A single digital droplet PCR assay to detect multiple KIT exon 11 mutations in tumor and plasma from patients with gastrointestinal stromal tumors

Levels of circulating tumor DNA correlate with tumor volume in gastro-intestinal stromal tumors: an exploratory long-term follow-up study

Patients with gastro-intestinal stromal tumors (GISTs) undergoing tyrosine kinase inhibitor therapy are monitored with regular computed tomography (CT) scans, exposing patients to cumulative radiation. This exploratory study aimed to evaluate circulating tumor DNA (ctDNA) testing to monitor treatment response and compare changes in ctDNA levels with RECIST 1.1 and total tumor volume measurements. Between 2014 and 2021, six patients with KIT proto-oncogene, receptor tyrosine kinase (KIT) exon-11-mutated GIST from whom long-term plasma samples were collected prospectively were included in the study. ctDNA levels of relevant plasma samples were determined using the KIT exon 11 digital droplet PCR drop-off assay. Tumor volume measurements were performed using a semi-automated approach. In total, 94 of 130 clinically relevant ctDNA samples were analyzed. Upon successful treatment response, ctDNA became undetectable in all patients. At progressive disease, ctDNA was detectable in five out of six patients. Higher levels of ctDNA correlated with larger tumor volumes. Undetectable ctDNA at the time of progressive disease on imaging was consistent with lower tumor volumes compared to those with detectable ctDNA. In summary, ctDNA levels seem to correlate with total tumor volume at the time of progressive disease. Our exploratory study shows promise for including ctDNA testing in treatment follow-up.

Detection and Monitoring of Tumor-Derived Mutations in Circulating Tumor DNA Using the UltraSEEK Lung Panel on the MassARRAY System in Metastatic Non-Small Cell Lung Cancer Patients

Analysis of circulating tumor DNA (ctDNA) is a potential minimally invasive molecular tool to guide treatment decision-making and disease monitoring. A suitable diagnostic-grade platform is required for the detection of tumor-specific mutations with high sensitivity in the circulating cell-free DNA (ccfDNA) of cancer patients. In this multicenter study, the ccfDNA of 72 patients treated for advanced-stage non-small cell lung cancer (NSCLC) was evaluated using the UltraSEEK® Lung Panel on the MassARRAY® System, covering 73 hotspot mutations in EGFR, KRAS, BRAF, ERBB2, and PIK3CA against mutation-specific droplet digital PCR (ddPCR) and routine tumor tissue NGS. Variant detection accuracy at primary diagnosis and during disease progression, and ctDNA dynamics as a marker of treatment efficacy, were analyzed. A multicenter evaluation using reference material demonstrated an overall detection rate of over 90% for variant allele frequencies (VAFs) > 0.5%, irrespective of ccfDNA input. A comparison of UltraSEEK® and ddPCR analyses revealed a 90% concordance. An 80% concordance between therapeutically targetable mutations detected in tumor tissue NGS and ccfDNA UltraSEEK® analysis at baseline was observed. Nine of 84 (11%) tumor tissue mutations were not covered by UltraSEEK®. A decrease in ctDNA levels at 4-6 weeks after treatment initiation detected with UltraSEEK® correlated with prolonged median PFS (46 vs. 6 weeks; p < 0.05) and OS (145 vs. 30 weeks; p < 0.01). Using plasma-derived ccfDNA, the UltraSEEK® Lung Panel with a mid-density set of the most common predictive markers for NSCLC is an alternative tool to detect mutations both at diagnosis and during disease progression and to monitor treatment response.

Development of multiplex drop-off digital PCR assays for hotspot mutation detection of KRAS, NRAS, BRAF and PIK3CA in the plasma of colorectal cancer patients

The detection of mutations in KRAS, NRAS, BRAF and PIK3CA has become essential in treatment management of metastatic colorectal cancer (mCRC), with the approval of new targeted therapies. We developed novel multiplex drop-off digital PCR (MDO-dPCR) assays, by combining amplitude-/ratio-based multiplexing with drop-off/double drop-off strategies, which allow for detection of at least 69 most frequent hotspot mutations in all four genes with only three reactions. We assessed the analytical performance of the assays using synthetic oligonucleotides, further validated on plasma cfDNA samples from a large cohort of CRC patients and compared with next generation sequencing (NGS) data. The MDO-dPCR assays showed a high sensitivity with a limit of detection (LOD) ranging from 0.084 to 0.182% in mutant allelic frequency (MAF). The screening of plasma cfDNAs from 106 CRC patients identified mutations in 42.45% of them, with a sensitivity of 95.24%, a specificity of 98.53% and an accuracy of 96.98% for mutation detection and a strong correlation of measured MAFs as compared to NGS results. The high sensitivity and comprehensive mutation coverage of the MDO-dPCR assays make them suitable for rapid and cost-effective detection of KRAS, NRAS, BRAF and PIK3CA mutations in the plasma of CRC patients, and could be useful in early response assessment and longitudinal disease monitoring.

