with FIT is currently unknown. The present study compared pre-operative cfDNA analyses to FIT for detection of patients with CRC who participated in a population-based screening program. Methods In the Dutch national CRC screening program, individuals aged 55-75 years are biennially invited to perform a single FIT. The database of the Dutch CRC screening program was queried to identify individuals with FIT data who also participated in two cfDNA studies, PLCRC-MEDOCC and PLCRC-PROVENC3 (AACR abstract C. Rubio Alarcón). Sensitivities with 95% confidence intervals (CI) for detecting individuals with CRC were determined for FIT, tumor-informed cfDNA analyses, as well as both tests combined. For FIT, sensitivities were determined at 20 µg and 47 µg hemoglobin (Hb)/g feces positivity cut-offs as these represent the most commonly used international and Dutch cut-offs, respectively. Liquid biopsy analyses were performed using next generation sequencing of cfDNA. Tumor-specific alterations were identified through parallel next generation sequence analysis of resected tumor tissues. Results The query identified 120 individuals with stage I (n=3, 2.5%), stage II (n= 57, 47.5%) and stage III (n=60, 50.0%) CRC who had participated in the Dutch CRC screening program and either PLCRC-MEDOCC or PLCRC-PROVENC3. All FIT samples were collected at a median time of 38 days before diagnosis (IQR 27-112 days). FIT sensitivity for detection of individuals with CRC was 83.3% (100/120 CRCs, 95% CI 75.4-89.5%) at a 20 µg Hb/g feces cut-off and 80.0% (96/120, 95% CI 71.7-86.7%) at a 47 µg Hb/g feces cut-off. Tumor-informed cfDNA analyses detected 75.8% (91/120, 95% CI 67.2-83.2%) of individuals with CRC in this population. The combination of cfDNA analyses and and FIT (20 µg Hb/g feces cut-off) identified almost all individuals with CRCs (119/120, sensitivity 99.2%, 95% CI 97.0-100%). The individual who was missed had a cancer that was a T3N0 microsatellite stable moderately differentiated adenocarcinoma in the ascending colon. Discussion While both FIT and cfDNA analyses identified most CRC cases (75-83%) in this series, both tests also demonstrated a substantial level of complementarity, indicating that in principle combining FIT with cell-free DNA testing would allow to increase sensitivity of CRC screening. Since the cell-free DNA tests used here are tumor-informed, which in real life screening practice is not feasible, it remains to be determined to what extent this result can be reached using non-tumor-informed approaches. Citation Format: Pieter Henk Abraham Wisse, Carmen Rubio-Alarcon, Suzanna J. Schraa, Adria C. Mosquera, Mark Sausen, Remond J. Fijneman, Geraldine R. Vink, Meike de Wit, Jillian Phallen, Victor E. Velculescu, Beatriz Carvalho, Gerrit A. Meijer. Comparison of FIT and cell-free DNA analyses for detection of individuals with colorectal cancer in population based screening [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6079.

Abstract 979: Cell-free DNA fragmentomics and second malignant neoplasm risk in patients with PTEN hamartoma tumor syndrome

Abstract Individuals with PTEN hamartoma tumor syndrome (PHTS) harbor germline PTEN variants that confer a significantly increased lifetime risk of various organ-specific cancers, and a 7-fold increased risk of second primary malignant neoplasms (SMNs). Currently, there is no reliable biomarker that can accurately predict which individuals with PHTS will develop malignancies, let alone SMN. Currently, there is no reliable biomarker that can accurately predict which individuals with PHTS will develop malignancies, let alone SMN. Despite the highly promising value of cell-free DNA (cfDNA) as a biomarker for underlying sporadic cancers, the utility of cfDNA in individuals with hereditary forms of cancer remains poorly understood. Thus, we performed a retrospective study in prospectively accrued patients with PHTS investigating whether plasma cfDNA profiles can be leveraged as a predictive marker of cancer risk. We performed ultra-low pass whole genome sequencing of cfDNA of archived plasma samples from patients with PHTS without cancer (N = 50), and those with cancer (N = 49). Those with cancer included patients with only a single primary malignant neoplasm (PMN, N = 23) and patients with second malignant neoplasms (SMN, N = 26). To investigate cfDNA profiles in patients with PHTS and subclinical cancer, we included nine patients with plasma archived before their cancer diagnosis. We observed that patients with PHTS and SMNs have significantly decreased proportion of di- and tri-nucleosome-associated cfDNA fragments compared to patients with PMNs and those without cancer. Furthermore, SMN status was associated with increased genome-wide fragmentation (ratio of short to long fragments) of mono- (OR 2.37, 95% CI [1.09, 7.27]; P = 0.025) and di-nucleosome-associated (OR 3.03, 95% CI [1.07, 15.7]; P = 0.029) cfDNA fragments, even after controlling for age at plasma draw and phenotypic burden. Fragment end profiling was performed by calculating the frequencies of the first 4-nucleotide sequence (4-mer end motif) at each 5’ end of cfDNA fragments. We identified 35 differentially abundant 4-mer end motifs when comparing patients with SMN to those without cancer. Patients with PHTS and SMNs were characterized by a decrease in A-end motifs with concurrent increases in G- and T-end motifs. Increased frequency of C-motifs—namely CC- and CA-end motifs—appeared to be unique to patients who had plasma drawn before their SMN diagnosis, a potential marker for active cancer. Our findings provide evidence that cfDNA fragmentomic features can be leveraged as a potential marker of individual SMN risk in PHTS. These results may facilitate earlier cancer detection and intervention as well as prevent unnecessary high-risk cancer surveillance and prophylactic surgeries in this vulnerable population. Citation Format: Darren Liu, Lamis Yehia, Andrew Dhawan, Ying Ni, Charis Eng. Cell-free DNA fragmentomics and second malignant neoplasm risk in patients with PTEN hamartoma tumor syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 979.

