Microsatellite Stable Patients Research Articles

The use of immune checkpoint inhibitors in advanced gastric/gastroesophageal adenocarcinomas - real-world evidence and the use of alternative dosing.

Immune check point inhibitors (ICIs) have an established role in Microsatellite-Instability-High (MSI-H) and Combined Positive Score (CPS) high advanced gastric/gastroesophageal (G/GE) adenocarcinomas, but there is limited real world data with regard to practice patterns, and efficacy of standard doses (SD-ICIs) and alternative lower doses (LD-ICIs). A retrospective study of patients with advanced G/GE adenocarcinomas receiving ICIs was conducted. The primary endpoint of the study was 12-month overall survival (OS), which was computed by Kaplan-Meier method. A total of 91 patients were available for analysis during the study period. Seventy-four patients (81%) received nivolumab, while the remaining received pembrolizumab. Fifteen patients (16%) had MSI-H status and had a 12-month OS of 60% and median OS of 15 months (median follow-up - 38.3 months). In the Microsatellite-Stable (MSS) cohort (84%; n = 76), ICIs (combined with chemotherapy) were used predominantly in pre-treated patients (54%; n = 41). Patients with CPS ≥5 (72%; n = 55) had improved survival compared to patients with CPS <5 (28%; n = 21) (12-month OS: 52% vs. 26%; Median OS: 12.8 months vs. 3.2 months; p = 0.005). There was no difference in survival between patients who received SD-ICIs (54%; n = 41) and LD-ICIs (46%; n = 35) (12-month OS: 42% vs. 48%; Median OS: 8.7 months vs. 11 months; p = 0.44). Patients with advanced G/GEJ adenocarcinomas in the real world predominantly received ICIs during later lines of therapy as opposed to first line therapy. Using a CPS cutoff of ≥5 as opposed to CPS <5 predicts for improved survivals in MSS patients and patients receiving low dose ICIs have similar survival outcomes to patients receiving standard dose ICIs within the confines of a heterogenous study cohort.

The Landscape and Prognosis of Microsatellite Stable (MSS) Esophageal, Gastro-Esophageal Junction and Gastric Adenocarcinomas with High Tumor Mutation Burden (TMB)

Background A minority of patients with MSS tumors present a high tumor mutation burden (TMB) without underlying MMR defects. Methods Publicly available genomic series were assessed for identification of patients with MSS gastric gastroesophageal junction, and esophageal adenocarcinomas and a high TMB, defined as more than 10 mutations per Mb. These were compared with MSS cancers and a low TMB for genetic alterations and for survival outcomes. Results Patients with MSS cancers with high TMB in the MSK series were older but did not differ in other clinicopathologic parameters compared with MSS patients with low TMB. Mutations in tumor suppressors TP53 and APC and oncogenes KRAS and ERBB4 as well as amplifications of ERBB2 were more prevalent in the high TMB group of MSS cancers. Mutations in DDR associated genes, in epigenetic modifiers and in genes associated with immune response were more prevalent in the hIgh TMB group patients. However, high TMB was not associated with an improved survival in MSS gastric/gastroesophageal junction/esophageal adenocarcinomas (Log Rank p = 0.5). Conclusion MSS Gastric/gastroesophageal junction/esophageal adenocarcinomas with TMB above 10 mutations per Mb possess a genomic landscape with increased alteration frequencies in common gastroesophageal cancer genes and pathways.

Deep learning for dual detection of microsatellite instability and POLE mutations in colorectal cancer histopathology

In the spectrum of colorectal tumors, microsatellite-stable (MSS) tumors with DNA polymerase ε (POLE) mutations exhibit a hypermutated profile, holding the potential to respond to immunotherapy similarly to their microsatellite-instable (MSI) counterparts. Yet, due to their rarity and the associated testing costs, systematic screening for these mutations is not commonly pursued. Notably, the histopathological phenotype resulting from POLE mutations is theorized to resemble that of MSI. This resemblance not only could facilitate their detection by a transformer-based Deep Learning (DL) system trained on MSI pathology slides, but also indicates the possibility for MSS patients with POLE mutations to access enhanced treatment options, which might otherwise be overlooked. To harness this potential, we trained a Deep Learning classifier on a large dataset with the ground truth for microsatellite status and subsequently validated its capabilities for MSI and POLE detection across three external cohorts. Our model accurately identified MSI status in both the internal and external resection cohorts using pathology images alone. Notably, with a classification threshold of 0.5, over 75% of POLE driver mutant patients in the external resection cohorts were flagged as “positive” by a DL system trained on MSI status. In a clinical setting, deploying this DL model as a preliminary screening tool could facilitate the efficient identification of clinically relevant MSI and POLE mutations in colorectal tumors, in one go.

