Is microsatellite instability a prognostic marker in gastric cancer? A systematic review with meta-analysis

Adjuvant Chemotherapy for Gastric Cancer may Worsen Prognosis in Elderly Women: Retrospective Analysis of Individual Patient Data from the CLASSIC Study

PURPOSE

This research aimed to identify significant prognostic factors that interact with the treatment effect of capecitabine and oxaliplatin (CapeOX), based on individual patient data from the CLASSIC study (NCT00411229), which evaluated the efficacy of adjuvant chemotherapy for gastric cancer.

METHODS

Stepwise variable selection of prognostic factors was performed using the Cox proportional hazards model, with patient data from 519 CapeOX-treated and 514 untreated patients.

RESULTS

For all-cause mortality, older women (≥ 55 years) with a serum albumin level ≥ 4.0 g/dL were identified as significant prognostic factors interacting with CapeOX treatment, and unexpectedly, the treatment was associated with poor outcomes in this group. The prognostic significance of serum albumin levels was primarily attributed to the particularly poor survival outcomes observed in untreated patients with serum albumin < 4.0 g/dL. Tumor stage and lymph node status were prognostic factors that interacted with treatment for disease-free survival (DFS). The results showed that in patients with tumor stage (T) ≥ T3 and lymph node metastasis (N) < N2, improvement in DFS with CapeOX was not significant.

CONCLUSION

As this was a post-hoc analysis, the results should be interpreted as hypothesis-generating rather than definitive. Nevertheless, the findings suggest the need for a more detailed consideration of patient baseline characteristics when determining the adjuvant chemotherapy strategy for gastric cancer.

The relationship between the gastric cancer microbiome and clinicopathological factors: a metagenomic investigation from the 100,000 genomes project and The Cancer Genome Atlas

BACKGROUND

Findings from previous gastric cancer microbiome studies have been conflicting, potentially due to patient and/or tumor heterogeneity. The intratumoral gastric cancer microbiome and its relationship with clinicopathological variables have not yet been characterized in detail. We hypothesized that variation in gastric cancer microbial abundance, alpha diversity, and composition is related to clinicopathological characteristics.

METHODS

Metagenomic analysis of 529 GC samples was performed, including whole exome sequencing data from The Cancer Genome Atlas (TCGA) and whole genome sequencing data from the 100,000 Genomes Project. Microbial abundance, alpha diversity, and composition were compared across patient age, sex, tumor location, geographic origin, pathological depth of invasion, pathological lymph node status, histological phenotype, microsatellite instability status, and TCGA molecular subtype.

RESULTS

Gastric cancer microbiomes resembled previous results, with Prevotella, Selenomonas, Stomatobaculum, Streptococcus, Lactobacillus, and Lachnospiraceae commonly seen across both cohorts. Within the TCGA cohort, microbial abundance and alpha diversity were greater in gastric cancers with microsatellite instability, lower pathological depth of invasion, intestinal-type histology, and those originating from Asia. Microsatellite instability status was associated with microbiome composition in both cohorts. Sex and pathological depth of invasion were associated with microbiome composition in the TCGA cohort.

CONCLUSION

The intratumoral gastric cancer microbiome appears to differ according to clinicopathological factors. Certain clinicopathological factors associated with favourable outcomes in gastric cancer were observed to be associated with greater microbial abundance and diversity. This highlights the need for further work to understand the underlying biological mechanisms behind the observed microbiome differences and their potential clinical and therapeutic impact.

Staging accuracy in patients with clinical T2N0 gastric cancer: Implications for treatment sequencing

BACKGROUND

Patients with clinical T2N0 (cT2N0) gastric adenocarcinoma are recommended to undergo either perioperative chemotherapy or upfront resection. If T2N0 disease is pathologically confirmed, patients may be observed without chemotherapy. These guidelines create the possibility of both systemic therapy overuse and underuse depending on clinical staging accuracy. Our objectives were to define factors associated with upstaging after upfront resection and describe the association between postoperative chemotherapy and survival.

METHODS

Patients with cT2N0 gastric adenocarcinoma were identified using the National Cancer Database. Factors associated with upstaging were assessed by logistic regression. Survival was assessed using Kaplan-Meier and Cox proportional hazard analyses.

RESULTS

Of 4,076 patients undergoing upfront resection for cT2N0 gastric cancer, 1,933 (47.4%) were pathologically upstaged. Patients were more likely to be upstaged if they had >3.0-cm (adjusted odds ratio [aOR] 2.31, 95% confidence interval [CI] 1.97-2.70; P < .001) or poorly differentiated tumors (aOR 2.22, 95% CI 1.89-2.60; P < .001). Patients were less likely to be upstaged if they had distal tumors (aOR 0.77, 95% CI 0.64-0.93; P = .006). Of those pathologically upstaged (n = 1,933), 1,111 (57.4%) received adjuvant chemotherapy that was associated with improved survival (HR 0.55, 95% CI 0.47-0.63; P < .001). Among those not upstaged (n = 2,143), 247 (11.5%) received adjuvant chemotherapy that was not associated with improved survival (HR 0.92, 95% CI 0.70-1.21; P = .54).

CONCLUSIONS

Pathologic upstaging after upfront resection in patients with cT2N0 gastric cancer is associated with patient and tumor characteristics. Adjuvant chemotherapy is associated with improved survival only in the patients upstaged at surgery. An upfront surgical approach may be preferred in select patients, especially if avoiding chemotherapy is desired.

How do I treat dMMR/MSI gastro-oesophageal adenocarcinoma in 2025? A position paper from the EORTC-GITCG gastro-esophageal task force

In less than a decade, immune checkpoint inhibitors (ICIs) have transformed the management of mismatch repair-deficient (dMMR) and microsatellite instability-high (MSI) cancers. However, beyond colorectal cancer (CRC), much of the evidence is mostly derived from non-randomized phase II studies or post-hoc analyses of broader clinical trials. dMMR/MSI tumours represent a specific subgroup of gastro-esophageal adenocarcinomas (GEA), accounting for approximately 9 % of cases, with a higher prevalence in early-stage compared to advanced-stage disease and older female patients. These tumours are predominantly sporadic, often linked to MLH1 promoter methylation, and rarely exhibit HER2 overexpression/ERBB2 amplification or other oncogenic drivers. The treatment landscape for early stage dMMR/MSI GEA is likely to change substantially soon, as ICIs have shown high pathological complete response (pCR) rates in small phase II trials, raising questions on optimisation of neoadjuvant therapy, and paving the way for organ preservation. The standard of treatment for untreated patients with advanced dMMR/MSI GEA is chemotherapy + ICI irrespectively of PDL-1 status. However, the role of chemotherapy-free regimen consisting of CTLA-4 plus PD-1 inhibitors remains undetermined. This review addresses these and other emerging questions, offering expert opinions and insights into the future therapeutic landscape for dMMR/MSI GEA.

