Detection Of Mutations In cfDNA Research Articles

Abstract 1299: Cost-effectiveness analysis of circulating tumor DNA-based molecular profiling platforms for the detection of EGFR mutations in lung cancer

Abstract Background The detection of mutations in circulating tumor DNA (ctDNA) in blood plasma of lung cancer patients can be used to monitor the tumor-response to therapy and for the early detection of resistance mechanisms. In 2017, the Roche Cobas® EGFR Mutation Test v2 for the detection of the EGFR c.2369C>T p.(T790M) mutation in plasma-derived ctDNA was FDA-approved to identify patients eligible for osimertinib treatment. Today, different platforms are available for EGFR mutation testing in plasma-derived cell-free DNA (cfDNA). In this study we compared the clinical utility of five platforms for the detection of EGFR mutations in cfDNA offering insights into their operational costs, target coverage, hands-on-time and turn-around-time. Methods Four PCR-based platforms and one NGS-based approach for the detection of EGFR mutations were compared. Operational, maintenance, material and personnel costs were calculated for each platform and used as input variables for our recently developed ctDNA micro-costing framework (doi.org/10.1016/j.jmoldx.2022.10.004). This was compared to target coverage and turn-around-time of each platform in the context of therapy resistance. Results Per sample costs decreased for all platforms at maximal weekly throughput. The BioCartis Idylla™ demonstrated the shortest turn-around-time while the Roche Cobas® was the least expensive. Despite being the most expensive and time-consuming, the AVENIO ctDNA Expanded kit covered the most known resistance mechanisms to EGFR inhibitors, many of which are targetable with other TKIs. Conclusion EGFR ctDNA mutation analysis is only cost-effective when the throughput is high. This implies that centralization of cfDNA-testing is necessary to optimize cost-efficiency. With the advent of ctDNA analysis beyond EGFR in the context of targeted therapies for lung cancer, multigene detection assays will become more cost-effective with high throughput. Overview of results Platform Turn-around time at maximal weekly throughput Per sample cost at maximal weekly throughput Coverage of resistance mutations in EGFR 1Additional testing necessary Coverage of genome-wide resistance mutations to EGFR-TKI 1Additional testing necessary BioCartis Idylla™ ctEGFR Mutation Assay 2,5 hours €571 33% 12%1 Roche Cobas® EGFR Mutation Test v2 4 hours €497 33% 6% Bio-Rad QX200 droplet digital PCR (ddPCR) 7,5 hours €766 100%1 24%1 Agena MassARRAY® UltraSEEK® Lung Panel 2 days €613 53% 12% Roche AVENIO ctDNA Expanded kit 1 week €1551 100% 65% Citation Format: Pim Rozendal, Paul van der Leest, Elise M. van der Logt, Naomi Rifaela, Inge Platteel, Frank J. Scherpen, Harry J. Groen, Léon C. van Kempen, Ed M. Schuuring. Cost-effectiveness analysis of circulating tumor DNA-based molecular profiling platforms for the detection of EGFR mutations in lung cancer [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 1299.

CTNI-55. A MULTICENTER STUDY OF LOW-INTENSITY FOCUSED ULTRASOUND WITH SYSTEMIC MICROBUBBLE OSCILLATORS FOR BLOOD-BRAIN BARRIER DISRUPTION FOR LIQUID BIOPSY IN GLIOBLASTOMA (LIBERATE)

Abstract BACKGROUND Liquid biopsy in glioblastoma (GBM) is hindered by a lack of requisite circulating-free DNA (cfDNA) blood levels in due to the blood-brain barrier (BBB). Real-time image-guided low-intensity focused ultrasound (LIFU) with intravenously administered microbubble oscillators non-invasively causes BBB disruption (BBBD). This clinical trial aimed to evaluate the utility of LIFU for increasing cfDNA in blood for liquid biopsy in GBM. METHODS LIBERATE is an ongoing, prospective, multi-center, self-controlled, ongoing, pivotal trial evaluating the safety and technical efficacy of LIFU for BBBD to increase cfDNA in blood for GBM. Patients aged 18-80 years with suspected GBM planned for tumor biopsy or resection at ten centers in the US are being included. Patients are administered intravenous oscillating microbubbles for enhancing sonication, after which MR-guided BBBD using 220 kHz LIFU device is performed, with real-time acoustic feedback for effective sonication. Pre- and post-procedure, phlebotomies, and MRI brain are performed. The primary study endpoint is defined, per subject, as the ratio between cfDNA levels in blood 1-hour post-LIFU procedure compared to cfDNA level in blood pre-procedure. The primary study hypothesis is that BBBD with LIFU leads to ≥2-fold increase in cfDNA in blood. The secondary hypothesis is that there exists ≥75% concordance between biomarker patterns in the cfDNA sample from 1-hour post-LIFU sample and tumor tissue obtained later. Exploratory endpoints include (1) sensitivity of detection of known somatic mutations in cfDNA from blood samples collected before and after LIFU, (2) estimation of cfDNA levels in samples collected at 30 minutes, 1 hour, 2 hours, and 3 hours post-LIFU to determine the time of greatest yield, (3) correlation of MRI parameters related to BBBD grading and biomarkers in cfDNA from post-LIFU samples. Patient enrollment commenced in 2022, and 13 patients have been recruited by 06/09/2023. Clinical trial information: NCT05383872.

