Meta-analysis of microsatellite instability in relation to clinicopathological characteristics and overall survival in gastric cancer

Genome-wide identification of CpG island methylator phenotype related gene signature as a novel prognostic biomarker of gastric cancer

Background

Gastric cancer (GC) is one of the most fatal cancers in the world. Results of previous studies on the association of the CpG island methylator phenotype (CIMP) with GC prognosis are conflicting and mainly based on selected CIMP markers. The current study attempted to comprehensively assess the association between CIMP status and GC survival and to develop a CIMP-related prognostic gene signature of GC.

Methods

We used a hierarchical clustering method based on 2,082 GC-related methylation sites to stratify GC patients from the cancer genome atlas into three different CIMP subgroups according to the CIMP status. Gene set enrichment analysis, tumor-infiltrating immune cells, and DNA somatic mutations analysis were conducted to reveal the genomic characteristics in different CIMP-related patients. Cox regression analysis and the least absolute shrinkage and selection operator were performed to develop a CIMP-related prognostic signature. Analyses involving a time-dependent receiver operating characteristic (ROC) curve and calibration plot were adopted to assess the performance of the prognostic signature.

Results

We found a positive relationship between CIMP and prognosis in GC. Gene set enrichment analysis indicated that cancer-progression-related pathways were enriched in the CIMP-L group. High abundances of CD8+ T cells and M1 macrophages were found in the CIMP-H group, meanwhile more plasma cells, regulatory T cells and CD4+ memory resting T cells were detected in the CIMP-L group. The CIMP-H group showed higher tumor mutation burden, more microsatellite instability-H, less lymph node metastasis, and more somatic mutations favoring survival. We then established a CIMP-related prognostic gene signature comprising six genes (CST6, SLC7A2, RAB3B, IGFBP1, VSTM2L and EVX2). The signature was capable of classifying patients into high‐and low‐risk groups with significant difference in overall survival (OS; p < 0.0001). To assess performance of the prognostic signature, the area under the ROC curve (AUC) for OS was calculated as 0.664 at 1 year, 0.704 at 3 years and 0.667 at 5 years. When compared with previously published gene-based signatures, our CIMP-related signature was comparable or better at predicting prognosis. A multivariate Cox regression analysis indicated the CIMP-related prognostic gene signature was an independent prognostic indicator of GC. In addition, Gene ontology analysis indicated that keratinocyte differentiation and epidermis development were enriched in the high-risk group.

Conclusion

Collectively, we described a positive association between CIMP status and prognosis in GC and proposed a CIMP-related gene signature as a promising prognostic biomarker for GC.

The Better Survival of MSI Subtype Is Associated With the Oxidative Stress Related Pathways in Gastric Cancer

Background: Gastric cancer (GC) is the third leading fatal cancer in the world and its incidence ranked second among all malignant tumors in China. The molecular classification of GC, proposed by the The Cancer Genome Atlas (TCGA), was added to the updated edition (2019) of WHO classification for digestive system tumor. Although MSI and EBV subtypes appeared as ever-increasingly significant roles in immune checkpoint inhibitor therapy, the underlying mechanisms are still unclear.

Methods: We systematically summarized the relationship between EBV, d-MMR/MSI-H subtypes and clinicopathological parameters in 271 GC cases. Furthermore, GSE62254/ACRG and TCGA-STAD datasets, originated from Gene Expression Omnibus (GEO) and TCGA respectively, were analyzed to figure out the prognosis related molecular characteristics by bioinformatics methods.

Results: Patients with MSI subtype had better prognosis than the MSS subtype (P = 0.013) and considered as an independent biomarker by the univariate analysis (P = 0.017) and multivariate analysis (P = 0.050). While there was no significant difference between EBV positive and negative tissues (P = 0.533). The positive prognostic value conferred by MSI in different cohorts was revalidated via the clinical analysis of GSE62254/ACRG and TCGA-STAD datasets regardless of race. Then key gene module that tightly associated with better status and longer OS time for MSI cases was obtained from weighted gene co-expression network analysis(WGCNA). NUBP2 and ENDOG were screened from the gene cluster and oxidative phosphorylation, reactive oxygen species(ROS) and glutathione metabolism were analyzed to be the differential pathways in their highly expressed groups.

Conclusions: Our results manifested the significant prognostic value of MSI in Chinese GC cohort and comparisons with other populations. More opportunities to induce apoptosis of cancer cells, led by the unbalance between antioxidant system and ROS accumulation, lay foundations for unveiling the better prognosis in MSI phenotype through the bioinformatics analysis.

Genetics and Epigenetics of Sex Bias: Insights from Human Cancer and Autoimmunity

High-throughput sequencing and genome-wide association studies have revealed a sex bias in human diseases. The underlying molecular mechanisms remain, however, unknown. Here, we cover recent advances in cancer and autoimmunity focusing on intrinsic genetic and epigenetic differences underlying sex biases in human disease. These studies reveal a central role of genome regulatory mechanisms including genome repair, chromosome folding, and epigenetic regulation in dictating the sex bias. These highlight the importance of considering sex as a variable in both basic science and clinical investigations. Understanding the molecular mechanisms underlying sex bias in human diseases will be instrumental in making a first step forwards into the era of personalized medicine.

Clinicopathological Significance of EBV-Infected Gastric Carcinomas: A Meta-Analysis

Background and objectives: The present study aims to elucidate the clinicopathologic significance of Epstein-Barr virus (EBV) infection in gastric carcinomas (GCs) through a meta-analysis. Materials and Methods: Sixty-one eligible studies were included in the present meta-analysis. The included patients, with and without EBV infection, were 2063 and 17,684, respectively. We investigated the clinicopathologic characteristics and various biomarkers, including programmed death-ligand 1 (PD-L1) expression and tumor-infiltrating lymphocytes (TILs). Results: The estimated EBV-infected rate of GCs was 0.113 (95% confidence interval (CI): 0.088-0.143). The EBV infection rates in GC cells were 0.138 (95% CI: 0.096-0.194), 0.103 (95% CI: 0.077-0.137), 0.080 (95% CI: 0.061-0.106), and 0.042 (95% CI: 0.016-0.106) in the population of Asia, America, Europe, and Africa, respectively. There was a significant difference between EBV-infected and noninfected GCs in the male: female ratio, but not other clinicopathological characteristics. EBV infection rates were higher in GC with lymphoid stroma (0.573, 95% CI: 0.428-0.706) than other histologic types of GCs. There were significant differences in high AT-rich interactive domain-containing protein 1A (ARID1A) and PD-L1 expressions, and high CD8+ TILs between EBV-infected and noninfected GCs. Conclusions: Our results showed that EBV infection of GCs was frequently found in male patients and GCs with lymphoid stroma. EBV infection was significantly correlated with ARID1A and PD-L1 expressions and CD8+ TILs in GCs.

Multicentre biomarker cohort study on the efficacy of nivolumab treatment for gastric cancer

Background

Predictive factors of nivolumab treatment response in patients with gastric cancer (GC) remain unclear.

Methods

In this retrospective cohort study, tissue specimens of patients with unresectable or recurrent GC and prior or scheduled treatment with nivolumab as third-line or higher therapy between September 2017 and February 2019 were collected from 23 institutions. The tumour-positive score (TPS) and combined positive score (CPS) of PD-L1 expression and mismatch repair (MMR) were analysed by immunohistochemistry. Associations between clinicopathological factors and tumour-response rate, hyperprogressive disease (HPD) rate and survival were assessed.

Results

Of 200 eligible patients, 143 had measurable lesions. The response and HPD rates were 17.5% and 22.1%, respectively. The response rate was significantly higher in patients with performance status (PS) 0–1 (P = 0.026), non-peritoneal metastasis (P = 0.021), PD-L1 TPS ≥ 1 (P = 0.012), CPS ≥ 5 (P = 0.007) or ≥ 10 (P < 0.001) or MMR deficiency (P < 0.001). The HPD rate was significantly higher in patients with PS 2–3 (P = 0.026), liver metastasis (P < 0.001) and CPS < 10 (P = 0.048). Multivariate analysis revealed that CPS (P = 0.001) and MMR (P = 0.002) were independent prognostic factors of progression-free survival, as well as liver metastasis (P < 0.001), peritoneal metastasis (P = 0.004) and CRP (P < 0.001).

