Molecular key to understand the gastric cancer biology in elderly patients-The role of microsatellite instability

Potent therapeutic strategy in gastric cancer with microsatellite instability-high and/or deficient mismatch repair

Gastric cancer (GC) is a common malignancy that presents challenges in patient care worldwide. The mismatch repair (MMR) system is a highly conserved DNA repair mechanism that protects genome integrity during replication. Deficient MMR (dMMR) results in an increased accumulation of genetic errors in microsatellite sequences, leading to the development of a microsatellite instability-high (MSI-H) phenotype. Most MSI-H/dMMR GCs arise sporadically, mainly due to MutL homolog 1 (MLH1) epigenetic silencing. Unlike microsatellite-stable (MSS)/proficient MMR (pMMR) GCs, MSI-H/dMMR GCs are relatively rare and represent a distinct subtype with genomic instability, a high somatic mutational burden, favorable immunogenicity, different responses to treatment, and prognosis. dMMR/MSI-H status is a robust predictive biomarker for treatment with immune checkpoint inhibitors (ICIs) due to high neoantigen load, prominent tumor-infiltrating lymphocytes, and programmed cell death ligand 1 (PD-L1) overexpression. However, a subset of MSI-H/dMMR GC patients does not benefit from immunotherapy, highlighting the need for further research into predictive biomarkers and resistance mechanisms. This review provides a comprehensive overview of the clinical, molecular, immunogenic, and therapeutic aspects of MSI-H/dMMR GC, with a focus on the impact of ICIs in immunotherapy and their potential as neoadjuvant therapies. Understanding the complexity and diversity of the molecular and immunological profiles of MSI-H/dMMR GC will drive the development of more effective therapeutic strategies and molecular targets for future precision medicine.

Management of Microsatellite Instability High (MSI-H) Gastroesophageal Adenocarcinoma

BACKGROUND

Gastroesophageal cancer is a major cause of cancer-related mortality worldwide. Treatment of both early stage and advanced disease remains highly reliant on cytotoxic chemotherapy. About 4-24% of gastroesophageal cancers are microsatellite instability high (MSI-H). The MSI-H subtype is associated with favorable prognosis, resistance to cytotoxic chemotherapy, and sensitivity to immune checkpoint inhibitors (ICI). Recent studies have demonstrated promising activity of ICIs in the MSI-H subtype, resulting in fundamental changes in the management of MSI-H gastroesophageal adenocarcinoma.

PURPOSE

In this review, we discuss the prevalence, characteristics, prognosis, and management of MSI-H gastroesophageal adenocarcinoma, with a focus on recent and ongoing studies that have changed the landscape of treatment for the MSI-H subtype. We also discuss current challenges in the management of resectable and advanced MSI-H gastroesophageal cancer, including the need for more accurate biomarkers of response to ICI therapy.

Utilizing nanotechnology and advanced machine learning for early detection of gastric cancer surgery

Nanotechnology has emerged as a promising frontier in revolutionizing the early diagnosis and surgical management of gastric cancers. The primary factors influencing curative efficacy in GIC patients are drug inefficacy and high surgical and pharmacological therapy recurrence rates. Due to its unique optical features, good biocompatibility, surface effects, and small size effects, nanotechnology is a developing and advanced area of study for detecting and treating cancer. Considering the limitations of GIC MRI and endoscopy and the complexity of gastric surgery, the early diagnosis and prompt treatment of gastric illnesses by nanotechnology has been a promising development. Nanoparticles directly target tumor cells, allowing their detection and removal. It also can be engineered to carry specific payloads, such as drugs or contrast agents, and enhance the efficacy and precision of cancer treatment. In this research, the boosting technique of machine learning was utilized to capture nonlinear interactions between a large number of input variables and outputs by using XGBoost and RNN-CNN as a classification method. The research sample included 350 patients, comprising 200 males and 150 females. The patients' mean ± SD was 50.34 ± 13.04 with a mean age of 50.34 ± 13.04. High-risk behaviors (P = 0.070), age at diagnosis (P = 0.034), distant metastasis (P = 0.004), and tumor stage (P = 0.014) were shown to have a statistically significant link with GC patient survival. AUC was 93.54%, Accuracy 93.54%, F1-score 93.57%, Precision 93.65%, and Recall 93.87% when analyzing stomach pictures. Integrating nanotechnology with advanced machine learning techniques holds promise for improving the diagnosis and treatment of gastric cancer, providing new avenues for precision medicine and better patient outcomes.

