Serial ctDNA Monitoring to Predict Response to Systemic Therapy in Metastatic Gastrointestinal Cancers

Early identification of disease progression in ALK-rearranged lung cancer using circulating tumor DNA analysis

Targeted kinase inhibitors improve the prognosis of lung cancer patients with ALK alterations (ALK+). However, due to the emergence of acquired resistance and varied clinical trajectories, early detection of disease progression is warranted to guide patient management and therapy decisions. We utilized 343 longitudinal plasma DNA samples from 43 ALK+ NSCLC patients receiving ALK-directed therapies to determine molecular progression based on matched panel-based targeted next-generation sequencing (tNGS), and shallow whole-genome sequencing (sWGS). ALK-related alterations were detected in 22 out of 43 (51%) patients. Among 343 longitudinal plasma samples analyzed, 174 (51%) were ctDNA-positive. ALK variant and fusion kinetics generally reflected the disease course. Evidence for early molecular progression was observed in 19 patients (44%). Detection of ctDNA at therapy baseline indicated shorter times to progression compared to cases without mutations at baseline. In patients who succumbed to the disease, ctDNA levels were highly elevated towards the end of life. Our results demonstrate the potential utility of these NGS assays in the clinical management of ALK+ NSCLC.

Perioperative ctDNA-based Molecular Residual Disease Detection for Non-Small Cell Lung Cancer: A Prospective Multicenter Cohort Study (LUNGCA-1)

PURPOSE

We assessed whether perioperative circulating tumor DNA (ctDNA) could be a biomarker for early detection of molecular residual disease (MRD) and prediction of postoperative relapse in resected non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Based on our prospective, multicenter cohort on dynamic monitoring of ctDNA in lung cancer surgery patients (LUNGCA), we enrolled 950 plasma samples obtained at three perioperative time points (before surgery, 3-day and 1-month after surgery) of 330 stage I-III NSCLC patients (LUNGCA-1), as a part of LUNGCA cohort. Using a customized 769-gene panel, somatic mutations in tumor tissues and plasma samples were identified with next-generation sequencing and utilized for ctDNA-based MRD analysis.

RESULTS

Preoperative ctDNA positivity was associated with lower recurrence-free survival (RFS) (HR=4.2; P<0.001). The presence of MRD (ctDNA positivity at postoperative 3-day and/or 1-month) was a strong predictor for disease relapse (HR=11.1; P<0.001). ctDNA-based MRD had a higher relative contribution to RFS prediction than all clinicopathological variables such as the TNM stage. Furthermore, MRD-positive patients who received adjuvant therapies had improved RFS over those not receiving adjuvant therapy (HR=0.3; P=0.008), whereas MRD-negative patients receiving adjuvant therapies had lower RFS than their counterparts without adjuvant therapy (HR=3.1; P<0.001). After adjusting for clinicopathological variables, whether receiving adjuvant therapies remained an independent factor for RFS in the MRD-positive population (P=0.002) but not in the MRD-negative population (P=0.283).

CONCLUSIONS

Perioperative ctDNA analysis is effective in early detection of MRD and relapse risk stratification of NSCLC, and hence could benefit NSCLC patient management.

Personalised, Rational, Efficacy-Driven Cancer Drug Dosing via an Artificial Intelligence SystEm (PRECISE): A Protocol for the PRECISE CURATE.AI Pilot Clinical Trial

Introduction: Oncologists have traditionally administered the maximum tolerated doses of drugs in chemotherapy. However, these toxicity-guided doses may lead to suboptimal efficacy. CURATE.AI is an indication-agnostic, mechanism-independent and efficacy-driven personalised dosing platform that may offer a more optimal solution. While CURATE.AI has already been applied in a variety of clinical settings, there are no prior randomised controlled trials (RCTs) on CURATE.AI-guided chemotherapy dosing for solid tumours. Therefore, we aim to assess the technical and logistical feasibility of a future RCT for CURATE.AI-guided solid tumour chemotherapy dosing. We will also collect exploratory data on efficacy and toxicity, which will inform RCT power calculations.