P14.11.B A MULTICENTER STUDY OF LOW-INTENSITY FOCUSED ULTRASOUND WITH SYSTEMIC MICROBUBBLE OSCILLATORS FOR BLOOD-BRAIN BARRIER DISRUPTION FOR LIQUID BIOPSY IN GLIOBLASTOMA (LIBERATE)

Abstract BACKGROUND Liquid biopsy in glioblastoma (GBM) is hindered by a lack of requisite circulating-free DNA (cfDNA) levels in blood due to the blood-brain barrier (BBB). This results in challenges to the identification of blood-based biomarkers and the development of novel biomarker-driven systemic therapies. Real-time image-guided low intensity focused ultrasound (LIFU) combined with intravenously administered microbubble oscillators non-invasively causes BBB disruption (BBBD). This clinical trial aimed to evaluate the utility of LIFU for increasing cfDNA in blood for liquid biopsy in GBM. METHODS LIBERATE is a prospective, multi-center, self-controlled, ongoing, pivotal trial evaluating the safety and technical efficacy of LIFU for BBBD to increase cfDNA in blood for GBM. Patients aged 18-80 years with suspected GBM planned for tumor biopsy or resection at ten centers in the US are being included. Patients with multifocal tumors or tumors arising from deep midline, thalamus, cerebellum, or brainstem are excluded. Patients are administered intravenous oscillating microbubbles for enhancing sonication, after which MR-guided BBBD using a 220 kHz LIFU device is performed with real-time acoustic feedback for effective cavitation. Before and after the procedure, phlebotomies and MRI brain are performed to evaluate outcomes. The primary study endpoint is defined, per subject, as the ratio between their cfDNA level in blood 1-hour post-LIFU procedure compared to cfDNA level in blood pre-procedure. The primary study hypothesis is that BBBD with LIFU leads to a ≥2-fold increase in cfDNA in blood. The secondary hypothesis is that there exists ≥75% agreement between biomarker pattern in cfDNA sample from 1-hour post-LIFU sample and biomarker pattern in tumor tissue obtained later. The trial has been powered to evaluate both primary and secondary hypotheses. Based on an assumed true agreement rate of 91% and a one-sided alpha of 0.025, an exact test for binomial proportions provides a sample of N=50 with 84% power for the secondary hypothesis. Exploratory endpoints include (1) sensitivity of detection of known somatic mutations in cfDNA from blood samples collected before and after LIFU, (2) estimation of cfDNA levels post-LIFU in samples collected at 30 minutes, 1 hour, 2 hours, and 3 hours to determine the time of greatest yield, (3) correlation of MRI parameters related to grading of BBBD and biomarkers positive in cfDNA from post-LIFU blood samples. RESULTS Patient enrollment commenced in 2022, and 8 patients have been recruited by 04/11/2023. CONCLUSION Findings from this trial will be critical to liquid biopsy in GBM (Clinical trial information: NCT05383872).

Low-intensity focused ultrasound with systemic microbubble oscillators for blood-brain barrier disruption for liquid biopsy in glioblastoma (LIBERATE).

TPS2084 Background: Liquid biopsy in glioblastoma (GBM) is hindered by a lack of requisite circulating-free DNA (cfDNA) levels in blood due to the blood-brain barrier (BBB). This results in challenges to the identification of blood-based biomarkers and the development of novel biomarker-driven systemic therapies. Real-time image-guided low intensity focused ultrasound (LIFU) combined with IV microbubble oscillators (DEFINITY), non-invasively causes BBB disruption (BBBD). This clinical trial aims to evaluate the utility of LIFU for increasing cfDNA in blood for liquid biopsy in GBM. Methods: LIBERATE is a prospective, multi-center, self-controlled, ongoing, pivotal trial evaluating safety and technical efficacy of LIFU for BBBD to increase cfDNA in blood for GBM. Patients aged >18-80 years with suspected GBM planned for tumor biopsy or resection at eleven centers in North America are being included. Patients with multifocal tumors or tumors arising from deep midline, thalamus, cerebellum, or brainstem are excluded. Patients are administered IV oscillating microbubbles for enhancing sonication, after which MR-guided BBBD using a 220 kHz LIFU device is performed with real-time acoustic feedback for effective cavitation. Before and after procedure, phlebotomies and MRI brain are performed to evaluate outcomes. The primary study endpoint is defined, per subject, as the ratio between their cfDNA level in blood 1-hour post-LIFU compared to cfDNA level in blood pre-procedure. The primary study hypothesis is that BBBD with LIFU leads to ≥2-fold increase in cfDNA in blood. The secondary hypothesis is that there exists ≥75% agreement between biomarker pattern in cfDNA sample from 1-hour post-LIFU sample and biomarker pattern in tumor tissue obtained later. The trial has been powered to evaluate both primary and secondary hypotheses. Based on an assumed true agreement rate of 91% and a one-sided alpha of 0.025, an exact test for binomial proportions provides a sample of N=50 with 84% power for the secondary hypothesis. Exploratory endpoints include (1) sensitivity of detection of known somatic mutations in cfDNA from blood samples collected before and after LIFU, (2) estimation of cfDNA levels post-LIFU in samples collected at 30 minutes, 1 hour, 2 hour, and 3 hour to determine time of greatest yield, (3) correlation of MRI parameters related to grading of BBBD and biomarkers positive in cfDNA from post-LIFU blood samples. Patient enrollment commenced in 2022 and 7 patients have been recruited by 02/13/2023. Clinical trial information: NCT05383872 .