Predictive Biomarkers for Immunotherapy in Gastric Cancer: Current Status and Emerging Prospects

Gastric cancer presents substantial management challenges, and the advent of immunotherapy has ignited renewed hope among patients. Nevertheless, a significant proportion of patients do not respond to immunotherapy, and adverse events associated with immunotherapy also occur on occasion, underscoring the imperative to identify suitable candidates for treatment. Several biomarkers, including programmed death ligand-1 expression, tumor mutation burden, mismatch repair status, Epstein-Barr Virus infection, circulating tumor DNA, and tumor-infiltrating lymphocytes, have demonstrated potential in predicting the effectiveness of immunotherapy in gastric cancer. However, the quest for the optimal predictive biomarker for gastric cancer immunotherapy remains challenging, as each biomarker carries its own limitations. Recently, multi-omics technologies have emerged as promising platforms for discovering novel biomarkers that may help in selecting gastric cancer patients likely to respond to immunotherapy. The identification of reliable predictive biomarkers for immunotherapy in gastric cancer holds the promise of enhancing patient selection and improving treatment outcomes. In this review, we aim to provide an overview of clinically established biomarkers of immunotherapy in gastric cancer. Additionally, we introduce newly reported biomarkers based on multi-omics studies in the context of gastric cancer immunotherapy, thereby contributing to the ongoing efforts to refine patient stratification and treatment strategies.

Assessment of the reliability of MSI status and dMMR proteins deficiency screening on endoscopic biopsy material in esophagus and gastric adenocarcinoma

BACKGROUND

Microsatellite instability (MSI) is a negative predictive factor for neoadjuvant chemotherapy in resectable oesogastric adenocarcinoma and a crucial determinant for immunotherapy. We aimed to evaluate reliability of dMMR/MSI status screening performed on preoperative endoscopic biopsies.

METHODS

Paired pathological samples from biopsies and surgical specimen of oesogastric adenocarcinoma were retrospectively collected between 2009 and 2019. We compared dMMR status obtained by immunohistochemistry (IHC) and MSI status by PCR. dMMR/MSI status on surgical specimen was considered as reference.

RESULTS

PCR and IHC were conclusive on biopsies respectively for 53 (96.4%) and 47 (85.5%) of the 55 patients enrolled. IHC was not contributive for 1 surgical specimen. A third reading of IHC was carried out for 3 biopsies. MSI status was observed in 7 (12.5%) surgical specimens. When analyses were contributive, sensitivity and specificity of biopsies for dMMR/MSI were respectively 85% and 98% for PCR vs. 86% and 98% for IHC. Concordance rate between biopsies and surgical specimen was 96.2% for PCR and 97.8% for IHC.

CONCLUSIONS

Endoscopic biopsies are a suitable source of tissue for dMMR/MSI status determination in oesogastric adenocarcinoma which should be routinely performed at diagnosis to better adapt neoadjuvant treatment.

MINIABSTRACT

By comparison of dMMR phenotype obtained by immunohistochemistry and MSI status by PCR between match-paired samples of oesogastric cancer's endoscopic biopsies and surgical specimen, we observed that biopsies are a suitable source of tissue for dMMR/MSI status determination.

Neoadjuvant Immunotherapy for Patients with dMMR/MSI-High Gastrointestinal Cancers: A Changing Paradigm

Immune checkpoint inhibitors have revolutionized the management of mismatch repair-deficient (MMR-D)/microsatellite instability-high (MSI-H) gastrointestinal cancers, particularly colorectal cancer. Cancers with the MMR-D/MSI-H genotype often carry a higher tumor mutation burden with frameshift alterations, leading to increased mutation-associated neoantigen (MANA) generation. The dramatic response seen with immune checkpoint inhibitors (ICIs), which are orchestrated by MANA-primed effector T cells, resulted in the rapid development of these novel therapeutics within the landscape of MSI-H gastrointestinal cancers. Recently, several clinical trials have utilized ICIs as potential neoadjuvant therapies for MSI-H gastrointestinal cancers and demonstrated deep clinical and pathological responses, creating opportunities for organ preservation. However, there are potential challenges to the neoadjuvant use of ICIs for certain disease types due to the clinical risk of overtreatment for a disease that can be cured through a surgery-only approach. In this review article, we discuss neoadjuvant management approaches with ICI therapy for patients with MSI-H gastrointestinal cancers, including those with oligometastatic disease. We also elaborate on potential challenges and opportunities for the neoadjuvant utilization of ICIs and provide further insight into the changing treatment paradigm of MMR-D/MSI-H gastrointestinal cancers.