Conclusions

PD-L1 CPS and MMR could be useful biomarkers for nivolumab treatment efficacy in GC.

Clinical trial registration

UMIN000032164.

Prediction of S-1 adjuvant chemotherapy benefit in Stage II/III gastric cancer treatment based on comprehensive gene expression analysis

BACKGROUND

Studies to identify predictive biomarkers of adjuvant chemotherapy with S-1 after gastrectomy in Stage II/III gastric cancer patients have been done; however, more clarity and understanding are needed. Our aim in the present study was to identify biomarkers predicting benefit due to S-1 adjuvant chemotherapy using comprehensive gene expression analysis.

METHODS

We retrospectively analyzed 102 patients receiving adjuvant chemotherapy with S-1 and 46 patients not receiving S-1 adjuvant chemotherapy after gastrectomy for gastric cancer treatment between January 2014 and December 2016. Hierarchical clustering analysis was performed based on the gene expression data obtained using cDNA microarray. Differentially expressed genes (DEGs) were identified using thresholds of absolute fold changes of > 4.0 and a false discovery rate P value of < 0.01. Gene Ontology (GO) analysis and GO network visualization were performed using the ClueGO app in Cytoscape.

RESULTS

Hierarchical clustering analysis in patients treated with S-1 adjuvant chemotherapy revealed two clusters with favorable and unfavorable survival outcomes. We identified 147 upregulated DEGs and 192 downregulated DEGs in the favorable outcome group. GO analysis to identify significantly upregulated genes showed enrichment in immune-related genes and GO terms. Upregulation of these immune-related genes was not associated with survival in patients not receiving S-1 adjuvant chemotherapy.

CONCLUSIONS

The upregulation and enrichment of immune-related genes and GO terms may be predictive biomarkers in patients who would benefit from adjuvant S-1 chemotherapy to treat Stage II/III gastric cancer.

Is Adjuvant Chemotherapy Necessary for Patients with Deficient Mismatch Repair Gastric Cancer?-Autophagy Inhibition Matches the Mismatched

PURPOSE

The use of microsatellite instability (MSI) and mismatch repair (MMR) as predictive biomarkers for fluorouracil-based adjuvant chemotherapy in colorectal cancer has been a paradigm shift. However, whether this applies to gastric cancer is questionable. Furthermore, we herein investigated whether and how autophagy plays a role in MSI-relevant chemoresistance.

MATERIALS AND METHODS

A total of 929 patients with deficient MMR (dMMR) and proficient MMR (pMMR) gastric cancers who underwent curative-intent gastrectomy were enrolled. We compared clinicopathological variables and survival among dMMR and pMMR cohorts and tested the responses of MSI-high and microsatellite stable (MSS) gastric cancer cell lines to 5-fluorouracil (5-FU) with or without chloroquine, an autophagy inhibitor.

RESULTS

We identified an 8.9% prevalence of dMMR cases (83 out of 929) in our cohort. This was associated with old age, tumor site at the distal stomach, an intestinal phenotype, fewer nodal metastasis, and early pathological stages. MMR was an independent prognostic factor after multivariate adjustment. Overall survival (OS) of dMMR patients was better than that of the pMMR patients but was only applicable to stage III patients. There was no difference in OS between dMMR patients treated with or without adjuvant chemotherapy, although the latter showed more medical morbidities. The MSI-high gastric cancer cell lines, versus the MSS counterparts, displayed increased resistance to 5-FU and increased autophagy. Interestingly, autophagy inhibition abrogated the chemoresistance.

CONCLUSION

Our data show that fluorouracil-based adjuvant chemotherapy does not work for dMMR cases, if not worse. Autophagy inhibition and/or immune checkpoint inhibition might be promising alternative strategies for gastric cancer treatment.

IMPLICATIONS FOR PRACTICE

The use of microsatellite instability (MSI) and mismatch repair (MMR) as predictive biomarkers for adjuvant chemotherapy in colorectal cancer has caused a paradigm shift in cancer therapy, although its implications in gastric cancer are still questionable. The data obtained in the current study indicate that MSI-MMR is an independent prognostic factor for gastric cancer. Standard fluorouracil-based adjuvant chemotherapy did not work for deficient MMR cases, and was likely worse. Instead, strategies like autophagy inhibition and/or immune checkpoint inhibition should be taken into consideration in the future.

MSI as a predictive factor for treatment outcome of gastroesophageal adenocarcinoma

Gastroesophageal cancers are a major cause of death worldwide and treatment outcomes remain poor. Adequate predictive biomarkers have not been identified. Microsatellite instability (MSI) as a result of mismatch repair deficiency is present in four to twenty percent of gastroesophageal cancers and has been associated with favorable survival outcomes compared to microsatellite stable tumors. This prognostic advantage may be related to immunosurveillance, which may also explain the favorable response to immune checkpoint inhibition observed in MSI high (MSI-H) tumors. The value of conventional cytotoxic treatment in MSI-H tumors is unclear and results on its efficacy range from detrimental to beneficial effects. Here the recent data on MSI as a predictive factor for outcome of gastroesophageal cancer treatment is reviewed.

Prognostic and Predictive Value of Microsatellite Instability, Inflammatory Reaction and PD-L1 in Gastric Cancer Patients Treated with Either Adjuvant 5-FU/LV or Sequential FOLFIRI Followed by Cisplatin and Docetaxel: A Translational Analysis from the ITACA-S Trial

BACKGROUND

Patients with high microsatellite instability (MSI) gastric cancer (GC) show improved survival and no benefit or harm from adjuvant and/or perioperative chemotherapy. The role of immune microenvironment in GC is largely unknown.

MATERIALS AND METHODS

In the present study, 256 tumor tissue blocks were centrally collected from patients enrolled in ITACA-S, a randomized adjuvant trial of 5-FU/LV versus sequential FOLFIRI and cisplatin-docetaxel. MSI status was assessed by multiplex PCR, inflammatory reaction by H&E morphological assessment, and programmed death-ligand 1 (PD-L1) expression by immunohistochemistry.

RESULTS

Overall, 9% patients had MSI-high tumors, 23% had high inflammatory reaction, 11% had tumor PD-L1 ≥ 1%, and 11% had stromal PD-L1 ≥ 1%. A significant association with disease-free survival (DFS) and overall survival (OS) was found for MSI-high (hazard ratio [HR], 0.43; p = .02; HR, 0.40; p = .02) and high inflammatory reaction (HR, 0.55; p = .010; HR, 0.53; p = .008) but not for PD-L1. At multivariable analysis, only MSI showed an independent association with both DFS (p = .02) and OS (p = .01), whereas inflammatory reaction showed an independent association only with OS (p = .04). Patients with tumor PD-L1 ≥ 1% had a significantly longer DFS in sequential chemotherapy than in than 5-FU/LV arm (interaction p = .04) and a trend for OS (interaction p = .12).

CONCLUSION

Our data suggest that MSI status could be a useful prognostic biomarker in patients with radically resected stage II-III GC and should be used as stratification factor in future trials. Tumor PD-L1 ≥ 1% should be further investigated as a potential predictor of benefit from intensive chemotherapy.

IMPLICATIONS FOR PRACTICE

In this post hoc analysis of patients with radically resected gastric cancer randomized to an intensive sequential chemotherapy regimen versus 5-FU/LV monotherapy as adjuvant treatment in the ITACA-S trial, MSI-high status was independently associated with better disease-free survival and overall survival (OS) and inflammatory reaction was independently associated with better OS. Moreover, tumor PD-L1 expression ≥1% was associated with greater benefit from intensive sequential chemotherapy compared with 5-fluorouracil plus leucovorin (5-FU/LV), whereas PD-L1 expression <1% was not, conditioning a statistically significant interaction between such biomarker and treatment arms. The meta-analysis of individual patients' data from available studies could yield data on the role of MSI status that could inform clinical decisions.

New Treatment Options for Advanced Gastroesophageal Tumours: Mature for the Current Practice?