Comparison of digital PCR systems for the analysis of liquid biopsy samples of patients affected by lung and colorectal cancer

Background and aimsHighly sensitive technologies are available for the molecular characterization of solid tumors, including digital PCR (dPCR). Liquid biopsy, based on the analysis of cell-free DNA (cfDNA), is often used to assess EGFR or RAS alterations in lung and colorectal cancers. Our study aimed to compare the results of two different dPCR platforms for the detection of mutations in cfDNA. MethodsPlasma samples from lung and colorectal cancer patients collected as per routine procedures have been tested. cfDNA Was extracted from plasma, and samples were screened on the droplet digital PCR (ddPCR, BioRad) and solid dPCR QIAcuity (Qiagen). ResultsA total of 42 samples were analyzed, obtained from 20 Non-Small Cell Lung Cancer (NSCLC) patients carrying an EGFR or a KRAS mutation on tissue at diagnosis, and from 22 samples of colorectal cancer (CRC) patients, 10 of which presenting a KRAS mutation. EGFR mutation detection was 58.8% for ddPCR and 100% for dPCR (κ = 0.54; 95% CI, 0.37–0.71), compared to tissue results. The detection rate for RAS mutations was 72.7% for ddPCR and 86.4% for dPCR (κ = 0.34; 95% CI, 0.01–0.68), compared to tissue results. ConclusionsThis study showed moderate agreement between dPCR and ddPCR. Sampling effect or threshold settings may potentially explain the differences in the cfDNA data between the two different platforms.

Tumor volume as a predictor of cell free DNA mutation detection in advanced non-small cell lung cancer.

BackgroundCell free DNA (cfDNA) is an exciting biomarker with applications across the cancer care continuum. Determinants of cfDNA shedding dynamics remain an active research area. We performed a detailed analysis of tumor volume and factors associated with detection of cfDNA mutations.MethodsPatients with advanced non-small cell lung cancers (NSCLCs) were prospectively enrolled on a plasma biomarker protocol. Next generation sequencing (NGS) was performed using a validated, bias-corrected, hybrid-capture panel assay of lung cancer-associated genes. Volume of tumor in different subsites and total tumor volume were determined through manual volume delineation using PET/CT and brain magnetic resonance imaging (MRI) imaging. The primary endpoint was detection of cfDNA mutation; secondary endpoints were overall survival (OS) and variant allele frequency (VAF).ResultsThere were 110 patients included, 78 of whom had at least one mutation detected. Median total tumor volume for the entire cohort, patients with mutation detected, and patients with no mutation detected were 66 mL (range, 2–1,383 mL), 76 mL (range, 5–1,383 mL), and 45 mL (range, 2–460 mL), respectively (P=0.002; mutation detected vs. not). The optimal total tumor volume threshold to predict increased probability of mutation detection was 65 mL (P=0.006). Total tumor volume greater than 65 mL was a significant predictor of mutation detection on multivariate analysis (OR: 4.30, P=0.003). Significant predictors of OS were age (HR: 1.04, P=0.002), detection of cfDNA mutation (HR: 2.11, P=0.024), and presence of bone metastases (HR: 1.66, P=0.047).ConclusionsTotal tumor volume greater than 65 mL was associated with cfDNA mutation detection in patients with advanced NSCLC.

Effects of Different Centrifugation Protocols on the Detection of EGFR Mutations in Plasma Cell-Free DNA.

ObjectivesVarious preanalytical factors, including the collection tube, storage conditions, and centrifugation, affect the detection results of plasma cell-free DNA (cfDNA). We compared the effect of different centrifugation protocols on the detection of EGFR mutations in cfDNA.MethodsWe analyzed 117 plasma specimens from 110 patients with non–small cell lung cancer using the cobas EGFR Mutation Test v2 (Roche Diagnostics). We compared the identified EGFR mutations and semiquantitative index values from the 1- and 2-step centrifugation groups and confirmed the clinical impact of differences in the results after further high-speed centrifugation.ResultsWe detected EGFR mutations in 44 (37.6%) and 47 (40.2%) samples that were centrifuged once and twice, respectively; the 2 groups showed an 89.7% (105/117) concordance and a strong correlation in their semiquantitative index values (r = 0.929). Among the 12 inconsistent result pairs, 9 samples of 2-step centrifugation (75%) were consistent with the results of a recent tissue biopsy.ConclusionsAdditional high-speed centrifugation has been shown to increase the sensitivity of EGFR mutation detection in a commercial in vitro diagnostic real-time polymerase chain reaction device and is an optimal preanalytical factor for detecting low-allele frequency gene mutations using low concentrations of cfDNA.

Early detection of colorectal cancer somatic mutations using cfDNA liquid biopsies in a murine carcinogenesis model.

Colorectal cancer (CRC) is one of the top five cancers in incidence and mortality worldwide. The early detection of this neoplasm through analysis of circulating free DNA (cfDNA), which carries tumor genetic alterations, as a liquid biopsy, could have a major impact in enhancing early detection and reducing the mortality rate. The aim of this work was to demonstrate the feasibility of using cfDNA as a liquid biopsy for the early detection of CRC. For this purpose, we implemented an azoxymethane and dextran sodium sulfate-induced murine carcinogenesis model to detect oncogenic somatic mutations in Ctnnb1 and Kras during CRC development. To enhance the sensitivity in the detection, E-ice-COLD-PCR was utilized to selectively enrich for mutant alleles, followed by massively parallel sequencing. Driving somatic mutations were detected in Ctnnb1 and Kras in the liquid biopsies of early stages of tumor development, corresponding to the formation of aberrant crypt foci, the first histological alterations that can be identified throughout the formation of CRC. The concentration of cfDNA was increased along the carcinogenic process. Polyclonality in Ctnnb1 was found in tumor samples and cfDNA in this model. On the other hand, the use of cfDNA as a non-invasive test resulted in superior early detection compared to microPET/CT imaging. As a proof-of-principle, this study shows the great potential use of allelic-specific PCR for the detection and enrichment of pathogenic alleles present in cfDNA samples, as a test for early non-invasive detection of CRC. This work provides scientific evidence to set methodological bases that allow early detection of mutations in cfDNA obtained from plasma of CRC in humans.

