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BackgroundOf the only 20% of patients with resectable pancreatic ductal adenocarcinoma (rPDA), cancer recurs in 80% of cases. Epigenetic dysregulation is an early hallmark of cancer cells acquiring metastatic potential, and epigenetic modulators may reactivate tumor suppressor genes, delay recurrence, and sensitize PDA to future chemotherapy.MethodsThis was a randomized phase II study (NCT01845805) of CC-486 (oral DNA methyltransferase inhibitor azacitidine) vs. observation (OBS) in rPDA patients harboring high-risk features (stage pN1-2, R1 margins, or elevated CA 19–9 level) with no evidence of disease following standard adjuvant therapy. Patients were randomized to oral CC-486 treatment (300 mg daily on days 1–21 on a 28-day cycle) or OBS for up to 12 cycles or until disease relapse/unacceptable toxicities. Following recurrence, records of next-line therapies, imaging, and survival were obtained. The primary endpoint was progression-free survival (PFS)—time from randomization to recurrence (imaging/biopsy confirmed or death). Secondary endpoints included OS and PFS and ORR and metastatic PFS with subsequent next-line systemic therapy in metastatic setting.ResultsForty-nine patients (24 in CC-486 arm, 25 in OBS arm) were randomized: median age 66 (range 36–81), 53% male, 73% node positive, 49% elevated CA 19–9, 20% R1 resection, 63% and 100% received perioperative concurrent chemoradiation and chemotherapy, respectively. Median time from surgery to randomization was 9.6 mo (range 2.9–36.8). For the CC-486 arm, median treatment duration was 5.6 mo (range 1.3 to 12.8) with 14 treatment-related grade 3 or 4 AEs among 5 patients (22%) resulting in dose-reduction. Four patients (17%) discontinued therapy due to AEs. With median follow-up of 20.3mo (IQR 12.8, 41.4), 38 (79%) of evaluable patients recurred (34 imaging-confirmed, 4 clinically). Median PFS in imagining-confirmed cases was 9.2 and 8.9mo (HR 0.94, 95% CI 0.46–1.87,p = 0.85) for CC-486 and OBS patients, respectively. Median OS (2-yr OS%) was 33.8 (50%) and 26.4 mo (61%) in CC-486 and OBS patients, respectively. (HR 0.98, 95% CI 0.46–2.05,p = 0.96). ORR with subsequent chemotherapy in the metastatic setting was minimal in both arms.ConclusionsTreatment with CC-486 following adjuvant therapy did not prolong time-to-relapse in patients with high-risk rPDA or improve disease response on 1st-line metastatic therapy.

Background: Fibrolamellar hepatocellular carcinoma (FLC) is a rare form of liver cancer primarily affecting children and young adults. Although considered a subset of hepatocellular carcinoma (HCC), FLC has unique molecular and pathologic characteristics, suggesting that it may require different treatment. Immune checkpoint inhibitors (ICIs) are used in the treatment of HCC, but efficacy and safety in FLC has not been characterized. Methods: We performed a multicenter retrospective analysis of patients with FLC to determine responses to ICI therapy. Response rates were assessed based on RECIST 1.1 criteria, and Kaplan–Meier statistics were used for progression-free survival (PFS) and overall survival (OS). Results: FLC tumors were characterized by low tumor mutational burden (TMB) and absent PD-L1 expression. We identified 19 patients who received ICIs, including 15 who received ICI therapy alone [programmed death receptor 1 (PD-1) inhibitor, +/− cytotoxic T lymphocyte antigen-4 (CTLA-4) inhibitor]. Objective tumor responses were observed in 3/19 patients (15.8%), including 2/15 patients (13.3%) who received ICIs alone, all partial responses. Median PFS and OS were 5.5 and 26.0 months, respectively. Grade 3–4 immune related adverse events were observed in 4/19 (21.1%) patients. Conclusions: ICI therapy has modest clinical activity in FLC, and novel therapeutic combinations are needed.