Several clinical trials attempted to identify novel treatment options for advanced gastroesophageal tumours in first, second and further lines. Although results of targeted therapy regimens were mainly disappointing, novel immunotherapy agents showed promising activity, which led to their approval in second and third lines in many countries. This review focuses on the results of recent clinical trials investigating novel agents including targeted therapies, immunotherapy components and chemotherapies and discuss their current impact as well as current approval status on the treatment armamentarium of advanced gastroesophageal tumours.

Extreme intratumour heterogeneity and driver evolution in mismatch repair deficient gastro-oesophageal cancer

Mismatch repair deficient (dMMR) gastro-oesophageal adenocarcinomas (GOAs) show better outcomes than their MMR-proficient counterparts and high immunotherapy sensitivity. The hypermutator-phenotype of dMMR tumours theoretically enables high evolvability but their evolution has not been investigated. Here we apply multi-region exome sequencing (MSeq) to four treatment-naive dMMR GOAs. This reveals extreme intratumour heterogeneity (ITH), exceeding ITH in other cancer types >20-fold, but also long phylogenetic trunks which may explain the exquisite immunotherapy sensitivity of dMMR tumours. Subclonal driver mutations are common and parallel evolution occurs in RAS, PIK3CA, SWI/SNF-complex genes and in immune evasion regulators. MSeq data and evolution analysis of single region-data from 64 MSI GOAs show that chromosome 8 gains are early genetic events and that the hypermutator-phenotype remains active during progression. MSeq may be necessary for biomarker development in these heterogeneous cancers. Comparison with other MSeq-analysed tumour types reveals mutation rates and their timing to determine phylogenetic tree morphologies.

Molecular Classification of Gastric Cancer among Alaska Native People

Gastric cancer is an aggressive and heterogeneous malignancy that often varies in presentation and disease among racial and ethnic groups. The Alaska Native (AN) people have the highest incidence and mortality rates of gastric cancer in North America. This study examines molecular markers in solid tumor samples from eighty-five AN gastric adenocarcinoma patients using next-generation sequencing, immunohistochemistry, and in situ hybridization analysis. AN patients have a low mutation burden with fewer somatic gene mutations in their tumors compared to other populations, with the most common mutation being TP53. Epstein-Barr virus (EBV) was associated with 20% of AN gastric cancers, which is higher than the world average of 10%. The inflammation marker, cyclooxygenase-2 (COX-2), is highly expressed in patients with the lowest survival rates. Mismatch repair deficiency was present in 10% of AN patients and was associated with patients who were female, 50 years or older, gene mutations, and tumors in the distal stomach. Program death-ligand 1 (PD-L1) was expressed in 14% of AN patients who were more likely to have MMR deficiency, EBV-associated gastric cancers, and mutations in the PIK3CA gene, all of which have been linked to clinical response to PD-1 inhibitors. These studies suggest a portion of AN gastric cancer patients could be candidates for immunotherapy. Overall, this study highlights future avenues of investigation for clinical and translational studies, so that we can improve early detection and develop more effective treatments for AN patients.

Evaluation of the prognostic impact of pathologic response to preoperative chemotherapy using Mandard's Tumor Regression Grade (TRG) in gastric adenocarcinoma

BACKGROUND

Perioperative chemotherapy is the gold standard in gastric cancer management. The prognostic significance of pathological response has been investigated in many malignancies, using Tumor Regression Grade (TRG). Its prognostic value in gastric cancer remains poorly known.

AIMS

This study aimed to assess the prognostic value of pathological response to chemotherapy, using Mandard's TRG in gastric cancer, and to identify factors predictive of response to chemotherapy.

METHODS

We retrospectively identified patients with gastric adenocarcinoma from two institutional surgical databases, with preoperative chemotherapy and subsequent gastrectomy. Pathological response was centrally reviewed using Mandard's TRG.

RESULTS

From 325 patients resected from a gastric cancer between 1997 and 2016, 109 underwent a preoperative chemotherapy. 42% were pathologic responders (TRG1-3) and 58% non-responders (TRG4-5). Five-years overall survival (OS) was 35% for non-responders, and 73% for responders (p = 0,006). Five-years disease-free survival (DFS) was 34% for non-responders and 65% for responders (p = 0,013). In multivariate analysis, pathological response was an independent prognostic factor of poor OS: HR = 2.736 (CI95% = 1.335-5.608; p = 0.006) and DFS: HR = 2.241 (CI95% = 1.130-4.446; p = 0.021).

CONCLUSION

TRG after preoperative chemotherapy is an important prognostic factor in patients resected for a gastric adenocarcinoma. Further studies should be performed to evaluate if adjuvant therapy should be adapted to pathological response.

Microsatellite instability and immune checkpoint inhibitors: toward precision medicine against gastrointestinal and hepatobiliary cancers

Recent innovations in the next-generation sequencing technologies have unveiled that the accumulation of genetic alterations results in the transformation of normal cells into cancer cells. Accurate and timely repair of DNA is, therefore, essential for maintaining genetic stability. Among various DNA repair pathways, the mismatch repair (MMR) pathway plays a pivotal role. MMR deficiency leads to a molecular feature of microsatellite instability (MSI) and predisposes to cancer. Recent studies revealed that MSI-high (MSI-H) or mismatch repair-deficient (dMMR) tumors, regardless of their primary site, have a promising response to immune checkpoint inhibitors (ICIs), leading to the approval of the anti-programmed cell death protein 1 monoclonal antibody pembrolizumab for the treatment of advanced or recurrent MSI-H/dMMR solid tumors that continue to progress after conventional chemotherapies. This new indication marks a paradigm shift in the therapeutic strategy of cancers; however, when considering the optimum indication for ICIs and their safe and effective usage, it is important for clinicians to understand the genetic and immunologic features of each tumor. In this review, we describe the molecular basis of the MMR pathway, diagnostics of MSI status, and the clinical importance of MSI status and the tumor mutation burden in developing therapeutic strategies against gastrointestinal and hepatobiliary malignancies.

Gender medicine and oncology: report and consensus of an ESMO workshop

BACKGROUND

The importance of sex and gender as modulators of disease biology and treatment outcomes is well known in other disciplines of medicine, such as cardiology, but remains an undervalued issue in oncology. Considering the increasing evidence for their relevance, European Society for Medical Oncology decided to address this topic and organized a multidisciplinary workshop in Lausanne, Switzerland, on 30 November and 1 December 2018.

DESIGN

Twenty invited faculty members and 40 selected physicians/scientists participated. Relevant content was presented by faculty members on the basis of a literature review conducted by each speaker. Following a moderated consensus session, the final consensus statements are reported here.

RESULTS

Clinically relevant sex differences include tumour biology, immune system activity, body composition and drug disposition and effects. The main differences between male and female cells are sex chromosomes and the level of sexual hormones they are exposed to. They influence both local and systemic determinants of carcinogenesis. Their effect on carcinogenesis in non-reproductive organs is largely unknown. Recent evidence also suggests differences in tumour biology and molecular markers. Regarding body composition, the difference in metabolically active, fat-free body mass is one of the most prominent: in a man and a woman of equal weight and height, it accounts for 80% of the man's and 65% of the woman's body mass, and is not taken into account in body-surface area based dosing of chemotherapy.

CONCLUSION

Sex differences in cancer biology and treatment deserve more attention and systematic investigation. Interventional clinical trials evaluating sex-specific dosing regimens are necessary to improve the balance between efficacy and toxicity for drugs with significant pharmacokinetic differences. Especially in diseases or disease subgroups with significant differences in epidemiology or outcomes, men and women with non-sex-related cancers should be considered as biologically distinct groups of patients, for whom specific treatment approaches merit consideration.

Expression Profile of Markers for Targeted Therapy in Gastric Cancer Patients: HER-2, Microsatellite Instability and PD-L1

BACKGROUND

The assessment of human epidermal growth factor receptor 2 (HER2), microsatellite instability (MSI) and programmed cell death-ligand 1 (PD-L1) expression is relevant for the selection and effectiveness of targeted therapy in gastric cancer (GC).

