New substituted molecular classifications of advanced gastric adenocarcinoma: characteristics and probable treatment strategies

Background

Gastric adenocarcinoma (GA) is a heterogeneous tumor, and the accurate classification of GA is important. Previous classifications are based on molecular analysis and have not focused on GA with the primitive enterocyte phenotype (GAPEP), a unique subtype with a poor prognosis and frequent liver metastases. New substituted molecular (SM) classifications based on immunohistochemistry (IHC) are needed.

Methods

According to the IHC staining results, we divided 582 cases into six types: mismatch repair deficient (dMMR), Epstein-Barr virus associated (EBVa), the primitive enterocyte phenotype (PEP), the epithelial mesenchymal transition (EMT) phenotype, not otherwise specified/P53 mutated (NOS/P53m) and not otherwise specified/P53 wild-type (NOS/P53w). We analyzed the clinicopathological features, the immune microenvironment (PD-L1, CD8) and expression of HER2 and VEGFR2 of those types.

Results

There were 31 (5.3%) cases of the dMMR type, 13 (2.2%) cases of the EBVa type, 44 (7.6%) cases of the PEP type, 122 (21.0%) cases of the EMT type, 127 (21.8%) cases of the NOS/P53m type and 245 (42.1%) cases of the NOS/P53w type. Patients with the dMMR type had the best survival (P < 0.001). Patients with the EBVa type were younger (P < 0.001) and had higher PD-L1 and CD8 expression (P < 0.001) than other patients. Patients with the EMT type exhibited poor differentiation and a higher rate of abdominal metastasis. Patients with the NOS/P53m and PEP types had the worst survival rates and the highest PD-L1/HER2/VEGFR2 expression levels among all patients (P < 0.001).

Conclusion

Different SM classifications have different clinicopathological features and expression patterns, which indicate the probable clinical treatment strategies for these subtypes.

Targeted Therapies in Advanced Gastric Cancer

OPINION STATEMENT

Despite a decreasing incidence in the USA, gastric cancer is highly prevalent worldwide. Furthermore, gastric cancer remains highly lethal with median survival of less than 1 year for metastatic disease. The backbone of therapy against metastatic gastric cancer remains cytotoxic chemotherapy, but recent advances in the molecular understanding of gastric cancer have renewed hope within that targeted agents can be leveraged to improve survival and reduce toxicity. For example, in patients with human epidermal growth factor-2 (HER2)-positive gastric cancer, the addition of trastuzumab to frontline chemotherapy improves survival. In the second line, oncologists can now administer a vascular endothelial growth factor (VEGF) receptor inhibitor, ramucirumab, as a single agent or in combination with chemotherapy, and the immune checkpoint inhibitor pembrolizumab is approved in multiple settings dependent on the Programmed Death Ligand 1 (PD-L1) status. For patients with metastatic disease, our approach to standard of care in the first-line setting is a 5FU/platinum doublet with trastuzumab for HER2-positive tumors. In the second-line setting, most patients receive ramucirumab + paclitaxel, but those that are MSI high receive pembrolizumab. For squamous cell carcinoma of the esophagus with high PD-L1 status (combined positive score (CPS) ≥ 10), we recommend pembrolizumab in the second line. While for PD-L1 ≥ 1% gastroesophageal adenocarcinoma, we do not recommend pembrolizumab before the third-line setting, although this may change in the near future for CPS ≥ 10. The future landscape for targeted therapy in gastric cancer is promising. Numerous clinical trials evaluating the combination immune therapy with molecularly targeted agents are generating much excitement. Moreover, genomic data from The Cancer Center Genome (TCGA) and Asian Cancer Research Group (ACRG) classifications is being used to identify molecular subtypes to enable future clinical trials to include biomarker-enriched patient populations.