The prognostic and immunomodulatory role of the MMR system in patients with stomach adenocarcinoma

The mismatch repair (MMR) system plays a crucial role in the maintenance of DNA replication fidelity and genomic stability. The clinical value of the MMR molecular marker as an immunotherapy for advanced solid tumors has been documented. However, this therapy is not effective in some patients. This study aimed to develop an MMR-related molecular prognostic model for identifying appropriate populations of stomach adenocarcinoma (STAD) for better treatment outcome. The MMR genes expression data were downloaded from TCGA and CCLE databases. The expression of four MMR genes, construction of a prognostic risk model, and assessment of immune infiltration in STAD were performed using Xiantao online tool. GEPIA2 was used to explore the association of MMR genes expression with clinical stage and overall survival. The frequency and prognostic value of MMR genes in STAD were conducted on the cBioPortal. The MLH1 co-expression network was established based on the LinkedOmics database. This study found that the expression of MSH2, MSH6 and PMS2 was up-regulated in STAD tissues. Moreover, differential MMR genetic expression levels were not significantly correlated with the clinical stages of STAD. Besides, no significant difference in PFS or OS was observed in STAD patients with or without MMR genetic alteration. Moreover, MLH1 and MSH2 were used to establish a prognostic risk model. The immune infiltration levels of most immune cells were upregulated in the high-risk group with elevated expression of PDCD1 and low TMB score. Finally, we found that MLH1 was an independent predictor of STAD prognosis among the four MMR genes. An MMR-related prognostic model for STAD was constructed based on genes. This model provides a new therapeutic concept for the diagnosis and treatment of STAD.

High levels of tumor cell-intrinsic STING signaling are associated with increased infiltration of CD8+ T cells in dMMR/MSI-H gastric cancer

Mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) gastric cancer (GC) exhibits an immune-active tumor microenvironment (TME) compared to MMR proficient (pMMR)/microsatellite stable/Epstein-Barr virus-negative [EBV (-)] GC. The tumor cell-intrinsic cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway has been considered a key regulator of immune cell activation in the TME. However, its significance in regulating the immune-active TME in dMMR/MSI-H GC remains unclear. Here, we demonstrated that tumor cell-intrinsic cGAS-STING was highly expressed in dMMR GC compared to pMMR/EBV (-) GC. The expression of tumor cell-intrinsic STING was significantly and positively associated with the number of CD8+ tumor-infiltrating lymphocytes in GC. Analysis of TCGA datasets revealed that the expression of interferon-stimulated genes and STING downstream T-cell attracting chemokines was significantly higher in MSI-H GC compared to other subtypes of GC with EBV (-). These results suggest that tumor cell-intrinsic STING signaling plays a key role in activating immune cells in the dMMR/MSI-H GC TME and might serve as a novel biomarker predicting the efficacy of immunotherapy for GC treatment.

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.

Prognostic value of mismatch repair deficiency in patients receiving first-line fluoropyrimidine plus platinum for metastatic, recurrent, or unresectable gastric cancer

BACKGROUND

We examined the impact of mismatch repair (MMR) status on efficacy of first-line fluoropyrimidine plus platinum (FP) chemotherapy in patients with HER2-negative metastatic, recurrent, or unresectable gastric cancer (mGC).

METHODS

Patients with mGC receiving first-line FP between 2015 and 2018 at Asan Medical Center, Korea, were reviewed. We evaluated the clinical characteristics and the efficacy of chemotherapy according to MMR status in patients with available immunohistochemistry results.

RESULTS

Of 895 patients, we analyzed 543 with available MMR protein expression results, and deficient MMR (dMMR) was detected in 4.4% (n = 24). Patients with dMMR exhibited a significantly higher median age than those with proficient MMR (pMMR) (64 vs. 58 years, p = 0.044). No signet ring cell carcinoma (SRCC) was detected among dMMR tumors, whereas SRCC was found in 17.5% of pMMR. Objective response rate was 27.3% in dMMR and 34.3% in pMMR (p = 0.556). No difference in progression-free survival was noted between patients with dMMR and pMMR (median, 5.6 vs. 5.8 months, p = 0.266). Patients with dMMR tended to have better overall survival than those with pMMR although this difference was not statistically significant (median, 17.9 vs. 12.2 months, p = 0.183).

CONCLUSIONS

Efficacy of first-line FP was not different by MMR status in mGC patients.

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.

Molecular classification and intratumoral heterogeneity of gastric adenocarcinoma

Gastric cancers frequently harbor striking histological complexity and diversity between lesions as well as within single lesions, known as inter- and intratumoral heterogeneity, respectively. The latest World Health Organization Classification of Tumors designated more than 30 histological subtypes for gastric epithelial tumors, assigning 12 subtypes for gastric adenocarcinoma (GAD). Meanwhile, recent advances in genome-wide analyses have provided molecular aspects to the histological classification of GAD, and consequently revealed different molecular traits underlying these histological subtypes. Moreover, accumulating knowledge of comprehensive molecular profiles has led to establishing molecular classifications of GAD, which are often associated with clinical biomarkers for therapeutics and prognosis. However, most of our knowledge of GAD molecular profiles is based on inter-tumoral heterogeneity, and the molecular profiles underlying intratumoral heterogeneity are yet to be determined. In this review, recently established molecular classifications of GAD are introduced in the aspect of pathological diagnosis and are discussed in the context of intratumoral heterogeneity.

Role of microsatellite instability and HER2 positivity in locally advanced esophago-gastric cancer patients treated with peri-operative chemotherapy

PURPOSE

Neoadjuvant chemotherapy (NAC) significantly improved the prognosis of patients with locally advanced gastric cancer (LAGC). Several biomarkers, including HER2 and MMR/MSI are crucial for treatment decisions in the advanced stage but, currently, no biomarkers can guide the choice of NAC in clinical practice. Our aim was to evaluate the role of MSI and HER2 status on clinical outcomes.