Plasma Sequencing for Patients with GIST-Limitations and Opportunities in an Academic Setting

Circulating tumor DNA (ctDNA) from circulating free DNA (cfDNA) in GIST is of interest for the detection of heterogeneous resistance mutations and treatment monitoring. However, methodologies for use in a local setting are not standardized and are error-prone and difficult to interpret. We established a workflow to evaluate routine tumor tissue NGS (Illumina-based next generation sequencing) panels and pipelines for ctDNA sequencing in an academic setting. Regular blood collection (Sarstedt) EDTA tubes were sufficient for direct processing whereas specialized tubes (STRECK) were better for transportation. Mutation detection rate was higher in automatically extracted (AE) than manually extracted (ME) samples. Sensitivity and specificity for specific mutation detection was higher using digital droplet (dd)PCR compared to NGS. In a retrospective analysis of NGS and clinical data (133 samples from 38 patients), cfDNA concentration correlated with tumor load and mutation detection. A clinical routine pipeline and a novel research pipeline yielded different results, but known and resistance-mediating mutations were detected by both and correlated with the resistance spectrum of TKIs used. In conclusion, NGS routine panel analysis was not sensitive and specific enough to replace solid biopsies in GIST. However, more precise methods (hybridization capture NGS, ddPCR) may comprise important research tools to investigate resistance. Future clinical trials need to compare methodology and protocols.

Circulating Tumor DNA Mutations in Progressive Gastrointestinal Stromal Tumors Identify Biomarkers of Treatment Resistance and Uncover Potential Therapeutic Strategies

Liquid biopsy circulating tumor DNA (ctDNA)-based approaches may represent a non-invasive means for molecular interrogation of gastrointestinal stromal tumors (GISTs). We deployed a customized 29-gene Archer^® LiquidPlex™ targeted panel on 64 plasma samples from 46 patients. The majority were known to harbor KIT mutations (n = 41, 89.1%), while 3 were PDGFRA exon 18 D842V mutants and the rest (n = 2) were wild type for KIT and PDGFRA. In terms of disease stage, 14 (30.4%) were localized GISTs that had undergone complete surgical resection while the rest (n = 32) were metastatic. Among ten patients, including 7 on tyrosine kinase inhibitors, with evidence of disease progression at study inclusion, mutations in ctDNA were detected in 7 cases (70%). Known somatic mutations in KIT (n = 5) or PDGFRA (n = 1) in ctDNA were identified only among 6 of the 10 patients. These KIT mutants included duplication, indels, and single-nucleotide variants. The median mutant AF in ctDNA was 11.0% (range, 0.38%–45.0%). In patients with metastatic progressive KIT-mutant GIST, tumor burden was higher with detectable KIT ctDNA mutation than in those without (median, 5.97 cm vs. 2.40 cm, p = 0.0195). None of the known tumor mutations were detected in ctDNA for localized cases (n = 14) or metastatic cases without evidence of disease progression (n = 22). In patients with serial samples along progression of disease, secondary acquired mutations, including a potentially actionable PIK3CA exon 9 c.1633G>A mutation, were detected. ctDNA mutations were not detectable when patients responded to a switch in TKI therapy. In conclusion, detection of GIST-related mutations in ctDNA using a customized targeted NGS panel represents an attractive non-invasive means to obtain clinically tractable information at the time of disease progression.