Methods and analysis: This is an open-label, single-arm, two-centre, prospective pilot clinical trial, recruiting adults with metastatic solid tumours and raised baseline tumour marker levels who are planned for palliative-intent, capecitabine-based chemotherapy. As CURATE.AI is a small data platform, it will guide drug dosing for each participant based only on their own tumour marker levels and drug doses as input data. The primary outcome is the proportion of participants in whom CURATE.AI is successfully applied to provide efficacy-driven personalised dosing, as judged based on predefined considerations. Secondary outcomes include the timeliness of dose recommendations, participant and physician adherence to CURATE.AI-recommended doses, and the proportion of clinically significant dose changes. We aim to initially enrol 10 participants from two hospitals in Singapore, perform an interim analysis, and consider either cohort expansion or an RCT. Recruitment began in August 2020. This pilot clinical trial will provide key data for a future RCT of CURATE.AI-guided personalised dosing for precision oncology.

Ethics and dissemination: The National Healthcare Group (NHG) Domain Specific Review Board has granted ethical approval for this study (DSRB 2020/00334). We will distribute our findings at scientific conferences and publish them in peer-reviewed journals.

Trial registration number: NCT04522284

Circulating DNA changes are predictive of disease progression after transarterial chemoembolization

Transarterial chemoembolization (TACE) is used to treat patients with unresectable hepatocellular carcinoma (HCC). We evaluated the clinical impact of a-fetoprotein (AFP) and circulating cell-free and tumor DNA (cfDNA and ctDNA) changes around the TACE procedure. Our prospective monocentric study enrolled consecutive patients treated with TACE, with samples collected at baseline (D - 1), Day 2 (D + 2) and 1 month (M + 1) after TACE. cfDNA was quantified by the fluorometric method, and ctDNA was quantified by digital polymerase chain reaction designed for two hotspot TERT mutations. Computerized tomography scans or magnetic resonance imaging were performed at M + 1 every 3 months following TACE and independently reviewed. The objective was to identify thresholds of cfDNA, ctDNA and AFP changes associated with progressive disease (PD) using receiver operating characteristic curves. Thirty-eight patients were included from March 2018 to March 2019. All markers significantly increased from D - 1 to D + 2 (P < .005), and cfDNA and ctDNA significantly decreased from D + 2 to M + 1 (P < .0001). The analysis of changes from D - 1 to M + 1 identified thresholds at +31.4% for cfDNA and 0% for ctDNA that were significantly associated with PD at M + 1 (44.4% [>+31.4%] vs 3.8% [≤+31.4%] and 50.0% [>0%] vs 5.0% [≤0%], respectively). No significant threshold was identified for AFP. Using a score combining cfDNA and ctDNA, the patients were classified into high- or low-risk PD groups at M + 1, with PD rates of 80.0% vs 4.3% (P = .001) and median progression-free survival times of 1.3 vs 10.3 months (P = .002). Our study suggests that cfDNA and ctDNA increases around the TACE procedure and are associated with therapeutic failure.

Precision Medicine for Colorectal Cancer with Liquid Biopsy and Immunotherapy

Simple Summary

There are some challenges to improve the clinical outcome of colorectal cancers (CRCs) by implementing new technologies, such as early detection of recurrence/relapse and selection of appropriate drugs based on the genomic profiles of tumors. For example, the genomic characteristics of tumors can be analyzed by blood-based tests, namely ‘liquid biopsies’, which are minimally-invasive and can be performed repeatedly during the treatment course. Hence, liquid biopsies are considered to hold great promise to fill these gaps in clinical routines. In this review, we addressed clinical usefulness of liquid biopsies in the clinical management of CRC patients, including cancer screening, detection of minimal residual disease, selection of appropriate molecular-targeted drugs, monitoring of the treatment responsiveness, and very early detection of recurrence/relapse of the disease. Furthermore, we discussed the possibility of adoptive T cell therapies and a future personalized immunotherapy based on tumor genome information.