Neoadjuvant Nivolumab Plus Ipilimumab and Adjuvant Nivolumab in Localized Deficient Mismatch Repair/Microsatellite Instability-High Gastric or Esophagogastric Junction Adenocarcinoma: The GERCOR NEONIPIGA Phase II Study

PURPOSE

In patients with resectable gastric/gastroesophageal junction (GEJ) adenocarcinoma, surgery plus perioperative platinum-based chemotherapy is the standard of care. Perioperative chemotherapy remains debatable for gastric/GEJ adenocarcinoma with deficient mismatch repair (dMMR)/microsatellite instability-high (MSI-H).

PATIENTS AND METHODS

NEONIPIGA (ClinicalTrials.gov identifier: NCT04006262) phase II study evaluated neoadjuvant nivolumab 240 mg once every two weeks ×6 and ipilimumab 1 mg/kg once every six weeks ×2, followed by surgery and adjuvant nivolumab 480 mg once every four weeks (nine injections) in patients with locally advanced resectable dMMR/MSI-H, clinical (c) tumor (T)2-T4 node (N)x metastasis (M)0 gastric/GEJ adenocarcinoma. The primary end point was a pathological complete response (pCR) rate.

RESULTS

Between October 2019 and June 2021, 32 patients with dMMR/MSI-H gastric/GEJ adenocarcinoma were enrolled. The median age was 65.5 years (range, 40-80). Clinical stages were cT2-T3N0 (n = 9), cT2-T3N1 (n = 22), and cT3N1M1 (n = 1, wrongly included). With a median follow-up of 14.9 months (95% CI, 10.6 to 17.6), 32 patients received neoadjuvant immunotherapy (27 patients completed all cycles). Neoadjuvant therapy-related grade 3/4 adverse events occurred in six patients (19%). Twenty-nine patients underwent surgery; three did not have surgery and had complete endoscopic response with tumor-free biopsies and a normal computed tomography scan (two refused surgery and one had metastasis at inclusion). The rate of surgical morbidity (Clavien-Dindo classification) was 55% (one postoperative death occurred). All 29 patients had an R0 resection, and 17 (58.6%; 90% CI, 41.8 to 74.1) had pCR (pathological T0N0). Becker tumor regression grades 1a, 1b, 2, and 3 were observed in 17 patients, three (including two pathological T0N1), two, and seven patients, respectively. Of the 29 patients with surgery, 23 received adjuvant nivolumab. At database lock, no patient had relapse and one died without relapse.

CONCLUSION

Nivolumab and ipilimumab-based neoadjuvant therapy is feasible and associated with no unexpected toxicity and a high pCR rate in patients with dMMR/MSI-H resectable gastric/GEJ adenocarcinoma.

Identification of senescence-associated long non-coding RNAs to predict prognosis and immune microenvironment in patients with hepatocellular carcinoma

Background: Cellular senescence plays a complicated and vital role in cancer development because of its divergent effects on tumorigenicity. However, the long non-coding RNAs (lncRNAs) associated with tumor senescence and their prognostic value in hepatocellular carcinoma (HCC) remain unexplored. Methods: The trans-cancer oncogene-induced senescence (OIS) signature was determined by gene set variation analysis (GSVA) in the cancer genome atlas (TCGA) dataset. The OIS-related lncRNAs were identified by correlation analyses. Cox regression analyses were used to screen lncRNAs associated with prognosis, and an optimal predictive model was created by regression analysis of the least absolute shrinkage and selection operator (LASSO). The performance of the model was evaluated by Kaplan-Meier survival analyses, nomograms, stratified survival analyses, and receiver operating characteristic curve (ROC) analyses. Gene set enrichment analysis (GSEA) and cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT) were carried out to explore the functional relevance and immune cell infiltration, respectively. Results: Firstly, we examined the pan-cancer OIS signature, and found several types of cancer with OIS strongly associated with the survival of patients, including HCC. Subsequently, based on the OIS signature, we identified 76 OIS-related lncRNAs with prognostic values in HCC. We then established an optimal prognostic model based on 11 (including NRAV, AC015908.3, MIR100HG, AL365203.2, AC009005.1, SNHG3, LINC01138, AC090192.2, AC008622.2, AL139423.1, and AC026356.1) of these lncRNAs by LASSO-Cox regression analysis. It was then confirmed that the risk score was an independent and potential risk indicator for overall survival (OS) (HR [95% CI] = 4.90 [2.74-8.70], p < 0.001), which outperforms those traditional clinicopathological factors. Furthermore, patients with higher risk scores also showed more advanced levels of a proinflammatory senescence-associated secretory phenotype (SASP), higher infiltration of regulatory T (Treg) cells and lower infiltration of naïve B cells, suggesting the regulatory effects of OIS on immune microenvironment. Additionally, we identified NRAV as a representative OIS-related lncRNA, which is over-expressed in HCC tumors mainly driven by DNA hypomethylation. Conclusion: Based on 11 OIS-related lncRNAs, we established a promising prognostic predictor for HCC patients, and highlighted the potential immune microenvironment-modulatory roles of OIS in HCC, providing a broad molecular perspective of tumor senescence.