OBJECTIVE

We aimed to investigate the clinicopathological characteristics and prognosis of GC patients according to these profiles.

METHODS

GC patients who underwent gastrectomy with D2 lymphadenectomy were eligible. HER2, MSI status and PD-L1 expression were analyzed by immunohistochemistry (IHC). Patients were grouped as follows: HER2+ group, immunotherapy (IT) group (MSI and/or PD-L1+), and non-targeted therapy (NTT) group (stable microsatellite and HER2/PD-L1-).

RESULTS

Among 282 patients, 50 (17.7%) were HER2+ and 79 (28%) MSI/PD-L1+. Fifteen had HER2+ and MSI/PD-L1+, while 168 (59.6%) were in the NTT group. HER2+ GCs were related to male gender (p = 0.007), intestinal type (p = 0.001) and less advanced pTNM stage (p = 0.029). Older age (p = 0.003), subtotal gastrectomy (p = 0.025), intestinal type (p = 0.008), pN0 status (p = 0.002) and less advanced pTNM stage (p = 0.001) were associated with the IT group. IT GC had better disease-free survival (DFS) and overall survival than the NTT group (p = 0.015 and p = 0.027, respectively). Concerning patients eligible for the standard adjuvant therapy, the treatment impacted positively on DFS for HER2+ and NTT groups (p = 0.003 and p = 0.042, respectively). No difference in DFS was seen between IT patients who received perioperative/adjuvant therapy and those treated only with surgery (p = 0.160).

CONCLUSIONS

GC patients who exhibited markers that can serve as an indication for known targeted therapy represent 40.4% of cases. The IT group was associated with a better prognosis. No benefit with standard adjuvant treatment appears to be achieved in MSI/PD-L1+ GCs.

A gastric cancer LncRNAs model for MSI and survival prediction based on support vector machine

BACKGROUND

Recent studies have shown that long non-coding RNAs (lncRNAs) play a crucial role in the induction of cancer through epigenetic regulation, transcriptional regulation, post-transcriptional regulation and other aspects, thus participating in various biological processes such as cell proliferation, differentiation and apoptosis. As a new nova of anti-tumor therapy, immunotherapy has been shown to be effective in many tumors of which PD-1/PD-L1 monoclonal antibodies has been proofed to increase overall survival rate in advanced gastric cancer (GC). Microsatellite instability (MSI) was known as a biomarker of response to PD-1/PD-L1 monoclonal antibodies therapy. The aim of this study was to identify lncRNAs signatures able to classify MSI status and create a predictive model associated with MSI for GC patients.

METHODS

Using the data of Stomach adenocarcinoma from The Cancer Genome Atlas (TCGA), we developed and validated a lncRNAs model for automatic MSI classification using a machine learning technology - support vector machine (SVM). The C-index was adopted to evaluate its accuracy. The prognostic values of overall survival (OS) and disease-free survival (DFS) were also assessed in this model.

RESULTS

Using the SVM, a lncRNAs model was established consisting of 16 lncRNA features. In the training cohort with 94 GC patients, accuracy was confirmed with AUC 0.976 (95% CI, 0.952 to 0.999). Veracity was also confirmed in the validation cohort (40 GC patients) with AUC 0.950 (0.889 to 0.999). High predicted score was correlated with better DFS in the patients with stage I-III and lower OS with stage I-IV.

CONCLUSION

This study identify 16 LncRNAs signatures able to classify MSI status. The correlation between lncRNAs and MSI status indicates the potential roles of lncRNAs interacting in immunotherapy for GC patients. The pathway of these lncRNAs which might be a target in PD-1/PD-L1 immunotherapy are needed to be further study.

Clinical Implications of Microsatellite Instability in Early Gastric Cancer

Purpose

We aimed to evaluate the clinical characteristics of microsatellite instability in early gastric cancer.

Materials and Methods

The microsatellite instability status of resected early gastric tumors was evaluated using two mononucleotide repeat markers (BAT25 and BAT26) and three dinucleotide repeat markers (D5S346, D2S123, and D17S250). Tumors with instability in two or more markers were defined as microsatellite instability-high (MSI-H) and others were classified as microsatellite stable (MSS).

Results

Overall, 1,156 tumors were included in the analysis, with 85 (7.4%) classified as MSI-H compared with MSS tumors. For MSI-H tumors, there was a significant correlation with the female sex, older age, tumor location in the lower gastric body, intestinal histology, lymphovascular invasion (LVI), and submucosal invasion (P<0.05). There was also a trend toward an association with lymph node (LN) metastasis (P=0.056). In mucosal gastric cancer, there was no significant difference in MSI status in tumors with LN metastasis or tumors with LVI. In submucosal gastric cancer, LVI was more frequently observed in MSI-H than in MSS tumors (38.9% vs. 25.0%, P=0.027), but there was no difference in the presence of LN metastases. The prognosis of MSI-H tumors was similar to that of MSS tumors (log-rank test, P=0.797, the hazard ratio for MSI-H was adjusted by age, sex, pT stage, and the number of metastatic LNs, 0.932; 95% confidence interval, 0.423–2.054; P=0.861).

Conclusions

MSI status was not useful in predicting prognosis in early gastric cancer. However, the frequent presence of LVI in early MSI-H gastric cancer may help guide the appropriate treatment for patients, such as endoscopic treatment or limited LN surgical dissection.

Tumor immune response and immunotherapy in gastric cancer

Remarkable developments in immuno-oncology have changed the landscape of gastric cancer (GC) treatment. Because immunotherapy intervenes with tumor immune response rather than directly targeting tumor cells, it is important to develop a greater understanding of tumor immunity. This review paper summarizes the tumor immune reaction and immune escape mechanisms while focusing on the role of T cells and their co-inhibitory signals, such as the immune checkpoint molecules programmed death-1 and programmed deathligand 1 (PD-L1). This paper also describes past clinical trials of immunotherapy for patients with GC and details their clinical implications. Strong predictive markers are essential to improve response to immunotherapy. Microsatellite instability, Epstein-Barr virus, PD-L1 expression, and tumor mutational burden are now regarded as potent predictive markers for immunotherapy in patients with GC. Novel immunotherapy and combination therapy targeting new immune checkpoint molecules such as lymphocyte-activation gene 3, T cell immunoglobulin, and mucin domain containing-3, and indoleamine 2,3-dioxygenase have been suggested, and trials are ongoing to evaluate their safety and efficacy. Immunotherapy is an important treatment option for patients with GC and has great potential for improving patient outcome, and further research in immuno-oncology should be carried out.

A polymorphism within the mismatch repair gene predicts prognosis and adjuvant chemotherapy benefit in gastric cancer

BACKGROUND

Defective mismatch repair (dMMR) and microsatellite instability (MSI) correlate with gastric cancer (GC) outcome. We hypothesized that MMR genetic polymorphisms that have low-penetrant effects but may cause heterogeneous MMR capability among individuals also affect GC outcome.

METHODS

The polymorphisms rs1800734 in MLH1, rs2303428 and rs3732183 in MSH2, rs735943 in EXO1, and rs11797 in TREX1 were selected and analyzed in independent discovery and validation sets that included 167 and 593 patients, respectively. MSI was determined.

RESULTS

In both the discovery and validation sets, the rs2303428 TC + CC genotype correlated with poor overall survival (OS) in non-cardia (P < 0.05) but not in cardia GC. Multivariate models showed that for OS of patients with non-cardia GC, the rs2303428 TC + CC genotype was an independent predictor in the validation set (HR 1.54; 95% CI 1.02-2.32; P = 0.040) and had a trend to be an independent predictor in the discovery set (HR 1.70; 95% CI 0.96-3.01; P = 0.067). Furthermore, in both patient sets, fluoropyrimidines-based adjuvant chemotherapy improved OS for non-cardia patients with the rs2303428 TC + CC genotype (HR 0.14; 95% CI 0.04-0.57; P = 0.006; and HR 0.29; 95% CI 0.15-0.58; P < 0.001, respectively) but not for those with the TT genotype. The rs2303428 genotypes were not associated with MSI frequency. The rs2303428 TC + CC genotype correlated with reduced expressions for thymidylate synthetase, P-glycoprotein and ERCC1 (P < 0.05) in non-cardia GC.