Abstract

In the field of colorectal cancer (CRC) treatment, diagnostic modalities and chemotherapy regimens have progressed remarkably in the last two decades. However, it is still difficult to identify minimal residual disease (MRD) necessary for early detection of recurrence/relapse of tumors and to select and provide appropriate drugs timely before a tumor becomes multi-drug-resistant and more aggressive. We consider the leveraging of in-depth genomic profiles of tumors as a significant breakthrough to further improve the overall prognosis of CRC patients. With the recent technological advances in methodologies and bioinformatics, the genomic profiles can be analyzed profoundly without delay by blood-based tests—‘liquid biopsies’. From a clinical point of view, a minimally-invasive liquid biopsy is thought to be a promising method and can be implemented in routine clinical settings in order to meet unmet clinical needs. In this review, we highlighted clinical usefulness of liquid biopsies in the clinical management of CRC patients, including cancer screening, detection of MRD, selection of appropriate molecular-targeted drugs, monitoring of the treatment responsiveness, and very early detection of recurrence/relapse of the disease. In addition, we addressed a possibility of adoptive T cell therapies and a future personalized immunotherapy based on tumor genome information.

Clinical and biological determinants of circulating tumor DNA detection and prognostication using a next-generation sequencing panel assay

Circulating tumor DNA (ctDNA) is utilized for molecular profiling of cancers, and is under investigation for a growing number of applications based on the assumption that ctDNA levels faithfully reflect disease burden. Our objective was to investigate whether patient and tumor characteristics may impact ctDNA detection or levels and the prognostic significance of ctDNA levels or mutations. We performed a retrospective cohort analysis of a comprehensively annotated cohort of 561 patients at a National Cancer Institute-designated comprehensive cancer center with advanced solid cancers who underwent ctDNA testing using a commercial targeted next-generation sequencing assay. ctDNA detection in advanced cancers was associated with older age, non-obese body mass index, and diabetes, but not with tumor diameter, volume, lesion number, or other pathological features. Regression models indicate that no more than 14.3% of the variance in ctDNA levels between patients was explained by known clinical factors and disease burden. Even after adjusting for established prognostic factors and tumor burden, ctDNA levels were associated with worse survival among patients without prior systemic therapy, while ctDNA mutations were associated with survival among patients who previously received systemic treatment. These findings uncover clinical factors that affect ctDNA detection in patients with advanced cancers and challenge the convention that ctDNA is a surrogate for tumor burden. Our study also indicates that the prognostic value of ctDNA levels and mutations are independent of tumor burden and dependent on treatment context.

CEA, CA19-9, circulating DNA and circulating tumour cell kinetics in patients treated for metastatic colorectal cancer (mCRC)

BACKGROUND

We previously reported that CEA kinetics are a marker of progressive disease (PD) in metastatic colorectal cancer (mCRC). This study was specifically designed to confirm CEA kinetics for predicting PD and to evaluate CA19-9, cell-free DNA (cfDNA), circulating tumour DNA (ctDNA) and circulating tumour cell (CTC) kinetics.

METHODS

Patients starting a chemotherapy (CT) with pre-treatment CEA > 5 ng/mL and/or CA19.9 > 30 UI/mL were prospectively included. Samples were collected from baseline to cycle 4 for CEA and CA19-9 and at baseline and the sixth week for other markers. CEA kinetics were calculated from the first to the third or fourth CT cycle.

RESULTS

A total of 192 mCRC patients were included. CEA kinetics based on the previously identified >0.05 threshold was significantly associated with PD (p < 0.0001). By dichotomising by the median value, cfDNA, ctDNA and CA19-9 were associated with PD, PFS and OS in multivariate analysis. A circulating scoring system (CSS) combining CEA kinetics and baseline CA19-9 and cfDNA values classified patients based on high (n = 58) and low risk (n = 113) of PD and was independently associated with PD (ORa = 4.6, p < 0.0001), PFS (HRa = 2.07, p < 0.0001) and OS (HRa = 2.55, p < 0.0001).

CONCLUSIONS

CEA kinetics alone or combined with baseline CA19-9 and cfDNA are clinically relevant for predicting outcomes in mCRC.

TRIAL REGISTRATION NUMBER

NCT01212510.