A multicenter study on the preoperative prediction of gastric cancer microsatellite instability status based on computed tomography radiomics

PURPOSE

To construct and validate a radiomics feature model based on computed tomography (CT) images and clinical characteristics to predict the microsatellite instability (MSI) status of gastric cancer patients before surgery.

METHODS

We retrospectively collected the upper abdominal or the entire abdominal-enhanced CT scans of 189 gastric cancer patients before surgery. The patients underwent postoperative gastric cancer MSI status testing, and the dates of their radiologic images and clinicopathological data were from January 2015 to August 2021. These 189 patients were divided into a training set (n = 90) and an external validation set (n = 99). The patients were divided by MSI status into the MSI-high (H) arm (30 and 33 patients in the training set and external validation set, respectively) and MSI-low/stable (L/S) arm (60 and 66 patients in the training set and external validation set, respectively). In the training set, the clinical characteristics and tumor radiologic characteristics of the patients were extracted, and the tenfold cross-validation method was used for internal validation of the training set. The external validation set was used to assess its generalized performance. A receiver-operating characteristic (ROC) curve was plotted to assess the model performance, and the area under the curve (AUC) was calculated.

RESULTS

The AUC of the radiomics model in the training set and external validation set was 0.8228 [95% confidence interval (CI) 0.7355-0.9101] and 0.7603 [95% CI 0.6625-0.8581], respectively, showing that the constructed radiomics model exhibited satisfactory generalization capabilities. The accuracy, sensitivity, and specificity of the training dataset were 0.72, 0.63, and 0.77, respectively. The accuracy, sensitivity, and specificity of the external validation dataset were 0.67, 0.79, and 0.60, respectively. Statistical analysis was carried out on the clinical data, and there was statistical significance for the tumor site and age (p < 0.05). MSI-H gastric cancer was mostly seen in the gastric antrum and older patients.

CONCLUSIONS

Radiomics markers based on CT images and clinical characteristics have the potential to be a non-invasive auxiliary diagnostic tool for preoperative assessment of gastric cancer MSI status, and they can aid in clinical decision-making and improve patient outcomes.

Considerations and Challenges in the Management of the Older Patients with Gastric Cancer

Gastric cancer is one of the commonest malignancies with high rates of mortality worldwide. Older patients represent a substantial proportion of cases with this diagnosis. However, there are very few 'elderly-specific' trials in this setting. In addition, the inclusion rate of such patients in randomised clinical trials is poor, presumably due to concerns about increased toxicity, co-existing comorbidities and impaired performance status. Therapeutic strategies for this patient group are therefore mostly based on retrospective subgroup analysis of randomised clinical trials. Review of currently available evidence suggests that older gastric cancer patients who are fit for trial inclusion may benefit from surgical intervention and peri-operative systemic chemotherapy strategies. For patients with metastatic disease, management has been revolutionized by the use of anti-HER2 directed therapies as well as immune checkpoint inhibitors with or without chemotherapy. Early data suggest that fit older patients may also benefit from these therapeutic interventions. However, once again there may be limitations in extrapolating these data to everyday clinical practice with older patients being less likely to have a good performance status and an intact immune system. Therefore, determining the functional age and not just the chronological age of a patient prior to initiating therapy becomes very important. The functional decline including reduced organ function that may occur in older patients makes the integration of some form of geriatric assessment in routine clinical practice very relevant.