METHODS

We retrospectively collected LAGC patients treated with NAC and surgery +/- adjuvant chemotherapy from 2006 to 2018. HER2 and MSI were assessed on endoscopic and surgical samples. Pathologic complete response (pCR) rate, overall survival (OS), and event-free survival (EFS) were estimated and evaluated for association with downstaging and MSI.

RESULTS

We included 76 patients, 8% were classified as MSI-H, entirely consistent between endoscopic and surgical samples. Six percent of patients were HER2 positive on endoscopic and 4% on surgical samples. Tumor downstaging was observed in 52.5% of cases, with three pCR (5.1%), none in MSI-H cancers. According to MSI status, event-free survival (EFS) and overall survival (OS) were higher for MSI-H patients to MSS [EFS not reached vs 30.0 months, p = 0.08; OS not reached vs 39.6 months, p = 0.10].

CONCLUSION

Our work confirms the positive prognostic effect of MSI-H in the curative setting of LAGC, not correlated with pathologic tumor downstaging. Prospective ad-hoc trial and tumor molecular profiling are eagerly needed.

Japanese Society of Medical Oncology/Japan Society of Clinical Oncology/Japanese Society of Pediatric Hematology/Oncology-led clinical recommendations on the diagnosis and use of immunotherapy in patients with DNA mismatch repair deficient (dMMR) tumors, third edition

BACKGROUND

Clinical trials have reported the efficacy of immune checkpoint inhibitors in the treatment of mismatch repair-deficient (dMMR) advanced solid tumors. The accumulated evidence of tumor agnostic agent has been made since PD-1 inhibitor was approved and used in clinical practice. Therefore, we have revised the guideline "Japan Society of Clinical Oncology provisional clinical opinion for the diagnosis and use of immunotherapy in patients with deficient DNA mismatch repair tumors, cooperated by Japanese Society of Medical Oncology, First Edition".

METHODS

Clinical questions regarding medical care were formulated for patients with dMMR advanced solid tumors. Relevant publications were searched by PubMed and Cochrane Database. Critical publications and conference reports were added manually. Systematic reviews were performed for each clinical question for the purpose of developing clinical recommendations. The committee members identified by Japan Society of Clinical Oncology (JSCO), Japanese Society of Medical Oncology (JSMO), and Japanese society of pediatric hematology/oncology (JSPHO) voted to determine the level of each recommendation considering the strength of evidence, expected risks and benefits to patients, and other related factors. Thereafter, a peer review by experts nominated from JSCO, JSMO, and JSPHO and the public comments among all societies' members were done.

RESULTS

The current guideline describes two clinical questions and eight recommendations for whom, when, and how MMR status should be tested.

CONCLUSION

In this guideline, the committee proposed eight recommendations for performing MMR testing properly to select patients who are likely to benefit from immunotherapy.

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.

Impact of Programmed Death-Ligand 1 Expression on Mismatch Repair Deficiency and Epstein-Barr Virus Status on Survival Outcomes in Patients with Stage II/III Gastric Cancer After Surgery

BACKGROUND

The aim of this study was to investigate the prognostic impact of mismatch repair (MMR) status, programmed death-ligand 1 (PD-L1) expression, and Epstein-Barr virus (EBV) status in stage II/III gastric cancer after surgery.

METHODS

This study included 679 patients diagnosed with pathological stage II/III gastric cancer who underwent curative gastrectomy followed by adjuvant chemotherapy (AC) or observation between 2007 and 2015. Clinical outcomes were retrospectively reviewed and compared with stratification by AC and other clinicopathological factors.

RESULTS

Patients were divided into AC (n = 484) or surgery alone (SA; n = 195) groups and were further stratified by MMR and EBV status: MMR-deficient (DMMR) and MMR-proficient (PMMR) groups. Comparing the AC-DMMR group versus the AC-PMMR group, 5-year overall survival was 92.0% versus 74.0% (log-rank p < 0.01), and comparing the SA-DMMR group versus the SA-PMMR group, 5-year overall survival was 71.1% versus 73.7% (log-rank p = 0.89). DMMR (hazard ratio 0.25, 95% confidence interval 0.07-0.81) was identified as an independent prognostic factor in the AC group but not in the SA group. In the subgroup analysis, PD-L1-negative patients among the EBV-positive patients or in the DMMR group had a poor prognosis in both the AC and SA groups. The prognosis of the PMMR and EBV-negative patients was similar regardless of PD-L1 expression.

CONCLUSIONS

DMMR was associated with a favorable prognosis in stage II/III gastric cancer after surgery and adjuvant therapy. PD-L1 expression may affect the prognosis of DMMR and EBV-positive gastric cancer.

Identification of RNF150 as the hub gene associated with microsatellite instability in gastric cancer

Gastric cancer (GC) is a common digestive tract malignancy with the sixth global incidence and third cancer-related deaths, respectively. Microsatellite instability (MSI), accounting for one of the molecular subtypes of GC, plays an important role in GC and is affected by a sophisticated network of gene interactions. In this study, we aimed to explore the expression pattern and clinical performance of MSI related gene in GC patients. Weighted gene co-expression network analysis (WGCNA) was exploited to single out the vital module and core genes in TCGA database. We applied the protein-protein interaction (PPI) and survival analysis to propose and confirm RNF150 as the hub gene in GC. Finally, we utilized immunohistochemistry (IHC) and reverse transcription-polymerase chain reaction (RT-PCR) to explore the expression pattern of RNF150 in GC patients. With the highest weight correlation and standard correlation, RNF150 was selected as the hub gene for following validation. In validation, data obtained from the test sets showed a lower expression of RNF150 in MSI GC compared to microsatellite stability (MSS) GC. Moreover, survival analysis shows that MSI GC patients with a lower RNF150 expression level displayed the longer OS time. Compared to the expression in normal gastric tissues, the protein level of RNF150 was virtually up-regulated in ten cases of GC tissues. Furthermore, RNF150 protein level was decreased in MSI GC samples compared to MSS GC samples. When validated the mRNA expression with RT-PCR in fresh GC tissues, we also found the similar trend. RNF150 was identified as a novel MSI-related gene in GC. It is expected to be an auspicious prognostic biomarker for GC patients.