Precision oncology in metastatic colorectal cancer - from biology to medicine

Remarkable progress has been made in the development of biomarker-driven targeted therapies for patients with multiple cancer types, including melanoma, breast and lung tumours, although precision oncology for patients with colorectal cancer (CRC) continues to lag behind. Nonetheless, the availability of patient-derived CRC models coupled with in vitro and in vivo pharmacological and functional analyses over the past decade has finally led to advances in the field. Gene-specific alterations are not the only determinants that can successfully direct the use of targeted therapy. Indeed, successful inhibition of BRAF or KRAS in metastatic CRCs driven by activating mutations in these genes requires combinations of drugs that inhibit the mutant protein while at the same time restraining adaptive resistance via CRC-specific EGFR-mediated feedback loops. The emerging paradigm is, therefore, that the intrinsic biology of CRC cells must be considered alongside the molecular profiles of individual tumours in order to successfully personalize treatment. In this Review, we outline how preclinical studies based on patient-derived models have informed the design of practice-changing clinical trials. The integration of these experiences into a common framework will reshape the future design of biology-informed clinical trials in this field.

Perspectives for circulating tumor DNA in clinical management of colorectal cancer

Growing evidence has demonstrated that circulating tumor DNA (ctDNA) detection in colorectal cancer might be a promising approach to address current important clinical questions. During chemotherapy for metastatic colorectal cancer, tumor cells acquire potential resistance by generating additional somatic mutations related to therapeutic resistance. ctDNA can capture the tumor landscape, including heterogeneity, which might provide the opportunity for additional treatment options. Moreover, ctDNA detection is advantageous, because it can monitor tumor heterogeneity serially, in a non-invasive manner. ctDNA is considered valid for detecting minimal residual disease after a curable resection. By utilizing ctDNA detection, adjuvant chemotherapy for patients with stage II-III colorectal cancer might be omitted for patients at low risk of recurrence; or conversely, adjuvant chemotherapy might be highly recommended for patients at high risk, based on ctDNA findings. During multidisciplinary treatments for locally advanced rectal cancer, it is essential to monitor the responses to sequential treatments to make appropriate decisions. Currently, these decisions are mainly based on radiological or pathological findings. ctDNA can add value by providing the real-time status of locally advanced rectal cancer. In this review, we summarized the current evidence and discussed future strategies for using ctDNA in the treatment of colorectal cancer.

ctDNA Clearance and Radiographic Resolution of Disease in Response to Dual Checkpoint Inhibition in Metastatic Microsatellite Stable Colorectal Cancer with a High Tumor Mutation Burden

Immunotherapy (IO) has increasingly been demonstrated to provide therapeutic benefit to patients with metastatic colorectal cancer (mCRC). However, only a subset of mCRC tumors respond to IO. Monitoring response with tumor biomarkers like carcinoembryonic antigen (CEA) has been challenging in patients with microsatellite stable (MSS) mCRC due to low expression of CEA (CEA/lo). Noninvasive blood-based biomarkers such as circulating tumor DNA (ctDNA) can inform early treatment response and augment radiographic monitoring. We describe a case study of a patient with chemotherapy-refractory CEA/lo MSS mCRC, with metastatic disease present in a cardiophrenic lymph node. The patient was given 2 cycles of combination IO (ipilimumab/nivolumab). Response was monitored by ctDNA using a multiplex PCR next-generation sequencing assay, CEA, and CT scan. After IO administration, ctDNA levels rapidly declined, becoming undetectable. This was concurrent with radiographic resolution of the lymph node metastasis. Serial monitoring of CEA during this same period was uninformative, with no significant changes observed. Significant decline in ctDNA identified metastatic response to IO in a patient with CEA/lo, MSS mCRC and was concurrently validated by CT scan. This case study provides evidence that ctDNA can be used as a prospective surrogate for radiographic tumor response.

Circulating biomarkers for monitoring therapy response and detection of disease progression in lung cancer patients

Liquid biopsies have become of interest as minimally invasive ways to monitor treatment response in lung cancer patients. Circulating tumor DNA (ctDNA) and protein biomarkers are evaluated for their added value in monitoring therapy response and early detection of disease progression. Plasma and serum samples of non-small cell or small cell lung cancer patients were analyzed for driver mutations in ctDNA (EGFR, KRAS or BRAF) using droplet digital PCR and protein biomarkers (CA125, CEA, CA15.3, Cyfra 21-1, HE4, NSE, proGRP and SCCA) using electrochemiluminescence immunoassays. Biomarker concentration changes were compared with the outcome of CT-scans during therapy. The median difference of the concentration of ctDNA, CA125 and Cyfra21-1 was significantly lower in patients with partial response (PR) compared to patients with progressive disease (PD) on the first evaluation CT-scan (P<0.001, P=0.042 and P=0.020, respectively). A substantial agreement between ctDNA or CA125 response and radiographic response was observed (k=0.692 and k=0.792, respectively). The median difference of the concentration of ctDNA and Cyfra21-1 was also significantly lower in PR patients compared to PD patients at the last CT-scan during therapy (P<0.001 and P=0.026, respectively). An almost perfect agreement between ctDNA and radiographic response (k=0.827) and a moderate agreement between Cyfra21-1 response and radiographic response was observed (k=0.553). Serial testing of the concentration of ctDNA, Cyfra21-1, and possibly CA125 could be a useful added tool for monitoring therapy response and early detection of disease progression in lung cancer patients.