Abstract 575: Enhancing cell-free DNA mutation detection with novel liquid-phase extraction

Abstract Background: Low yields of extracted cell-free DNA (cfDNA) from plasma limit further development of liquid biopsies for early-stage cancer diagnostics and cancer screening applications. Conventional nucleic acid extraction methods have limitations in capturing low levels of cfDNA and risk capturing high levels of high molecular weight contaminating genomic DNA. We developed a liquid-phase based DNA extraction method (PHASIFY™ ENRICH; Phase Scientific International Ltd., Kwun Tong, Hong Kong) that leverages aqueous two-phase systems (ATPS) to purify, concentrate, and enrich for cfDNA to improve mutant signal detection. Methods: The PHASIFY ATPS consists of unique formulations that are optimized to drive cfDNA into one liquid phase and plasma contaminants into the other, achieving simultaneous target isolation and concentration. In a previous study using the PHASIFY technique, we demonstrated improved cfDNA and mutant copy yield over solid-phase methods. We further developed an additional size-selection feature (PHASIFY ENRICH) to remove high molecular weight genomic DNA (>500 bp) and to reduce signal noise for molecular diagnostics. We compared cfDNA recovery and mutation detection from plasma samples extracted with the industry standard QIAamp Circulating Nucleic Acid kit (QCNA; Qiagen, Hilden, Germany) and PHASIFY ENRICH cfDNA extraction kit. According to the respective kit protocols, the cfDNA was extracted from plasma from patients with advanced cancers, including those known to shed low amounts of cfDNA into circulation (e.g., low grade serious ovarian, appendiceal, thyroid, and pancreatic cancer), with known tissue mutation status. Total DNA recovery was determined with the Quant-iT PicoGreen dsDNA Assay Kit. Mutation status was determined with probe-based Droplet Digital PCR (ddPCR; Bio-Rad, Hercules, CA). In a follow up study, we tested a similar cohort of plasma samples that were previously tested negative for cfDNA mutation status when using QCNA cfDNA extraction, despite known positive mutation status from corresponding tumor tissue genotyping. Results: In the head-to-head study against QCNA, 57 plasma samples from 23 unique patients with diverse advanced cancers with known tissue mutation status were used for cfDNA extraction. The PHASIFY ENRICH method resulted in a 153% increase in median mutant copy recovery compared to QCNA (P = 0.01 Wilcoxon Signed-Rank). In the follow up study, 47 plasma samples from 31 patients with diverse advanced cancers and prior cfDNA negative mutation status with tissue positive mutation status were used for extraction. Of the 47samples extracted by PHASIFY ENRICH, 9 samples resulted in a conversion to positive cfDNA mutation status compared to no mutant signals when previously using QCNA. Conclusion: Our results indicate that PHASIFY ENRICH provides improved cfDNA mutation detection by increasing cfDNA recovery and reducing contaminating genomic DNA background. Citation Format: Filip Janku, Helen Huang, David Y. Pereira, Masae Kobayashi, Steven G. Call, Kristen T. Woodbury, Felix Chao, Daniel R. Marshak, Ricky Y. Chiu. Enhancing cell-free DNA mutation detection with novel liquid-phase extraction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 575.

Detection of Low-Frequency KRAS Mutations in cfDNA From EGFR-Mutated NSCLC Patients After First-Line EGFR Tyrosine Kinase Inhibitors.

BackgroundMolecular profiling of advanced EGFR mutated NSCLC has recently demonstrated the co-existence of multiple genetic alterations. Specifically, co-existing KRAS-mutations in EGFR NSCLCs have been described, despite their prevalence at progression and their role in the response to EGFR tyrosine kinase inhibitors (TKIs) remain marginally explored. Aim of our study was to investigate the prevalence of co-existing KRAS mutations at the time of progressive disease and explore their impact on clinical outcome.Materials and MethodsWe retrospectively analyzed by digital droplet PCR prevalence of KRAS co-mutations in 106 plasma samples of EGFR mutated NSCLC patients, in progressive disease after EGFR TKI treatment as first-line therapy.Results KRAS co-mutations (codon 12 and 13) were identified in 3 patients (2.8% of analyzed samples), with low allelic frequency (<0.2%), and had a negative impact on clinical outcome to first-line EGFR TKI.ConclusionDetection of KRAS mutations in cell-free DNA of EGFR mutant NSCLC patients at progression after first or second generation EGFR TKI is a rare event. Due to their low abundance, the negative impact of KRAS mutations on the response to EGFR TKI remains to be confirmed in larger studies.

Detection of EGFR Mutations in cfDNA and CTCs, and Comparison to Tumor Tissue in Non-Small-Cell-Lung-Cancer (NSCLC) Patients.