Monitoring Circulating Tumor DNA During Surgical Treatment in Patients with Gastrointestinal Stromal Tumors

The majority of patients diagnosed with advanced gastrointestinal stromal tumors (GISTs) are successfully treated with a combination of surgery and tyrosine kinase inhibitors (TKIs). However, it remains challenging to monitor treatment efficacy and identify relapse early. Here, we utilized a sequencing strategy based on molecular barcodes and developed a GIST-specific panel to monitor tumor-specific and TKI resistance mutations in cell-free DNA and applied the approach to patients undergoing surgical treatment. Thirty-two patients with GISTs were included, and 161 blood plasma samples were collected and analyzed at routine visits before and after surgery and at the beginning, during, and after surgery. Patients were included regardless of their risk category. Our GIST-specific sequencing approach allowed detection of tumor-specific mutations and TKI resistance mutations with mutant allele frequency < 0.1%. Circulating tumor DNA (ctDNA) was detected in at least one timepoint in nine of 32 patients, ranging from 0.04% to 93% in mutant allele frequency. High-risk patients were more often ctDNA positive than other risk groups (P < 0.05). Patients with detectable ctDNA also displayed higher tumor cell proliferation rates (P < 0.01) and larger tumor sizes (P < 0.01). All patients who were ctDNA positive during surgery became negative after surgery. Finally, in two patients who progressed on TKI treatment, we detected multiple resistance mutations. Our data show that ctDNA may become a clinically useful biomarker in monitoring treatment efficacy in patients with high-risk GISTs and can assist in treatment decision making.

Circulating tumor DNA as a biomarker for monitoring early treatment responses of patients with advanced lung adenocarcinoma receiving immune checkpoint inhibitors

Immunotherapy for metastasized non-small-cell lung cancer (NSCLC) can show long-lasting clinical responses. Selection of patients based on programmed death-ligand 1 (PD-L1) expression shows limited predictive value for durable clinical benefit (DCB). We investigated whether early treatment effects as measured by a change in circulating tumor DNA (ctDNA) level is a proxy of early tumor response to immunotherapy according to response evaluation criteria in solid tumors v1.1 criteria, progression-free survival (PFS), DCB, and overall survival (OS). To this aim, blood tubes were collected from advanced-stage lung adenocarcinoma patients (n = 100) receiving immune checkpoint inhibitors (ICI) at baseline (t0 ) and prior to first treatment evaluation (4-6 weeks; t1 ). Nontargetable (driver) mutations detected in the pretreatment tumor biopsy were used to quantify tumor-specific ctDNA levels using droplet digital PCR. We found that changes in ctDNA levels were strongly associated with tumor response. A > 30% decrease in ctDNA at t1 correlated with a longer PFS and OS. In total, 80% of patients with a DCB of ≥ 26 weeks displayed a > 30% decrease in ctDNA levels. For patients with a PD-L1 tumor proportion score of ≥ 1%, decreasing ctDNA levels were associated with a higher frequency a DCB (80%) and a prolonged median PFS (85 weeks) and OS (101 weeks) compared with patients with no decrease in ctDNA (34%; 11 and 39 weeks, respectively). This study shows that monitoring of ctDNA dynamics is an easy-to-use and promising tool for assessing PFS, DCB, and OS for ICI-treated NSCLC patients.

Liquid Biopsies in Sarcoma Clinical Practice: Where Do We Stand?

Sarcomas are rare tumors of bone and soft tissue with a mesenchymal origin. This uncommon type of cancer is marked by a high heterogeneity, consisting of over 70 subtypes. Because of this broad spectrum, their treatment requires a subtype-specific therapeutic approach. Tissue biopsy is currently the golden standard for sarcoma diagnosis, but it has its limitations. Over the recent years, methods to detect, characterize, and monitor cancer through liquid biopsy have evolved rapidly. The analysis of circulating biomarkers in peripheral blood, such as circulating tumor cells (CTC) or circulating tumor DNA (ctDNA), could provide real-time information on tumor genetics, disease state, and resistance mechanisms. Furthermore, it traces tumor evolution and can assess tumor heterogeneity. Although the first results in sarcomas are encouraging, there are technical challenges that need to be addressed for implementation in clinical practice. Here, we summarize current knowledge about liquid biopsies in sarcomas and elaborate on different strategies to integrate liquid biopsy into sarcoma clinical care.

A Nationwide Study on the Impact of Routine Testing for EGFR Mutations in Advanced NSCLC Reveals Distinct Survival Patterns Based on EGFR Mutation Subclasses