Impact of mismatch repair deficiency on tumour regression grade after neoadjuvant chemotherapy in localized gastroesophageal adenocarcinoma

BACKGROUND

The use of neoadjuvant chemotherapy (NAC) in patients with mismatch repair (MMR) deficient (dMMR) localized gastric and oeso-gastric junction (OGJ) adenocarcinoma is subject of debate. Histological response assessment might help to better evaluate the impact of dMMR on response to NAC.

METHODS

Patients with localized gastric/OGJ adenocarcinoma resected after NAC were retrospectively identified. MMR protein expression status was assessed by immunohistochemistry. The primary objective was the frequency of histological responders to NAC defined by tumour regression grade (TRG) using Mandard's (TRG1-2) and Becker's (TRG1) classifications, according to the MMR status.

RESULTS

In total, 247 patients with 43 dMMR and 204 pMMR gastric/OGJ adenocarcinoma were identified. Among dMMR tumours, 18 (42%) arose from the OGJ. Histological response (Becker TRG1-2) was observed for 28% and 35% of dMMR and pMMR tumours, respectively (p = 0.35). Similar results were observed with Mandard classification. With a median follow-up of 37.5 months, median disease-free and overall survival were not reached for the dMMR group.

CONCLUSION

Histological response after NAC in patients with localized dMMR gastric/OGJ adenocarcinoma is not statistically different to those with pMMR tumours. This study provides additional data for the discussion about avoiding NAC in patients with dMMR gastric/OGJ adenocarcinomas.

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.

The integrated landscape of eRNA in gastric cancer reveals distinct immune subtypes with prognostic and therapeutic relevance

The comprehensive regulation effect of eRNA on tumor immune cell infiltration and the outcome remains obscure. We comprehensively identify the eRNA-mediated immune infiltration patterns of gastric cancer (GC) samples. We creatively proposed a random forest machine-learning (ML) algorithm to map eRNA to mRNA expression patterns. The eRNA score was constructed using principal component analysis algorithms and validated in an independent cohort. Three subtypes with distinct eRNA expression patterns were determined in GC. There were significant differences between the three subtypes in the overall survival rate, immune cell infiltration characteristics, and immunotherapy response indicators. The patients in the high eRNA score group have a higher overall survival rate and might benefit from immunotherapy. This work revealed that eRNA regulation might be a new prognostic index and might offer a potential biomarker in the response of immunotherapy. Evaluating the eRNA regulation manner of GC will contribute to guiding more effective immunotherapy strategies.

Immunotherapy in MSI/dMMR tumors in the perioperative setting: The IMHOTEP trial

BACKGROUND

Immune checkpoint inhibitors (ICI) targeting Programmed death-1 (PD-1) have shown their efficacy in advanced MSI/dMMR (microsatellite instability/deficient mismatch repair) tumors. The MSI/dMMR status predicts clinical response to ICI. The promising results evaluating ICI in localized MSI/dMMR tumors in neoadjuvant setting need to be confirmed in MSI/dMMR solid tumors. The aim of the IMHOTEP trial is to assess the efficacy of neoadjuvant anti-PD-1 treatment in MSI/dMMR tumors regarding the pathological complete response rate.

METHODS

This study is a prospective, multicenter, phase II study including 120 patients with localized MSI/dMMR carcinomas suitable for curative surgery. A single dose of pembrolizumab will be administered before the surgery planned 6 weeks later. Primary objective is to evaluate the efficacy of neoadjuvant pembrolizumab according to pathological complete tumor response. Secondary objectives are to assess safety, recurrence-free survival and overall survival. Ancillary studies will assess molecular and immunological biomarkers predicting response/resistance to ICI. First patient was enrolled in December 2021.

DISCUSSION

The IMHOTEP trial will be one of the first clinical trial investigating perioperative ICI in localized MSI/dMMR in a tumor agnostic setting. Assessing neoadjuvant anti-PD-1 is mandatory to improve MSI/dMMR patient's outcomes. The translational program will explore potential biomarker to improve our understanding of immune escape and response in this ICI neoadjuvant setting.

Traitements péri-opératoires des adénocarcinomes œsogastriques localisés

Gastric cancer is the 6th most common cancer in the world. Gastric adenocarcinomas can be divided into two groups: gastroesophageal junction adenocarcinomas and distal gastric adenocarcinomas, with different risk factors and potentially different therapeutic strategies. Therapeutic strategy for esogastric adenocarcinoma is multimodal. Gastric adenocarcinomas are managed with surgery and peri-operative chemotherapy. Gastroesophageal junction adenocarcinomas can either be treated surgically after neoadjuvant chemoradiotherapy or in the same way than gastric adenocarcinomas. There is currently no evidence of superiority of either treatment strategy. Recently, nivolumab has been validated as an adjuvant therapy for patients with esophageal cancer who received preoperative chemoradiotherapy and had residual tumor on the surgical specimen. In the absence of preoperative treatment, adjuvant chemoradiotherapy or chemotherapy should be discussed on a patient-by-patient basis. Currently, there is not indication for targeted therapies, nor for adapting postoperative treatment according to the response to preoperative treatment. The only validated indication for immunotherapy is as adjuvant treatment of esophageal cancer, but many studies are ongoing and may change practices in the future. The objective of this review is to synthesize the literature concerning the management of localized esogastric adenocarcinoma.

Ovarian Endometrioid and Clear Cell Carcinomas with Low Prevalence of Microsatellite Instability: A Unique Subset of Ovarian Carcinomas Could Benefit from Combination Therapy with Immune Checkpoint Inhibitors and Other Anticancer Agents

Ovarian cancer has the highest mortality rate among all gynecological malignancies; therefore, a novel treatment strategy is needed urgently. Utilizing immune checkpoint inhibitors has been considered for microsatellite instability (MSI)-high (MSI-H) tumors. However, the prevalence of MSI-H tumors in ovarian endometrioid and clear cell carcinomas remains unclear. Here, polymerase chain reaction was used to analyze 91 cases of ovarian endometrioid and clear cell carcinomas for the MSI status and the relationship between MSI-H, immune checkpoint molecules, and clinicopathological factors (including patient survival). Only 5 of 91 (5%) cases were MSI-H endometrioid carcinomas. In these cases, CD-8 expression was significantly higher (p = 0.026), confirming an enhanced immune response. From the survival curve, no statistical correlations were found between the MSI-H group and the microsatellite stable (MSS) group; however, the MSS group trended towards better progression-free survival than the MSI-H group (p = 0.056). Patients with PD-L1 expression had shorter overall survival than those without (p = 0.022). Thus, MSI-H is a rare event and not a favorable prognostic factor in ovarian endometrioid and clear cell carcinomas. Thus, to improve the prognosis of ovarian endometrioid carcinoma and clear cell carcinomas, a combination therapy of immune checkpoint inhibitors and other molecular targeted therapies may be required.