Abstract CT217: First-line durvalumab and tremelimumab with chemotherapy in RAS-mutated metastatic colorectal cancer: a phase 1b-2 trial

Abstract Metastatic colorectal cancer (mCRC) remains a difficult-to-treat disease. While patients with microsatellite instable metastatic colorectal cancer (mCRC) benefit from immune checkpoint blockade, chemotherapy with targeted therapies remains the only therapeutic option for microsatellite stable (MSS) tumors. The single arm, phase IB/II MEDITREME trial evaluated the safety and efficacy of durvalumab plus tremelimumab combined with mFOLFOX6 chemotherapy in first line, in 57 patients with RAS-mutant unresectable mCRC. Safety was the primary objective of phase IB; no safety issue was observed. The phase II primary objective of efficacy in terms of 3-month PFS in MSS patients was met, with 3-month PFS of 90.7% [95% CI: 79.2-96%]. For secondary objectives, response rate was 64.5%, median PFS was 8.2 months [95% CI: 5.9-8.6] and overall survival was not reached in MSS patients. We observed higher tumor mutational burden and lower genomic instability in responders. Integrated transcriptomic analysis underlined that high immune signature, and low epithelio-mesenchymal transition were associated with better outcome. Immunomonitoring showed induction of neoantigen and NY-ESO1 and TERT blood tumor specific T cell response, associated with better PFS. The combination of durvalumab-tremelimumab with mFOLFOX6 was tolerable with promising clinical activity in MSS mCRC. Clinicaltrials.gov identifier: NCT03202758. Citation Format: Marion Thibaudin, Jean-David Fumet, Emeric Limagne, Léa Hampe, Susy Daumoine, Valentin Derangère, Caroline Laheurte, Olivier Adotevi, Caroline Truntzer, François Ghiringhelli. First-line durvalumab and tremelimumab with chemotherapy in RAS-mutated metastatic colorectal cancer: a phase 1b-2 trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT217.

The Expression Patterns of Immune Checkpoint Molecules in Colorectal Cancer: An Analysis Based on Microsatellite Status.

Recently, immunotherapy has arisen as a novel treatment approach for patients with colorectal cancer (CRC), but the effectiveness of immunotherapy varies in these patients. We hypothesized that immune checkpoint molecules (ICMs), which are the targets of immunotherapy, are often exhibited concomitantly. Our objective was to investigate the patterns of ICM expression in patients with CRC and the differences in ICM expression based on microsatellite instability status. The immunohistochemical expression of programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), T cell immunoglobulin and mucin-domain containing-3 (TIM-3), and lymphocyte-activation gene 3 (LAG-3) in the tumor center and periphery was assessed in patients with non-metastatic colorectal cancer. We enrolled 83 patients with CRC: a total of 40 microsatellite-stable (MSS) and 43 microsatellite-instability-high (MSI-H) cancer patients. PD-L1 was more frequently expressed in the tumor center in the MSI-H patients with than that in the MSS patients (18 [41.9%] vs. 3 [7.5%], respectively; p < 0.001), and the same trend was observed for TIM-3 expression (30 [69.8%] vs. 19 [47.5%], respectively; p = 0.047). The concomitant expression of two or more ICMs was more frequently observed than no expression or the expression of a single molecule in both the MSS and MSI-H groups; a total of 34 (79.7%) patients with MSI-H cancer and 23 (57.5%) with MSS cancer showed ICM expression at the tumor center, whereas 34 (79.7%) patients with MSI-H cancer and 22 (55%) with MSS cancer showed expression at the tumor periphery. Patients with the genetic characteristics of MSI-H cancer showed higher expression levels of ICMs than those in patients with MSS cancer, and predominantly, two or more ICMs were concurrently expressed. Our findings highlight the potential efficacy of the dual-blockade approach in immunotherapy, particularly in patients with MSI-H CRC.

Abstract 1517: Tc1 cytotoxic T-cells and Th1 helper T-cell rich tumor microenvironment is a hallmark of MSI colorectal cancers

Abstract Background: Microsatellite instability (MSI-h) is a strong biomarker to predict response to immune checkpoint therapy and patient’s outcome in colorectal cancer. Although enrichment of distinct T-cell subpopulations, such as type 1 cytotoxic T-cells (Tc1) or type 1 helper T-cells (Th1), have been identified to impact patient’s outcome and response to immune checkpoint therapy, only little is known about the underlying changes in the composition of the immune tumor microenvironment. Material and Methods: To assess the density, composition, degree of functional marker expression, and spatial interplay of T-cell subpopulations in 93 MSI and 1153 microsatellite stable (MSS) colorectal cancers, a tissue microarray as well as large sections were stained with antibodies directed against CD3, CD4, CD8, FOXP3, T-bet, GATA3, RORyT, BCL6, CD27, CD56, TIM3, PD-1, CTLA-4 Granzym B, and Ki67 using our BLEACH&amp;STAIN multiplex fluorescence immunohistochemistry approach. A deep learning-based framework comprising two different convolutional neuronal networks (U-Net and DeepLabv3+) was used for image analysis. Results: The composition of Type 1 (T-bet+), Type 2 (GATA3+), Type 17 (RORyT+), NKT-like (CD56+), regulatory (FOXP3+), and follicular (BCL6+) cytotoxic (CD3+CD8+) or helper (CD3+CD4+) T-cells showed marked differences between MSI and MSS patients. For instance, the density and proportion of Tc1 as well as Th1 was significantly higher (p&amp;lt;0.001 each) in MSI compared to MSS patients. In contrast, the density and composition of Tregs, Th2, Th17 T-cells was significantly lower in MSI compared to MSS patients in the intraepithelial tumor compartment. In addition, among the MSI colorectal cancers, NKT-cells showed the highest level of Granzyme B that was significantly higher than in MSS patients (p&amp;lt;0.05). The degree of immune checkpoint expression (i.e., TIM3, PD-1, CTLA-4) was significantly higher in MSI compared to MSS patients for most T-cell subpopulations (p&amp;lt;0.05 each). The additional analysis of 10 large sections confirmed the observations from the TMA analysis and revealed that the alterations in the T-cell composition seen in the center of the tumor largely reflect the T-cell composition at the invasive margin in both MSI and MSS patients. Conclusion: This study identified a higher proportion of Tc1 cytotoxic T-cells and Th1 helper T-cells accompanied by a paucity of regulatory T-cell subpopulations, Th17 and Th2 T- helper cells in MSI colorectal cancers compared to MSS patients. Citation Format: Tim Mandelkow, Zhihao Huang, Elena Bady, Jan H. Müller, Guido Sauter, Julia Ebner, Maximilian Lennartz, Natalia Gorbokon, Ronald Simon, Martina Kluth, Claudia Hube-Magg, Sarah Minner, Niclas C. Blessin. Tc1 cytotoxic T-cells and Th1 helper T-cell rich tumor microenvironment is a hallmark of MSI colorectal cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1517.