EGFR mutation analysis in non-small-cell lung cancer (NSCLC) patients is currently standard-of-care. We determined the uptake of EGFR testing, test results and survival of EGFR-mutant NSCLC patients in the Netherlands, with the overall objective to characterize the landscape of clinically actionable EGFR mutations and determine the role and clinical relevance of uncommon and composite EGFR mutations. Non-squamous NSCLC patients diagnosed in 2013, 2015 and 2017 were identified in the Netherlands Cancer Registry (NCR) and matched to the Dutch Pathology Registry (PALGA). Overall, 10,254 patients were included. Between 2013-2017, the uptake of EGFR testing gradually increased from 72.7% to 80.9% (p < 0.001). Multi-gene testing via next-generation sequencing (increased from 7.8% to 78.7% (p < 0.001), but did not affect the number of detected EGFR mutations (n = 925; 11.7%; 95% confidence interval (CI), 11.0-12.4) nor the distribution of variants. For patients treated with first-line EGFR inhibitors (n = 651), exon 19 deletions were associated with longer OS than L858R (HR 1.58; 95% CI, 1.30-1.92; p < 0.001) or uncommon, actionable variants (HR 2.13; 95% CI, 1.60-2.84; p < 0.001). Interestingly, OS for patients with L858R was similar to those with uncommon, actionable variants (HR 1.31; 95% CI, 0.98-1.75; p = 0.069). Our analysis indicates that grouping exon 19 deletions and L858R into one class of 'common' EGFR mutations in a clinical trial may mask the true activity of an EGFR inhibitor towards specific mutations.

Double Drop-Off Droplet Digital PCR: A Novel, Versatile Tool for Mutation Screening and Residual Disease Monitoring in Acute Myeloid Leukemia Using Cellular or Cell-Free DNA

In acute myeloid leukemia (AML), somatic gene mutations are important prognostic markers and increasingly constitute therapeutic targets. Therefore, robust, sensitive, and fast diagnostic assays are needed. Current techniques for mutation screening and quantification, including next-generation sequencing and quantitative PCR, each have weaknesses that leave a need for novel diagnostic tools. We established double drop-off digital droplet PCR (DDO-ddPCR) assays for gene mutations in NPM1, IDH2, and NRAS, which can detect and quantify diverse alterations at two nearby hotspot regions present in these genes. These assays can be used for mutation screening as well as quantification and sequential monitoring. The assays were validated against next-generation sequencing and existing ddPCR assays and achieved high concordance with an overall sensitivity comparable to conventional digital PCR. In addition, the feasibility of detecting and monitoring genetic alterations in peripheral blood cell-free DNA (cfDNA) of patients with AML by DDO-ddPCR was studied. cfDNA analysis was found to have similar sensitivity compared to quantitative PCR-based analysis of peripheral blood. Finally, the cfDNA-based digital PCR in several clinical scenarios was found to be useful in long-term monitoring of target-specific therapy, early response assessment during induction chemotherapy, and identification of mutations in patients with extramedullary disease. Thus, DDO-ddPCR-based cfDNA analysis may complement existing genetic tools for diagnosis and disease monitoring in AML.

Liquid Biopsy in Gastrointestinal Stromal Tumors: Ready for Prime Time?

OPINION STATEMENT

Gastrointestinal stromal tumor (GIST) constitutes a paradigm for clinically effective targeted inhibition of oncogenic driver mutations. Therefore, GIST has emerged as a compelling clinical and biological model to study oncogene addiction and to validate preclinical concepts for drug response and drug resistance. Oncogenic activation of KIT or PDGFRA receptor tyrosine kinases is the essential drivers of GIST progression throughout all stages of the disease. Interestingly, KIT/PDGFRA genotype predicts the response to first-line imatinib and to all tyrosine kinase inhibitors (TKIs) approved or in investigation after imatinib failure. Considering that TKIs are effective only against a subset of KIT or PDGFRA resistance mutations, close monitoring of tumor dynamics with non-invasive methods such as liquid biopsy emerges as a necessary step forward in the field. Liquid biopsy, in contrast to solid tumor biopsy, aims to characterize tumors irrespective of heterogeneity. Although there are several components in the peripheral blood, most recent studies have been focused on circulating tumor (ct)DNA, due to the technological feasibility, the stability of DNA itself and DNA alterations, and the therapeutic development in precision oncology largely based on the identification of genetic driver mutations. In the present review, we systematically dissect the current wealth of data of ctDNA in GIST. To do so, a critical understanding of the promises and limitations of the current technologies will be followed by an exposition of the knowledge gathered with such studies in GIST. Collectively, our goal is to establish clear premises that can be used as the foundations to build future studies towards the clinical implementation of ctDNA evaluation in GIST patients.