Allicin and Digestive System Cancers: From Chemical Structure to Its Therapeutic Opportunities

Digestive system cancer tumors are one of the major causes of cancer-related fatalities; the vast majority of them are colorectal or gastric malignancies. Epidemiological evidence confirmed that allium-containing food, such as garlic, reduces the risk of developing malignancies. Among all compounds in garlic, allicin has been most researched, as it contains sulfur and produces many second degradation compounds, such as sulfur dioxide, diallyl sulfide (DAS), diallyl trisulfide (DATS), and diallyl disulfide (DADS) in the presence of enzymatic reactions in gastric juice. These substances have shown anti-inflammatory, antidiabetic, antihypertensive, antifungal, antiviral, antibacterial, and anticancer efficacy, including gastrointestinal (GI) cancers, leukemia, and skin cancers. Herein, we summarize the therapeutic potential of allicin in the treatment of GI cancers.

Use of Circulating Cell-Free DNA to Guide Precision Medicine in Patients with Colorectal Cancer

Patient-specific biomarkers form the foundation of precision medicine strategies. To realize the promise of precision medicine in patients with colorectal cancer (CRC), access to cost-effective, convenient, and safe assays is critical. Improvements in diagnostic technology have enabled ultrasensitive and specific assays to identify cell-free DNA (cfDNA) from a routine blood draw. Clinicians are already employing these minimally invasive assays to identify drivers of therapeutic resistance and measure genomic heterogeneity, particularly when tumor tissue is difficult to access or serial sampling is necessary. As cfDNA diagnostic technology continues to improve, more innovative applications are anticipated. In this review, we focus on four clinical applications for cfDNA analysis in the management of CRC: detecting minimal residual disease, monitoring treatment response in the metastatic setting, identifying drivers of treatment sensitivity and resistance, and guiding therapeutic strategies to overcome resistance.

Associations of baseline patient-reported outcomes with treatment outcomes in advanced gastrointestinal cancer

BACKGROUND

Patient-reported outcomes (PROs) assessing quality of life (QOL) and symptom burden correlate with clinical outcomes in patients with cancer. However, to the authors' knowledge, data regarding associations between PROs and treatment response are lacking.

METHODS

The authors prospectively approached consecutive patients with advanced gastrointestinal cancer who were initiating a new treatment. Prior to treatment, patients reported their QOL (Functional Assessment of Cancer Therapy-General [FACT-G], 4 subscales: Functional, Physical, Emotional, Social; higher scores indicate better QOL) and symptom burden (Edmonton Symptom Assessment System [ESAS], Patient Health Questionnaire-4 [PHQ-4]; higher scores represent greater symptoms). Regression models were used to examine associations of baseline PROs with treatment response (clinical benefit or progressive disease [PD] at time of first scan), healthcare utilization, and survival.

RESULTS

From May 2019 to April 2020, a total of 112 patients with advanced gastrointestinal cancer were enrolled. For treatment response, 64.3% had CB and 35.7% had PD. Higher baseline ESAS-Physical (odds ratio, 1.04; P = .027) and lower FACT-G Functional (odds ratio, 0.92; P = .038) scores were associated with PD. Higher ESAS-Physical (hazard ratio [HR], 1.03; P = .044) and lower FACT-G Total (HR, 0.96; P = .005), FACT-G Physical (HR, 0.89; P < .001), and FACT-G Functional (HR, 0.87; P < .001) scores were associated with a greater hospitalization risk. Lower FACT-G Total (HR, 0.96; P = .009) and FACT-G Emotional (HR, 0.86; P = .012) scores as well as higher ESAS-Total (HR, 1.03; P = .014) and ESAS-Physical (HR, 1.04; P = .032) scores were associated with worse survival.

