Current treatment and recent progress in gastric cancer.

Objective: Panel-based sequencing is widely used to measure tumor mutational burden (TMB) in clinical trials and is ready to enter routine diagnostics. However, cut-off points to distinguish “TMB-high” from “TMB-low” tumors are not consistent and the clinical implications of TMB in predicting responses to immune checkpoint blockade (ICB) in gastric cancer are not clearly defined. We aimed to assess whether TMB is associated with the response to immunotherapy and to examine its relation with other biomarkers of immunotherapy response in advanced gastric cancer.Design: In total, 63 patients with advanced gastric cancer treated with ICB were included in the study. Panel-based TMB in gastric tumor samples, treatment responses to ICB, clinicopathological data, and time to progression were retrospectively analyzed. Microsatellite instability (MSI) status, Epstein–Barr virus (EBV) positivity, and programmed death-ligand 1 (PD-L1) combined positive score (CPS) were also analyzed.Results: TMB ranged from 0 to 446 mutations/megabase (mt/mb) and was significantly associated with MSI (P < 0.001), PD-L1 CPS (P = 0.022), response to ICB (P = 0.04), chemotherapy (P = 0.02) and older patient age (≥65 years; P = 0.0014). The cut-off point of 14.31 mt/mb determined by log-rank statistics for progression-free survival divided the tumors into eight (12.7%) TMB-high and 55 (87.3%) TMB-low tumors. The median TMB of the chemo-refractory group was significantly higher (8.43 mt/mb) compared to that of chemo-naïve group (3.42 mt/mb) (P = 0.02). Patients with TMB-high tumors showed prolonged progression-free survival in univariate [HR, 0.32; 95% confidence interval (CI), 0.12–0.90] and multivariate (HR, 0.21; 95% CI, 0.07–0.69) analyses. In area under the receiver operating curve (AUC) analysis of TMB, PD-L1, EBV, MSI, and their combination, the AUC value was the highest for EBV (0.97), followed by MSI (0.96), PD-L1 (0.81), the combination (0.78), and TMB (0.56).Conclusion: In addition to EBV, MSI, and PD-L1 CPS, TMB could be used as a predictive biomarker in patients with advanced gastric cancer treated with ICB and may aid clinical decision making.

Programmed death-ligand 1 (PD-L1) is an important screening biomarker to select patients with gastric cancer (GC) for optimized treatment, including immune checkpoint inhibitors (ICI). In this single-institution retrospective cohort study, patients with metastatic GC with available PD-L1 results between October 2019 and September 2021 were identified by reviewing their electronic medical records. Genomic data were obtained from the Samsung Medical Center Clinical Sequencing Platform. Among the 399 patients, 276 (69%) had a PD-L1 combined positive score (CPS) ≥1, 155 (39%) had a CPS between 1 and 5, and 121 (30%) had a CPS ≥5. Of the 121 patients with CPS ≥5, 28 (23%) had a known etiology for "inflamed tumor," with Epstein-Barr virus (EBV) positivity (N = 11) or high tumor mutational burden (TMB) (N = 17), which included microsatellite instability (MSI) (N = 9). PD-L1 CPS ≥5 was observed in 11/11 (100%) patients with EBV positivity, 9/12 (75%) patients with MSI, and 17/33 (52%) patients with high TMB. For the 108 patients who received ICI therapy, CPS ≥5 was the only predictor significantly associated with survival in multivariable analyses, including TMB, MSI, or EBV. Objective response rate (ORR) was 49% in patients with CPS ≥5, 30% in patients with 1 ≤ CPS <5, and 19% in patients with CPS <1. Among the 31 responders to ICI therapy, 27 (87%) had a CPS of ≥1. Mutations in TET2, IRS2, DOT1L, PTPRT, and LRP1B were associated with a higher ORR (63%-100%), whereas MDC1 mutations were associated with a low ORR (22%). PD-L1 expression is an independent and sensitive biomarker for ICI therapy. Considering its significant association with several gene alterations, including PIK3CA mutations and MET amplification, combining ICI therapy with other targeted agents may be a promising therapeutic strategy for GC.