Lung cancer is the leading cause of cancer-related mortality worldwide. Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapies, based on the evaluation of EGFR mutations, have shown dramatic clinical benefits. EGFR mutation assays are mainly performed on tumor biopsies, which carry risks, are not always successful and give results relevant to the timepoint of the assay. To detect secondary EGFR mutations, which cause resistance to 1st and 2nd generation TKIs and lead to the administration of a 3rd generation drug, effective and non-invasive monitoring of EGFR mutation status is needed. Liquid biopsy analytes, such as circulating tumor cells (CTCs) and circulating tumor DNA (cfDNA), allow such monitoring over the course of the therapy. The aim of this study was to develop and optimize a workflow for the evaluation of cfDNA and CTCs in NSCLC patients all from one blood sample. Using Vortex technology and EntroGen ctEGFR assay, EGFR mutations were identified at 0.5 ng of DNA (∼83 cells), with a sensitivity ranging from 0.1 to 2.0% for a total DNA varying from 25 ng (∼4 CTCs among 4000 white blood cells, WBCs) to 1 ng (∼4 CTCs among 200 WBCs). The processing of plasma-depleted-blood provided comparable capture recovery as whole blood, confirming the possibility of a multimodality liquid biopsy analysis (cfDNA and CTC DNA) from a single tube of blood. Different anticoagulants were evaluated and compared in terms of respective performance. Blood samples from 24 NSCLC patients and 6 age-matched healthy donors were analyzed with this combined workflow to minimize blood volume needed and sample-to-sample bias, and the EGFR mutation profile detected from CTCs and cfDNA was compared to matched tumor tissues. Despite the limited size of the patient cohort, results from this non-invasive EGFR mutation analysis are encouraging and this combined workflow represents a valuable means for informing therapy selection and for monitoring treatment of patients with NSCLC.

Abstract 1979: Enhancing cell-free DNA and mutant copy recovery from plasma with novel liquid-liquid extraction

Abstract Background: Low yields of extracted cell-free DNA (cfDNA) from plasma limit further development of liquid biopsies especially in early-stage cancer diagnostics and cancer screening applications. We developed a novel liquid-liquid based DNA isolation method (PHASIFY™ MAX; Phase Scientific International Ltd., Kwun Tong, Hong Kong) that leverages aqueous two-phase systems (ATPS) to purify and concentrate circulating cfDNA, which can result in increase of cfDNA recovery and mutant signal detection. Methods: The PHASIFY™ ATPS consists of unique formulations of polymer and salt components that can intrinsically separate into two distinct phases. The formula can be optimized to drive cfDNA into one phase and contaminants from plasma into the other, achieving simultaneous target isolation and concentration. We compared cfDNA recovery and mutation detection from plasma samples extracted with the industry standard QIAamp Circulating Nucleic Acid kit (QCNA; Qiagen, Hilden, Germany) and PHASIFY™ MAX cfDNA extraction kit. According to the respective kit protocols, the cfDNA was extracted from 1mL of plasma from patients with advanced cancers, including those known to shed low amounts of cfDNA into circulation (e.g., thyroid, pancreatic), with known tissue BRAF, KRAS, or NRAS mutation status. Total DNA recovery was determined with the Quant-iT PicoGreen dsDNA Assay Kit. Mutation status was determined with probe-based (BRAF, KRAS, NRAS) Droplet Digital PCR (ddPCR; Bio-Rad, Hercules, CA). Results: Plasma samples from 89 patients with diverse advanced cancers (colorectal, N=36; ovarian, N=18; lung N=7; thyroid, N=6; pancreatic, N=6; others, N=16) with known BRAF, KRAS or NRAS mutation status were used for cfDNA extraction with standard QCNA and PHASIFY™ MAX kits. On average, PHASIFY™ MAX demonstrated a 288% increase in total cfDNA recovery compared to the QCNA kit (p-value &amp;lt;0.0001 Wilcoxon Signed-Rank). The ddPCR analysis of samples extracted by PHASIFY™ MAX demonstrated clinical sensitivity and specificity (against tissue genotyping) of 55% (46/82) and 100% (6/6) respectively and 46% (38/82) and 100% (6/6) respectively with samples extracted by QCNA. PHASIFY™ MAX had a sensitivity of 87% (33/38) against QCNA extracted plasma samples as reference. Of the samples for which both methods confirmed mutations, on average, PHASIFY™ MAX achieved a 142% increase in recovery of mutant copies compared to the QCNA kit (p-value 0.0006 Wilcoxon Signed-Rank). In 13 samples, mutations were detected in samples extracted with PHASIFY™ MAX, but not with QCNA. Of the 13, 3 were from pancreatic cancer patients, suggesting that PHASIFY™ MAX may improve mutation detection in low cfDNA shedding tumors. Conclusion: Our early results indicate that the PHASIFY™ MAX extraction technique offers higher cfDNA recovery resulting in higher sensitivity of cfDNA mutation detection compared to the industry standard. Citation Format: Filip Janku, Helen J. Huang, David Y. Pereira, Masae Kobayashi, Chung Hei Chiu, Steven G. Call, Kristen T. Woodbury, Felix Chao, Daniel R. Marshak, Ricky Y. Chiu. Enhancing cell-free DNA and mutant copy recovery from plasma with novel liquid-liquid extraction [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1979.