Advanced oesophago-gastric adenocarcinoma in older patients in the era of immunotherapy. A review of the literature

Gastric (G) and gastro-esophageal junction (GEJ) adenocarcinomas are of the most common and deadly cancers worldwide and affect mainly patients over 70 years at diagnosis. Older age has been associated in gastric cancers with distal tumour location, well-differentiated adenocarcinoma and microsatellite instability and is not identified itself as an independent prognostic factor. As immune checkpoint inhibitors recently changed the landmark of advanced G and GEJ adenocarcinomas treatment, we decided to perform a literature review to define the evidence-level of clinical data in older patients. This work underlined the lasting low -inclusion rate of older patients and -implementation rate of frailty screening tools in clinical trials in G/GEJ carcinomas. In the first-line metastatic setting, two prospective randomized phase III studies have specifically assessed the efficacy of chemotherapy in older patients with HER2-negative gastric cancers, demonstrating the feasibility of reduced dose oxaliplatin-based chemotherapy regimen in this population. Only few data are available in HER2-positive tumors, or in the second-line setting. Furthermore, no specific trial with immune checkpoint inhibitors was performed in older frail patients whereas their benefit/adverse events ratio make them attractive candidates in this patient's population. We conclude that older fit patients can be treated in the same way as younger ones and included in clinical trials. Improving the outcome of older frail patients should be the oncology community next focus by implementing targeted interventions before initiating cancer therapy and designing specific clinical trials. Frailty screening tools and geriatric data collection have to be implemented in routine-practice and clinical trials.

Prevalence and prognosis of microsatellite instability in oesogastric adenocarcinoma, NORDICAP 16-01

BACKGROUND

The prevalence and prognosis association of microsatellite instability (MSI) in oesogastric junction and gastric adenocarcinoma (OGC) have been reported with conflicting results.

METHODS

Patients with OGC from 2010 to 2015 were enrolled in this retrospective multicenter study. MSI was determined by genotyping. MLH1 promoter methylation and BRAFV600E mutation were screened in the MSI tumors.

RESULTS

Among 315 tumors analyzed, 39 (12.4%) were of the MSI phenotype. Compared to MSS tumors, MSI tumors were more frequent in patients >70 years (17% vs 9%, p=0.048) and in gastric antral primary (20% versus 5% in junction tumor and 12% in fundus tumor. Among 29 MSI tumors analyzed, 28 had a loss of MLH1 protein expression and 27 had MLH1 promotor hypermethylation. None had a BRAF V600E mutation. The 4-year cumulative incidence of recurrence for patients with resected tumor was significantly lower in dMMR tumors versus pMMR tumors (17% versus 47%, p=0.01). For the patients with unresectable tumor the median overall survival was 11 months in MSS group and 14 months in MSI group (p=0.24).

CONCLUSION

MSI prevalence in OGC was 12.4%, associated with antral localization and advanced age. Patients with MSI tumors had a lower cumulative incidence of recurrence after surgery. MSI phenotype was mainly associated with loss of MLH1 protein expression, MLH1 promotor hypermethylation and had no BRAFV600E mutation.

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.

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.

Correlations between microsatellite instability and the biological behaviour of tumours

Purpose

Microsatellites are widely distributed repetitive DNA motifs, accounting for approximately 3% of the genome. Due to mismatch repair system deficiency, insertion or deletion of repetitive units often occurs, leading to microsatellite instability. In this review, we aimed to explore the relationship between MSI and biological behaviour of colorectal carcinoma, gastric carcinoma, lymphoma/leukaemia and endometrial carcinoma, as well as the application of frameshift peptide vaccines in cancer therapy.

Methods

The relevant literature from PubMed and Baidu Xueshu were reviewed in this article. The ClinicalTrials.gov database was searched for clinical trials related to the specific topic.

Results

Microsatellite instability is divided into three subtypes: high-level, low-level microsatellite instability, and stable microsatellites. The majority of tumour patients with high-level microsatellite instability often show a better efficacy and prognosis than those with low-level microsatellite instability or stable microsatellites. In coding regions, especially for genes involved in tumourigenesis, microsatellite instability often results in inactivation of proteins and contributes to tumourigenesis. Moreover, the occurrence of microsatellite instability in coding regions can also cause the generation of frameshift peptides that are thought to be unknown and novel to the individual immune system. Thus, these frameshift peptides have the potential to be biomarkers to raise tumour-specific immune responses.