Sarcoma treatment in the era of molecular medicine

Sarcomas are heterogeneous and clinically challenging soft tissue and bone cancers. Although constituting only 1% of all human malignancies, sarcomas represent the second most common type of solid tumors in children and adolescents and comprise an important group of secondary malignancies. More than 100 histological subtypes have been characterized to date, and many more are being discovered due to molecular profiling. Owing to their mostly aggressive biological behavior, relative rarity, and occurrence at virtually every anatomical site, many sarcoma subtypes are in particular difficult-to-treat categories. Current multimodal treatment concepts combine surgery, polychemotherapy (with/without local hyperthermia), irradiation, immunotherapy, and/or targeted therapeutics. Recent scientific advancements have enabled a more precise molecular characterization of sarcoma subtypes and revealed novel therapeutic targets and prognostic/predictive biomarkers. This review aims at providing a comprehensive overview of the latest advances in the molecular biology of sarcomas and their effects on clinical oncology; it is meant for a broad readership ranging from novices to experts in the field of sarcoma.

Utility of Circulating Tumor DNA in the Management of Patients With GI Stromal Tumor: Analysis of 243 Patients

PURPOSE

GI stromal tumor (GIST) is the most common sarcoma of the GI tract. Management of patients with GIST is determined by KIT, PDGFRA, or other genomic alterations. Tissue-based next-generation sequencing (NGS) analysis is the standard approach for diagnosis, prognosis, and treatment selection. However, circulating tumor DNA (ctDNA)–based NGS is a novel and noninvasive alternative.

METHODS

ctDNA sequencing results were evaluated in blood samples from 243 de-identified patients within the Guardant360 database. Under an approved institutional review board protocol, a retrospective analysis was performed on 45 single-institution patients.

RESULTS

Of 243 patients, 114 (47%) were women, and the median age was 59 years (range, 17-90 years). Patients with no alterations and variations of uncertain significance were excluded. Of the 162 patients with known pathogenic mutations, KIT was the most common (56%), followed by NF (7%), PDGFRA (6%), PI3KCA (6%), KRAS (5%), and others (6%). Most tumors harbored an actionable KIT or PDGFRA mutation. Our institutional cohort (n = 45) had 16 (35%) KIT exon 11 mutations, 3 (6%) KIT exon 9 mutations, and 1 (2%) PDGFRA mutation detected on ctDNA. Resistance mutations were observed in KIT exon 17 (8 patients), exon 13 (3 patients), and in both (3 patients). Our comparison of ctDNA with tissue NGS revealed a positive predictive value (PPV) of 100%. Failure of concordance was observed in patients with localized or low disease burden. From the time of ctDNA testing, the median overall survival was not reached, whereas the median progression-free survival was 7 months.

CONCLUSION

ctDNA provides a rapid, noninvasive analysis of current mutations with a high PPV for patients with metastatic GIST. ctDNA-based testing may help to define the optimal choice of therapy on the basis of resistance mutations and should be studied prospectively.

Mutational Testing in Gastrointestinal Stromal Tumor

Targeted treatment has become a major modality in cancer management. Such cancer drugs are generally designed to treat tumors with certain genetic/genomic makeups. Mutational testing prior to prescribing targeted therapy is crucial in identifying who can receive clinical benefit from specific cancer drugs. Over the last two decades, gastrointestinal stromal tumors (GISTs) have evolved from histogenetically obscure to being identified as distinct gastrointestinal mesenchymal tumors with well-defined clinical and molecular characteristics, for which multiple lines of targeted therapies are available. Although the National Comprehensive Cancer Network (NCCN) strongly recommends mutational testing for optimal management of GIST, many GIST patients still have neither a mutation test performed or any mutation-guided cancer management. Here, we review the mutation-guided landscape of GIST, mutational testing methods, and the recent development of new therapies targeting GIST with specific mutations.

The new horizon of liquid biopsy in sarcoma: the potential utility of circulating tumor nucleic acids

The diagnosis, treatment and prognosis of sarcoma are mainly dependent on tissue biopsy, which is limited in its ability to provide a panoramic view into the dynamics of tumor progression. In addition, effective biomarkers to monitor the progression and therapeutic response of sarcoma are lacking. Liquid biopsy, a recent technological breakthrough, has gained great attention in the last few decades. Nucleic acids (such as DNA, mRNAs, microRNAs, and long non-coding RNAs) that are released from tumors circulate in the blood of cancer patients and can be evaluated through liquid biopsy. Circulating tumor nucleic acids reflect the intertumoral and intratumoral heterogeneity, and thus liquid biopsy provides a noninvasive strategy to examine these molecules compared with traditional tissue biopsy. Over the past decade, a great deal of information on the potential utilization of circulating tumor nucleic acids in sarcoma screening, prognosis and therapy efficacy monitoring has emerged. Several specific gene mutations in sarcoma can be detected in peripheral blood samples from patients and can be found in circulating tumor DNA to monitor sarcoma. In addition, circulating tumor non-coding RNA may also be a promising biomarker in sarcoma. In this review, we discuss the clinical application of circulating tumor nucleic acids as blood-borne biomarkers in sarcoma.