CONCLUSIONS

The rs2303428 genotypes may predict prognosis and adjuvant chemotherapy benefit in non-cardia GC patients.

Prognostic implication of molecular subtypes and response to neoadjuvant chemotherapy in 760 gastric carcinomas: role of Epstein-Barr virus infection and high- and low-microsatellite instability

Epstein-Barr virus positivity (EBV(+)) and high-microsatellite instability (MSI-H) have been identified as molecular subgroups in gastric carcinoma. The aim of our study was to determine the prognostic and predictive relevance of these subgroups in the context of platinum/5-fluorouracil (5-FU) based preoperative chemotherapy (CTx). Additionally, we investigated the clinical relevance of the low-MSI (MSI-L) phenotype. We analysed 760 adenocarcinomas of the stomach or the gastro-oesophageal junction encompassing 143 biopsies before CTx and 617 resected tumours (291 without and 326 after CTx). EBV was determined by PCR and in situ hybridisation for selected cases. MSI was analysed by PCR using five microsatellite markers and classified as MSI-H and MSI-L. Frequencies of EBV(+), MSI-H and MSI-L in the biopsies before CTx were 4.2, 10.5 and 4.9% respectively. EBV(+) or MSI-H did not correlate with response, but MSI-L was associated with better response (p = 0.011). In the resected tumours, frequencies of EBV(+), MSI-H and MSI-L were 3.9, 9.6 and 4.5% respectively. Overall survival (OS) was significantly different in the non-CTx group (p = 0.014). Patients with EBV(+) tumours showed the best OS, followed by MSI-H. MSI-L was significantly associated with worse OS (hazard ratio [HR], 2.21; 95% confidence interval [CI], 1.21-4.04, p = 0.01). In the resected tumours after CTx, MSI-H was also associated with increased OS (HR, 0.54; 95% CI, 0.26-1.09, p = 0.085). In multivariable analysis, molecular classification was an independent prognostic factor in the completely resected (R0) non-CTx group (p = 0.035). In conclusion, MSI-H and EBV(+) are not predictive of response to neoadjuvant platinum/5-FU based CTx, but they are indicative of a good prognosis. In particular, MSI-H indicates a favourable prognosis irrespective of treatment with CTx. MSI-L predicts good response to CTx and its negative prognostic effect for patients treated with surgery alone suggests that MSI-L might help to identify patients with potentially high-benefit from preoperative CTx.

Prognostic value of mismatch repair deficiency in patients with advanced gastric cancer, treated by surgery and adjuvant 5-fluorouracil and leucovorin chemoradiotherapy

OBJECTIVE

The predictive value of mismatch repair protein deficiency (MMRD) for chemoradiotherapeutic outcome has rarely been reported in gastric cancer. This study investigated the clinical significance of MMRD as a prognostic factor for tumor recurrence, and as a predictor of response to adjuvant chemoradiotherapy in advanced gastric cancer patients.

METHODS

Between 1995 and 2008, tissue specimens of 881 patients who underwent radical gastrectomy for stage II and III gastric cancer were analyzed. MMRD was assessed using immunohistochemical stains for MLH1, PMS2, MSH2, and MSH6. Patients were divided into two groups according to adjuvant treatment: a 5-fluorouracil/leucovorin (FL) adjuvant chemoradiotherapy group and a surgery alone group. Disease-free survival (DFS) was compared between the two groups correlated to MMRD. Risk factors for tumor recurrence were analyzed using multivariate analysis.

RESULTS

Of the 881 gastric cancer patients, 88 (10.0%) exhibited MMRD and 398 (45.2%) patients received adjuvant FL chemoradiotherapy. The multivariate analysis revealed that MMRD was a good independent prognostic factor (hazard ratio, 0.572; 95% confidence interval, 0.370-0.883; P = 0.012). For stage III gastric cancer displaying mismatch repair protein proficiency (MMRP), adjuvant FL chemoradiotherapy after surgery resulted in better DFS than surgery alone (P = 0.001). Among the stage II gastric cancer patients, adjuvant FL chemoradiotherapy did not show survival benefit, regardless of MMRD.

CONCLUSION

MMRD is a good independent prognostic factor in advanced gastric cancer. Adjuvant FL chemoradiotherapy was beneficial in patients with stage III gastric cancer with MMRP but not in those with MMRD.

Checkpoint inhibition in advanced gastroesophageal cancer: clinical trial data, molecular subtyping, predictive biomarkers, and the potential of combination therapies

The development of checkpoint inhibitors has redefined the treatment paradigm for advanced gastroesophageal cancer. While recent developments have improved clinical outcomes, the prognosis for the disease remains meager. In this review, we discuss the rationale and detail the results from recent phase I-III trials supporting the activity of PD-1 inhibitors. Specifically, we highlight the seminal clinical trials leading to the FDA approval of pembrolizumab for advanced gastroesophageal cancer. Finally, we review the current understanding and future considerations of molecular subtyping and predictive biomarkers to help guide therapy and the promise of combination therapy to further improve the efficacy of checkpoint inhibitors.

Clinical and molecular prognostic markers of survival after surgery for gastric cancer: tumor-node-metastasis staging system and beyond

For accurately predicting prognosis and for effectively describing cancer states at a certain point during treatment to other care providers and patients, various staging systems have been utilized in gastric cancer. Among these, the UICC/AJCC tumor-node-metastasis (TNM) staging system is most widely used. However, even within the same substage, gastric cancers can vary substantially in regards to prognosis after treatment. For more accurate and individualized prognostication, staging systems have been found to benefit from including molecular markers and genomic subtypes, in addition to clinicopathological parameters, such as age, sex, tumor size, tumor location, Lauren classification, number of lymph nodes resected, extent of surgical resection, lymphovascular invasion, and adjuvant chemotherapy. In this review article, we review and summarize relevant biomarkers for gastric cancer that can be incorporated into the current anatomy-based TNM staging system, as well as results from validation studies thereof.

ESMO recommendations on microsatellite instability testing for immunotherapy in cancer, and its relationship with PD-1/PD-L1 expression and tumour mutational burden: a systematic review-based approach

BACKGROUND

Cancers with a defective DNA mismatch repair (dMMR) system contain thousands of mutations most frequently located in monomorphic microsatellites and are thereby defined as having microsatellite instability (MSI). Therefore, MSI is a marker of dMMR. MSI/dMMR can be identified using immunohistochemistry to detect loss of MMR proteins and/or molecular tests to show microsatellite alterations. Together with tumour mutational burden (TMB) and PD-1/PD-L1 expression, it plays a role as a predictive biomarker for immunotherapy.

METHODS

To define best practices to implement the detection of dMMR tumours in clinical practice, the ESMO Translational Research and Precision Medicine Working Group launched a collaborative project, based on a systematic review-approach, to generate consensus recommendations on the: (i) definitions related to the concept of MSI/dMMR; (ii) methods of MSI/dMMR testing and (iii) relationships between MSI, TMB and PD-1/PD-L1 expression.

RESULTS

The MSI-related definitions, for which a consensus frame-work was used to establish definitions, included: 'microsatellites', 'MSI', 'DNA mismatch repair' and 'features of MSI tumour'. This consensus also provides recommendations on MSI testing; immunohistochemistry for the mismatch repair proteins MLH1, MSH2, MSH6 and PMS2 represents the first action to assess MSI/dMMR (consensus with strong agreement); the second method of MSI/dMMR testing is represented by polymerase chain reaction (PCR)-based assessment of microsatellite alterations using five microsatellite markers including at least BAT-25 and BAT-26 (strong agreement). Next-generation sequencing, coupling MSI and TMB analysis, may represent a decisive tool for selecting patients for immunotherapy, for common or rare cancers not belonging to the spectrum of Lynch syndrome (very strong agreement). The relationships between MSI, TMB and PD-1/PD-L1 expression are complex, and differ according to tumour types.

CONCLUSIONS

This ESMO initiative is a response to the urgent questions raised by the growing success of immunotherapy and provides also important insights on the relationships between MSI, TMB and PD-1/PD-L1.