OBJECTIVES The aim of this study was to characterize the tumor microenvironment of patients with gastroenteropancreatic neuroendocrine tumors relative to progression-free survival (PFS). METHODS Immune profiling for CD3, CD8, programmed death-1/programmed death-ligand 1, and indoleamine 2,3-dioxygenase expression in 2 cohorts of gastroenteropancreatic neuroendocrine tumors: patients with short PFS (

PURPOSE Biliary tract cancers (BTCs) are aggressive cancers that carry a poor prognosis. An enhanced understanding of the immune landscape of anatomically and molecularly defined subsets of BTC may improve patient selection for immunotherapy and inform immune-based combination treatment strategies. METHODS We analyzed deidentified clinical, genomic, and transcriptomic data from the Tempus database to determine the mutational frequency and mutational clustering across the three major BTC subtypes (intrahepatic cholangiocarcinoma [IHC], extrahepatic cholangiocarcinoma, and gallbladder cancer). We subsequently determined the relationship between specific molecular alterations and anatomical subsets and features of the BTC immune microenvironment. RESULTS We analyzed 454 samples of BTC, of which the most commonly detected alterations were TP53 (42.5%), CDKN2A (23.4%), ARID1A (19.6%), BAP1 (15.5%), KRAS (15%), CDKN2B (14.2%), PBRM1 (11.7%), IDH1 (11.7%), TERT (8.4%), KMT2C (10.4%) and LRP1B (8.4%), and FGFR2 fusions (8.7%). Potentially actionable molecular alterations were identified in 30.5% of BTCs including 39.1% of IHC. Integrative cluster analysis revealed four distinct molecular clusters, with cluster 4 predominately associated with FGFR2 rearrangements and BAP1 mutations in IHC. Immune-related biomarkers indicative of an inflamed tumor-immune microenvironment were elevated in gallbladder cancers and in cluster 1, which was enriched for TP53, KRAS, and ATM mutations. Multiple common driver genes, including TP53, FGFR2, IDH1, TERT, BRAF, and BAP1, were individually associated with unique BTC immune microenvironments. CONCLUSION BTC subtypes exhibit diverse DNA alterations, RNA inflammatory signatures, and immune biomarkers. The association between specific BTC anatomical subsets, molecular alterations, and immunophenotypes highlights new opportunities for therapeutic development.

Background: Novel strategies are needed to decrease the high recurrence rates of pancreatic ductal adenocarcinoma (PDAC) after curative-intent surgery. Mutant KRAS (mKRAS) is an oncogenic driver found in approximately 90% of PDAC that has emerged as a target for neoantigen-specific vaccination. Methods: This is a single-arm, open-label, first-in-human phase I study of a pooled synthetic long peptide (SLP) vaccine targeting six mKRAS subtypes (G12D, G12R, G12V, G12A, G12C, G13D) combined with ipilimumab/nivolumab (ipi/nivo) in patients with resected PDAC (NCT04117087). Key inclusion criteria: presence of a vaccine-targeted KRAS mutation, disease-free status after completing adjuvant chemotherapy within 6 months of enrollment. Priming phase: mKRAS vaccine given on days 1, 8, 15, and 22 along with ipi 1 mg/kg every 6 weeks for 2 doses and nivo 3 mg/kg every 3 weeks for 4 doses. Boost phase: mKRAS vaccine given on weeks 13, 21, 29, 37, and 45 along with nivo 480 mg every 4 weeks for 10 doses. Co-primary endpoints: safety, mKRAS-specific T cell response. Secondary endpoints: disease-free survival (DFS), overall survival (OS). Results: At the time of data cutoff (December 1, 2022), 11 patients were treated with a median follow-up time of 10.7 months. 8/11 patients achieved a mKRAS-specific T cell response, defined as >5-fold change in IFN-gamma-producing mKRAS-specific T cells within 17 weeks post-vaccination, as assessed by serial ELISpot. The median fold change in IFN-gamma-producing mKRAS-specific T cells within 17 weeks post-vaccination was 10.2 (range: 1.5-686.3). The majority of all adverse events were grade 1 (79.5%) or grade 2 (15.2%) in severity per NCI CTCAE v5.0. Four grade 3 immune-related adverse events (pneumonitis, adrenal insufficiency, arthralgias, myalgias) and discontinuation of checkpoint blockade occurred in 2/11 patients. The median DFS for the entire cohort was 6.4 months and not reached for OS. Patients who mounted a mKRAS-specific T cell response demonstrated a significant improvement in median DFS compared to immune non-responders (not reached vs 2.8 months, p = 0.045). Conclusions: The combination of a pooled SLP mKRAS vaccine and dual checkpoint blockade is tolerable and immunogenic in patients with resected PDAC. Induction of an mKRAS-specific T cell response is associated with improved DFS in this cohort. Ongoing correlative studies will apply multi-omic approaches to identify novel biomarkers of immune response and resistance. Citation Format: Saurav D. Haldar, Amanda Huff, Thatcher R. Heumann, Maureen Berg, Anna Ferguson, Su Jin Lim, Hao Wang, Amy M. Thomas, Julie M. Nauroth, Marina Baretti, Katherine M. Bever, Mark Yarchoan, Daniel A. Laheru, Elizabeth M. Jaffee, Nilofer S. Azad, Neeha Zaidi. Safety and immunogenicity of a first-in-human mutant KRAS long peptide vaccine combined with ipilimumab/nivolumab in resected pancreatic cancer: Preliminary analysis from a phase I study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT036.