Abstract 3597: Multimodal γδ T cell cytotoxicity overcomes cellular therapy reprogramming

Abstract Colorectal cancer (CRC) is a devastating disease that kills ~700,000 people worldwide annually. Current immunotherapies struggle against both microsatellite stable (MSS) disease and the immunosuppressive CRC tumor microenvironment (TME). Despite these challenges, tumor infiltrating γδ T cells confer a prognostic benefit to CRC patients and can kill cancer via antibody independent cytotoxicity (AIC) and antibody-dependent cellular cytotoxicity (ADCC). We hypothesized that γδ T cells can be exploited as an ‘off-the-shelf’ anti-CRC biotherapeutic but their complex interactions within the CRC TME need to be elucidated. To explore the patient-, donor-, and mechanism-specific interactions of γδ T cells with CRC, we performed single-cell profiling of &amp;gt;1,000 CRC patient-derived organoid (PDO) and human Vγ9Vδ2 T cell cultures. γδ T cells from multiple donors were used either unmodified or engineered to secrete a modified IL-15 cytokine (stIL15-γδs). The addition of anti-B7-H3 IgG further allowed us to study anti-PDO ADCC, with antigen specificity assessed with B7-H3KO PDO models. Using 126-plex Thiol Organoid Barcoding in situ (TOBis) mass cytometry (MC) (Qin et al., Nature Methods, 2020) (Sufi and Qin et al., Nature Protocols, 2021), we measured cell-type specific signaling across multiple γδ donors and CRC PDOs, including post-translational modifications (PTMs), cell-state, and immunological phenotype. We found that stIL15-γδs exhibit superior proliferation, purity and viability both in vitro and in vivo. stIL15-γδs demonstrated significant cytotoxicity against all CRC PDOs tested, commonly outperforming standard-of-care chemotherapies even when challenged against our previously-defined chemorefractory MSS patients (Zapatero et al., Cell, 2023). The susceptibility of PDOs to anti-B7-H3 ADCC differs substantially and is not associated with B7-H3 antigen density and %positivity or PDO tumor mutational burden. Minimal differences in ADCC capability were seen between stIL15-γδs donors which were not associated with γδ phenotype or pre- and post-experiment FcγR CD16 expression. Crucially, we found that stIL15-γδ signaling is reciprocally regulated in a PDO-specific manner, with significant regulation of stIL15-γδ cell-state, PTM signaling and immunological phenotype observed. Increased dysregulation of stIL15-γδs during AIC negatively correlates with PDO cytotoxicity — indicating PDOs negatively reprogram γδ T cellular therapies. However, when γδ T cells engage in ADCC (via anti-B7-H3 IgG), stIL15-γδ signaling recovers, leading to substantial anti-PDO cytotoxicity. Furthermore, stIL15-γδs could perform significant cytotoxicity against all chemoresistant MSS PDOs tested, representing the patient population with greatest unmet clinical need. These results demonstrate that multimodal γδ T cell cytotoxicity can overcome tumor-specific cellular therapy reprogramming. Citation Format: Callum Baird Nattress, Daniel Fowler, Petra Vlckova, Colin Hutton, Maria Ramos Zapatero, Jahangir Sufi, Ferran Cardoso Rodriguez, Ashley Campbell, Angeliki Kanouta, Magdalena Buschhaus, Kerry Chester, John Anderson, Vivian Li, Marta Barisa, Jonathan Fisher, Christopher Tape. Multimodal γδ T cell cytotoxicity overcomes cellular therapy reprogramming [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3597.

Association of Microsatellite Instability and Gene Expression Profile in Colorectal Carcinoma and Potential Implications for Therapy.