Towards precision oncology for HER2 blockade in gastroesophageal adenocarcinoma

Gastroesophageal adenocarcinoma (GEA) represents a very heterogeneous disease and patients in advanced stages have a very poor prognosis. Although several molecular classifications have been proposed, precision medicine for HER2-amplified GEA patients still represents a challenge. Despite improvement in clinical outcomes obtained by adding trastuzumab to first-line platinum-based chemotherapy, no other anti-HER2 agents used first-line or beyond progression have demonstrated any benefit. Several factors contribute to this failure. Among them, variable HER2 amplification assessment, tumour heterogeneity, molecular mechanisms of resistance and microenvironmental factors could limit the effectiveness of anti-HER2 blockade. Identifying the factors responsible for both primary and acquired resistance is a priority for providing an improved, personalised approach. In this review, we examine current treatments for HER2-amplified GEA, their potential mechanisms of resistance and the ways to overcome them, investigating the most relevant translational studies with anti-HER2 agents in GEA, as well as novel agents under development in this field.

Targeted and novel therapy in advanced gastric cancer

The systemic treatment options for advanced gastric cancer (GC) have evolved rapidly in recent years. We have reviewed the recent data of clinical trial incorporating targeted agents, including inhibitors of angiogenesis, human epidermal growth factor receptor 2 (HER2), mesenchymal-epithelial transition, epidermal growth factor receptor, mammalian target of rapamycin, claudin-18.2, programmed death-1 and DNA. Addition of trastuzumab to platinum-based chemotherapy has become standard of care as front-line therapy in advanced GC overexpressing HER2. In the second-line setting, ramucirumab with paclitaxel significantly improves overall survival compared to paclitaxel alone. For patients with refractory disease, apatinib, nivolumab, ramucirumab and TAS-102 have demonstrated single-agent activity with improved overall survival compared to placebo alone. Pembrolizumab has demonstrated more than 50% response rate in microsatellite instability-high tumors, 15% response rate in tumors expressing programmed death ligand 1, and non-inferior outcome in first-line treatment compared to chemotherapy. This review summarizes the current state and progress of research on targeted therapy for advanced GC.

Circulating Tumor DNA Sequencing Analysis of Gastroesophageal Adenocarcinoma

PURPOSE

Gastroesophageal adenocarcinoma (GEA) has a poor prognosis and few therapeutic options. Utilizing a 73-gene plasma-based next-generation sequencing (NGS) cell-free circulating tumor DNA (ctDNA-NGS) test, we sought to evaluate the role of ctDNA-NGS in guiding clinical decision-making in GEA.

EXPERIMENTAL DESIGN

We evaluated a large cohort (n = 2,140 tests; 1,630 patients) of ctDNA-NGS results (including 369 clinically annotated patients). Patients were assessed for genomic alteration (GA) distribution and correlation with clinicopathologic characteristics and outcomes.

RESULTS

Treatment history, tumor site, and disease burden dictated tumor-DNA shedding and consequent ctDNA-NGS maximum somatic variant allele frequency. Patients with locally advanced disease having detectable ctDNA postoperatively experienced inferior median disease-free survival (P = 0.03). The genomic landscape was similar but not identical to tissue-NGS, reflecting temporospatial molecular heterogeneity, with some targetable GAs identified at higher frequency via ctDNA-NGS compared with previous primary tumor-NGS cohorts. Patients with known microsatellite instability-high (MSI-High) tumors were robustly detected with ctDNA-NGS. Predictive biomarker assessment was optimized by incorporating tissue-NGS and ctDNA-NGS assessment in a complementary manner. HER2 inhibition demonstrated a profound survival benefit in HER2-amplified patients by ctDNA-NGS and/or tissue-NGS (median overall survival, 26.3 vs. 7.4 months; P = 0.002), as did EGFR inhibition in EGFR-amplified patients (median overall survival, 21.1 vs. 14.4 months; P = 0.01).

CONCLUSIONS

ctDNA-NGS characterized GEA molecular heterogeneity and rendered important prognostic and predictive information, complementary to tissue-NGS.See related commentary by Frankell and Smyth, p. 6893.

Progress and challenges in HER2-positive gastroesophageal adenocarcinoma

HER2 expression remains an important biomarker to guide the addition of the monoclonal antibody trastuzumab to first-line systemic chemotherapy in unresectable, metastatic gastroesophageal adenocarcinomas (GEA). However, in contrast to breast cancer, other HER2-targeted strategies to date have not improved outcomes in this molecular subtype of GEA. Since the initial development of HER2 biomarker testing guidelines, significant spatial intratumoral heterogeneity of HER2 overexpression has been recognized as a major characteristic of this disease. In this review, we aim to survey the seminal positive and negative trials investigating HER2-targeted agents for GEA. We also highlight emerging data on the genomic and temporal heterogeneity of molecular resistance alterations that have yielded further insight into the heterogeneity of therapeutic responses. We conclude with an overview of promising novel agents and strategies which may refine the therapeutic landscape.