Molecular alterations and PD-L1 expression in non-ampullary duodenal adenocarcinoma: Associations among clinicopathological, immunophenotypic and molecular features

Non-ampullary duodenal adenocarcinoma (NADC) is extremely rare. Little is known about its clinicopathological and molecular features or its management. Herein we retrospectively analyzed the cases of 32 NADC patients, focusing on microsatellite instability (MSI), genetic mutations, CpG island methylator phenotype (CIMP), and immunostaining including mucin phenotype and PD-L1 expression. The incidence of MSI, KRAS/BRAF/GNAS mutations and CIMP was 51.6%, 34.4%/3.1%/6.5% and 28.1%, respectively. PD-L1 expression was seen in 34.4% of patients. No significant associations between clinicopathological features and KRAS/BRAF/GNAS genetic mutations or CIMP were found. Histologically non-well-differentiated-type NADCs and those in the 1st portion of the duodenum were significantly associated with later stages (stages III–IV) (P = 0.006 and P = 0.003, respectively). Gastric-phenotype NADCs were frequently observed in the 1st portion and in late-stage patients; their cancer cells more frequently expressed PD-L1. Histologically, the non-well-differentiated type was an independent predictor of PD-L1 expression in cancer cells (OR 25.05, P = 0.04) and immune cells (OR 44.14, P = 0.02). Only late-stage disease (HR 12.23, P = 0.01) was a prognostic factor for worse overall survival in a Cox proportional hazards regression model. Our observation of high proportions of MSI and PD-L1 expression may prompt the consideration of immune checkpoint inhibitors as a new treatment option for NADCs.

Assessing molecular subtypes of gastric cancer: microsatellite unstable and Epstein-Barr virus subtypes. Methods for detection and clinical and pathological implications

Background

The molecular classification of gastric cancer recognises two subtypes prone to immune checkpoint blockade: the microsatellite unstable and the Epstein-Barr virus (EBV)-related tumours. We aim to assess the concordance between immunohistochemistry and PCR for microsatellite status evaluation, and explore the value of microsatellite instability (MSI) and EBV as predictive survival factors.

Material and methods

We collected 246 consecutively diagnosed gastric cancer cases in all stages and evaluated the microsatellite status using immunohistochemistry for mismatched repair (MMR) proteins and PCR. EBV expression was studied through in situ hybridisation.

Results

Forty-five (18%) cases presented MSI and 13 (6%) were positive for EBV. MSI was associated with female sex, older age, distal location and distal non-diffuse type of the modified Lauren classification. EBV expression was most frequent in proximal location and proximal non-diffuse type. The sensitivity, specificity, positive predictive value and negative predictive value of immunohistochemistry for the microsatellite study were 91%, 98%, 91% and 98%, respectively. In the multivariate analysis, MSI was an independent predictor of favourable tumour-specific survival (TSS) in stages I–III (MSI: HR: 0.37, 95% CI 0.12 to 0.95, p=0.04).

Conclusions

The MSI status and the EBV expression should be incorporated in routine pathological report for two reasons. First, MSI defines a different pathological entity with a better outcome. Second, MSI and EBV may be useful biomarkers to identify patients who will respond to immune checkpoint blockade inhibitors. For this purpose, immunohistochemical study for MMR proteins and in situ hybridisation study for EBV evaluation are feasible and cost-effective methods.

Perioperative Treatment in Resectable Gastric Cancer: Current Perspectives and Future Directions

Gastric cancer (GC) is the fifth-most common cancer worldwide and an important cause of cancer-related-death. The growing knowledge of its molecular pathogenesis has shown that GC is not a single entity, but a constellation of different diseases, each with its own molecular and clinical characteristics. Currently, surgery represents the only curative approach for localized GC, but only 20% of patients (pts) showed resectable disease at diagnosis and, even in case of curative resection, the prognosis remains poor due to the high rate of disease relapse. In this context, multimodal perioperative approaches were developed in western and eastern countries in order to decrease relapse rates and improve survival. However, there is little consensus about the optimal treatment for non-metastatic GC. In this review, we summarize the current status and future developments of perioperative chemotherapy in resectable GC, attempting to find clear answers to the real problems in clinical practice.

Expression of PD-L1 and PD-1 in Chemoradiotherapy-Naïve Esophageal and Gastric Adenocarcinoma: Relationship With Mismatch Repair Status and Survival

Background: The outlook for patients with esophageal and gastric (EG) cancer remains poor. Hence, there is a compelling need to identify novel treatment strategies and complementary biomarkers. Programmed death ligand 1 (PD-L1) and mismatch repair deficiency (dMMR) are putative biomarkers of response to immune-checkpoint blockade, but their prognostic value and interrelationship in EG cancer have been sparsely investigated.

Methods: Immunohistochemical expression of PD-L1 on tumour cells (TC) and tumour-infiltrating immune cells (TIC), and of PD-1 (programmed death receptor 1) on TIC was assessed using tissue microarrays with primary tumours and a subset of paired lymph node metastases from a consecutive, retrospective cohort of 174 patients with chemoradiotherapy-naïve EG adenocarcinoma. MMR proteins MLH1, PMS2, MSH2, and MSH6 were assessed by immunohistochemistry. The total number (intratumoural, tumour-adjacent, and stromal) of CD8⁺ T cells in each core was calculated by automated analysis.

Results: High PD-L1 expression on both TC and TIC, but not PD-1 expression, was significantly associated with dMMR. PD-L1 expression on TIC was significantly higher in lymph node metastases than in primary tumours. High expression of PD-L1 or PD-1 on TIC was significantly associated with a prolonged survival, the former independently of established prognostic factors. A significant stepwise positive association was found between CD8⁺ T cells and categories of PD-L1 expression on TIC.

Conclusion: PD-L1 expression on TIC is higher in lymph node metastases compared to primary tumours, correlates with dMMR, and is an independent factor of prolonged survival in patients with chemoradiotherapy-naïve EG adenocarcinoma. These findings suggest that PD-L1 expression on TIC may be a useful biomarker for identifying patients who may not need additional chemo- or chemoradiotherapy, and who may benefit from PD-1/PD-L1 immune-checkpoint blockade.

Subtraction of Epstein-Barr virus and microsatellite instability genotypes from the Lauren histotypes: Combined molecular and histologic subtyping with clinicopathological and prognostic significance validated in a cohort of 1,248 cases

Limited studies investigated clinicopathological and prognostic significance of histologic and molecular subgroups of gastric cancer concurrently. We retrospectively enrolled 1,248 patients with gastric cancer who received radical gastrectomy with lymphadenectomy and classified these cases into the Epstein-Barr virus (EBV)-associated and microsatellite instability (MSI)-associated subtypes by EBV-encoded small RNA in situ hybridization and immunohistochemical stains for DNA mismatch repair proteins, respectively. The remaining cases were categorized as the Lauren intestinal and diffuse/mixed subtypes. The clinicopathological and prognostic significance of the subtypes was examined by statistical analysis. In total, 65 (5.2%), 116 (9.3%), 496 (39.7%), 431 (34.5%) and 140 (11.2%) cases were identified as EBV-associated, MSI-associated, intestinal, diffuse and mixed subtypes, respectively. The EBV-associated, MSI-associated, intestinal and diffuse/mixed subtypes exhibited distinctive clinicopathological characteristics, including differences in age, gender, stump cancer, gastric location, tumor size, TNM stage, margin involvement, lymphatic/perineural invasion, HER2 status and recurrence pattern. The log-rank test showed survival discrimination (p < 0.001), and the multivariate analysis identified EBV-associated and MSI-associated cases demonstrated better outcomes than the diffuse/mixed subtype (EBV, HR 0.464, 95% CI 0.296-0.727, p = 0.001; MSI, HR 0.590, 95% CI 0.407-0.856, p = 0.005). EBV-associated lymphoepithelioma-like carcinoma cases had the most favorable outcome (HR 0.138, 95% CI 0.033-0.565, p = 0.006). In different clinical groups, the subtypes exhibited survival discrepancies. The EBV-associated and diffuse/mixed cases exhibited more favorable response to chemotherapy. In conclusion, this combined classification, in parallel with the molecular subtypes specified in the Cancer Genome Atlas study, has implications for the clinical management of gastric cancer.