Background and Objective: In sporadic colorectal carcinomas (CRC), microsatellite instability (MSI) pathways play important roles. Previously, we showed differences in DNA methylation patterns in microsatellite stable (MSS) colorectal carcinomas and MSI-CRC. In the current study, we explore the similarities and differences in gene expression profiles in MSS and MSI at the gene level and at the pathway level to better understand CRC pathogenesis and/or the potential for therapeutic opportunities. Material and Methods: Seventy-one CRC patients (MSI = 18, MSS = 53) were studied. Paired tumor and adjacent normal tissues were used for genome-wide gene expression assays. Result: At the gene level, we compared the list of differentially expressed genes (fold change (FC) ≥ 3 and FDR < 0.05) in tumor tissues compared to corresponding normal tissue in CRC patients with MSI tumors (190 genes) and MSS tumors (129 genes). Of these, 107 genes overlapped. The list of genes that were differentially expressed in MSI tumors only showed enrichment predominantly in two broad categories of pathways-(a) Inflammation-related pathways including the interleukin-17 (IL-17) signaling pathway, tumor necrosis factor (TNF) signaling pathway, chemokine signaling, nuclear factor kappa B (NFκB) signaling, and cytokine-cytokine interactions, and (b) metabolism-related pathways, including retinol metabolism, steroid hormone biosynthesis, drug metabolism, pentose and glucoronate interconversions, and ascorbate and aldarate metabolism. The genes in inflammation-related pathways were up-regulated whereas genes in metabolism-related pathways were down-regulated in MSI tumor tissue. Pathway-level analysis also revealed similar results confirming the gene enrichment findings. For example, the 150 genes involved in the IL-17 signaling pathway were on average up-regulated by 1.19 fold (CI 1.16-1.21) in MSI compared to 1.14 fold (CI 1.13-1.16) in MSS patients (interaction p = 0.0009). Conclusions: We document an association between MSI status and differential gene expression that broadens our understanding of CRC pathogenesis. Furthermore, targeting one or more of these dysregulated pathways could provide the basis for improved therapies for MSI and MSS CRC.

A novel immune-related gene signature for diagnosis and potential immunotherapy of microsatellite stable endometrial carcinoma

An immune-related gene signature (IRGS) was established to better understand the molecular and immunologic characteristics of microsatellite instable (MSI) and microsatellite stable (MSS) endometrial carcinoma (EC), and provide potential immunotherapy directions for MSS patients. Top 20 immune-related hub genes were screened by weight gene coexpression network analysis (WGCNA), and an IRGS was further established through Cox regression analysis. The molecular and immune characteristics were clarified in IRGS high and low risk groups. Expression and MS status validation of the IRGS were conducted through quantitative real-time Polymerase Chain Reaction (rt-qPCR) and immunohistochemistry (IHC) analysis. The IRGS includes 2 oncogenes (AGTR1 and HTR3C) and 2 tumor suppressor genes (CD3E and SERPIND1). Patients in IRGS high-risk group were more with MSS status, higher tumor grade, later FIGO stage, serous histology and elder ages compared with IRGS low-risk group (P < 0.05). Besides, patients in MSS group were more FIGO stages II–IV (42.7% vs. 26%), serous histology (35.7% vs. 5.3%) and with higher IRGS risk score (1.51 ± 3.11 vs. 1.02 ± 0.67) (P < 0.05) than patients in MSI group. Furthermore, patients in IRGS high-risk group had higher tumor purity, more Macrophages M1 and Macrophages M2 infiltrating, higher proportion of Macrophages M2 and Dendritic cells activated, lower proportion of T cells regulatory (Tregs), lower tumor mutation burden (TMB). Correspondingly, subjects in IRGS low-risk group had higher immunphenoscores than IRGS high-risk group. The relative mRNA level of AGTR1 and HTR3C were gradually increase, while CD3E and SERPIND1 were reversed in rt-qPCR. Through IHC experiments, AGTR1(69.2% vs 30%, P = 0.074) and HTR3C (76.9% vs 30%, P = 0.024) had higher positive staining rates in ECs than non-ECs. While SERPIND1 (84.6% vs 20%, P = 0.003) and CD3E (61.5% vs 40%, P = 0.000) had higher positive staining rates in non-ECs. IRGS is a potential diagnostic and prognostic biomarker for EC. IRGS low risk group might benefit from immune checkpoint inhibitors, while IRGS high risk group deserve other potential immunotherapy.

Association of RNF43 Genetic Alterations With BRAFV600E and MSIhigh in Colorectal Cancer.

Recent studies have provided evidence for a predictive value of RNF43 genetic alterations (GAs) as biomarkers for targeted therapies in microsatellite-stable (MSS) colorectal cancer (CRC). These data have the potential to prioritize treatment strategies in patients with BRAFV600E-mutant CRC and help to identify a subgroup that is more likely to derive benefit versus those patients for whom alternative treatment approaches are needed. We were therefore interested in defining the precise frequency of BRAFV600E and RNF43 GAs and their respective overlap in a large cohort of patients with CRC. To address this question, we performed a retrospective analysis that included 52,969 patients diagnosed with CRC from the FoundationCORE database. We observed a striking association of RNF43 GAs with MSI and tumor mutational burden status and BRAFV600E mutations. Overall, 23% of MSS patients with confirmed BRAFV600E mutation harbor an RNF43 GA-which accounts for 1.1% of all patients with CRC and for 15.7% of all CRC BRAFV600E cases. Ongoing phase III clinical trials, such as BREAKWATER, should aim to incorporate broader genetic profiling to further validate the superior sensitivity of patients with RNF43-mutant, MSS BRAFV600E CRC to anti-EGFR-/BRAFi-based therapies.

Exploring the connection between microsatellite instability and inflammatory indicators in cancers.

