Citations

4108 Background: Circulating tumor DNA (ctDNA) testing can be used for the assessment of molecular residual disease (MRD) in patients with early-stage or advanced colorectal cancer (CRC). Prospective evaluation of this methodology in clinical practice has been limited to-date. Methods: A personalized and tumor-informed multiplex PCR assay (Signatera 16-plex bespoke mPCR NGS assay) was used for the detection and quantification of ctDNA for MRD assessment. We analyze and present results from an ongoing early adopter program of ctDNA testing across the spectrum of CRC management. Results: Here we present a total of 250 patients with colon (n=200), rectal (n=40), and other lower gastrointestinal cancers (n =10; anal, appendiceal, small bowel). MRD positivity rates and ctDNA quantification (mean tumor molecules/mL) are shown in Table. ctDNA detection was significantly associated with stage of disease (p<0.0001 Chi-square: 70.33). Additionally, in patients with radiologically measurable active metastatic disease, ctDNA detection rate was 100%. On the contrary, patients with advanced/metastatic disease who had partial response to treatment or no evidence of disease (NED) showed 28.5% and 19.2% of ctDNA-positivity, respectively. Conclusions: This is the first large, real-world study reporting on the results from a clinically validated MRD assay. For the first time we delineate MRD rates and quantify ctDNA concentration in patients with early-stage and advanced CRC. Furthermore, we provide an initial readout that effective ongoing treatment in patients with CRC may be correlated with ctDNA clearance. Ongoing analysis expanded to a cohort of 1200 clinical cases including correlation with genomic and serial testing will be presented. [Table: see text]

TPS791 Background: FOLFIRINOX or gemcitabine/nab-paclitaxel are both frontline chemotherapy options for patients with metastatic pancreas cancer. For most who cannot tolerate the triplet, the latter doublet is the preferred option. Through previous work by our group, pharmacologic ascorbate is known to synergize with gemcitabine; preliminary in vitro data from our group suggests a similar synergistic response with paclitaxel. Though ascorbate has been utilized in cancer therapy, few robust trials have investigated intravenous delivery of ascorbate to deliver plasma concentrations that are cytotoxic to tumor cells. Our prior studies have demonstrated ascorbate induces oxidative stress and cytotoxicity in pancreatic cancer cells; this cytotoxicity appears to be greater in tumor vs. normal cells. We hypothesize that production of hydrogen peroxide mediates the increased susceptibility of pancreatic cancer cells to ascorbate-induced metabolic oxidative stress, resulting in improved treatment outcomes, which has led to the development of the clinical trial (NCT02905578). Methods: All participants receive gemcitabine (1000 mg/m2 weekly) and nab-paclitaxel (125 mg/m2) on cycle days 1, 8, and 15 of a 28-day cycle. Participants are randomized to ± pharmacologic ascorbate (75-gram infusion 3x weekly) in addition to chemotherapy. Study therapy continues until tumor progression. The primary objective is to determine overall survival in patients when treated with combination gemcitabine, nab-Paclitaxel and high-dose ascorbic acid compared to gemcitabine and nab-paclitaxel in patients with non-resectable pancreatic cancer. Secondary objectives include determining objective response rate as well as progression free survival using RECIST 1.1 criteria employing a blinded reviewer for RECIST measurements. The study opened to accrual in 2018 with a goal of enrolling 65 participants. Oversight.Study is conducted under IND 105715 (J. Cullen, sponsor). The University of Iowa Biomedical IRB (IRB-01) serves as the IRB of record. Clinical trial information: NCT02905578.

TPS276 Background: Immune checkpoint inhibitors have revolutionized the treatment of a number of cancers. In colorectal cancers, their efficacy is limited to mismatch repair deficient or microsatellite stability-high (dMMR/MSI-High) tumors only. These constitute only 4-5% of all metastatic colorectal cancers (mCRC). Novel approaches are needed to make immunotherapy a viable option for mismatch repair proficient or microsatellite stable (pMMR/MSS) tumors. Increasing exposure of neo-antigens to the immune system could be one potential strategy to enhance the response of immunotherapy. Yttrium 90-radioembolization (Y90-RE) in combination with immunotherapy may work synergistically to enhance efficacy of each other. Additionally, radiation can potentially make the tumor microenvironment conducive to effector T-cell recruitment and function. Therefore, we hypothesize and propose the clinical trial of combining immunotherapy with Y90-RE as a feasible and safe strategy that will improve outcomes in patients with mCRC with liver-predominant metastases. Methods: This clinical trial will be conducted as a single-center, open-label, Phase I/II trial to evaluate initially the feasibility and safety of Y90-RE in combination with a fixed dose of immunotherapy (durvalumab) in subjects with liver-predominant, mCRC (Table). It will be offered in the refractory setting. The trial will be performed in 18 subjects with mCRC with liver metastasis and the safety of immunotherapy (durvalumab) with Y90-RE will be investigated in an accelerated titration design. This would allow a maximum tolerated dose with the minimum number of subjects. Correlative studies pertaining to serial circulating tumor DNA (ctDNA - liquid biopsies) testing as well as immune-panel based profiling will be performed alongside pre- and post-biopsies to study changes in the tumor microenvironment. Clinical trial information: NCT04108481. [Table: see text]