Conclusion

MSI has the potential to become a key predictor for evaluating the degree of malignancy, efficacy and prognosis of tumours. Clinically, MSI patterns will provide more valuable information for clinicians to create optimal individualized treatment strategies based on frameshift peptides vaccines.

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.

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.

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

BACKGROUND

Several associations between microsatellite instability (MSI) and other clinicopathological factors have been reported in gastric cancer, but the results have been ambiguous. This systematic review and meta-analysis investigated the relationship between MSI and overall survival and clinicopathological characteristics of patients with gastric cancer.

METHODS

A systematic literature search of the PubMed, Cochrane and Ovid databases until 31 January 2016 was performed in accordance with the PRISMA statement. The articles were screened independently according to PICO (population, intervention, comparator, outcome) eligibility criteria. All eligible articles were evaluated independently by two reviewers for risk of bias according to the Quality In Prognosis Study tool.

RESULTS

Overall, 48 studies with a total of 18 612 patients were included. MSI was found in 9·2 per cent of patients (1718 of 18 612), and was associated with female sex (odds ratio (OR) 1·57, 95 per cent c.i. 1·31 to 1·89; P < 0·001), older age (OR 1·58, 2·20 to 1·13; P < 0·001), intestinal Laurén histological type (OR 2·23, 1·94 to 2·57; P < 0·001), mid/lower gastric location (OR 0·38, 0·32 to 0·44; P < 0·001), lack of lymph node metastases (OR 0·70, 0·57 to 0·86, P < 0·001) and TNM stage I-II (OR 1·77, 1·47 to 2·13; P < 0·001). The pooled hazard ratio for overall survival of patients with MSI versus those with non-MSI gastric cancer from 21 studies was 0·69 (95 per cent c.i. 0·56 to 0·86; P < 0·001).

CONCLUSION

MSI in gastric cancer was associated with good overall survival, reflected in several favourable clinicopathological tumour characteristics.

Correlation between gastric carcinoma and ZAC gene-associated microsatellite instability and loss of heterozygosity

The present study explored the association between loss of heterozygosity (LOH) or microsatellite instability (MSI) of the zinc finger regulator of apoptosis and cell-cycle arrest (ZAC) gene and the clinicopathological factors of gastric cancer. Samples of cancer and cancer-adjacent normal tissue from 30 patients with gastric cancer were collected. The genomic DNA was extracted from each and amplified with primers specific to ZAC microsatellite mutations, then run on a polyacrylamide gel for analysis. The CA197 microsatellite locus exhibited LOH in cancer sample 4. There was LOH in the 15AAAG locus in cancer sample 27 and cancer-adjacent tissue 23, and MSI at 15AAAG in cancer-adjacent tissue 27. There was MSI at the D6S1703 microsatellite locus in cancer-adjacent tissue 28. There was no LOH or MSI in the CA340 microsatellite locus in the gastric cancer or adjacent tissues analyzed. Thus, the frequency of LOH or MSI at ZAC gene-associated microsatellite loci for all patients was 13.3% (4/30). The present study has demonstrated that LOH and MSI events may contribute to the downregulation of ZAC; however, it is unlikely to be the primary cause, as it was only identified in 13.3% of cases.

Lymphadenectomy: state of the art

The extent of lymphadenectomy in gastric cancer (GC) surgery has been for long time a matter of debate. Randomized trials performed in the West reported worse results of D2 dissection, in terms of postoperative complications and long-term survival benefit, than Eastern series and observational studies from specialized Western centers. However, long-term re-evaluation of such trials and in depth-analysis of other experiences demonstrated the potential benefit of D2 in reducing the probability of cancer-related death and the safety of this procedure when avoiding unnecessary spleno-pancreatectomy and in centers with ad adequate surgical volume. Nowadays, the D2 is considered the standard treatment in most guidelines all over the world. More limited procedures (D1, D1 plus) may be adequate in selected cases, and more extended dissections (D2 plus) could be indicated in advanced forms with high risk of metastases to distant nodes, but in specialized centers or in the setting of clinical studies. The integration with neoadjuvant therapies and multimodality approach could offer a chance of cure in groups of patients with poor results when approached with standard treatment.