Diverse 'just-right' levels of chromosomal instability and their clinical implications in neoadjuvant treated gastric cancer

BACKGROUND

The Cancer Genome Atlas (TCGA) consortium described EBV positivity(+), high microsatellite instability (MSI-H), genomic stability (GS) and chromosomal instability (CIN) as molecular subtypes in gastric carcinomas (GC). We investigated the predictive and prognostic value of these subtypes with emphasis on CIN in the context of neoadjuvant chemotherapy (CTx) in GC.

METHODS

TCGA subgroups were determined for 612 resected adenocarcinomas of the stomach and gastro-oesophageal junction (291 without, 321 with CTx) and 143 biopsies before CTx. EBV and MSI-H were analysed by standard assays. CIN was detected by multiplex PCRs analysing 22 microsatellite markers. Besides the TCGA classification, CIN was divided into four CIN-subgroups: low, moderate, substantial, high. Mutation profiling was performed for 52 tumours by next-generation sequencing.

RESULTS

EBV(+) (HR, 0.48; 95% CI, 0.23-1.02), MSI-H (HR, 0.56; 95% CI, 0.35-0.89) and GS (HR, 0.72; 95% CI, 0.45-1.13) were associated with increased survival compared to CIN in the resected tumours. Considering the extended CIN-classification, CIN-substantial was a negative prognostic factor in uni- and multivariable analysis in resected tumours with CTx (each p < 0.05). In biopsies before CTx, CIN-high predicted tumour regression (p = 0.026), but was not prognostically relevant.

CONCLUSION

A refined CIN classification reveals tumours with different biological characteristics and potential clinical implications.

The Impact of Mismatch Repair Status on Prognosis of Patients With Gastric Cancer: A Multicenter Analysis

BACKGROUND

The clinical role of deficient DNA mismatch repair (dMMR)/microsatellite instability-high (MSI-H) in gastric cancer (GC) is still controversial. We aimed to analyze the relationship between dMMR/MSI-H and clinicopathological features along with survival.

METHODS

Patients who were diagnosed with GC at the three big cancer centers in China from 2015 to 2020 were evaluated retrospectively. MMR/MSI status was assessed using immunohistochemistry/PCR. Clinical and pathological data were collected from the medical record system.

RESULTS

A total of 196 patients with dMMR/MSI-H status were enrolled for analysis. The prevalence of MSI-H/dMMR in GC was 6.6%. Another 694 proficient MMR (pMMR) GC patients were enrolled for comparison. Compared with pMMR patients, dMMR/MSI-H patients were associated with older age, female predominance, distal location in the stomach, earlier TNM stage, intestinal subtype, better differentiation, and more negative HER2 status. The median overall survival (OS) of the dMMR/MSI-H group was better than that of the pMMR/microsatellite stability (MSS) group (not reached vs. 53.9 months, p = 0.014). Adjuvant chemotherapy had no impact in both disease-free survival (DFS) and OS of dMMR/MSI-H patients (p = 0.135 and 0.818, respectively). dMMR/MSI-H patients had poorer response and progression-free survival (PFS) of first-line chemotherapy, though they were statistically significant (p = 0.361 and 0.124, respectively).

CONCLUSIONS

dMMR/MSI-H GC patients have specific clinicopathological characteristics and better prognosis than pMMR patients.

Prognostic influence of microsatellite alterations of muscle-invasive bladder cancer treated with radical cystectomy

OBJECTIVE

To examine the prognostic effect of microsatellite instability (MSI) and loss of heterozygosity (LOH) on cancer-specific survival (CSS) in patients with muscle-invasive bladder cancer (MIBC).

PATIENTS AND METHODS

The liquid nitrogen-preserved specimens of 220 patients between March 2009 and December 2012 were analyzed for the presence of MSI and LOH in 12 loci (ACTBP2, D16S310, D16S476, D18S51, D4S243, D9S162, D9S171, D9S747, FGA, INF-α, MBP, MJD) using polymerase chain reaction. MSI was defined as MSI-stable, MSI-Low, or MSI-High if instability was detected in 0, 1, or 2 or more of the examined markers, respectively. The association between MSI-High and LOH and CSS was analyzed using uni- and multivariate analyses and the degree of agreement between tumor and urine samples were determined.

RESULTS

MSI were found in 1030 (39%) and 1148 (43.5%) in tumor and urine specimens, respectively (Kappa = 0.77). On the other hand, LOH was found in 163 (6.2%) of tumor tissues and 44 (1.7%) in urine specimens (Kappa = 0.34). Microsatellite alterations were significantly associated with worse CSS at 1- and 5-year in tumor tissue (95% and 83.7% vs. 65.8% and 3.5%, respectively; P < 0.001) and in urine sample (90% and 64% vs. 46.5% and 9.3%, respectively; P < 0.001). MSI and/or LOH was an independent predictor of CSS (HR: 9.8; 95%CI: 5.1-18.9; P < 0.001).

CONCLUSIONS

Microsatellite alterations were potentially an independent predictor of CSS in patients with MIBC. The agreement was good between tumor and urine MSI but weak for LOH.

Prognostic and predictive value of mismatch repair deficiency in gastric and gastroesophageal junction adenocarcinoma patients receiving neoadjuvant or adjuvant chemotherapy

BACKGROUND AND OBJECTIVES

Evidence is inconclusive regarding the prognostic significance of deficient DNA mismatch repair (dMMR) in gastric and gastroesophageal junction (GEJ) adenocarcinoma patients receiving chemotherapy. We aim to explore such associations with a large cohort.

METHODS

We retrospectively identified a consecutive cohort of patients who had histology proven gastric or GEJ adenocarcinoma and received neoadjuvant chemotherapy plus surgery or upfront surgery plus adjuvant chemotherapy. MMR status was assessed by immunohistochemistry staining on surgical specimen. The association of MMR status with tumor regression grade (TRG), overall survival (OS), and disease-free survival (DFS) were analyzed.