Aim: This study aimed to investigate the association between microsatellite instability (MSI) status and inflammatory indicators in patients with cancer. Patients & methods: A total of 204 patients with various cancer diagnoses, including 102 with MSI-high (MSI-H) and 102 with microsatellite stabletumors, were enrolled. Neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), C-reactive protein (CRP)-to-albumin ratio and systemic immune-inflammation indexwere evaluated. Results: In microsatellite stable patients, NLR, LMR, PLR and systemic immune-inflammation index were significantly linked to worse survival in univariate analysis, and having aLMR ≤2.6 negatively affected survival in multivariate analysis, although these indicators did notaffect the survival of MSI-H patients. Conclusion: The impact of chronic inflammationon survival varies with MSI status. Further research is needed for targeted therapies in different tumors.

Microsatellite instability in gastric cancer: An institutional case series analysis in patients treated with neoadjuvant therapy

IntroductionPast studies documented that microsatellite instability (MSI) is associated with improved survival in gastric cancer (GC). The aim of this study was to evaluate MSI status in a series of GCs treated with neoadjuvant therapy in relation to the tumors' characteristics and oncological outcomes. MethodsPatients with GCs treated between 2017 and 2022 ​at a single Italian high-volume Institution undergoing pre-operative treatment followed by resection were included if studied for their microsatellite status. Clinicopathological data were analyzed for the association with MSI. The same features were analyzing pooling the series with a subset of patients from another European trial.Secondary outcomes included the overall (OS), and disease-free (DFS) survivals comparing MSI vs microsatellite stable (MSS) GCs, and GCs presenting complete-major response (TRG1-2) vs partial response (TRG3-4) and absence of response (TRG5). ResultsAmong 73 patients selected, 12.3% were MSI. In the single institutional analysis, we documented a difference in the distribution of ypT stages with a prevalence of ypT0 patients in MSI vs MSS patients (ypT0 respectively 11.1% vs 1.6%, p ​< ​0.0001). However, this difference was not of statistical value when pooling patients with those from the European trial (overall 108 patients, 9.2% MSI; ypT0 respectively 10.0% vs 2.0%, p 0.144). In the pooled analysis, a prevalence of female patients was reported in the MSI group comparing MSS (respectively, 70.0% vs 27.6%, p 0.01). At a mean follow-up of 27.7 months, OS and DFS survivals were reported similar comparing MSS and MSI (log-rank test respectively p 0.18 and p 0.96), however TRG1-2 ​GCs had improved OS and DFS comparing other sub-groups (TRG1-2 vs TRG3-4 vs TRG5, OS and DFS log-rank test respectively p 0.017 and p 0.0029). ConclusionThis study could not demonstrate a correlation between microsatellite status and survival in gastric cancer patients who underwent pre-operative treatment. A complete/major response was the only variable correlated with mid-term survival.

Lymph Node Metastases and Associated Recurrence-Free Survival in Microsatellite Stable and Unstable Colon Cancer.

In contrast to microsatellite stable (MSS) colon cancer, predictors of lymph node metastases and their association with recurrence are not well-defined in microsatellite instability (MSI) colon cancer. A cohort of nonmetastatic colon cancer patients undergoing surgery between 2015 and 2021 were evaluated for predictors of lymph node metastases (LNMs) and their association with recurrence-free survival (RFS). Of 1466 patients included in the analyses, 361 (25 %) had MSI. Compared with MSS, MSI was associated with earlier stage, fewer LNMs in the patients with N1 or N2 disease, and fewer high-risk features. Compared with the T3-T4 MSS patients, the odds ratios for LNM were 0.52 (95% confidence interval [CI], 0.38-0.71) for the T3-T4 MSI patients, 0.27 (95% CI, 0.38-0.71) for the T1-T2 MSS patients, and 0.15 (95 % CI, 0.08-0.26) for the T1-T2 MSI patients. In both groups, LNMs were associated with T category, patient age, and venous, lymphatic, or perineural invasion. In the MSS patients, LNMs were additionally associated with patient sex and histologic grade. Compared with the MSS patients, the MSI patients with N0 and N1 disease had a better 3-year RFS. However, the MSI patients with N2 disease had a lower rate of 3-year RFS than the MSS patients (hazard ratio, 19.75 vs 4.49). In MSI colon cancer, LNMs are 50 % less prevalent, but the factors associated withLNM are like those in MSS colon cancer. The improved prognosis traditionally associated with early-stage MSI colon cancers dissipates with four or more LNMs. These findings should be taken into consideration by clinicians selecting the most appropriate course of treatment for MSI colon cancer.