Hypomethylated gene NRP1 is co-expressed with PDGFRB and associated with poor overall survival in gastric cancer patients

Gastric cancer (GC) has been an increasingly serious problem in public health. However, there is still a lack of efficient approach to diagnosis and treatment in time, especially in the field of targeted therapy. Increasing evidences demonstrated that DNA methylation plays an essential role in tumorigenesis and progression of GC. Thus the present study aims to identify DNA methylation-based prognostic biomarkers in GC. Two methylation array datasets (GSE25869 and GSE30601) and RNA-seq based gene profiling dataset (TCGA-STAD) were employed for exploring candidate DNA methylation-based biomarkers. Univariate Cox regression analysis was used to select the most efficient prognostic genes in GC patients. Weighted gene correlation network analysis (WGCNA) was performed to screen the cluster of co-expressed genes. As a result, our data proved that NRP1 was a hypomethylated / upregulated gene in GC tissues, and PDGFRB was strongly co-expressed with it. Both of them were significantly associated with the overall survival of patients. More importantly, high expression levels of NRP1 and PDGFRB were associated with malignant phenotypes in GC patients, including Laurén histological diffuse type and higher histological grade. Patients carrying high expression level of NRP1 and PDGFRB had a nearly two-fold increased death risk than others. In summary, the hypomethylated gene, NRP1, and its co-expressed gene, PDGFRB, were significantly correlated with tumor malignant phenotypes, which might serve as potential prognostic biomarkers for GC patients.

KRAS Mutation in Gastric Cancer and Prognostication Associated with Microsatellite Instability Status

Microsatellite instability (MSI) is one of the subgroups based on the new molecular classification of gastric cancer (GC). In this study, we analyzed the role of KRAS status in MSI GC and the impact of MSI status on KRAS mutation. We performed analysis on 595 GC patients. Polymerase chain reaction (PCR) was used for the screening of KRAS mutation (exon 2) and 5 quasi-monomorphic mononucleotide repeats, namely, BAT-26, BAT-25, NR -24, NR-21, and NR-27 were used to determine the MSI status. The KRAS and MSI status were then compared with clinicopathologic data of the GC patients. MSI GC was found in 20.3% of all cases. KRAS mutation was seen in 24 patients; 18 were MSI (75%) and 6 were microsatellite stable (MSS) (25%). MSI GC patients with KRAS mutation were older and mostly female, but MSS presented more advanced T and N stage of the disease, more cardia tumors, and adjuvant treatment. Five-year survival was 72.2% for KRAS mutation patients with MSI and 0% for MSS (p < 0.001). Although KRAS mutations in GC are linked with MSI in the majority of cases, KRAS mutations with MSS status presented with a poor prognosis and a worse outcome. In multivariate analysis, MSI was associated with better survival (p < 0.001) but KRAS was with worse survival (p = 0.304). Our study suggests that KRAS mutations are based on MSI status rather than different codon subtypes of mutation, and such a division could be used to determine the GC patient outcome.

Microsatellite instability in gastric cancer: molecular bases, clinical perspectives, and new treatment approaches

Gastric cancer is one of the most aggressive malignancies, with limited treatment options in both locally advanced and metastatic setting, resulting in poor prognosis. Based on genomic characterization, stomach tumour has recently been described as a heterogeneous disease composed by different subtypes, each of them with peculiar molecular aspects and specific clinical behaviour. With an incidence of 22% among all western gastric tumour cases, stomach cancer with microsatellite instability was identified as one of these subgroups. Retrospective studies and limited prospective trials reported differences between gastric cancers with microsatellite stability and those with instability, mainly concerning clinical and pathological features, but also in regard to immunological microenvironment, correlation with prognostic value, and responses to treatment. In particular, gastric cancer with microsatellite instability constitutes a small but relevant subgroup associated with older age, female sex, distal stomach location, and lower number of lymph-node metastases. Emerging data attribute to microsatellite instability status a favourable prognostic meaning, whereas the poor outcomes reported after perioperative chemotherapy administration suggest a detrimental role of cytotoxic drugs in this gastric cancer subgroup. The strong immunogenicity and the widespread expression of immune-checkpoint ligands make microsatellite instability subtype more vulnerable to immunotherapeutic approach, e.g., with anti-PD-L1 and anti-CTLA4 antibodies. Since gastric cancer with microsatellite instability shows specific features and clinical behaviour not overlapping with microsatellite stable disease, microsatellite instability test might be suitable for inclusion in a diagnostic setting for all tumour stages to guarantee the most targeted and effective treatment to every patient.

The Thomsen-Friedenreich Antigen: A Highly Sensitive and Specific Predictor of Microsatellite Instability in Gastric Cancer

Microsatellite instability (MSI) is a distinct molecular subtype of gastric cancer. In recent years, the clinical consequences of MSI and the therapeutic opportunities to target this peculiar cancer subtype became evident. However, despite the importance of MSI for the stratification of patients, the time and resources required for diagnosis still present an obstacle. In an attempt to identify a new marker for MSI in gastric cancer, we evaluated the expression of five cancer-associated glycan epitopes in a cohort of 13 MSI and 17 microsatellite stable (MSS) cases. Our analysis revealed a highly significant (p < 0.001) association between the expression of the Thomsen-Friedenreich (TF) antigen and MSI status. Hence, we present here the identification of the first single marker for MSI in gastric cancer, excelling with a specificity of 94% (16/17), sensitivity of 69.2% (9/13), negative predictive value of 80% (16/20), and positive predictive value of 90% (9/10). The TF antigen, detected by simple antibody-based assays, is highly specific for carcinoma being undetectable in gastric healthy and premalignant epithelia. This finding lays the basis for new studies and holds promise in improving the rapid identification of MSI in the clinical setting.

Multilevel omic data clustering reveals variable contribution of methylator phenotype to integrative cancer subtypes

AIM

We aimed to assess to what extent CpG island methylator phenotype (CIMP) contributes to cancer subtypes obtained by multilevel omic data analysis.

MATERIALS & METHODS

16 The Cancer Genome Atlas datasets encompassing three data layers in 4688 tumor samples were analyzed. We identified cancer integrative subtypes (ISs) by the use of similarity network fusion and consensus clustering. CIMP high (CIMP-H) associated ISs were profiled by gene sets and transcriptional regulators enrichment analysis.

RESULTS & CONCLUSION

In nine out of 16 cancer datasets CIMP-H clusters significantly overlaped with unique ISs. The contribution of CIMP-H on integrative molecular profiling is variable; therefore, only in a subset of cancer types does CIMP-H contribute to homogenous integrative subtype. CIMP-H associated ISs are heterogenous groups with regard to deregulated pathways and transcriptional regulators.

Hereditary diffuse gastric cancer: how to look for and how to manage it

With a current molecular revolution, hereditary gastric cancer represents a small group of patients that require a special multidisciplinary treatment. Surgeons being a member of the multidisciplinary teams are an important part of the diagnosis, treatment and follow-up of these patients. The prophylactic nature of the gastrectomy with all different problems associated with this procedure need to be widely discussed with patients. We present a review of how to look for and how to manage a hereditary diffuse-type gastric cancer.

Clinical impact of molecular classifications in gastric cancer

Treatment options to gastric cancer (GC) have been changing in recent years from a standard to a tailored approach. Different individualized procedures can range from endoscopic resection, D2 with open or minimally invasive approach, to neo-adjuvant therapy followed by extended surgery. In more advanced stages, a combined approach with the inclusion of intraperitoneal chemo-hyperthermia (HIPEC) may represent a new advanced option. The inclusion of histological type according to Laurén classification in the flowchart of treatment could increase both accuracy and effectiveness of such tailored approach. New molecular classifications of GC have been introduced recently and translational clinical studies are ongoing. These classifications are expected to be included in multidisciplinary treatment of GC. In particular, in the group with microsatellite instability a less extended lymphadenectomy may be proposed. Also tailored neo-adjuvant treatment may be proposed according to molecular classifications. The group of patients with epithelial-to-mesenchymal transition shows very high propensity to peritoneal dissemination, as well as N-metastases, and may benefit from prophylactic HIPEC and extended lymphadenectomy when confirmed in prospective trials.