RESULTS

In total, 1568 patients received neoadjuvant or adjuvant chemotherapy, of which 128 (8.2%) had dMMR tumors. No significant difference was found in the frequencies of TRG categories between proficient MMR (pMMR) and dMMR tumors (p = .62). Among patients receiving neoadjuvant chemotherapy, dMMR status was associated with better OS (log-rank p = .044) and DFS (log-rank p = .022) in the univariate analysis; this association became nonsignificant after adjusting for pathologic stages and other prognostic factors. Similar results were found for patients receiving adjuvant chemotherapy.

CONCLUSIONS

dMMR status was not significantly associated with OS and DFS among gastric and GEJ adenocarcinoma patients with neoadjuvant and adjuvant platinum and fluorouracil-based chemotherapy.

Combined Therapy of Locally Advanced Oesophageal and Gastro-Oesophageal Junction Adenocarcinomas: State of the Art and Aspects of Predictive Factors

The following main treatment approaches are currently used in locally advanced adenocarcinomas of the oesophagus and gastrooesophageal junction (GOJ): preoperative chemoradiotherapy and surgery, and perioperative chemotherapy and surgery. While preoperative chemoradiotherapy is used primarily in oesophageal tumours, perioperative chemotherapy is the treatment of choice in Western countries for gastric cancer. The optimal treatment strategy for GOJ adenocarcinoma is still not clear. In comparison to other malignancies, biomarkers are used as predictive factors in distal oesophageal and GOJ adenocarcinomas in a very limited way, and moreover, only in metastatic stages (e.g., HER2 status, or microsatellite instability status). The aim of the article is to provide an overview of current treatment options in locally advanced adenocarcinomas of oesophagus and GOJ based on the latest evidence, including the possible potential of predictive biomarkers in optimizing treatment.

Advances in immune therapies for the treatment of microsatellite instability‑high/deficient mismatch repair metastatic colorectal cancer (Review)

Microsatellite instability-high/deficient mismatch repair colorectal cancer (MSI-H/dMMR CRC) is a molecular subtype characterized by high-frequency mutations within DNA mismatch repair genes. Defects in the DNA mismatch repair machinery lead to subsequent frame-shift mutations, resulting in the generation of frame-shift peptides that serve as neoantigens. This has translated into exquisite sensitivity to immune checkpoint inhibitors (ICIs) and a significant clinical benefit from immune therapies in this patient population. The present article provides a comprehensive review of the advances in the field of immune therapies for MSI-H/dMMR metastatic CRC, with a focus on the major randomized clinical trials that led to Food and Drug Administration approval of specific ICIs for this population, a detailed review of the molecular background responsible for tumor response, as well as the mechanisms of resistance to ICI therapy. Finally, ongoing investigations of other immunotherapeutic strategies to address and overcome the challenges that currently limit response and long-term response to ICIs were presented.

Microsatellite Instability Analysis in Gastric Carcinomas of Moroccan Patients

Aim: To investigate correlations between microsatellite instability (MSI) and the phenotype, clinicopathological features, and overall survival (OS) in Moroccan gastric cancer (GC) patients. We evaluated the mutation frequency of 22 MSI-target genes in MSI-positive tumors. Materials and Methods: MSI evaluation were performed for 97 gastric tumors by multiplex polymerase chain reaction (PCR) using a panel of five quasimonomorphic mononucleotide repeat markers (NR27, NR21, NR24, BAT25, and BAT26). The mutation profiles of 22 MSI-target genes were assessed by multiplex PCR and genotyping. Kaplan-Meier curves, the log-rank test, and the Cox proportional hazard regression model were used to conduct survival analyses. Results: Microsatellite stable (MSS) status was observed in 77/97 (79.4%) gastric cancer samples, MSI-Low in 7 (7.2%) samples, and MSI-High (MSI-H) in 13 (13.4%) cases. The MSI-H phenotype was significantly associated with older age (p = 0.004), tumor location (p < 0.001), and intestinal-type of Lauren classification (p < 0.001). Among the 22 MSI target genes analyzed, the most frequently altered genes were HSP110 (84.6%), EGFR (30.8%), BRCA2 (23.1%), MRE11 (23.1%), and MSH3 (23.1%). Multivariate analysis revealed the MSS phenotype (Hazard ratio, 0.23; 95% confidence interval, 0.7-7.4; p = 0.014) as an independent indicator of poor prognosis in our population. Conclusions: This study is the first analysis of MSI in Moroccan GC patients. MSI-H GCs have distinct clinicopathological features and an improved OS. We have identified candidate target genes altered in MSI-positive tumors with potential clinical implications. These findings can guide immunotherapy designed for Moroccan GC patients.

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.

Characterization and clinical evaluation of microsatellite instability and loss of heterozygosity in tumor-related genes in gastric cancer

Microsatellite instability (MSI) detection is widely used in the diagnosis and prognosis evaluation of colorectal cancer. However, for gastric cancer (GC), there is no standard panel of microsatellites (MSs) used in clinical guidance. The present study aimed to identify useful predictors of the clinical features and for the prognosis of GC, based on an investigation of MSI and loss of heterozygosity (LOH) in tumor-related genes. First, from 20 tumor-related genes which were proven to be important to the development of GC, 91 MSs were identified, and PCR amplification, short tandem repeat scanning analysis and TA clone sequencing were used to analyze MSI and LOH in the first set of 90 GC samples. Subsequently, the same method was used to detect the MSI/LOH of the optimized loci in the second set of 136 GC samples. MSI/LOH in the mismatch repair genes was highly consistent with that in oncogenes and tumor suppressor genes, respectively. The length of the core sequence was a main factor for the MSI/LOH rate. The MSI of 12 single loci was significantly associated with lymph node metastasis. The MSI in TP53-1 and the LOH in MGMT-10 were significantly associated with early stages of tumor infiltration depth. The LOH in MGMT-10, PTN-2 and MCC-17 was significantly associated with TNM stage. The LOH in TP53-1 and ERBB2-12 was associated with adenocarcinoma. The MSI/LOH in 6 single loci of 5 tumor-related genes was associated with poor prognosis of GC. The present study demonstrated that the MSI/LOH of loci in tumor-associated genes was associated with 4 clinicopathological characteristics and outcomes of GC. These results may provide potential specific biomarkers for the clinical prediction and treatment of GC.

Impact of microsatellite status on negative lymph node count and prognostic relevance after curative gastrectomy

BACKGROUND AND OBJECTIVES

The impact of microsatellite instability-high (MSI-H) phenotype on lymph node yield after lymphadenectomy has never been discussed in gastric cancer (GC). In this study, we aimed to assess the association of microsatellite status with negative lymph node count (NLNC) as well as its prognostic value.