Integrated clinico-molecular analysis of gastric cancer in European and Latin American populations: LEGACY project.

e15609 Background: Recent data supports a potentially significant role for immune checkpoint inhibitors in the treatment of gastric cancer. However, there are few data on the clinical implications of immunotherapy markers in gastric signet-ring cell carcinoma (SRCC). We evaluated the expression of programmed cell death protein-1 (PD-1), programmed cell death ligand 1 (PD-L1), infiltration by CD3+ T cell, microsatellite instability (MSI), and Epstein-Barr Virus (EBV), and the relationship of each factor to survival in SRCC patients. Methods: SRCC samples from 89 patients were stained by immunohistochemistry to evaluate PD-L1, PD-1, CD3+ T cells, and MSI. EBV was detected by DNA in-situ hybridization. Results: All 89 patients had advanced gastric SRCC (89.9% were stage III, 10.1% were stage IV). All patients received 5-FU-based first-line chemotherapy. PD-L1 and PD-1 were expressed in 40.4% and 18.0% of the patients, respectively. There was a significant correlation between PD-L1 and PD-1 expression (r = 0.363, p &lt; 0.001). There was loss of at least 1 of the 4 DNA mismatch repair (DNA-MMR) gene proteins in 32.6% of samples. However, there was no association between the expression of PD-L1, PD-1 or MSI status to overall survival (OS). Only 1 case out of 89 was EBV positive, with concurrent PD-L1 positivity, a high degree of CD3+ T cell infiltration and MSI. Increased CD3+ T cells numbers was associated with increased PD-1 expression (r = 0.256, p = 0.012) and MSI status (r = 0.208, p = 0.05). High CD3+ T cell infiltration was related to better OS (23.7 months, 95% CI: 19.0-38.0 vs 15.8 months, 95% CI: 13.0-22.0, p = 0.033), but was not an independent prognostic factor for survival after multivariate analysis (HR = 0.68, 95% CI: 0.42-1.10, p = 0.116). Conclusions: CD3+ T cell was more infiltrated in PD-1 positive, tumors with MSI and were associated with better OS, indicating an adaptive immune resistance may be occurring. Further research into the cancer characteristics and immunotherapy markers of the gastric SRCC immune microenvironment may highlight targets for immunotherapy.

BackgroundThe prognostic potential of PD-L1 is currently unclear in gastric carcinomas, although the immune checkpoint PD-1/PD-L1 inhibitors have produced promising results in clinical trials.MethodsWe explored the prognostic implications of programmed death ligand 1 (PD-L1) in 514 consecutive surgically-resected gastric carcinomas. Overall survival and recurrence-free survival were evaluated. Immunohistochemistry for PD-L1, CD8, FOXP3, and PD-1, and molecular grouping by in situ hybridization for Epstein-Barr virus (EBV)-encoded small RNAs and multiplex PCR for microsatellite instability (MSI) markers were performed. Additionally, to explore the function inherent to PD-L1, PD-L1-specific siRNA transfection, cell proliferation, invasion, migration and apoptosis assays were conducted in five gastric carcinoma cell lines.ResultsPD-L1(+) tumor and immune cells were observed in 101 (20%) and 244 patients (47%), respectively. “Tumoral PD-L1(+)/immune cell PD-L1(-)/CD8+/low tumor-infiltrating lymphocytes (TILs),” and more advanced-stage tumors were associated with unfavorable clinical outcomes in the entire cohort through multivariate analysis. Furthermore, tumoral PD-L1(+)/FOXP3+/low TILs were associated with worse clinical outcomes in EBV-positive and MSI-high carcinomas. Tumoral PD-L1(+) alone was an adverse prognostic factor in EBV-positive carcinomas, but not in MSI-high carcinomas, whereas PD-L1(+) immune cells or FOXP3+/high TILs alone were correlated with a favorable prognosis. PD-L1 knockdown in gastric carcinoma cells suppressed cell proliferation, invasion and migration, and increased apoptosis, which were all statistically significant in two EBV(+) cell lines, but not all in three EBV(−) cell lines.ConclusionsThe prognostic impact of PD-L1 may depend on the tumor microenvironment, and statuses of EBV and MSI, although PD-L1 innately promotes cancer cell survival in cell-based assays. The combination of “tumoral PD-L1/immune cell PD-L1/CD8+ TILs” may serve as an independent prognostic factor. Tumoral PD-L1(+)/immune cell PD-L1(−)/CD8+/low TILs showing a worse prognosis may be beneficial for combinatorial therapies of anti-PD-L1/PD-1 and anti-cytotoxic T-lymphocyte associated antigen 4 (CTLA4) that would promote effector T cells, thus attack the tumor.