Synchronous metastatic gastric cancer-molecular background and clinical implications with special attention to mismatch repair deficiency

BACKGROUND

Current guidelines recommend that metastatic gastric cancer should not be treated with surgery unless this is required for symptom control. We hypothesized that patients with mismatch repair deficiency (MMRd) gastric cancer and metastatic disease detected at the timepoint of surgical resection would have superior survival compared to patients with MMRd cancers in the same setting.

METHODS

Clinicopathological details and survival data were collected from prospective databases at two large European centers on patients who had undergone surgery and were diagnosed with synchronous stage IV gastric cancer (distant lymph nodes, positive peritoneal cytology, peritoneal, and distant metastases) at the timepoint of surgery. Resection specimens were tested for the presence of microsatellite instability using a standard 5 mononucleotide repeat panel.

RESULTS

One hundred and seventy six patients with resected stage IV gastric cancer were identified. 14/176 (8.0%) had MSI-H (high) disease. There was no significant difference between the clinical and pathological characteristics of MSI and microsatellite stable (MSS) patients. No differences in the type of metastases were observed between MSI and MSS groups. Patients who were MSI-H had superior OS compared to MSS patients (median OS 15.9 vs. 8 months, p = 0.023). However, in Cox regression multivariate analysis only liver and peritoneal metastases were independent predictors of survival.

CONCLUSIONS

Surgically treated patients with MSI-H stage IV gastric cancer have a better survival than patients with MSS gastric cancer. Further analysis of the role of surgery in MSI stage IV GC is required.

Translational research and application of basic biology to clinical trial development in GI cancers

Cancers of the gastrointestinal tract have limited available treatments and are often associated with a poor prognosis. Clinical trials and translational work associated with these trials provide the opportunity to increase understanding of the mechanisms of sensitivity and resistance to cytotoxic chemotherapy and targeted therapy in these diseases. In this review we discuss the rationale for intensive translational work within the context of academic clinical trials and the successes and challenges which have been associated with translational work at our institution over the past number of years. We reflect on tissue, plasma and radiological biomarker work including a novel patient derived organoid programme and discuss the iterative application of previous results to next generation trial design.

Distinct molecular subtypes of gastric cancer: from Laurén to molecular pathology

In Western countries the majority of gastric cancers (GC) are usually diagnosed in advanced stages reporting a 5-year survival rate of only 26%. The Laurén classification of GC was most widely used in clinical practice since it reflects GC morphology, epidemiology, tumor biology, clinical management and outcome. Despite the initial promise of individualizing antitumor treatment, the management of GC still remains relatively broad and general. Apart from clinical staging, molecular profiling enables targeting of the identified underlying alterations, rather than histology. In contrast to breast carcinoma, molecular classification of GC does not yet imply treatment modality. Molecular classifications of GC and their therapeutic implications are therefore extensively studied. The current proposed molecular divisions of GC come from three different parts of the world where different standard treatment modalities for advanced GC are recommended. Wider use of GC molecular subtyping may solve problems, such as susceptibility to novel systemic therapy regimens or selection of patients for aggressive surgery and targeted adjuvant/conversion therapy. In any case, the rapid entry of novel molecular targeted therapies into routine oncology practice clearly underscores the urgent need for clinicians to be aware of these new possibilities.

The Role of Microsatellite Instability in Positive Margin Gastric Cancer Patients

PURPOSE

A positive resection margin (RM+) is acknowledged as a poor prognostic factor after gastrectomy. Microsatellite instability (MSI-H) gastric cancer has been identified as a subgroup of gastric cancer that may be associated with an improved prognosis. The aim of the study was an analysis of MSI status on patients with margin involvement after gastrectomy and examination of the association between MSI, margin status, and survival outcomes.

METHODS

From a large prospectively annotated surgical database we collected clinicopathological and survival data on patients who had undergone a potentially curative resection for gastric cancer. MSI status was assessed using a standard 5-marker quasi-monomorphic mononucleotide repeat panel. Patients who were R+ and either microsatellite stable (MSS) or MSI-H were identified and clinicopathological characteristics and disease specific survival was compared.

RESULTS

Three hundred and eighty-six patients were identified; 102 (26.4%) cancers were MSI-H. The proportion of R+ resections was not significantly different in MSS and MSI-H groups. For MSS patients 3-, 5-, and 10-year disease-specific survival rates were 9.1%, 0%, and 0%, respectively; for patients with MSI-H R+ tumors these were 38.5%, 30.8%, and 15.4%, respectively. In Cox analysis MSI-H, female gender, and T ≥3 were significantly associated with survival.

CONCLUSIONS

Patients with MSI-H gastric cancer may have long-term survival despite R+ margin status. The molecular division of gastric cancer may be an important step in identifying possible tailored surgical treatments corresponding to clinical and pathological factors.

High immune cell score predicts improved survival in pancreatic cancer

Increasing evidence suggests that cancer progression is strongly influenced by host immune response, which is represented by immune cell infiltrates. T-lymphocyte-based immunoscore has proved to be a prognostic factor in colon cancer, but its significance in pancreatic cancer is poorly known. Total of 108 patients operated (R0/R1) for pancreatic ductal adenocarcinoma (PDAC) (TNM stage I-II) were included in the study. Immune cell score (IS) was determined by scoring the samples from grade 0 to 4 according to the number of immune cells (CD3⁺ and CD8⁺) in tumor core and invasion margin using tissue microarrays, immunohistochemistry, and digital analysis. Tumors with microsatellite instability were identified by MLH1 immunostaining. High IS and low histological grade were significantly associated with better disease-specific survival (DSS) and overall survival (OS). The 5-year DSS rate for low, moderate, and high IS groups were 5.0, 15.2, and 33.4%, respectively (p = 0.007). The 5-year OS rate for the low, moderate, and high IS groups were 4.2, 13.4, and 31.5%, respectively (p = 0.004). In addition, IS and prognosis varied within a single TNM stage. There was no association between IS and any of the clinicopathological variables. IS was shown to be an independent prognostic factor for better DSS and OS in multivariate analysis, together with the histological grade of the tumor and perineural invasion. Five MLH1-negative tumors (4.6%) were found showing no correlation with IS. IS could be a useful prognostic marker in patients with PDAC treated by primary surgery.

The pattern of lymph node metastases in microsatellite unstable gastric cancer

BACKGROUND

Microsatellite instability (MSI) is one of the new groups of molecular divisions of gastric cancer (GC). The aim of this study was to investigate the pattern of lymph node metastasis according to MSI status.

METHODS

MSI analysis of 361 GC patients with information about lymph node stations was performed using 5 quasimonomorphic mononucleotide repeats. The metastasis rates for each lymphatic station was analyzed, combined with clinicopathologic characteristics. Stations were divided into compartments 1-3 on the basis of Japanese Classification. A median number (interquartile range, IQR) of 33 (18-50) lymph nodes were removed and analyzed.

RESULTS

N0 status was observed in 53.7% MSI patients, and in 29.7% microsatellite stable (MSS) (p < 0.001).The median value of involved nodes was 1 in MSI vs. 5 in MSS (p < 0.001). Furthermore, the number of involved node stations was significantly lower in the MSI group (p < 0.001). MSS tumors showed a higher propensity to spread to second and third compartment nodes. In absence of lymphovascular invasion only 3.2% cases demonstrated positive nodes beyond the first compartment. Skip metastases were seen in 6.1% MSS patients and 0% MSI (p = 0.011). No difference in the 10-year cancer related survival among MSI and MSS patients was found, for both those with 1st compartment (p = 0.223) and with 2nd compartment involvement (p = 0.814).

CONCLUSIONS

MSI GC shows a high rate of N0 stage, a lower number of lymph node metastases, and a less extensive spread to lymph node stations than MSS tumors. These data indicate that tailored lymphadenectomy may be investigated for these patients.