Comparison of Circulating Cell-Free DNA Extraction Methods for Downstream Analysis in Cancer Patients

Circulating cell-free DNA (ccfDNA) may contain DNA originating from the tumor in plasma of cancer patients (ctDNA) and enables noninvasive cancer diagnosis, treatment predictive testing, and response monitoring. A recent multicenter evaluation of workflows by the CANCER-ID consortium using artificial spiked-in plasma showed significant differences and consequently the importance of carefully selecting ccfDNA extraction methods. Here, the quantity and integrity of extracted ccfDNA from the plasma of cancer patients were assessed. Twenty-one cancer patient-derived cell-free plasma samples were selected to compare the Qiagen CNA, Maxwell RSC ccfDNA plasma, and Zymo manual quick ccfDNA kit. High-volume citrate plasma samples collected by diagnostic leukapheresis from six cancer patients were used to compare the Qiagen CNA (2 mL) and QIAamp MinElute ccfDNA kit (8 mL). This study revealed similar integrity and similar levels of amplified short-sized fragments and tumor-specific mutants comparing the CNA and RSC kits. However, the CNA kit consistently showed the highest yield of ccfDNA and short-sized fragments, while the RSC and ME kits showed higher variant allelic frequencies (VAFs). Our study pinpoints the importance of standardizing preanalytical conditions as well as consensus on defining the input of ccfDNA to accurately detect ctDNA and be able to compare results in a clinical routine practice, within and between clinical studies.

Progress in determining response to treatment in gastrointestinal stromal tumor

Introduction: Gastrointestinal stromal tumor (GIST) is the most common malignant mesenchymal tumor of the gastrointestinal system. Multiple advances in the management of GIST from the discovery of KIT/PDGRA and other genetic alterations have led to the development of multiple tyrosine kinase inhibitors. Response assessment in GIST is determined with iRECIST (Response Evaluation Criteria in Solid Tumors), PERCIST (PET response criteria in solid tumors), or Choi criteria. Molecular genotyping of the tissue samples is the recent standard for diagnosis, treatment, and response to treatment.Areas covered: In this study, we provide a brief overview of the history of the GIST, molecular sequencing, available treatment options and clinical trials, radiologic response assessment, and the role of ctDNA in response evaluation.Expert opinion: Future GIST management is related to the development of sensitive assays to detect genetic alterations for initial diagnosis, treatment selection, monitoring the response to treatment, resistant mutations, and predicting survival.

Clinical value of next generation sequencing of plasma cell-free DNA in gastrointestinal stromal tumors

Background

Gastrointestinal stromal tumor (GIST) initiation and evolution is commonly framed by KIT/PDGFRA oncogenic activation, and in later stages by the polyclonal expansion of resistant subpopulations harboring KIT secondary mutations after the onset of imatinib resistance. Thus, circulating tumor (ct)DNA determination is expected to be an informative non-invasive dynamic biomarker in GIST patients.

Methods

We performed amplicon-based next-generation sequencing (NGS) across 60 clinically relevant genes in 37 plasma samples from 18 GIST patients collected prospectively. ctDNA alterations were compared with NGS of matched tumor tissue samples (obtained either simultaneously or at the time of diagnosis) and cross-validated with droplet digital PCR (ddPCR).

Results

We were able to identify cfDNA mutations in five out of 18 patients had detectable in at least one timepoint. Overall, NGS sensitivity for detection of cell-free (cf)DNA mutations in plasma was 28.6%, showing high concordance with ddPCR confirmation. We found that GIST had relatively low ctDNA shedding, and mutations were at low allele frequencies. ctDNA was detected only in GIST patients with advanced disease after imatinib failure, predicting tumor dynamics in serial monitoring. KIT secondary mutations were the only mechanism of resistance found across 10 imatinib-resistant GIST patients progressing to sunitinib or regorafenib.

Conclusions

ctDNA evaluation with amplicon-based NGS detects KIT primary and secondary mutations in metastatic GIST patients, particularly after imatinib progression. GIST exhibits low ctDNA shedding, but ctDNA monitoring, when positive, reflects tumor dynamics.