Abstract B03: Urine cell-free DNA (cfDNA) concentration and stability test for future clinical use

Abstract Introduction: Urine was shown to be a liquid biopsy source with high sensitivity for cfDNA mutation detection in both early- and late-stage cancer patients, outperforming plasma cfDNA and tissue samples in some patients. In addition, obtaining a urine sample is completely noninvasive. Limitations of using urine samples in the clinical setting include their unknown nucleic acid stability and the large total volume of one deposit, and therefore the presence of highly diluted cfDNA. Urine volume concentration, cfDNA stability, cfDNA quantity, and detection of wild-type (wt) EGFR alleles were explored to determine the future suitability of urine cfDNA as a diagnostic or prognostic biosource. Methods: First-void urine samples, with a higher fraction of nucleic acids due to overnight concentration, were collected from 5 healthy donors and 5 cancer patients. Cell-free urine samples were concentrated using Amicon filter tubes to determine differences in cfDNA concentration. In addition, we tested the ability to detect wild-type EGFR exon 19 in cfDNA from concentrated and unconcentrated urine samples using a peptide nucleic acid (PNA) Taqman Assay. Hereafter, stability of urine cfDNA was explored using variable storage temperatures and times and addition of a urine cfDNA preservative directly after sample collection. cfDNA was extracted using the automated QIAsymphony system with the DSP virus/pathogen kit and quantified using the Qubit dsDNA HS Assay in all experiments. Results: Amicon filter-based concentration of urine samples from 15 mL to 1.2 mL yielded a two-fold increase in cfDNA concentration. Importantly, while wild-type EGFR could not be detected in first-void urine using a PNA Taqman Assay, detection was possible using concentrated urine samples. Therefore, in all following experiments, samples were concentrated unless specified otherwise. Stability tests indicated that storage temperature matters when samples are not processed within two hours, with nearly doubled cfDNA concentrations found in samples stored at four degrees for 26 hours, compared to room temperature (RT). Addition of a cfDNA preservative yielded a six-fold higher cfDNA concentration after 26 hours of storage at RT, compared to samples without a preservative added. For this reason, we tested the use of only cfDNA preservative without concentrating the sample and found a four-fold increase in cfDNA concentration when adding only preservative, versus a 15-fold increase when using both after sample storage at RT for 24 hours. Conclusion: Patient urine samples should be either concentrated and processed within two hours, or a urine cfDNA preservative should be added directly after sample collection to prevent cfDNA degradation. Depending on the downstream application, samples where preservative was added may be concentrated to enhance the cfDNA yield, for example, when downstream NGS analysis will be performed. Citation Format: Jillian W. P. Bracht, Niki Karachaliou, Jordi Berenguer, Manuel Fernandez-Bruno, Mónica Garzón, Ana Gimenez-Capitan, Clara Mayo-de-las-Casas, Miguel Angel Molina-Vila, Rafael Rosell. Urine cell-free DNA (cfDNA) concentration and stability test for future clinical use [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B03.

A novel xenonucleic acid mediated molecular clamping technology for early colorectal cancer diagnostics.

e16106 Background: Colorectal cancer (CRC) is one of the leading causes of cancer-related death. Early detection is critical to reduce CRC morbidity and mortality. In order to meet this need, we developed a molecular clamping assay called ColoScape for early colorectal cancer diagnostics. Methods: Nineteen mutations in four genes APC, KRAS, BRAF and CTNNB1 associated with early events in CRC pathogenesis are targeted in the ColoScape assay. Xenonucleic Acid (XNA) mediated qPCR clamping technology was applied to minimize the wild-type background amplification in order to improve assay sensitivity of CRC mutation detection. The assay analytical performance was verified and validated, cfDNA and FFPE CRC patient samples were assessed for clinical performance, and a ROC curve was applied to evaluate its performance. Results: The data showed that the assay analytical sensitivity is 0.5% Variant Allele Frequency, corresponding to ~7-8 copies of mutant DNA with 5ng total DNA input per test. This assay is highly reproducible with intra-assay CV &lt; 3% and inter-assay CV &lt; 5%. We have investigated 380 clinical samples including plasma cfDNA and FFPE samples from patients with different stages of CRC. The preliminary assay clinical specificity and sensitivity for cfDNA were 100% (95% CI, 80.3-97.5%) and 92.2% (95% CI, 94.7-100%) respectively with AUC being about 0.96; and 96% (95% CI, 77.6-99.7%) specificity and 92% (95% CI, 86.1-95.6%) sensitivity with AUC 0.94 for FFPE. Conclusions: XNA mediated molecular clamping assay is a rapid, precise, and sensitive assay for the detection of CRC mutations in cfDNA or FFPE samples.

Cell-free Circulating Tumor DNA Variant Allele Frequency Associates with Survival in Metastatic Cancer.

Physicians are expected to assess prognosis both for patient counseling and for determining suitability for clinical trials. Increasingly, cell-free circulating tumor DNA (cfDNA) sequencing is being performed for clinical decision making. We sought to determine whether variant allele frequency (VAF) in cfDNA is associated with prognosis. We performed a retrospective analysis of 298 patients with metastatic disease who underwent clinical comprehensive cfDNA analysis and assessed association between VAF and overall survival. cfDNA mutations were detected in 240 patients (80.5%). Median overall survival (OS) was 11.5 months. cfDNA mutation detection and number of nonsynonymous mutations (NSM) significantly differed between tumor types, being lowest in appendiceal cancer and highest in colon cancer. Having more than one NSM detected was associated with significantly worse OS (HR = 2.3; P < 0.0001). VAF was classified by quartiles, Q1 lowest, Q4 highest VAF. Higher VAF levels were associated with a significantly worse overall survival (VAF Q3 HR 2.3, P = 0.0069; VAF Q4 HR = 3.8, P < 0.0001) on univariate analysis. On multivariate analysis, VAF Q4, male sex, albumin level <3.5 g/dL, number of nonvisceral metastatic sites >0 and number of prior therapies >4 were independent predictors of worse OS. Higher levels of cfDNA VAF and a higher number of NSMs were associated with worse OS in patients with metastatic disease. Further study is needed to determine optimal VAF thresholds for clinical decision making and the utility of cfDNA VAF as a prognostic marker in different tumor types.