Abstract 6101: PLASMUT: An R Package for estimating the probability of tumor-specific mutations in cell-free DNA

Abstract Noninvasive approaches for detection of tumor-specific mutations in cell-free DNA (cfDNA) have the potential to track a patient’s response to treatment, enabling effective and timely decisions on therapy. However, mutations in cfDNA arising from clonal hematopoeisis (CH) are common and tumor biopsies for definitive identification of the origin of these mutations are not always available. Sequencing of matched cells from buffy coat and the absence of mutations in these cells has been used to rule-out white blood cell (WBC) mutations, but uneven sequencing depths between matched cfDNA and buffy coat and the fraction of mutant alleles are generally ignored by rule-based tests. A probabilistic approach that quantifies the evidence of tumor-derived mutations in cfDNA is needed. We developed a Bayesian framework to estimate the probability that a mutation identified in cfDNA is tumor specific. Our approach requires the number of reads with a mutant allele in plasma (yp) and WBCs (yw) and the corresponding number of total distinct reads at these locations. The posterior odds that a mutation is tumor-derived (S) versus CH or germline (H) is given by the ratio of the probabilities of observing the distinct reads given each model times the prior odds. Estimation of the Bayes factor is obtained by integrating over the unobserved mutant allele fractions in plasma and WBCs using Monte Carlo importance sampling. We applied this approach to 52 patients with initially unresectable colorectal cancer (CRC) liver metastases in the CAIRO5 clinical trial (NCT02162563), using ultra-deep targeted sequencing of cfDNA from plasma and matched WBCs. Among the CAIRO5 patients analyzed, we identified 95 mutations with moderate evidence of tumor-derived cfDNA mutations (Bayes factor &amp;gt; 10) and 19 mutations that were CH-derived (Bayes factor &amp;lt; 0.1). For a subset of 47 cfDNA mutations with no corresponding mutation identified by WBC sequencing, the evidence of tumor origin was highly variable (Bayes factor range: 0.03 to 5.6). While the standard rule-based approach identifies all of these mutations as tumor-derived, none of these mutations reach a moderate evidence cutpoint (all Bayes factors &amp;lt; 6). As a false positive would lead to identification of cfDNA mutations that do not track tumor burden, requiring even higher levels of evidence (Bayes factor &amp;gt; 99) for the selection of cfDNA mutations could be warranted, and still identifies one or more cfDNA mutations in 43 of the patients. This approach is implemented in the R package PLASMUT available from Bioconductor (doi:10.18129/B9.bioc.plasmut). We developed an approach that quantifies the evidence between two competing models for the origin of mutations in cfDNA. A cutpoint for determination of the probability of tumor-derived cfDNA mutations can be tailored to the disease application, balancing the potential benefits of noninvasive testing with the harms of false positives and negatives. Citation Format: Adith S. Arun, Jamie E. Medina, Stephen Cristiano, Daniel C. Bruhm, Remond J. Fijneman, Gerrit A. Meijer, Alessandro Leal, Victor E. Velculescu, Robert B. Scharpf. PLASMUT: An R Package for estimating the probability of tumor-specific mutations in cell-free DNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6101.