Fibrolamellar hepatocellular carcinoma (FLC) is a rare and often lethal form of liver cancer that primarily affects children and young adults. A fusion between DNAJB1, a heat shock chaperone protein, and PRKACA, the catalytic domain of protein kinase A (PKA) has been identified as a signature genomic event in FLC, but the effect of this fusion on the tumor immune microenvironment is not understood. We created an orthotopic, syngeneic model of FLC (TIBx-FLC) by inducing the DNAJB1-PRKACA fusion in a murine hepatoblastoma-derived cell line (TIBx). CD8 T cells isolated from TIBx-FLC tumors demonstrated markedly impaired activation as compared to CD8 T cells isolated from control TIBx tumors. We investigated metabolic programming as a potential mechanism for DNAJB1-PRKACA immunosuppression in FLC. Labeled glucose metabolomics performed on TIBx-FLC and TIBx tumor cells demonstrated a metabolic shift away from aerobic metabolism to an increased glucose contribution towards the hexosamine biosynthetic pathway and purine synthesis, which requires glutamine as a nitrogen source. As compared to the parental TIBx cell line, the TIBx-FLC cell line demonstrated high sensitivity to glutamine antagonism in vitro, consistent with glutamine addiction. Systemic treatment of BALB/c mice bearing TIBx-FLC tumors with JHU-083, a glutamine antagonist, in combination with immune checkpoint inhibitor therapy enhanced survival as compared to vehicle or monotherapy. These data identify altered glutamine metabolism as a target in FLC, and may provide an explanation for immune suppression seen in the FLC tumor microenvironment. Citation Format: Zeal Kamdar, Tamara Lopez-Vidal, Kathryn Howe, Kabeer Munjal, Ali Saeed, Daniel Zabransky, Daniel Shu, Gabriella Longway, Emma Kartalia, James Leatherman, Aditya Mohan, Pratik Khare, Cissy Zhang, Anne Le, Erika Pearce, Mark Furth, Marina Baretti, Robert Leone, Elizabeth Jaffee, Mark Yarchoan. DNAJB1-PRKACA fusion in fibrolamellar hepatocellular carcinoma induces glutamine addiction and an immunosuppressive tumor microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3679.

A 26-year-old male with a two-year history of FLC developed progressive somnolence and disorientation. Treatment history for FLC had included cytotoxic chemotherapy, lenvatinib, and immunotherapy. A CT scan confirmed extensive stage FLC with numerous liver, lung, and pelvic metastasis. Laboratory results showed bilirubin 0.3 mg/dL, creatinine 0.4 mg/dl, leukocytes of 9.5x109 /L, hemoglobin 11.2 g/dL, platelets 369x109 /L, and ammonia 247 µmol/L (reference range: 0-32 µmol/L). Plasma amino acid analysis revealed relatively low citrulline (14 µmol/L), arginine (32 µmol/L), and ornithine (35 µmol/L). Urinary orotic acid excretion was markedly elevated at 149 mmol/mol creat (reference range: 0.68-3.52 mmol/mol creat).

In a recent Lancet Oncology article, Yau et al. report the CheckMate 459 trial results. This is the first phase III trial comparing the single-agent anti-programmed death protein 1 (PD-1) therapy nivolumab to the tyrosine kinase inhibitor sorafenib for treatment-naive patients with advanced hepatocellular carcinoma.