Circulating tumor cells in lung cancer are prognostic and predictive for worse tumor response in both targeted- and chemotherapy

Background

It is unknown whether the presence of circulating tumor cells (CTC), a known prognostic factor, influences treatment outcome. We investigated whether baseline CTC in non-small cell lung cancer (NSCLC) patients treated with tyrosine kinase inhibitors (TKI) or chemotherapy was associated with response to therapy.

Methods

We included consecutive advanced NSCLC patients, stratified by therapy. Before treatment the number of CTC was measured by CellSearch. Tumor response rates, progression free survival (PFS) and overall survival (OS) in patients with and without CTC at baseline were compared.

Results

We included 86 patients (34 treated by TKI). Response rates of patients with CTC were lower than in patients without CTC (OR =0.22, P<0.01, adjusted for performance score and smoking status). In both treatment groups, the difference in response rates between patients with and without CTC was similar (TKI response: 25% with CTC versus 73% without CTC, chemotherapy response: 35% versus 51% respectively, interaction P=0.17). CTC was associated with a worse PFS [hazard ratio (HR) =2.0, 95% confidence interval (CI): 1.2-3.2, P=0.01] and OS (HR =1.7, 95% CI: 1.1-2.8, P=0.03) after adjustment for performance score and stage. The association remained significant after adding tumor response to the model (PFS: HR =1.9, 95% CI: 1.0-3.0, P=0.01, OS: HR =1.6, 95% CI: 1.0-2.6, P=0.05). No significant interaction between CTC presence and therapy was observed (P=0.42 for PFS and P=0.83 for OS).

Conclusions

Presence of CTC in advanced NSCLC patients is associated with low response rates, shorter PFS and OS, independent of the received therapy.

Circulating tumor cells in advanced non-small cell lung cancer patients are associated with worse tumor response to checkpoint inhibitors

Background

Non-small cell lung cancer (NSCLC) patients treated with checkpoint inhibitors show long lasting responses, but it is hard to predict which patients will profit from this treatment with the currently used marker, programmed death ligand 1 (PD-L1). We hypothesized that circulating tumor cells (CTC) or tumor derived extracellular vesicles (tdEV) are markers of treatment efficacy.

Methods

Patients with advanced NSCLC treated with checkpoint inhibitors were included. Blood was drawn at baseline (T0) and at 4 weeks of treatment (T1) for analysis of CTC and tdEV using CellSearch®. Tumor response was classified as partial or complete response based on the response evaluation criteria in solid tumors (RECISTv1.1) measured 4–6 weeks after start of treatment. Durable response was defined as stable disease, partial or complete response without disease progression at 6 months. Analyses were adjusted for covariables including PD-L1 expression.

Results

We included 104 patients (30 with a tumor response, 74 non-responders, 2 responses not evaluable due to early death); 63 patients provided T1 samples. All patients were treated with PD-L1 inhibitors. The majority of patients received second (85%) or third line (treatment with nivolumab monotherapy (89%).

CTC were present in 33/104 patients at T0 (32%) and 17/63 at T1 (27%), 9/63 patients had CTC (14%) at both time points. The presence of CTC, both at T0 (OR = 0.28, p = 0.02,) and T1 (OR = 0.07, p < 0.01), was an independent predictive factor for a lack of durable response and was associated with worse progression free and overall survival. More tdEV were associated with shorter survival but not with response rate.

Conclusion

CTC occur in one third of advanced NSCLC patients and their presence is a predictive factor for a worse durable response rate to checkpoint inhibitors. tdEV are associated with shorter survival but not with response.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0649-2) contains supplementary material, which is available to authorized users.

IQN path ASBL report from the first European cfDNA consensus meeting: expert opinion on the minimal requirements for clinical ctDNA testing