The National Comprehensive Cancer Network (NCCN) issued the clinical practice guidelines for gastric cancer 2017 edition version 5, which has been fully updated for the treatment of gastric cancer, including systematic treatment, surgery and radiotherapy. This article review and summarize the updated NCCN clinical practice guidelines for gastric cancer in 2017 and try to interpret it. (1)Biomarkers: mismatch repair defect (dMMR) or high microsatellite instability (MSI-H), programmed death ligand 1 (PD-L1) and tumor Epstein Barr virus (EBV) status should be considered for patients with gastric cancer. (2)Treatment of advanced gastric cancer: the major update is the application of immunotherapy (Pembrolizumab, Nivolumab combined with Ipilimumab). (3)Adjuvant therapy after D2 resection and perioperative treatment: the guidelines recommended Capecitabine combined with Oxaliplatin as adjuvant therapy after radical operation, updated from category 2A to 1; although the 2017 edition of the NCCN guidelines have not yet been adopted, Docetaxel-based FLOT scheme has certain potential in adjuvant therapy for gastric cancer. (4) Radiotherapy: a more detailed definition of radiotherapy for gastric cancer in different locations, especially in high-risk lymphatic drainage areas, was updated. (5) Genetic risk assessment: the guidelines recommended genetic screening for gastric cancer, including hereditary diffuse gastric cancer (HDGC), Lynch syndrome, juvenile polyposis (JPS), Peutz-Jephers syndrome (PJS) and familial adenomatous polyposis (FAP). The NCCN guidelines continue to update based on new evidences, which is the embodiment of precision medicine in the treatment of gastric cancer. The biggest change in the 2017 gastric cancer guidelines is the updates of immunotherapy, which also suggests that the direction of the gastric cancer treatment began to turn to immunotherapy.

e21564 Background: Tissue biomarkers like programmed cell death ligand-1 (PD-L1), microsatellite instability (MSI) and high tumor mutational burden (TMB) are surrogates in identifying patients with non-small cell lung cancer (NSCLC) for treatment with immune checkpoint blockade (ICB) therapy. Although tissue biopsy is widely used for identifying the tumor biology, the invasive nature as well as insufficiency of tissue biopsy specimens limits its application. Liquid biopsy is a minimally invasive procedure and has gained interest in recent times for profiling cancer. We sought to study the correlation in the molecular tumor profile specifically PD-L1, MSI and TMB markers between the tissue and liquid biopsies. Methods: We conducted a retrospective review of patients with Stage 3, 4 and recurrent NSCLC that underwent tissue next generation sequencing (NGS) using Caris life sciences and liquid biopsy using Circulogene molecular diagnostics from January 2018 to December 2019 at East Carolina University. A total of 524 patients were reviewed out of which 199 patients had both liquid and tissue NGS performed at the time of initial diagnosis. TMB high was defined as greater than 10 mut/Mb whereas TMB low as less than or equal to 10 mut/Mb. PD-L1 was divided into negative (0%), 1-49% and ≥50%. The blood MSI was classified as positive or negative. We used frequency table, logistic regression and Pearson bivariate correlation for statistical analysis using SPSS platform. Results: The study cohort had 60% (n = 119) male and 40% (n = 80) female patients of which 53% (n = 105) were Caucasians and 45% (n = 89) were African Americans. A total of 87 patients (44%) had negative tissue PD-L1, 59 patients (30%) had tissue PD-L1 ≥ 50%. A linear correlation was seen between negative tissue PD-L1 and negative blood PD-L1 in 92% of patients (n = 80). However, only 15.3% (n = 9) had correlating tissue PD-L1 and blood PD-L1 ≥ 50%, p = 0.024. The negative blood MSI correlated to low tissue TMB in 83% ( n = 60) whereas positive blood MSI correlated to high tissue TMB in 25% (n = 19), p = 0.023. Conclusions: Our results indicate a linear correlation between tissue PD-L1 and blood PD-L1. Similarly, a linear correlation was seen between blood MSI and tissue TMB. Further studies are needed to elucidate the efficacy of ICB therapy using blood MSI and blood PD-L1 as biomarkers for response to therapy.