Detection of breast cancer stem cell gene mutations in circulating free DNA during the evolution of metastases

Limited knowledge exists on the detection of breast cancer stem cell (BCSC)-related mutations in circulating free DNA (cfDNA) from patients with advanced cancers. Identification of new cancer biomarkers may allow for earlier detection of disease progression and treatment strategy modifications. We conducted a prospective study to determine the feasibility and prognostic utility of droplet digital polymerase chain reaction (ddPCR)-based BCSC gene mutation analysis of cfDNA in patients with breast cancer. Detection of quantitative BCSC gene mutation in cfDNA by ddPCR mirrors disease progression and thus may represent a valuable and cost-effective measure of tumor burden. We have previously shown that hematological and neurological expressed 1-like (HN1L), ribosomal protein L39 (RPL39), and myeloid leukemia factor 2 (MLF2) are novel targets for BCSC self-renewal, and targeting these genetic alterations could be useful for personalized genomic-based therapy. BCSC mutation detection in cfDNA may have important implications for diagnosis, prognosis, and serial monitoring.

Tumor volumetric correlation with plasma cell free DNA (cfDNA) mutation detection in metastatic lung cancers.

e14610 Background: In patients with metastatic lung cancers, analysis of cfDNA is increasingly used to detect oncogenes, frequently allowing matched targeted therapy. Mutation detection in cfDNA may be influenced by several factors, such as disease burden. We hypothesized that volumetrics, as routinely analyzed during radiation simulation, correlates with mutation detection in cfDNA. Methods: Patients underwent cfDNA analysis between 10/2016 and 1/2018. Those with metastatic NSCLC, adequate imaging for volumetric analysis (PET/CT and MRI brain), and who were treatment naïve at plasma draw were included. Plasma underwent a 21-gene next generation sequencing assay (Resolution Bioscience). A single observer segmented tumor volumes. Volume of disease was correlated with mutation detection in cfDNA for all 21 genes including the 8 NCCN oncogenes (EGFR, ALK, ROS1, BRAF, KRAS, HER2, RET, MET) with univariate Mann-Whitney. Results: Of the 210 pts with plasma, 52 met inclusion criteria. There were 22 males (42%), median age 67yo (IQR 59-74), 24 former smokers (median pack-years: 25), 44 adenocarcinomas (85%), 21 matched to targeted therapy based on cfDNA results (40%), and median cfDNA extracted concentration was 1.56 ng/mL (IQR 1.1 – 2.6 ng/mL). Involved sites included lymph nodes (n = 43), bone (n = 25), brain (n = 15), liver (n = 13), and adrenals (n = 12). Median total tumor volume was 67.0 mL (IQR 36.6-184.6 mL). When evaluating all 21 genes, cfDNA was mutation positive in 40 pts and negative in 12 pts. Median tumor volume was 77.6 mL and 40.4 mL for positive and negative, respectively (p = 0.12). For the 8 NCCN oncogenes, cfDNA was positive in 18 pts and negative in 34 pts. Median tumor volume was 105.3 mL and 67.0 mL for positive and negative, respectively (p = 0.40). Conclusions: Volumetric analysis showed there was a non-significant trend toward larger tumor volume among pts with positive cfDNA mutation detection. As the use of cfDNA continues to expand into earlier disease stage settings, volumetrics at diagnosis may become an increasingly important tool to help predict cfDNA mutation detection to guide targeted therapy. Further studies of volumetrics and cfDNA analysis are warranted.

Accuracy of analysis of cfDNA for detection of single nucleotide variants and copy number variants in breast cancer

BackgroundGene variants are dependable and sensitive biomarkers for target-specific therapies in breast cancer (BC). However, detection of mutations within tissues has many limitations. Plasma circulating free DNA (cfDNA) has been reported in many studies as an alternative tool for detection of mutations. But the diagnostic accuracy of cfDNA for most mutations in BC needs to be reviewed. This study was designed to perform comparative assessment of the diagnostic performance of cfDNA and DNA extracted from tissues for detection of single nucleotide variants (SNV) and copy number variants (CNV).MethodsTrue-positive (TP), false-positive (FP), false-negative (FN), and true-negative (TN) values were extracted from each selected study. Pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) were calculated. Subgroup analysis and single study omitted analysis were performed to quantify and explain the study heterogeneity.ResultsTwenty eligible studies that involved 1055 cases were included in this meta-analysis. SNV studies in early breast cancer (EBC) subgroup are not suitable for meta-analysis owing to high heterogeneity. However, in advanced breast cancer (ABC) subgroup, the pooled sensitivity and specificity of detection of SNVs were 0.78 (0.71–0.84) and 0.92 (0.87–0.95), respectively. The summary receiver operative curve (SROC) exhibited an area under the curve (AUC) of 0.91(0.88–0.93). The pooled results of studies involving subgroups of PIK3CA, TP53, and ESR1 indicate that the diagnostic value of different genes is different, such as AUC for PIK3CA and TP53 were reported to be 0.96 (0.94–0.98) and 0.94 (0.91–0.95), respectively, and ESR1 had the lowest diagnostic value of 0.80 (0.76–0.83). Owing to the low sensitivity and AUC in the cases of CNV, there is no value for cfDNA-based detection of CNV based on insufficient amount of CNV data.ConclusionThis meta-analysis suggests that the detection of gene mutations in cfDNA have adequate diagnostic accuracy and can be used as an alternative to the tumor tissue for detection of SNV but not for CNV in BC yet.