Liquid biopsy testing is a new laboratory-based method that detects tumour mutations in circulating free DNA (cfDNA) derived from minimally invasive blood sampling techniques. Recognising the significance for clinical testing, in 2017, IQN Path provided external quality assessment for liquid biopsy testing. Representatives of those participating laboratories were invited to attend a workshop to discuss the findings and how to achieve quality implementation of cfDNA testing in the clinical setting, the discussion and outcomes of this consensus meeting are described below. Predictive molecular profiling using tumour tissue in order to select cancer patients eligible for targeted therapy is now routine in diagnostic pathology. If insufficient tumour tissue material is available, in some circumstances, recent European Medicines Agency (EMA) guidance recommends mutation testing with plasma cfDNA. Clinical applications of cfDNA include treatment selection based on clinically relevant mutations derived from pre-treatment samples and the detection of resistant mutations upon progression of the disease. In order to identify tumour-related mutations in amongst other nucleic acid material found in plasma samples, highly sensitive laboratory methods are needed. In the workshop, we discussed the variable approaches taken with regard to cfDNA extraction methods, the tests, and considered the impact of false-negative test results. We explored the lack of standardisation of complex testing procedures ranging from plasma collection, transport, processing and storage, cfDNA extraction, and mutation analysis, to interpretation and reporting of results. We will also address the current status of clinical validation and clinical utility, and its use in current diagnosis. This workshop revealed a need for guidelines on with standardised procedures for clinical cfDNA testing and reporting, and a requirement for cfDNA-based external quality assessment programs.

Clinical relevance of circulating molecules in cancer: focus on gastrointestinal stromal tumors

In recent years, growing research interest has focused on the so-called liquid biopsy. A simple blood test offers access to a plethora of information, which might be extremely helpful in understanding or characterizing specific diseases. Blood contains different molecules, of which circulating free DNA (cfDNA), circulating tumor DNA (ctDNA), circulating tumor cells (CTCs) and extracellular vesicles (EVs) are the most relevant. Conceivably, these molecules have the potential for tumor diagnosis, monitoring tumor evolution, and evaluating treatment response and pharmacological resistance. This review aims to present a state-of-the-art of recent advances in circulating DNA and circulating RNA in gastrointestinal stromal tumors (GISTs). To date, progress in liquid biopsy has been scarce in GISTs due to several issues correlated with the nature of the pathology. Namely, heterogeneity in primary and secondary mutations in key driver genes has greatly slowed the development and application in GISTs, unlike in other tumor types in which liquid biopsy has already been translated into clinical practice. However, meaningful novel data have shown in recent years a significant clinical potential of ctDNA, CTCs, EVs and circulating RNA in GISTs.

Diagnosis and Treatment Monitoring of a Patient with Gastrointestinal Stromal Tumor by Next-Generation Sequencing and Droplet Digital Polymerase Chain Reaction Assay of a PDGFRA Mutation in Plasma-Derived Cell-Free Tumor DNA

In patients with a suspected malignancy, standard-of care management currently includes histopathologic examination and analysis of tumor-specific molecular abnormalities. Herein, we present a 77-year-old patient with an abdominal mass suspected to be a gastrointestinal stromal tumor (GIST) but without the possibility to collect a tumor biopsy. Cell-free DNA extracted from a blood sample was analyzed for the presence of mutations in GIST-specific genes using next generation sequencing. Furthermore, liquid biopsies were used to monitor the levels of mutant DNA copies during treatment with a tumor-specific mutation droplet digital PCR assay that correlated with the clinical and radiological response. Blood-based testing is a good alternative for biopsy-based testing. However, it should only be applied when biopsies are not available or possible to obtain because overall, in only 50%-85% of the cell-free plasma samples is the known tumor mutation detected.

International pilot external quality assessment scheme for analysis and reporting of circulating tumour DNA

BACKGROUND

Molecular analysis of circulating tumour DNA (ctDNA) is becoming increasingly important in clinical treatment decisions. A pilot External Quality Assessment (EQA) scheme for ctDNA analysis was organized by four European EQA providers under the umbrella organization IQN Path, in order to investigate the feasibility of delivering an EQA to assess the detection of clinically relevant variants in plasma circulating cell-free DNA (cfDNA) and to analyze reporting formats.

METHODS

Thirty-two experienced laboratories received 5 samples for EGFR mutation analysis and/or 5 samples for KRAS and NRAS mutation analysis. Samples were artificially manufactured to contain 3 mL of human plasma with 20 ng/mL of fragmented ctDNA and variants at allelic frequencies of 1 and 5%.

RESULTS

The scheme error rate was 20.1%. Higher error rates were observed for RAS testing when compared to EGFR analysis, for allelic frequencies of 1% compared to 5%, and for cases including 2 different variants. The reports over-interpreted wild-type results and frequently failed to comment on the amount of cfDNA extracted.

CONCLUSIONS

The pilot scheme demonstrated the feasibility of delivering a ctDNA EQA scheme and the need for such a scheme due to high error rates in detecting low frequency clinically relevant variants. Recommendations to improve reporting of cfDNA are provided.