DNA damage and resulting neoantigen formation is considered a mechanism for synergy between radiotherapy and PD-1/PD-L1 pathway inhibition to induce antitumor immune response. We investigated neoadjuvant chemoradiotherapy (nCRT)-induced changes in CD8+ tumor infiltrating lymphocyte, PD-L1 and mucin expression in rectal cancer patients.Tumor samples of rectal adenocarcinoma patients undergoing resection between 2008-2014 with (PD-L1 expression on TCs was identified in 7.6% (6/79) of nCRT specimens (nCRT exposure was associated with a non-significant difference in PD-L1 expression in rectal adenocarcinoma patients, possibly due to sample size limitations. Further mechanistic investigations and comprehensive immune analysis are needed to understand nCRT-induced immunologic shift in rectal cancer and to expand the applicability of checkpoint inhibitors in this setting.

Although immune-checkpoint inhibitors (ICIs) have been a remarkable advancement in bladder cancer treatment, the response rate to single-agent ICIs remains suboptimal. There has been substantial interest in the use of epigenetic agents to enhance ICI efficacy, although precisely how these agents potentiate ICI response has not been fully elucidated. We identified entinostat, a selective HDAC1/3 inhibitor, as a potent antitumor agent in our immune-competent bladder cancer mouse models (BBN963 and BBN966). We demonstrate that entinostat selectively promoted immune editing of tumor neoantigens, effectively remodeling the tumor immune microenvironment, resulting in a robust antitumor response that was cell autonomous, dependent upon antigen presentation, and associated with increased numbers of neoantigen-specific T cells. Finally, combination treatment with anti–PD-1 and entinostat led to complete responses and conferred long-term immunologic memory. Our work defines a tumor cell–autonomous mechanism of action for entinostat and a strong preclinical rationale for the combined use of entinostat and PD-1 blockade in bladder cancer.

Advances in high-throughput technologies have yielded impressive insights into the molecular biology behind cancers, resulting in a powerful ally for the development of biomarkers-selected clinical trials, which are critical for translating our genomic knowledge into clinically meaningful outcomes. "Basket studies" or histology-agnostic clinical trials in biomarker-defined populations represent an important research strategy to continue making progress in this field. The recent accelerated US Food and Drug Administration approvals of anti-programmed death 1 pembrolizumab and nivolumab for mismatch repair-deficient cancers, as well as larotrectinib for cancers carrying TRK fusions, support the fundamental premise that some cancers may be best classified based on molecular phenotype and not site of origin. The studies that were conducted showing the efficacy of this approach serve as validation of the basket study paradigm. In the field of immune oncology, the advent of tumor agnostic strategies represents an important step toward discovering biomarkers of response and elucidating mechanisms of treatment efficacy and resistance across a variety of cancer types. We present a review and discussion of the progress in biomarker-defined approaches to drug development in immunology.

Although developments in the diagnosis and therapy of colorectal cancer (CRC) have been made in the last decade, much work remains to be done as it remains the second leading cause of cancer death. It is now well established that epigenetic events, together with genetic alterations, are key events in initiation and progression of CRC. Epigenetics refers to heritable alterations in gene expression that do not involve changes in the DNA sequence. These alterations include DNA methylation, histone alterations, chromatin remodelers, and noncoding RNAs. In CRC, aberrations in epigenome may also involve in the development of drug resistance to conventional drugs such as 5-fluorouracil, oxaliplatin, and irinotecan. Thus, it has been suggested that combined therapies with epigenetic agents may reverse drug resistance. In this regard, DNA methyltransferase inhibitors and histone deacetylase inhibitors have been extensively investigated in CRC. The aim of this review is to provide a brief overview of the preclinical data that represent a proof of principle for the employment of epigenetic agents in CRC with a focus on the advantages of combinatorial therapy over single-drug treatment. We will also critically discuss the results and limitations of initial clinical experiences of epigenetic-based therapy in CRC and summarize ongoing clinical trials. Nevertheless, since recent translational research suggest that epigenetic modulators play a key role in augmenting immunogenicity of the tumor microenvironment and in restoring immune recognition, we will also highlight the recent developments of combinations strategies of immunotherapies and epigenetic therapies in CRC, summarizing preclinical, and clinical data to signify this evolving and promising field for CRC treatment.