Utility of cfDNA Fragmentation Patterns in Designing the Liquid Biopsy Profiling Panels to Improve Their Sensitivity.

Genotyping of cell-free DNA (cfDNA) in plasma samples has the potential to allow for a noninvasive assessment of tumor biology, avoiding the inherent shortcomings of tissue biopsy. Next generation sequencing (NGS), a leading technology for liquid biopsy analysis, continues to be hurdled with several major issues with cfDNA samples, including low cfDNA concentration and high fragmentation. In this study, by employing Ion Torrent PGM semiconductor technology, we performed a comparison between two multi-biomarker amplicon-based NGS panels characterized by a substantial difference in average amplicon length. In course of the analysis of the peripheral blood from 13 diagnostic non-small cell lung cancer patients, equivalence of two panels, in terms of overall diagnostic sensitivity and specificity was shown. A pairwise comparison of the allele frequencies for the same somatic variants obtained from the pairs of panel-specific amplicons, demonstrated an identical analytical sensitivity in range of 140 to 170 bp amplicons in size. Further regression analysis between amplicon length and its coverage, illustrated that NGS sequencing of plasma cfDNA equally tolerates amplicons with lengths in the range of 120 to 170 bp. To increase the sensitivity of mutation detection in cfDNA, we performed a computational analysis of the features associated with genome-wide nucleosome maps, evident from the data on the prevalence of cfDNA fragments of certain sizes and their fragmentation patterns. By leveraging the support vector machine-based machine learning approach, we showed that a combination of nucleosome map associated features with GC content, results in the increased accuracy of prediction of high inter-sample sequencing coverage variation (areas under the receiver operating curve: 0.75, 95% CI: 0.750–0.752 vs. 0.65, 95% CI: 0.63–0.67). Thus, nucleosome-guided fragmentation should be utilized as a guide to design amplicon-based NGS panels for the genotyping of cfDNA samples.

Abstract P5-11-05: Concordance of genomic alterations with targeted sequencing of circulating tumor DNA (ctDNA) and circulating tumor cells (CTC) in endocrine-resistant metastatic breast cancer

Abstract Background: Liquid biopsy has emerged as a valuable strategy for analyzing resistance biomarkers in advanced breast cancer. Differences in genomic alterations between CTC and cfDNA has been reported before and may reflect differences in the cell compartments of origin. Our aim was to determine the mutational concordance between CTC and cfDNA in luminal metastatic breast cancer (MBC) with different levels of endocrine resistance. Methods: We evaluated the mutational spectrum in matched cfDNA and CTC samples of 38 patients with luminal (hormone receptors [HR] positive, HER2 negative) MBC. Using QIAmp Circulating Nucleic Acid Kit, cfDNA was isolated from plasma samples (5 mL), and from CTC samples obtained from plasma (7.5 mL). CTC were isolated by Epcam-based immune-magnetic enrichment and confirmed with AdnaTest Breast Cancer Detect (Epcam, Muc1, HER2). Sequencing of both cfDNA and CTC was performed using the Oncoming Breast cfDNA Assay (150 hotspots, 10 genes). Limit of detection range was 0.01-0.15%, with 92.1% cases equal or less than 0.1%. Concordance between mutational profile of CTC and cfDNA was analyzed and correlated with endocrine resistance and patient characteristics. Results: Forty-seven patients with HR+ HER2- MBC were included, yielding enough cfDNA for analysis in 38 cases (80%), with isolation of CTC in 8 cases (16.7%). Rate of mutation detection in CTC was 87.5% (7/8), with TP53 mutations in all cases and no cases of ESR1 mutations; two cases of ERBB3 and PIK3CA mutations were found only in CTC, without a correlate in cfDNA. In cfDNA, genetic alterations were observed in 63.4% of cases, with 70.8% of TP53 mutations, 37.5% of PI3KCA mutations and 25% ESR1 mutations (2 D538G, 3 Y537S, 2 V392I). Average number of mutations was 2.28 in CTC and 1.96 in cfDNA, with a range of 1-4 in both cases. Concordance between cfDNA and CTC was low, with only 20% of CTC mutations simultaneously detected in cfDNA. CTC were only detected in cases with primary or secondary endocrine resistance. The percentage of patients with genetic alterations in cfDNA varied according to the degree of endocrine resistance (no resistance, 42.8%; secondary resistance, 65.2%; primary resistance, 75%), although the difference was not statistically significant. An association was found between the rate of detection of mutations in cfDNA and the response status (progression disease: 90.9%; stable disease: 57.1%; objective response: 33.3%) (p=0.04). Conclusions: The low rate of CTC detection in HR positive MBC may limit its utility for guiding therapeutic decisions. However, the information provided by CTC sequencing does not completely overlap with the data provided by cfDNA, and may be complementary to cfDNA in endocrine-resistant MBC. Citation Format: Ayala de la Peña F, Navarro Manzano E, Fernández Pérez MP, García Martínez E, de la Morena Barrio P, Ivars Rubio A, González Billalabeitia E, Fernández Sánchez A, Teruel Montoya R, Marín Zafra G. Concordance of genomic alterations with targeted sequencing of circulating tumor DNA (ctDNA) and circulating tumor cells (CTC) in endocrine-resistant metastatic breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-11-05.