Simple SummaryBiomarkers for predicting the response to immune checkpoint blockade (ICB) includes programmed death-ligand 1 (PD-L1) immunohistochemistry (IHC), microsatellite instability (MSI), and tumor mutation burden (TMB). This study investigated the relationship of these biomarkers using comprehensive cancer panel assay (CCPA) with >500 genes in 588 advanced cancer patients. The work demonstrates that PD-L1 expression is significantly associated with TMB and MSI score, according to primary tumor origin.Programmed death-ligand 1 (PD-L1) immunohistochemistry (IHC), microsatellite instability (MSI), and tumor mutation burden (TMB) have been proposed as a predictive biomarker to predict response to immune checkpoint blockade (ICB). We aimed to find the relationship of PD-L1 IHC to TMB and MSI using a comprehensive cancer panel assay (CCPA) with >500 genes in advanced cancer patients. CCPA results from 588 archived tissue samples were analyzed for TMB and MSI. In seven samples, whole exome sequencing confirmed TMB with Pearson’s correlation coefficient of 0.972 and all MSI-high cases were validated by pentaplex PCR. Association of TMB and MSI with their corresponding PD-L1 IHC was analyzed. The median TMB value of 588 cases was 8.25 mutations (mut)/Mb (range 0–426.8) with different distributions among the tumor types, with high proportions of high-TMB (>10mut/Mb) in tumors from melanoma, colorectal, gastric, and biliary tract. The TMB values significantly correlated with PD-L1 expression, and this correlation was prominent in gastric and biliary tract cancers. Moreover, the MSI score, the proportion of unstable MSI sites to total assessed MSI sites, showed a significant correlation with the TMB values and PD-L1 scores. This study demonstrates that PD-L1 expression is significantly associated with TMB and MSI score and this correlation depends on the location of the primary tumor.

Understanding mechanisms of primary resistance to checkpoint inhibitors will lead to precision immunotherapy of advanced gastric cancer

e14268 Background: Checkpoint inhibitor-based immunotherapy has varying success among tumor types and patients. Predictive biomarkers are in high demand to assist with patient selection. Responses to these agents are correlated with programmed cell death ligand 1 (PD-L1) expression, microsatellite instability (MSI), and tumor mutational burden (TMB). Here we evaluated PD-L1 expression, MSI status and TMB in a variety of solid tumors to determine their relationships. Methods: A total of 109 specimens were identified in patients diagnosed with solid tumors that underwent a Paradigm Diagnostic Cancer Test. MSI scores were determined by the number of indels present in runs of 6 homopolymer bases per megabase, with a cut-off of 6 to distinguish between MSI-high (MSI-H) and MSI-stable (MSI-S). TMB scores greater than or equal to 10 muts/Mb were designated as high (TMB-H). Results: Of all tumors, 19.3% were MSI-high. PD-L1 testing was performed in 71.5% of all samples; of these, 21.8% were PD-L1 positive. TMB scores of PD-L1 positive tumors (mean = 10.3 muts/Mb) and PD-L1 negative tumors (mean = 8.6 muts/Mb) did not differ significantly (p = 0.57). All MSI-H tumors were TMB-H, and MSI-H tumors had higher mean TMB scores than MSI-S tumors (57 muts/Mb versus 7.6 muts/Mb; p = 0.06). Among TMB-H tumors, MSI-H status was associated with higher TMB scores compared to MSI-S tumors (55.2 muts/Mb versus 22.1 muts/Mb, p = 0.18). Of the both MSI-S and TMB-H tumors, 68.8% were lung cancers and 18.8% were breast cancers. Tumors both MSI-H and TMB-H were 47.6% gastrointestinal carcinomas and 33.3% endometrial carcinomas. Conclusions: In our analysis, TMB was independent of PD-L1 status. All MSI-H tumors were also TMB-H; these were primarily gastrointestinal and endometrial carcinomas whereas TMB-H tumors that were MSI-S consisted predominantly of lung cancers. This difference may be due to the different mechanisms of acquiring mutations during carcinogenesis in these two tumor types. These data also highlight the need for integrated PD-L1, MSI and TMB testing to identify potential responders to immunotherapy.