CONCLUSIONS

Baseline PROs are associated with treatment response in patients with advanced gastrointestinal cancer, namely physical symptoms and functional QOL, in addition to health care use and survival. The findings of the current study support the association between PROs and important clinical outcomes, including the novel finding of treatment response.

Multiplex detection of ctDNA mutations in plasma of colorectal cancer patients by PCR/SERS assay

Molecular diagnostic testing of KRAS and BRAF mutations has become critical in the management of colorectal cancer (CRC) patients. Some progress has been made in liquid biopsy detection of mutations in circulating tumor DNA (ctDNA), which is a fraction of circulating cell-free DNA (cfDNA), but slow analysis for DNA sequencing methods has limited rapid diagnostics. Other methods such as quantitative PCR and more recently, droplet digital PCR (ddPCR), have limitations in multiplexed capacity and the need for expensive specialized equipment. Hence, a robust, rapid and facile strategy is needed for detecting multiple ctDNA mutations to improve the management of CRC patients. To address this significant problem, herein, we propose a new application of multiplex PCR/SERS (surface-enhanced Raman scattering) assay for the detection of ctDNA in CRC, in a fast and non-invasive manner to diagnose and stratify patients for effective treatment.

Methods: To discriminate ctDNA mutations from wild-type cfDNA, allele-specific primers were designed for the amplification of three clinically important DNA point mutations in CRC including KRAS G12V, KRAS G13D and BRAF V600E. Surface-enhanced Raman scattering (SERS) nanotags were labelled with a short and specific sequence of oligonucleotide, which can hybridize with the corresponding PCR amplicons. The PCR/SERS assay was implemented by firstly amplifying the multiple mutations, followed by binding with multicolor SERS nanotags specific to each mutation, and subsequent enrichment with magnetic beads. The mutation status was evaluated using a portable Raman spectrometer where the fingerprint spectral peaks of the corresponding SERS nanotags indicate the presence of the mutant targets. The method was then applied to detect ctDNA from CRC patients under a blinded test, the results were further validated by ddPCR.

Results: The PCR/SERS strategy showed high specificity and sensitivity for genotyping CRC cell lines and plasma ctDNA, where as few as 0.1% mutant alleles could be detected from a background of abundant wild-type cfDNA. The blinded test using 9 samples from advanced CRC patients by PCR/SERS assay was validated with ddPCR and showed good consistency with pathology testing results.

Conclusions: With ddPCR-like sensitivity yet at the convenience of standard PCR, the proposed assay shows great potential in sensitive detection of multiple ctDNA mutations for clinical decision-making.

The Application of Circulating Tumor DNA in the Screening, Surveillance, and Treatment Monitoring of Colorectal Cancer

Precision medicine with genetic profiling of tumor tissue has become an essential part of routine clinical practice in colorectal cancer. However, tissue genetic profiling suffers from clonal evolution, tumor heterogeneity, and time needed to deliver critical information for prompt clinical decision making. In contrast, liquid biopsy with plasma circulating tumor DNA provides genetic and epigenetic information from both the primary and metastatic colorectal cancer, which can potentially capture tumor heterogeneity and evolution with time and treatment. In addition, liquid biopsy with circulating tumor DNA is minimally invasive, quicker, and easily repeatable with high patient compliance to provide both qualitative and quantitative molecular information in real-time. We provide an overview on the potential clinical applications of circulating tumor DNA in the screening, surveillance, and treatment monitoring of colorectal cancer.

Patient specific circulating tumor DNA fingerprints to monitor treatment response across multiple tumors

BACKGROUND

Circulating tumor DNA (ctDNA) offers a convenient way to monitor tumor progression and treatment response. Because tumor mutational profiles are highly variable from person to person, a fixed content panel may be insufficient to track treatment response in all patients.

METHODS

We design ctDNA fingerprint panels specific to individual patients which are based on whole exome sequencing and target to high frequency clonal population clusters in patients. We test the fingerprint panels in 313 patients who together have eight tumor types (colorectal, hepatocellular, gastric, breast, pancreatic, and esophageal carcinomas and lung cancer and cholangiocarcinoma) and exposed to multiple treatment methods (surgery, chemotherapy, radiotherapy, targeted-drug therapy, immunotherapy, and combinations of them). We also monitor drug-related mutations in the patients using a pre-designed panel with eight hotspot genes.