Nouvelles stratégies innovantes en immunothérapie

NOVEL STRATEGY IN ONCOIMMUNOLOGY

Recent advances in immuno-oncology with the development of anti-PD1/PD-L1 antibodies are revolutionizing oncological management. Immuno-oncology I currently developing in most histological types of cancer. However, the rate of success of anti-PD1/PD-L1 antibodies in monotherapy is limited by a limited to a subpopulation of patients accounting for about 25-30 % of patients in most indications. The development of new strategies is based on this observation with the aim to predict response or enhancing response rate. Thus, we note the development of different strategies aimed at better selecting patients or combining inhibitory checkpoints with other therapies in order to increase their effectiveness. This review will study therapeutic test strategies to validate these new associations.

Pharmacotherapy for metastatic esophageal cancer: where do we need to improve?

INTRODUCTION

Esophageal cancer is a heterogeneous cancer comprised of differing cells of origin, molecular changes, and immune microenvironments. To date, most advances have been made in chemotherapy regimens where a one-size-fits-all approach is used. As a result, there remains a lack of tailored treatment options for such a heterogeneous cancer. This paper highlights the current standard of care treatment options as well as active areas of clinical research.

AREAS COVERED

The authors review the key trials that have led to current standard of care treatment including pivotal chemotherapy and targeted therapy trials. The authors then discuss the current approved uses and future directions for immunotherapy.

EXPERT OPINION

Current treatment options lack tailored treatment strategies based on the tumor's biology. To date, approved targeted approaches only include HER2-directed and anti-VEGFR2 therapies. Furthermore, while immunotherapy treatment response is often durable, few clear predictive biomarkers for response have been identified. Future research should focus on characterizing additional molecular targets for therapeutic intervention and predictive biomarkers for immunotherapy, as well as combination approaches of immunotherapy with other therapeutic modalities to increase response rate. Ultimately, the field should strive to develop personalized treatment options based on a tumor's molecular profile, microenvironment, and neo-antigen expression.

New drug developments in metastatic gastric cancer

Metastatic gastric cancer is associated with a poor prognosis and novel treatment options are desperately needed. The development of targeted therapies heralded a new era for the management of metastatic gastric cancer, however results from clinical trials of numerous targeted agents have been mixed. The advent of immune checkpoint inhibitors has yielded similar promise and results from early trials are encouraging. This review provides an overview of the systemic treatment options evaluated in metastatic gastric cancer, with a focus on recent evidence from clinical trials for targeted therapies and immune checkpoint inhibitors. The failure to identify appropriate predictive biomarkers has hampered the success of many targeted therapies in gastric cancer, and a deeper understanding of specific molecular subtypes and genomic alterations may allow for more precision in the application of novel therapies. Identifying appropriate biomarkers for patient selection is essential for future clinical trials, for the most effective use of novel agents and in combination approaches to account for growing complexity of treatment options.

Emerging Therapies in the Management of Advanced-Stage Gastric Cancer

Globally, gastric malignancy contributes to significant cancer-related morbidity and mortality. Despite a recent approval of two targeted agents, trastuzumab and ramucirumab, the treatment options for advanced-stage gastric cancer are limited. Consequently, the overall clinical outcomes for patients with advanced-stage gastric cancer remain poor. Numerous agents that are active against novel targets have been evaluated in the course of randomized trials; however, most have produced disappointing results because of the molecular heterogeneity of gastric cancer. The Cancer Genome Atlas (TCGA) project proposed a new classification system for gastric cancer that includes four different tumor subtypes based on molecular characteristics. This change led to the identification of several distinct and potentially targetable pathways. However, most agents targeting these pathways do not elicit any meaningful clinical benefit when employed for the treatment of advanced-stage gastric cancer. Most advanced-stage gastric cancer trials currently focus on agents that modulate tumor microenvironments and cancer cell stemness. In this review, we summarize data regarding novel compounds that have shown efficacy in early phase studies and show promise as effective therapeutic agents, with special emphasis on those for which phase III trials are either planned or underway.