Sintilimab plus bevacizumab, oxaliplatin and capecitabine as first-line therapy in RAS-mutant, microsatellite stable, unresectable metastatic colorectal cancer: an open-label, single-arm, phase II trial

Microsatellite stable (MSS) and RAS-mutant metastatic colorectal cancer (mCRC) patients are characterized by an immunosuppressive microenvironment and a low response rate to immunotherapy. Chemotherapy and anti-angiogenesis therapy have been reported to potentially promote immunotherapy response. This study aims to assess the preliminary anti-tumor activity and safety of sintilimab plus bevacizumab, oxaliplatin and capecitabine as a treatment option for patients with RAS-mutant MSS mCRC. This study was an open-label, single-arm, phase II trial in China. Patients with unresectable, RAS-mutant and MSS metastatic colorectal adenocarcinoma received treatment by intravenous sintilimab (200mg, day 1) plus bevacizumab (7.5mg/kg, day 1), oxaliplatin (135mg/m2, day 1) and oral capecitabine (1g/m2, day 1-14) in each 21-day cycle. The primary endpoints included objective response rate (ORR) and adverse events. Biomarker analysis was performed to identify potential predictors of good response to treatment. This study is registered with ClinicalTrials.gov, number NCT04194359. Between April 2021 and December 2021, 25 patients were enrolled. Two (8%) patients showed complete response (CR), 19 (76%) had partial response (PR) and 4 (16%) presented with stable disease. ORR reached 84% (95% CI, 63.9-95.5) and the disease control rate was 100% (95% CI, 86.3-100). The median progression-free survival (PFS) was 18.2 months for the full analysis set. The most common treatment-related adverse events (TRAEs) in all grades were anemia (21/25, 84%), neutropenia (20/25, 80%), and hand-foot syndrome (14/25, 56%). The most frequent grade 3 or 4 TRAEs were neutropenia (3/25, 12%) and increased alanine transaminase (2/25, 8%). No grade 5 adverse events occurred. In the exploration of biomarkers, 5 patients could be characterized as TTN/OBSCN "double-hit" after treatment, and the copy number variants burden was significantly decreased in tumor tissues after treatment compared with the baseline. Nanostring panel RNA sequencing analysis indicated a better tumor immune microenvironment cell infiltration in CR/PR patients compared with non-CR/PR patients as well as the PFS-long (≥12.5 months) group compared with the PFS-short group. Combination treatment with sintilimab plus bevacizumab, oxaliplatin and capecitabine as first-line treatment demonstrated a promising antitumor activity and a manageable safety profile in RAS-mutant, MSS and unresectable mCRC. Exploratory biomarker assessment analysis showed that some RAS-mutant and MSS patients changed into "immune-hot" subtype after the treatment. This study was supported by the Key R&D Program of Zhejiang Province (2021C03125 to Ying Yuan), the National Natural Science Foundation of China (81872481 to Ying Yuan, 82072624 to Kefeng Ding), the Fundamental Research Funds for the Central Universities (No. 226-2022-00009 to Kefeng Ding), and the Zhejiang Provincial Natural Science Foundation of China (No. LY22H160024 to Hanguang Hu).

Survival impact of microsatellite instability in stage II gastric cancer patients who received S-1 adjuvant monotherapy after curative resection

Adjuvant S-1 monotherapy is the standard of care for stage II gastric cancer (GC) after curative resection in Japan, but its efficacy for microsatellite instability–high (MSI-H) tumors has remained unknown. Among a multi-institutional cohort of patients with stage II GC who underwent R0 resection followed by S-1 adjuvant chemotherapy between February 2008 and December 2018, we assessed MSI status with an MSI-IVD Kit (Falco). MSI status was assessable for 184 (88.5%) of the 208 enrolled patients, with MSI-H being identified in 24 (13.0%) individuals. Although neither relapse-free survival (RFS) (hazard ratio [HR] = 1.00, p = 0.997) nor overall survival (OS) (HR = 0.66, p = 0.488) differed between MSI-H versus microsatellite-stable (MSS) patients, MSI-H patients showed a nonsignificant but better RFS (HR = 0.34, p = 0.064) and OS (HR = 0.22, p = 0.057) than did MSS patients after adjustment for background characteristics by propensity score (PS) analysis. Gene expression analysis in the PS-matched cohort suggested that recurrence was associated with the immunosuppressive microenvironment in MSI-H tumors but with expression of cancer/testis antigen genes in MSS tumors. Our data reveal a better adjusted survival for MSI-H versus MSS stage II GC treated with S-1 adjuvant therapy, and they suggest that mechanisms of recurrence differ between MSI-H and MSS tumors.

Immunohistochemical expression of ER and p53 as predictive biomarkers of immunotherapy in endometrial cancer.

e17626 Background: Immune Checkpoint Inhibitors (ICIs), either as monotherapy or in combination with tyrosine kinase inhibitors (TKIs), were recently incorporated into the therapeutic guidelines for recurrent/metastatic endometrial cancer (EC). Microsatellite Instability (MSI) is the only biomarker to guide treatment. We evaluated the predictive significance of Estrogen Receptor (ER) and p53 expression. Methods: Medical charts of EC patients that received ICIs in our institution for advanced/metastatic disease were retrospectively reviewed. TP53 and ER expression were determined by immunohistochemistry. Survival analysis was performed using IBM SPSS statistics v.25. Results: Thirty-two patients were included in our analysis. The median age was 63.1 years (25th-75th percentile: 57.6 – 69.6). 62.5% of the patients had endometrioid histology, 21.9% serous histology and 15.6% of them displayed other histology. 46.9% of the patients had grade 1-2 tumors and 53.1% grade 3 tumors. 21.9% of them were diagnosed with stage 1-2 disease, while 78.1% presented with stage 3 disease. 62.5% received 0-1 prior lines of treatment and 37.5% of them received more than 2 prior lines. Molecular characteristics are presented in the table. All MSI-High patients received anti-PD1 monotherapy with a median PFS of 11.9 months (95% CI:2.3-21.5). Microsatellite Stable (MSS) patients received pembrolizumab-lenvatinib combination with median PFS 7.54 months (95% CI:2.6-11.5). ER positivity was associated with significant PFS benefit in both the ICI monotherapy group (11.9 vs. 0.63 months, p=0.061) and the group that received ICI/TKI combination (11.3 vs. 1.75 months, p=0.001). Analogous benefit was noted in the Overall Survival post start of IO or IO/TKI treatment (9.8 vs 0.6 months in MSI-high patients and 20.6 vs 5.9 months in MSS patients). ER-positivity remained an independent predictive factor favoring PFS in the Multivariate Cox regression analysis when adjusting for immunotherapy type, histology, and previous lines of therapy (HR=0.216, p=0.013). Conclusions: ER expression proved to be an independent prognostic factor regarding PFS in our cohort of patients. Further studies are needed to investigate the role of ER as a predictive biomarker for immunotherapy in EC. [Table: see text]