ObjectivesGastric cancer (GC) is the 4th most common type of cancer worldwide. Different GC subtypes have unique molecular features that may have different therapeutic methods. The aim of the present study was to investigate Epstein-Barr virus (EBV) infection, microsatellite instability (MSI) status, the expression of programmed death-ligand 1 (PD-L1) and gene mutations in GC patients.MethodsThe data of 2504 GC patients, who underwent curative gastrectomy with lymphadenectomy at Peking University Cancer Hospital between 2013 and 2018, were reviewed. We analyzed the clinicopathological factors associated with the immunohistochemistry (IHC) profiles of these patients, and genetic alterations were analyzed using next generation sequencing (NGS).ResultsMismatch repair-deficient (d-MMR) GC patients were found to have a higher probability of expressing PD-L1 (p = 0.000, PD-L1 cutoff value = 1%). In addition, 4 and 6.9% of the 2504 gastric cancer patients were EBV-positive and d-MMR, respectively. The number of MLH1/PMS2-negative cases was 126 (6%), and the number of MSH2/MSH6-negative cases was 14 (0.9%). d-MMR status was associated with a intestinal group (p = 0.012), but not with tumor differentiation. Furthermore, MSI and d-MMR GC status (detected by NGS and IHC, respectively) were consistently high, and the rate of MSI was higher in patients with d-MMR GC. A number of genes associated with DNA damage repair were detected in GC patients with MSI, including POLE, ETV6, BRCA and RNF43. In patients with a high tumor mutation burden, the most significantly mutated genes were LRP1B (79.07%), ARID1A (74.42%), RNF43 (69.77%), ZFHX3 (65.12%), TP53 (58.14%), GANS (51.16%), BRCA2 (51.16%), PIK3CA (51.16%), NOTCH1 (51.16%), SMARCA4 (48.84%), ATR (46.51%), POLE (41.86%) and ATM (39.53%).ConclusionsUsing IHC and NGS, MSI status, protein expression, tumor mutation burden (TMB) and genetic alterations were identified in patients with GC, which provides a theoretical basis for the future clinical treatment of GC.

BackgroundThe Cancer Genome Atlas (TCGA) has identified four distinct molecular subtypes of gastric cancer (GC) with prognostic significance: Epstein-Barr virus (EBV)-positive, microsatellite instability (MSI)-high, genomically stable (GS), and chromosomal instability (CIN). Unfortunately, the complex analysis required for TCGA classification limits its practical use in clinical settings. Our study sought to devise a next-generation sequencing (NGS)-based method to classify GC more efficiently, serving as a promising biomarker for prognosis and immunotherapy efficacy.MethodsThis study was a retrospective observation study, and we employed 2 independent GC cohorts. The 3DMed cohort (n=765), comprising data on 733 cancer-related genes along with 4 EBV-encoded genes, was utilized to develop the new NGS classification. Additionally, the secondary Korean cohort (n=55), which includes both genomic data and information on immune checkpoint inhibitor (ICI) treatment, was employed to establish a correlation between NGS subtypes and ICI responsiveness.ResultsIn the 3DMed cohort, we identified 5.2% EBV, 4.6% MSI, 30.6% GS, and 59.6% CIN subtypes. The MSI subtype exhibited the highest number of mutation events, along with the highest tumor mutational burden (TMB) and strong programmed cell death ligand 1 (PD-L1) expression. CIN tumors showed extensive copy number variations (CNVs) and genomic heterogeneity. The EBV subtype presented recurrent ARID1A and PIK3CA mutations and fewer TP53 mutations. GS tumors exhibited specific mutations in CDH1 and ARID1A. In the Korean cohort, ICIs were most effective in MSI and EBV cases, showing disease control rates of 100%, compared to 62.9% in GS and 12.5% in CIN subtypes.ConclusionsThe NGS method successfully maps the mutational landscape of GC, providing a practical TCGA classification surrogate to optimize patient-specific treatment strategies.