763 Background: Non-invasive biomarkers with high sensitivity and specificity would be of great value for patients with Pancreatic Ductal Adenocarcinoma (PDAC). This would aid in early detection and serve other purposes that 'liquid biopsies' are being explored in. Besides circulating tumor DNA (ctDNA) and methylation markers, glycosylation markers hold great potential promise. We developed a novel workflow using high-resolution quantification of site-specific protein glycosylation by liquid chromatography and tandem mass spectrometry to evaluate the clinical utility of glycoprotemics signature for patients with PDAC. Methods: Serum samples from newly diagnosed PDAC patients and controls were obtained from a commercial biobank (Indivumed, Hamburg, Germany), and a panel of 504 glycan motifs, representing 73 previously reported proteomic markers, was determined. Age-adjusted generalized linear regression models were used to evaluate the differential abundance of each marker, and stepwise variable selection was used for model construction. Results: We analyzed 45 PDAC and 136 control samples. PDAC patients (60% male) had a mean age of 67 (±11) years. with 4.4%, 71.1%, 4.4%, and 20% at stage 1, 2, 3,4, respectively. Controls were women with benign histology after pelvic mass surgery; with a mean age of 61 (±11) years. Twenty-six glycoproteomic markers showed statistically highly significant differential abundance among cases and controls (p<1e-4 each) and were highly reproducible(Pearson’s r > 0.85), which were glycoforms in proteins that have previously been found to be associated with PDAC. Fourteen of these markers displayed >0.8 area under the curve of the receiver operating characteristic (AUC). Multivariate logistic regression modeling with backward selection yielded a classification model with an AUC of 0.94 (95% CI: 0.89-0.99), sensitivity of 91% (95% CI: 75-97%) and specificity of 86% (95% CI: 81-92%). Conclusions: Circulating glycoproteomic biomarkers may be useful in the early detection and clinical management of PDAC patients; offering a new platform to explore and validate.

404 Background: Concurrent chemoradiation(CRT) followed by esophagectomy is a standard of care for locally advanced esophageal(LA-EAC) and GEJ adenocarcinoma. Approximately 50% of patients(pts) experience disease relapse within the 1st yr after treatment(tx) completion. No adjuvant tx has been shown to improve survival in these pts. Immune checkpoint inhibitors have activity in metastatic PD-L1 positive EAC. Preclinical studies have shown radiation +/- chemotherapy upregulate PD-1/PD-L1 pathway. Methods: We conducted a phase II trial evaluating safety and efficacy of durvalumab(durva) in pts with LA-EAC and GEJ adenocarcinoma who have residual disease in surgical specimen after neoadjuvant CRT and R0 resection. Pts received durva 1500mg IV every 4 weeks for up to 1yr. Results: 24 pts were enrolled from 4/2016-1/2018(median age: 60yrs (range, 43-70). 18 received carbo/paclitaxel and 6 received cis/5-FU concurrently with radiation. Staging at diagnosis: T2N0(n = 3, 12.5%), T2N2(n = 3, 12.5%),T3N0(n = 6, 25%), T3N1(n = 6, 25%), T3N2(n = 4, 17%), T3N3(n = 1, 4%), T3Nx(n = 1, 4%).19 pts(79%) had positive lymph nodes(LNs) at the time of surgery following CRT. 12 pts completed 1yr of tx, 12 came off tx because of relapse(6), AEs(5), and consent withdrawal(1). Most common AEs were fatigue(n = 8, 33.3%) and nausea(n = 6, 25%). 3pts (12.5%) developed grade 3 irAEs: pneumonitis(1), hepatitis(1), colitis(1). At median follow up of 21.9mo(range, 1.7-23.9mo), 11 pts have relapsed: 9 distant and 2 locoregional. Two of 3 pts with grade 3 irAEs are alive and disease free at 17 and 23 mo respectively. 1-yr RFS and OS were 79.2% and 95.5%, respectively. RFS at 26 mo was 20.6%. Overall mOS and mOS after relapse were 28.1mo(range, 22.9-28.1) and 11.1 mo(range, 0.1-11.3mo) respectively. The study was expanded to enroll 14 additional pts who are currently undergoing tx. Conclusions: Adjuvant durvalumab following trimodality therapy for LA-EAC and GEJ adenocarcinoma is safe with improvement in 1-yr RFS to 79.2% compared to historical rate of 50%. RFS was 20.6% at 26 months. Evaluation of predictive biomarkers of RFS with durva is underway. Clinical trial information: NCT02639065.