A pan-cancer statistical study of microsatellite instability and Lynch syndrome–associated mismatch repair genes germline mutations.

10593 Background: Lynch Syndrome (LS), known as hereditary nonpolyposis colorectal cancer (HNPCC1), is caused by germline mutations in the mismatch repair (MMR) genes ( MLH1, MSH2, PMS2, MSH6), or epigenetic silencing of MSH2 which caused by deletion of 3-prime exons of the EPCAM gene and intergenic regions directly upstream of the MSH2 gene. DNA mismatches commonly occur in regions of repetitive nucleotide sequences called microsatellites, and the status of microsatellite instability (MSI) is the key feature in LS-associated cancers. Although there are sporadic reports of MSI and LS in certain cohorts, the real-world status of MSI in large pan-cancer cohort remains to be analyzed. Methods: We retrospectively reviewed all 18189 solid tumor patients from August 1, 2020 to February 5, 2023 from HaploX Genomic Sequencing Center and analyzed their germline mutations in MMR genes ( MLH1,MSH2,PMS2,MSH6 and EPCAM). MSI status was determined using Sanger sequencing or Next-generation sequencing, with tumor MSI status classified as microsatellite instability-high (MSI-H), or microsatellite-stable (MSS). Results: LS-associated germline mutations were detected in 0.313% (n = 57) of patients, and75.4% (n = 43) of patients were identified as MSI-H, and 24.6% (n = 14) of patients were MSS. The patients were grouped into CRC/EC group (colorectal cancer and endometrial cancer) and non-CRC/EC (lung cancer, central nervous system tumor, gastric cancer, esophageal cancer, hepatological cancer, pancreatic adenocarcinoma, small bowel carcinoma, kidney cancer, etc.). Among MSI-H patients, the CRC/EC group accounted for 90.7% (n = 39) and the non-CRC/EC group accounted for 9.3% (n = 4). In MSS patients, the CRC/EC patients accounted for 35.7% (n = 5), and the non-CRC/EC patients accounted for 60% (n = 9). Among patients with MSI-H, the most frequently mutated gene was MSH6 (n = 9): MSH6 (NM_000179) c.3261dup (p.F1088Lfs*5) mutation was detected in 4 patients, of which 2 patients were paternal and both were diagnosed as colorectal cancer; MSH6 c.718C &gt; T (p.R240*) mutation was detected in 2 patients with available MMR IHC results, and one of them was MSH6 negative in IHC staining. Conclusions: Traditionally, a family history of colorectal cancer or endometrial cancers was the primary clinical feature to diagnose Lynch syndrome. Once it was recognized that Lynch-associated CRCs were microsatellite unstable, tumor testing became an additional tool for identification of Lynch syndrome. Some previous studies also reported Lynch syndrome mutations, primarily MSH6 and PMS2, were present in a few MSS patients. Thus, MSI status or family history as diagnostic factor alone may result in Lynch syndrome under-recognized, and additional NGS test on MMR genes should facilitate more accurate diagnosis.

A survey on the detection of HPD-related genes by liquid biopsy in patients with lung cancer in China.

e20502 Background: he prognosis for lung cancer patients receiving immunotherapy is impacted by hyper-progression disease (HPD). Assays for HPD-associated gene mutations were anticipated to be crucial for immunotherapy. Although easy and non-invasive, the liquid biopsy technique is not widely employed in immunotherapy. Here, we want to study details of HPD-related gene mutations in the detection of tissue and liquid biopsy and dig out some relevant information from Chinese Lung Cancer (CLC) patients. Methods: 10 genes with HPD-associated mutation were collected by literature, like SNV ( EGFR, KEAP1, STK11, DNMT3A, PTEN), CNV ( ALK fusion, amplification of MDM2, MDM4, FGF3, FGF4). 3540 cell-free DNA (cfDNA) samples and 6553 tumor tissue samples of LC patients download from Haplab database (HaploX, Shenzhen, China). Genetic alterations were sequenced by NGS platform and microsatellite instability status was calculated through msisensor analysis. The chi-square test was used for statistical hypothesis test. Results: In general, all mutation genes tested except EGFR were detected significantly differently between tissue and cfDNA samples (p &lt; 0.05). 193 samples (156 tDNA, 37cfDNA) with microsatellite instability (MSI) were screened to test HPD-related gene consistency. Results showed no significant difference in 10 HPD-related genes between MSI tissue and blood samples (p &gt; 0.05). Microsatellite stable (MSS) samples of 4499 tumor DNA and 1173 cfDNA were also performed on consistency test. EGFR and the other 4 genes ( FGF3, FGF4, KEAP1, PTEN) were found consistency in tDNA and cfDNA, and ALK (p 0.0051), MDM2 (p 0.0004), MDM4 (p 0.0052), STK11 (p 0.0344), DNMT3A (p &lt; 0.0001) showed significant difference of two type of samples. Conclusions: In overall samples and subtypes tested, only EGFR had no significant differences between tissue and cfDNA, which might make EGFR a perfect biomarker candidate in HPD detection and prognosis. Our outcomes also proved that liquid biopsy has some limitations in monitoring HPD-related genes of CLC compared with tissue biopsy. MSS patients presented more reliable results than MSI patients. When monitoring HPD-related genes except for EGFR using cfDNA, appropriate patients should be considered.