In recent years, remarkable progress has been made in the molecular profiling of gastric cancer. This progress has led to the development of various molecular classifications to uncover subtype-specific dependencies that can be targeted for therapeutic interventions. Human epidermal growth factor receptor 2 (HER2) is a crucial biomarker for advanced gastric cancer. The recent promising results of novel approaches, including combination therapies or newer potent agents such as antibody-drug conjugates, have once again brought attention to anti-HER2 targeted treatments. In HER2-negative diseases, the combination of cytotoxic chemotherapy and programmed cell death-1/programmed cell death ligand-1 (PD-1/PD-L1) inhibitors has become the established standard of care in first-line settings. In the context of gastric cancer, potential biomarkers such as PD-L1 expression, Epstein-Barr virus, microsatellite instability, and tumor mutational burden are being considered for immunotherapy. Recently, promising results have been reported in studies on anti-Claudin18.2 and fibroblast growth factor receptor 2 treatments. Currently, many ongoing trials are aimed at identifying potential targets using novel approaches. Further investigations will be conducted to enhance the progress of these therapies, addressing challenges such as primary and acquired resistance, tumor heterogeneity, and clonal evolution. We believe that these efforts will improve patient prognoses. Herein, we discuss the current evidence of potential targets for systemic treatment, clinical considerations, and future perspectives.

Recently, the global incidence of gastric/gastroesophageal junction (G/GEJ) cancer has remained high. China is also a large country with a high gastric cancer (GC) incidence rate, where the cases of GC account for 40% of all cases worldwide. More than 90% of GEJ cancers are the adenocarcinoma pathological type. Patients with early-stage G/GEJ adenocarcinoma may have a better prognosis after surgery. In contrast, patients with advanced metastatic G/GEJ adenocarcinoma usually choose comprehensive treatment based on systemic pharmacotherapy, but the subsequent long-term survival is not optimistic. The discovery of various biomarkers, especially microsatellite instability (MSI), programmed cell death-ligand 1 (PD-L1), human epidermal growth factor receptor 2 (HER2), tumor mutational burden (TMB) and Epstein–Barr virus (EBV), has led to the identification of an increasing number of targeted populations and has greatly improved the clinical efficacy of treatments for G/GEJ adenocarcinoma. The ToGA trial added trastuzumab to standard chemotherapy, showed improved survival of patients with HER2-positive advanced G/GEJ adenocarcinoma and brought these patients into a new era of HER2-targeted therapy. Moreover, many HER2-targeted agents have been developed and studied in patients with advanced HER2-positive G/GEJ adenocarcinoma who have demonstrated excellent clinical outcomes. However, many patients experience disease progression with HER2-targeted therapy; hence, new anti-HER2 drugs keep being developed, significantly reducing HER2 resistance. This paper reviews HER2-targeted drugs for advanced metastatic G/GEJ adenocarcinoma, potential resistance mechanisms and future directions.

BackgroundImmunotherapies targeting programmed cell death 1 (PD-1) and programmed death-ligand 1 (PD-L1) have been approved for gastric cancer (GC) patients. However, a large proportion of patients with T-cell-inflamed tumor microenvironment do not respond to the PD-1/PD-L1 blockade. The stromal component of the tumor microenvironment has been associated with immunotherapy. This study aims to explore the clinical significance of the non-immune cells in the tumor microenvironment and their potential as biomarkers for immunotherapy.MethodsA total of 383 patients with GC from the Cancer Genome Atlas (TCGA) cohort, 300 patients with GC from the GSE62254 cohort in Gene Expression Omnibus (GEO) were included in the study. A stromal score was generated using the ESTIMATE algorithm, and the likelihood of response to PD-1/PD-L1 immunotherapy of GC patients was predicted using the TIDE algorithm. The prognostic value of the stromal score from GC cases was evaluated by the Kaplan–Meier method and Cox regression analysis. Gene set enrichment analysis (GSEA) was also conducted.ResultsThe stromal score showed significant differences in different molecular subtypes and T stages. Multivariate analyses further confirmed that the stromal score was an independent indicator of overall survival (OS) in the two cohorts. The low stromal score group showed higher tumor mutation burden (TMB) and micro-satellite instability (MSI), and was more sensitive to immune checkpoint inhibitor according to the TIDE algorithm. Activation of the transforming growth factor and epithelial–mesenchymal transition were observed in the high stromal score subtype, which is associated with T-cell suppression, and may be responsible for resistance to PD-1/PD-L1 therapy. BPIFB2 was confirmed as a hub gene relevant to immunotherapy.ConclusionThe stromal score was associated with cancer progression and molecular subtypes, and may serve as a novel biomarker for predicting the prognosis and response to immunotherapy in patients with GC.