Contains fulltext : 235395.pdf (Publisher’s version ) (Open Access) We previously reported CHFR methylation in a subset of colorectal cancer (CRC; ∼30%) with high concordance with microsatellite instability (MSI). We also showed that CHFR methylation predicted for sensitivity to docetaxel, whereas the MSI-high phenotypes were sensitive to gemcitabine. We hypothesized that this subset of patients with CRC would be selectively sensitive to gemcitabine and docetaxel. We enrolled a Phase 2 trial of gemcitabine and docetaxel in patients with MSI-high and/or CHFR methylated CRC. The primary objective was Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 response rate. Enrolled patients were treated with gemcitabine 800 mg/m(2) on days 1 and 8 and docetaxel 70 mg/m(2) on day 8 of each 21-day cycle. A total of 6 patients with CHFR-methylated, MSI-high CRC were enrolled from September 2012 to August 2016. The study was closed in September of 2017 due to poor accrual prior to reaching the first interim assessment of response rate, which would have occurred at 10 patients. No RECIST criteria tumor responses were observed, with 3 patients (50%) having stable disease as best response, 1 lasting more than 9 months. Median progression-free survival (PFS) was 1.79 months (95% confidence interval [CI] = 1.28, not available [NA]) and median overall survival (OS) was 15.67 months (95% CI = 4.24, NA). Common grade 3 toxicities were lymphopenia (67%), leukopenia (33%), and anemia (33%). Although negative, this study establishes a proof-of-concept for the implementation of epigenetic biomarkers (CHFR methylation/MSI) as inclusion criteria in a prospective clinical trial to optimize combinatorial strategies in the era of personalized medicine. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? CHFR silencing via DNA methylation has been suggested to be predictive of taxane sensitivity in diverse tumors. The frequent association of CHFR methylation with microsatellite instability (MSI) suggested a possible combination therapy with gemcitabine, because the MSI phenotype may result in sensitivity to nucleoside analogues. WHAT QUESTION DID THIS STUDY ADDRESS? We hypothesized that metastatic colorectal cancer (mCRC), which have CHFR methylation and MSI phenotype were sensitive to gemcitabine and docetaxel, and have designed this Phase 2 trial in biomarker-selected mCRC to test this prediction. WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? The study enrolled a molecularly defined subgroup of patients with colorectal cancer (CRC) and showed that the combination is safe in this population. Nevertheless, due to poor enrollment and early termination, no conclusions on the primary and secondary end points could be made. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? This study supports the feasibility of implementing DNA methylation markers in a prospective clinical trial and further efforts toward their application as predictive biomarkers for therapeutic agents in defined subsets of patients are warranted.

Microsatellite instability (MSI) refers to the hypermutator phenotype secondary to frequent polymorphism in short repetitive DNA sequences and single nucleotide substitution, as consequence of DNA mismatch repair (MMR) deficiency. MSI secondary to germline mutation in DNA MMR proteins is the molecular fingerprint of Lynch syndrome (LS), while epigenetic inactivation of these genes is more commonly found in sporadic MSI tumors. MSI occurs at different frequencies across malignancies, although original methods to assess MSI or MMR deficiency have been developed mostly in LS related cancers. Here we will discuss the current methods to detect MSI/MMR deficiency with a focus of new tools which are emerging as highly sensitive detector for MSI across multiple tumor types. Due to high frequencies of non-synonymous mutations, the presence of frameshift-mutated neoantigens, which can trigger a more robust and long-lasting immune response and strong TIL infiltration with tumor eradication, MSI has emerged as an important predictor of sensitivity for immunotherapy-based strategies, as showed by the recent FDA's first histology agnostic-accelerated approval to immune checkpoint inhibitors for refractory, adult and pediatric, MMR deficient (dMMR) or MSI high (MSI-H) tumors. Moreover, it is known that MSI status may predict cancer response/resistance to certain chemotherapies. Here we will describe the complex interplay between the genetic and clinical-pathological features of MSI/dMMR tumors and the cancer immunotherapy, with a focus on the predictive and prognostic role of MMR status for immune checkpoint inhibitors (ICIs) and providing some suggestions on how to conceive better predictive markers for immunotherapy in the next future.

Genetic intratumoural heterogeneity is a natural consequence of imperfect DNA replication. Any two randomly selected cells, whether normal or cancerous, are therefore genetically different. Here, we review the different forms of genetic heterogeneity in cancer and re-analyse the extent of genetic heterogeneity within seven types of untreated epithelial cancers, with particular regard to its clinical relevance. We find that the homogeneity of predicted functional mutations indriver genes is the rule rather than the exception. In primary tumours with multiple samples, 97% of driver-gene mutations in 38 patients were homogeneous. Moreover, among metastases from the same primary tumour, 100% of the driver mutations in 17 patients were homogeneous. With a single biopsy of a primary tumour in 14 patients, the likelihood of missing a functional driver-gene mutation that was present in all metastases was 2.6%. Furthermore, all functional driver-gene mutations detected in these 14 primary tumours were present among all their metastases. Finally, we found that individual metastatic lesions responded concordantly to targeted therapies in 91% of 44patients. These analyses indicate that the cells within the primary tumours that gave rise to metastases are genetically homogeneous with respect to functional driver-gene mutations, and we suggest that future efforts to develop combination therapies have the potential to be curative.