METHODS

We retrospectively analyzed 1491 GC patients and divided them into two groups: MSI-H_GC (n = 141 [9.5%]) and microsatellite stability (MSS_GC ) (n = 1350 [90.5%]). The NLNC and survival data were compared between the two groups. The log odds of positive lymph nodes (LNs) to negative LNs and the target lymph node examined threshold (TLNT) were calculated in both groups.

RESULTS

A statistically significant difference was found in median NLNC (26 vs. 23, p < .001) between MSI-H_GC and MSS_GC patients. MSI status was an independent factor for NLNC (p < .001). NLNC showed positive prognostic value for cases with metastatic lymph node (LN₊ ) in both MSI-H_GC and MSS_GC groups. The TLNT_(90%) for MSI-H_GC and MSS_GC were 33 and 26, respectively.

CONCLUSIONS

MSI-H_GC was associated with higher NLNC in GC patients and this was independent of the presence of LN₊ . However, more LNs are needed during pathological examination to capture LN₊ cases in MSI-H_GC.

Prognostic impact of microsatellite instability in gastric cancer

Gastric cancer is a common and deadly cancer. Several factors are associated with its prognosis; however, controversy exists about the role of microsatellite instability (MSI). We aimed to determine the 5-year overall survival (OS) of MSI in gastric adenocarcinoma. A cross-sectional study was carried out on gastric adenocarcinoma in clinical stages I to III treated with D2 gastrectomy between 2010-2013. MSI was demonstrated by immunohistochemistry. We performed a survival analysis comparing cases with and without MSI. From 102 cases, 9.8% showed MSI. The median age was 63 years (range 33-91 years), and 57.8% were men. The more prevalent site of occurrence was the antrum (46.1%), 78.5% of the cases presented in stage III, 47.1% were of the diffuse type, 45.1% were of an intestinal type, and 7.8% were mixed. MSI cases were associated with lower clinical stages (stages I-II) and with better 5-year OS (100 vs. 47 months, p = 0.017). In a multivariate analysis, MSI was independently associated with better survival (HR = 0.209, 95% CI: 0.046-0.945, p = 0.042). MSI gastric cancers presented in early clinical stages and had favourable prognosis compared with non-MSI cancers.

Panel of significant risk factors predicts early stage gastric cancer and indication of poor prognostic association with pathogens and microsatellite stability

BACKGROUND

There are very few studies covering the epidemiological risk factors associated with Epstein Barr Virus (EBV) and Microsatellite stability for Gastric Cancer (GC) cases. Early diagnosis of GC through epidemiological risk factors is very necessary for the clinical assessment of GC. The aim of this study was to find out the major risk factors to predict GC in early stage and the impact of pathogen infection and MSI on survival rate of patients. GC samples were screened for Helicobacter pylori, Epstein Barr Virus, and Mismatch repair (MMR) gene status (microsatellite stable or instable). Chi-square and logistic regression analysis of Odd ratio and 95% confidence interval (OR, 95% CI) were performed to find out the association between epidemiological factors and the risk of gastric cancer. The pathogen and MMR gene status were analysed to predict their effect on overall survival and the risk score and hazard ratio was calculated for prognostic assessment.

RESULTS

Excess body weight, consumption of extra salt, smoked food, alcohol, and smoking were the major risk factors for GC development. This study achieved a high area under the curve (AUC 0.94) for the probable GC patients in early-stage using the five-panel epidemiological risk factors. H. pylori infected cases were significant with smoked food, while EBV was found to be associated with tuibur intake and smoked food. In overall survival analysis EBV infected and microsatellite stable (HR: 1.32 and 1.34 respectively) GC cases were showing poor prognosis.

CONCLUSION

This study might provide new opportunities for personalized treatment options using this epidemiological factor risk score and clinicopathological factors assessment for early detection and prognosis in high-risk GC populations.

Management of Non-Colorectal Digestive Cancers with Microsatellite Instability

Microsatellite instability (MSI) is a hallmark of genetic predisposition to DNA damage. It arises from either germline or somatic events leading to impaired function of the mismatch repair system. It can be detected via genetic sequencing or immunohistochemistry with relatively high concordance rates. The presence of MSI in a tumor reflects a high neoantigen load and predicts favorable treatment response to immune checkpoint inhibitors (ICIs). In gastrointestinal cancers, MSI is a predictive biomarker for ICIs with potential prognostic impact but its clinical utility varies widely depending on tumor type. This may be explained by the complexity of tumor microenvironment as highlighted by recent translational studies. In this review, we will discuss the predictive and prognostic value of MSI status in non-colorectal cancers of the digestive system, important clinical trials involving ICIs and potential strategies to overcome resistance to immunotherapy.

Protein expression-based classification of gastric cancer by immunohistochemistry of tissue microarray

Recently, the Cancer Genome Atlas and Asian Cancer Research Group propose two new classifications system of gastric cancer by using multi-platforms of molecular analyses. However, these highly complicated and cost technologies have not yet been translated into full clinical utility. In addition, the clinicians are expected to gain more guidance of treatment for different molecular subtypes. In this study, we developed a panel of gastric cancer patients in population from Southern China using commercially accessible TMA and immunohistochemical technology. A cohort of 259 GC patients was classified into 4 subtypes on the basis of expression of mismatch repair proteins (PMS2, MLH1, MSH2, and MSH6), E-cadherin and p21 protein. We observed that the subtypes presented distinct prognosis. dMMR-like subtype was associated with the best prognosis, and E-cadherin-a subtype was associated with the worst prognosis. Patients with p21-High and p21-Ligh subtypes had intermediate overall survival. In multivariate analysis, the dMMR-like subtype remained an independent prediction power for overall survival in the model. We described a molecular classification of gastric cancers using clinically applicable assay. The biological relevance of the four subtypes was illustrated by significant differences in prognosis. Our molecular classification provided an effective and inexpensive screening tool for improving prognostic models. Nevertheless, our study should be considered preliminary and carries a limited predictive value as a single-center retrospective study.

Clinicopathologic Characteristics and Long-Term Outcome of Gastric Cancer Patients with Family History: Seven-Year Follow-Up Study for Korean Health Check-Up Subjects

Methods

This study was conducted on asymptomatic healthy individuals who underwent upper gastrointestinal endoscopy for the purpose of GC screening. Patients who were diagnosed with GC between October 2003 and December 2013 at Seoul National University Hospital Healthcare System Gangnam Center were identified. Demographic and clinicopathologic characteristics were compared between the groups with and without FHx of GC. Overall survival (OS) and recurrence-free survival (RFS) were assessed as primary outcomes.