RESULTS

291 (93.0%) designed fingerprint panels harbor less than ten previously known tumor genes. We detected 7475 ctDNA mutations in 238 (76%) patients and 6196 (96.0%) of the mutations are detected in only one test. Both the level of ctDNA content fraction (CCF) and fold change of CCF (between the definitive and proceeding tests) are highly correlated with clinical outcomes (p-values 1.36e-6 for level and 5.64e-10 for fold change, Kruskal-Wallis test). The CCFs of PD patients are an order of magnitude higher than the CCFs of SD and OR patients (median/mean 2.22%/8.96% for SD, 0.18/0.21% for PD, and 0.31/0.54% for OR; pairwise p-values 7.8e-6 for SD ~ PD, 2.7e-4 for OR ~ PD, and 7.0e-3 for SD ~ OR, Wilcoxon rank sum test). The fold change of CCF distinguishes the patient groups even better, which increases for PD, remains stable for SD, and decreases for OR patients (p-values 0.002, ~ 1, and 0.0001 respectively, Wilcoxon signed-rank test). Eleven drug-related mutations are identified from nine out of the 313 patients.

CONCLUSIONS

The ctDNA fingerprint method improves both specificity and sensitivity of monitoring treatment response across several tumor types. It can identify tumor relapse/recurrence potentially earlier than imaging-based diagnosis. When augmented with tumor hotspot genes, it can track acquired drug-related mutations in patients.

Circulating Tumor DNA as a Novel Biomarker Optimizing Chemotherapy for Colorectal Cancer

Liquid biopsy is a minimally invasive method for detecting soluble factors, including circulating tumor DNA (ctDNA), in body fluids. ctDNA carrying tumor-specific genetic or epigenetic alterations is released into circulation from tumor cells. ctDNA in the plasma contains somatic mutations that have occurred in the tumor, and reflects tumor progression and therapeutic effects promptly and accurately. Furthermore, ctDNA is useful for early detection of recurrence and estimation of prognosis and may be utilized for diagnosis and personalized medicine for treatment selection. Thus, in the near future, it will be possible to select the most appropriate treatment based on real-time genetic information using ctDNA.

Favorable Outcomes in FGFR Fusion-Positive Cholangiocarcinomas and Evolution on Treatment Noted on Circulating Tumor DNA Liquid Biopsies

Cholangiocarcinoma is a very heterogenous cancer and "target-rich" disease. While the current classifications are based on the anatomic location of these tumors (intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, and gallbladder cancer), tumors within and across these disease groups have unique and often mutually exclusive molecular aberrations. Amongst these, fibroblast growth factor receptor 2 (FGFR2) fusion is one of the first amongst the list of "actionable" targets for which the US Food and Drug Administration just approved pemigatinib. This is for patients with cholangiocarcinoma who have received prior treatment and have FGFR2 fusion or another rearrangement. This was based on the results from the clinical trial FIGHT-202 (NCT02924376). At present, several FGFR inhibitors are actively being tested in several agnostic and tumor-specific clinical trials. Patients also have had the opportunity of getting access to some of these oral drugs through compassionate use programs. As a consequence, these patients have more options in addition to chemotherapy. These all tend to have "good" initial responses and improvement in performance status and later "acquired" mechanisms of resistance. The latter tend to often be gatekeeper mutations that bypass the inhibitory effects of these selective FGFR inhibitors and/or cause steric hindrance. These tumors, therefore, evolve on selective pressure (temporal heterogeneity). This can be captured noninvasively using "liquid biopsies" (circulating tumor DNA testing). Here we present cases (several years into treatment on average) showing the feasibility of using liquid biopsies (ctDNA testing) as well as the gain and later potential loss of intratumoral and temporal heterogeneity exhibited under selective pressure of these novel FGFR inhibitors, chemotherapy and/or locoregional therapies. Despite limitations in sample size and provider bias, it is important to identify these "exceptional responders" and/or better outcomes that may be inherent to the biology of FGFR fusion-positive cholangiocarcinomas.