OBJECTIVE: Limited data exist on the impact of ascites in pancreatic ductal adenocarcinoma (PDAC). We evaluated the survival outcomes of patients with PDAC and ascites. METHODS: Retrospective, single-institution, case-control study including patients with newly diagnosed PDAC from 2007 to 2016. One hundred fifty-four patients with ascites at diagnosis (case group) and 154 controls were matched on age, sex, stage, Eastern Cooperative Oncology Group performance, surgical treatment, lymph node, and margin status. Ascites was defined as computed tomography–detected fluid in the pelvic/peritoneal cavity. Overall survival was compared between groups via Cox proportional hazards models with a gamma frailty term to account for the correlation between matched pairs on entire cohort and by disease stages for subgroup analysis. RESULTS: The 154 matched cases included 24 resectable, 19 borderline resectable, 51 locally advanced, and 60 metastatic disease. Patients with ascites had higher risk of death compared with those without (conditional hazard ratio, 1.58; 95% confidence interval, 1.23–2.03; P < 0.001). Stratified analysis showed a significant association between ascites and poor prognosis in patients with localized disease (conditional hazard ratio, 1.62; 95% confidence interval, 1.18–2.24; P = 0.003). CONCLUSIONS: Radiographic ascites is a poor prognostic factor in PDAC. Our findings may aid physicians in considering systemic therapy prior to attempting local treatments.

The detection of circulating DNA is considered a promising strategy in cancer patients. Digital PCR has emerged as a sensitive method able to quantify both circulating free and tumour DNA.The aim of this study was to prospectively evaluate the clinical value of a chip-based digital PCR for the detection of circulating DNA.Digital PCR was used in 34 metastatic colorectal cancer patients to detect and quantify circulating free and tumour DNA based on K-ras mutational status. Clinical outcomes were analyzed according to circulating DNA measurements.Digital PCR yielded a detection rate of 69% for circulating tumour DNA. The median concentrations of circulating free and tumour DNA were 20 and 6.8 ng/mL, respectively, with significant correlation between both biomarkers (p0.001). Median overall survival was 4.8 months in patients with high circulating free DNA (75% quartile) versus not reached in patients with a low level (25% quartile) (p=0.029). Moreover, median overall survival was significantly decreased in patients with detectable circulating tumour DNA compared to those without (respectively 11.8 months versus not reached, p=0.04).Chip-based digital PCR is a simple and non-invasive method allowing the efficient detection of circulating DNA. Our results highlight that levels of these circulating markers may have a potential prognostic value.

Background Previously our group showed the potential use of a score based on MGMT, NDRG-1 and PHLDA-3 immunohistochemistry (IHC) expression as predictor of outcome in operated PanNET. The present multicenter project is retrospectively analyzing the predictive/prognosis role of MGMT, NDRG-1 and PHLDA-3 in patients with advanced PanNET treated CAPTEM or everolimus. Methods IHC nuclear staining for MGMT and PHLDA-3 is being scored as 0, 1-5%, 6-50% and ≥ 51%. For NDRG-1, we are using a cytoplasmic score from 0 to 3 based on staining intensity and distribution pattern (patched or diffuse). Results Until now, clinical and samples data from 96 patients (110 samples) has been collected ad are currently being analyzed. Based on our previous results, we will develop an imunohistochemistry prognostic score (IPS, score from 0 to 4) and try to correlate it with clinical variables collected in our database. Conclusions As we described previously in operated PanNET, we will try to describe the potential role of IPS as predictive/ prognostic factor in advanced PanNET. More mature results of this work will be presented during 2019 ESMO Congress. Legal entity responsible for the study Navarrabiomed Biomedical Research Center, Pamplona, Navarra, Spain. Funding GETNE. Disclosure All authors have declared no conflicts of interest.