362 Background: Most pts with mGEA do not respond to ICI or ramucirumab/paclitaxel (RAM/TAX). Emerging data suggest that ICI may potentiate subsequent therapy (Tx). In KN059 we unexpectedly observed durable responses in 2 pts on RAM/TAX after ICI (PMID 29674442). We examined if ICI impacts efficacy of subsequent RAM/TAX in a larger cohort and explored alterations in the tumor microenvironment. Methods: All pts with mGEA at Mayo Clinic (MN, AZ, FL) who received RAM/TAX (2014-19) were included. We compared best objective response rate (ORR: complete [CR] or partial response [PR]) per RECIST1.1 and overall survival (OS) in pts who received RAM/TAX with (Group A) vs without (Group B) immediately preceding PD-1 blockade. Chi square and multivariate logistic and Cox regression were used. We adjusted for total lines of Tx received and the line of Tx in which RAM/TAX was given, to control for potential differences in the biology of heavily treated pts or those receiving RAM/TAX as 2nd vs 3rd line Tx. We also adjusted for age and ECOG PS. Results: In total 87 pts met inclusion criteria. In the 19 pts (Group A) who received RAM/TAX (usually as 3rd line Tx) after progression on ICI, there was a 77% relative risk reduction of death after initiation of RAM/TAX compared to the 68 pts (Group B) who received RAM/TAX (usually as 2nd line) without preceding ICI (median OS 15.0 vs 7.6 mo; HR 0.23; P < .001). The ORR was also significantly higher (58% vs 18%; P < .001) including the CR rate (16% vs 1%; P = .006). Two CRs in Group A are ongoing (10 - 34 mo). Of note, 95% of Group A pts did not respond to ICI, and all had irRECIST progression on ICI. Immunofluorescent analysis from a responder showed 65-fold reduction (post vs pre-Tx) in intratumoral density of immunosuppressive FOXP3+ Tregs, with preserved density of antitumor CD8+ T cells. Conclusions: Higher than expected efficacy was observed on RAM/TAX when immediately preceded by ICI, suggesting ICI may enhance efficacy of subsequent anti-VEGFR/taxane therapy. This serial immunotherapy combination may be a novel option for pts with primary resistance to ICI and will be tested prospectively in a new randomized phase 2 trial (NCT04069273).

Introduction: Pharmacogenomics is about selecting the “right drug in the right amount for the right patient.” In metastatic colorectal cancer, germline pharmacogenomics testing presents a unique opportunity to improve outcomes, since the genes dihydropyrimidine dehydrogenase and UDP-glucuronosyltransferase metabolizing the chemotherapy drugs, 5-fluorouracil, and irinotecan are already well known. In a retrospective analysis of the landmark TRIBE clinical trial [(TRIBE - TRIplet plus BEvacizumab multicenter, phase III trial by the Italian Cooperative GONO (Gruppo Oncologico Nord Ovest) group (NCT00719797)], the proportion of patients with serious adverse events was higher in those with dihydropyrimidine dehydrogenase/UDP-glucuronosyltransferase aberrations and was dose dependent. We aimed to report on the feasibility and the results of incorporating pharmacogenomics testing into clinical practice. Methods: As a quality improvement initiative and a center of individualized medicine grant, we integrated the use of OneOme RightMed comprehensive test, which reports on 27 genes related to pharmacogenomics and over 300 medications of interest. We limited initial testing to patients with colorectal cancer. Pharmacists provided dosage recommendations based on test results in real-time. Results: At our cancer center, 155 patients underwent pharmacogenomics testing from November 2017 to January 2019. Results were available within 3 to 5 days of testing for most patients and were integrated into treatment decision-making. Of 155 sampled participants, a total of 89 (57.4%) participants had an UGT1A1 variant genotype, NM_000463.2: c.-53_-52[8] *1/*28, n = 74 (47.7%); *28/*28, n = 15 (9.7%). Additionally, 4 (2.6%) participants were heterozygous for dihydropyrimidine dehydrogenase. Two (1.3%) individuals were heterozygous for both UDP-glucuronosyltransferase and dihydropyrimidine dehydrogenase genes. All (100%) the patients had at least 1 actionable aberration related to supportive care medications ( CYP-family) of all the possible medications listed on their pharmacogenomics report. Conclusion: Preemptive comprehensive pharmacogenomics testing can be integrated into clinical practice in real-time for patients with cancer given faster turnaround and low cost. Pharmacist-driven, patient-specific medication management consults add further value given the number of genes/drugs. This sets the stage for a prospective randomized clinical trial to demonstrate the amount of benefit this can result in these patients.