Results

There were no significant differences in tumor characteristics according to FHx of GC. However, preexisting adenoma was more frequent in patients with FHx than in those without FHx (14.5% vs. 6.3%, p = 0.035). The proportion of patients with microsatellite instability (MSI) was also higher in groups with FHx of GC (43.2% vs. 13.2%, p = 0.006). Helicobacter pylori infection rates of patients with FHx of GC tended to be higher although not significant (70.5% vs. 61.3%, p = 0.188). However, OS and RFS at 5 years of the GC patients with FHx were not significantly different from those of patients without FHx.

Conclusion

Preexisting adenoma and GC with MSI are more common in patients with FHx of GC than in those without. There were no significant differences in the survival rate according to FHx.

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.

[Localized MSI/dMMR gastric cancer patients, perioperative immunotherapy instead of chemotherapy: The GERCOR NEONIPIGA phase II study is opened to recruitment]

INTRODUCTION

Perioperative chemotherapy is the standard strategy for localized gastric cancers. Nevertheless, this strategy seems to be inefficient, if not deleterious, for patients with tumors harboring microsatellite instability (MSI) and/or mismatch repair deficiency (dMMR), a tumor phenotype predictive for the efficacy of immune checkpoint inhibitors (ICKi).

AIM

The GERCOR NEONIPIGA single-arm phase II study (NCT04006262; EUDRACT 2018-004712-22) aims at evaluating the efficacy of a peri-operative strategy with nivolumab and ipilimumab in neoadjuvant setting, then nivolumab alone after surgery for patients with resectable MSI/dMMR gastric cancer.

MATERIAL AND METHODS

Main inclusion criteria are: gastric and oesogastric junction adenocarcinoma (GOA), T2-T4, all N stage and M0, MSI/dMMR. Patients will be treated with nivolumab 240mg Q2W, 6 infusions, and ipilimumab 1mg/kg Q6W, 2 infusions in neoadjuvant setting. Following surgery, patients with TRG 1-2-3 (Mandard tumor regression grade), acceptable tolerance of neoadjuvant treatment and postoperative ECOG performance status 0-1, will be treated with adjuvant nivolumab 480mg Q4W, 9 infusions.

RESULTS

The primary endpoint is pathological complete response rate (pCR-R). Based on a Fleming design, with α=5% and β=20%, 27 patients have to be evaluated (H0=5%; H1=20%). Secondary endpoints include disease-free survival, overall survival and safety.

CONCLUSION

This study is planned to include 32 patients to evaluate the pCR-R with the combination of nivolumab and ipilimumab in neoadjuvant setting for MSI/dMMR localized GOA. The MSI/MMR status should be systematically assessed on diagnostic biopsies of all GOA. If it meets its primary endpoint, the GERCOR NEONIPIGA study might mark a turning point in the management of localized MSI/dMMR GOA patients.

Proteome Instability Is a Therapeutic Vulnerability in Mismatch Repair-Deficient Cancer

Deficient DNA mismatch repair (dMMR) induces a hypermutator phenotype that can lead to tumorigenesis; however, the functional impact of the high mutation burden resulting from this phenotype remains poorly explored. Here, we demonstrate that dMMR-induced destabilizing mutations lead to proteome instability in dMMR tumors, resulting in an abundance of misfolded protein aggregates. To compensate, dMMR cells utilize a Nedd8-mediated degradation pathway to facilitate clearance of misfolded proteins. Blockade of this Nedd8 clearance pathway with MLN4924 causes accumulation of misfolded protein aggregates, ultimately inducing immunogenic cell death in dMMR cancer cells. To leverage this immunogenic cell death, we combined MLN4924 treatment with PD1 inhibition and found the combination was synergistic, significantly improving efficacy over either treatment alone.

Gastric cancer is associated with a high rate of microsatellite instability versus chronic gastritis: A retrospective study

Objective: Microsatellite instability (MSI) in gastric cancer contributes to genetic complexities of gastric cancer. In the current study, we employed a panel of mononucleotide and dinucleotide markers to detect MSI in 99 gastric cancer patients and 91 chronic gastritis patients and further analyzed the association of MSI with clinicopathologic variables of the study patients.

Methods: We retrospectively analyzed the clinicopathologic data of primary gastric cancer patients and chronic gastritis patients. MSI was analyzed using five microsatellite markers, including D2S12, D5S346, D17S799, BAT26, and D18S34. MSI was defined as either a band shift or the appearance of a novel band in DNA. Multivariate logistic regression analysis was used to predict risk of MSI.

Results: Seventeen (17.2%) gastric cancer patients and 7 (7.7%) chronic gastritis patients were positive for MSI (P=0.012). Multivariate analysis further showed that gastric cancer was associated with a significantly higher likelihood for MSI versus gastritis (OR 3.73; 95% CI 1.19, 11.72; P=0.024) while age, drinking or smoking was not associated with increased MSI.

Conclusion: Gastric cancer is associated with a high rate of MSI. MSI should be further explored in future studies with a larger sample size for its role in gastric cancer development and as a predictive biomarker.

Genomics and Targeted Therapies in Gastroesophageal Adenocarcinoma

Gastroesophageal adenocarcinomas (GEA) are devastating diseases with stark global presence. Over the past 10 years, there have been minimal improvements in treatment approach despite numerous clinical trials. Here, we review recent progress toward understanding the molecular features of these cancers and the diagnostic and therapeutic challenges posed by their intrinsic genomic instability and heterogeneity. We highlight the potential of genomic heterogeneity to influence clinical trial outcomes for targeted therapies and emphasize the need for comprehensive molecular profiling to guide treatment selection and adapt treatment to resistance and genomic evolution. Revising our clinical approach to GEA by leveraging genomic advances will be integral to the success of current and future treatments, especially as novel targets become therapeutically tractable. SIGNIFICANCE: GEAs are deadly cancers with few treatment options. Characterization of the genomic landscape of these cancers has revealed considerable genetic diversity and spatial heterogeneity. Understanding these fundamental properties of GEA will be critical for overcoming barriers to the development of novel, more effective therapeutic strategies.

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.

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.

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.