In 2018, there was an estimated 55,440 new cases of pancreatic adenocarcinoma (PDAC) in the United States. Generally, most new cases are in an advanced stage, usually due to the lack of symptoms during the early stages of the disease. Currently, the vast majority of therapeutic regimens have shown only modest effects in this setting, and median survival ranges from 6 to 11 months. Indeed, better therapies for these patients are urgently needed. Epigenetics refers to the somatically heritable differences in gene expression not attributable to intrinsic alterations in the primary sequence of DNA. Core elements of the epigenetic regulation of gene expression include how DNA is packaged around nucleosomes, how chromatin and nucleosomes are modified by a complex series of enzymes and their subsequent interactions with proteins that recognize these modifications. The recognition of the essential role of epigenetic alterations in the development and progression of PDAC has revolutionized our knowledge of this disease and has immediate translational implications for targeting epigenetic abnormalities in PDAC for therapeutic purposes. Moreover, recent work with epigenetic modulatory drugs (EMDs) has shown that these agents may be capable of altering the immunogenicity of the tumor microenvironment (TME), to reverse immune suppression and to ‘prime’ tumors for immunotherapy. This review summarizes the current knowledge of epigenetic alterations in PDAC with a focus on the translational application of targeting epigenetic-based events as new therapeutic approach for this disease.

BACKGROUND: Immune checkpoint inhibitors (ICIs) have unlocked the promise of modulating the immune tumor microenvironment (TME) in the battle against cancer, but it remains unclear whether they might be useful for cholangiocarcinoma (CCA). Our laboratory has explored entinostat, a histone deacetylase inhibitor (HDACi) to alter the function of suppressive myeloid derived suppressor cells (MDSC) in favor of recruiting T cells in murine pancreatic ductal adenocarcinoma (PDAC) models, showing improved survival when given with anti-PD1 therapy. We hypothesize that the HDACi entinostat may prime an ICI-insensitive cancer into a more sensitive one. METHODS: An open-label, two-arm study enrolling patients with histologically confirmed advanced CCA or PDAC, who have progressed after at least one line of therapy. Eligibility criteria include measurable disease, PS ≤1, good end organ function and no history of autoimmune disease. Patients receive entinostat 5 mg oral once a week. After a fourteen-day lead in with entinostat monotherapy, patients receive entinostat 5 mg oral once a week plus nivolumab 240 mg every two weeks until progression or unacceptable toxicities. Patients undergo tumor biopsy and have research bloods drawn at baseline and after two weeks of entinostat lead-in therapy, and on week 6. An optional biopsy is performed at the time of progression. The study is planned with 27 subjects per histology based on a Simon’s two-stage design that allows early termination for lack of efficacy. The primary objective of the trial is ORR, by RECIST 1.1. Secondary objectives include PFS, OS, safety and immunological correlates to evaluate the effect of HDAC inhibition on the TME by interrogating clinical specimens. RESULTS: The clinical study has been activated in November 2017. The accrual is still ongoing. Ten patients with a diagnosis of CCA and 22 with PDAC have been enrolled. Blood samples and tumor biopsies are being drawn, processed, and stored for accrued patients. The analysis will be performed in a single batched analysis at the conclusion of the study accrual. CONCLUSIONS: This clinical trial is the first to test HDAC + immune checkpoint inhibition in pancreatobiliary cancers. If our project is successful, we have the potential to increase therapeutic options for CCA and PDAC patients (clinical trial information: NCT03250273).