Abstract Background: Colorectal cancer (CRC) is the second leading cause of cancer death among men and women in the United States, and additional treatment strategies are needed for patients with advanced disease. Prospective therapeutic studies based on tissue-detected genomic targets such as ERBB2 (HER2), BRAF V600E, gene rearrangements/fusions, and microsatellite instability (MSI) have demonstrated clinical benefit for mCRC patients. Although correlative studies and/or retrospective case series utilizing circulating cell-free DNA (cfDNA) next generation sequencing (NGS) have shown that plasma detection of these genomic targets shows promise in mCRC, prospective studies are lacking. We hypothesize that comprehensive genomic profiling of cfDNA will identify actionable targets and improve outcomes for patients with mCRC. Methods: COLOMATE (Colorectal Cancer and Liquid Biopsy Screening Protocol for Molecularly Assigned Therapy; NCT03765736) is a phase II umbrella screening protocol sponsored by the Academic and Community Cancer Research United (ACCRU) consortium. This study utilizes Guardant360™ (Guardant Health, Redwood City, CA) - a blood-based targeted NGS panel - to identify actionable genomic alterations in mCRC patients and to assess the impact of molecularly assigned therapy accordingly under its individual companion studies. Eligible mCRC patients must have progressed on, been intolerant to, or have a contraindication to treatment with a fluoropyrimidine, oxaliplatin, irinotecan, anti-vascular endothelial growth factor (VEGF) monoclonal antibodies (mAbs) and anti-epidermal growth factor receptor (EGFR) mAbs if RAS wild-type. Companion studies are dynamic and currently include those for patients whose tumors are either RAS/BRAF wild-type, HER2 amplified, FGFR altered, RAS mutated, or without any known actionable alteration. Additional companion studies are under active development. The primary objectives of this study are to perform blood-based genomic profiling on patients with treatment refractory mCRC to facilitate accrual to molecularly assigned therapies, and to obtain patient-matched tumor tissue and cell free DNA from peripheral blood to facilitate clinically annotated genomic analyses. Secondary correlative objectives are to explore mechanisms of acquired resistance to molecularly assigned therapy and to explore the correlation between cfDNA mutational burden (allele frequency, copy number) and clinical outcomes such as objective response rate, progression-free survival, and overall survival. Citation Format: Kristen K. Ciombor, Fang-Shu Ou, Andrew Dodge, Tyler Zemla, Christina Wu, Kimmie Ng, Katrina Pedersen, Shumei Kato, Pashtoon M. Kasi, Daniel Ahn, Rebecca Nagy, Richard Lanman, Scott Kopetz, John H. Strickler, Tanios Bekaii-Saab. COLOMATE: Colorectal cancer and liquid biopsy screening protocol for molecularly assigned therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-235.

Abstract Doublet chemotherapies are the mainstay in the management of metastatic anal cancer. Immunotherapy has been incorporated into guidelines in a refractory setting. Treatment options remain limited with tumor progression beyond immunotherapy. Modified docetaxel, cisplatin, and fluorouracil (mDCF) chemotherapy, after progression postimmunotherapy, has shown a near‐complete response in our patient with metastatic anal cancer. This likely is secondary to the sequence of immunotherapy followed by chemotherapy that is yielding greater than historical responses.