570 Background: DNA damage and subsequent neoantigen formation has been hypothesized as a mechanismfor radiotherapy and PD-1/PD-L1 pathway inhibition to synergize in an antitumor immune response. We investigated neoadjuvant chemoradiotherapy (nCRT)-induced changes in CD8+ tumor infiltrating lymphocyte, PD-L1 and mucin expression in rectal cancer patients as compared to patients who did not receive nCRT. Methods: Tumor samples were collected from rectal adenocarcinoma patients who had undergone resection between 2008-2014 with (n = 62) or without (n = 17) nCRT treatment. Tissue sections were stained with CD8 and PD-L1 antibodies for immunohistochemistry. Whole slides images were acquired at 20x magnification. The prevalence of positive CD8 stained cells was recorded in tumor, interface tumor side, interface background rectal side. Image analysis (HALO Indica Labs) was used to determine the density (# of cells/surface area analyzed) of CD8 expressing lymphocytes. The percentage of PD-L1 membranous expression was manually counted in tumor cells (TC), tumor stroma (TS) and invasive front (IF). Mucin expression was determined as the percentage of the mucin area in the whole tumor mass area. Results: PD-L1 expression on TCs was identified in 7.7 % (6/78) of specimens. All 6 cases had received nCRT (p = 0.33). 80% and 75.5% of the nCRT cases showed PD-L1 expression on TS and IF respectively, versus 20% (p = 0.55) and 24.5% (p = 0.56) in non-nCRT cases. The median densities of CD8+ infiltrating T lymphocytes in tumor, interface tumor side, interface background rectal side did not differ significantly between the two groups (p = 0.79, p = 0.47, p = 0.22). No nCRT-changes in mucin expression observed in the 28 evaluable cases (p = 0.25). Conclusions: nCRT exposure was associated with a non-significant difference in PD-L1 expression on TS and IF cells in patients with rectal adenocarcinoma as compared to non-nCRT case, possibly due to sample size limitations. Further mechanistic investigations and comprehensive analysis of other immune checkpoints are needed to understand nCRT-induced immunologic shift in rectal cancer and to expand the potential applicability of checkpoint inhibitors in this setting.

267 Background: The immune microenvironment in neuroendocrine tumors (NETs) remains largely unexplored with very limited data evaluating its impact on survival. We aimed to characterize the immune microenvironment and lymphocytic infiltrate in patients with gastroenteropancreatic (GEP) NET. Methods: We performed comprehensive immune profiling for CD3, CD8, PD-1, IDO, and PD-L1 expression in two cohorts of patients with primary GEP-NET: patients who had short progression free survival (PFS) ≤ 4 years (n = 12) or long PFS > 4 years (n = 14) following surgical resection. Tumor associated immune infiltrates in the tumor, inner and outer invasive front were recorded and quantified. The percentage of PD-L1 membranous expression was manually counted in tumor, stroma and invasive front. To account for the correlation among multiple samples within the same patient, generalized estimating equations (GEE) were used for model estimation and hypothesis testing. Results: Patients with shorter PFS had larger primary tumor size compared to patients with longer PFS (Wilcoxon p value = 0.02), with no statistically significant differences in Ki-67 expression. For all patients univariate GEE results showed a higher mean expression of CD3+, CD8+, and PD-1+ cells at the interface (inner and outer) as compared to the tumor region: 1.28 (95% CI: 0.98, 1.58, p < 0.0001), 0.99 (95% CI: 0.67, 1.32, p = 0.0005) and 1.38 (95% CI: 0.90, 1.38, p < 0.0001) respectively. Comparison between the two groups showed that tumors from patients with a longer PFS had higher intratumoral CD3+ TILs densities than did those from patients who had a shortened PFS (0.88, 95% CI: 0.44, 1.31, p = 0.004). Intratumoral expression of CD8+TILs, and IDO+ cells tended to be higher in the long PFS group (p = 0.143 and 0.29 respectively). While the probability of positive PD-L1 expression did not differ according to location, it was higher in patients with shortened PFS (odds ratio = 1.96; 95% CI: 0.64, 5.93), though not significant. Conclusions: Higher intratumoral T cell infiltrate (CD3+) is associated with a favorable outcome and longer PFS following resection for GEP-NETs. Immune escape is a potential mechanism for disease progression and warrants further investigation as a therapeutic strategy for this disease.

TPS4151Background: The use of antibody therapy targeting immune checkpoints has become a major focus of cancer immunotherapy, with the most compelling activity seen in the minority of patients with...

Recent progress in cancer biology has led to the discovery of increasing number of oncogene alterations that have dramatically changed the paradigm of lung cancer treatment. MET is a tyrosine kinase receptor for the hepatocyte growth factor (HGF) that is deregulated in several malignancies, including non-small cell lung cancer (NSCLC). Abnormal MET-HGF signaling pathway activation can occur via different mechanisms, including HGF and/or MET overexpression, MET gene amplification, mutations or rearrangements. MET protein overexpression and increased MET gene number have been identified as poor prognostic factors in several series of surgically resected NSCLC making this receptor an attractive target for cancer treatment. Several clinical trials have recently evaluated the activity of a variety of anti-MET strategies in NSCLC patients with or without molecular selection with a variable degree of success, underscoring the need of establishing the best predictive biomarker for the identification of responding patients.