Poly-G for tumor matched samples chronicles the evolution of human colorectal cancer

Objective: To analyze poly-guanine (poly-G) genotypes and construct the phylogenetic tree of colorectal cancer (CRC) and provide an efficient and convenient method for the study of intra-tumor heterogeneity and tumor metastasis pathway. Methods: The clinicopathological information of patients with primary colorectal cancer resection with regional lymph node metastases were retrospectively collected in the Department of General Surgery, General Hospital of Tianjin Medical University from January 2017 to December 2017. The paraffin sections of the paired tumor samples were performed consecutively, and multi-region microdissection was performed after histogene staining. The phenol-chloroform extraction and ethanol precipitation scheme was used to obtain DNA, and Poly-G multiplex PCR amplification and capillary electrophoresis detection were performed. The correlation between Poly-G mutation frequency and clinicopathological parameters was analyzed. Based on the difference of Poly-G genotypes between paired samples, the distance matrix was calculated, and the phylogenetic tree was constructed to clarify the tumor metastasis pathway. Results: A total of 237 paired samples were collected from 20 patients including 134 primary lesions, 66 lymph node metastases, 37 normal tissues, and Poly-G mutation was detected in 20 patients (100%). The mutation frequency of Poly-G in low and undifferentiated patients was (74.10±23.11)%, higher than that in high and medium differentiated patients [(31.36±12.04)%, P<0.001]. In microsatellite instability patients, the mutation frequency of Poly-G was (68.19±24.80)%, which was higher than that in microsatellite stable patients [(32.40±14.90)%, P=0.003]. The Poly-G mutation frequency was not correlated with age, gender, and pathological staging (all P>0.05). Based on Poly-G genotype difference of the paired samples, the phylogenetic trees of 20 patients were constructed, showing the evolution process of the tumor, especially the subclonal origins of lymph node metastasis. Conclusion: Poly-G mutations accumulate in the occurrence and development of CRC, and can be used as genetic markers to generate reliable maps of intratumor heterogeneity in large numbers of patients with minimal time and cost expenditure.

Association of punctate TAK1 expression with mortality in patients with microsatellite-stable colorectal cancer.

220 Background: Microsatellite stable (MSS) colorectal cancer continues to have limited options for personalised therapeutic targets. The NFKB pathway is known to play an important role in inflammation-related carcinogenesis but has yet to be translated into therapies for the clinical patient. The aim of this study was to investigate the expression of cytoplasmic and punctate TAK1 (transforming growth factor β-activated protein kinase 1) in colorectal cancer and its relationship to immune checkpoint expression and prognosis. Methods: Patients undergoing primary colorectal cancer resection between 1997 and 2007 at Glasgow Royal Infirmary (UK) were studied for clinicopathological data and immunohistochemistry (IHC) performed on archival FFPE tissue from resected specimens. Antibodies for TAK1, PD-1, PD-L1, IKK alpha and other proteins were used for IHC, with digital analysis (QuPath) for quantification of cytoplasmic staining and punctate score for juxta-nuclear TAK1 assessment. Kaplan-Meier curves were created with log-rank test to determine survival. Cox-proportional hazards regression were used to determine multivariate hazard ratios (HR) and 95% confidence intervals (CI). Results: A total of 898 patients who underwent colorectal resection were identified. Higher TAK1 punctate expression was observed in left colon and rectal cancer, compared with right sided disease (p = 0.045). MMR proficient tumours had higher frequencies of high TAK1 punctate expression (p &lt; 0.001). Both cytoplasmic and punctate TAK1 expression correlated with IKK expression (p &lt; 0.050). High cytoplasmic TAK1 expression was associated with increased PD-1 and PD-L1 expression (p &lt; 0.001). Punctate TAK1 expression was associated with worse survival (p = 0.037). These differences were accentuated in patients with MSS status (p = 0.016). On multivariate analysis, high punctate TAK1 expression remained a predictor of worse cancer-specific survival (HR 1.843, CI 1.129-2.956, p = 0.011). Conclusions: TAK1 expression was associated with MSI status, and higher TAK1 expression correlates with upregulated PD-1 and PD-L1 expression. High punctate TAK1 expression predicted cancer-specific survival. In subgroup analysis of MSS patients, high punctate TAK1 expression was associated with poor survival. Further interrogation into this pathway may identify inflammation-related therapeutic targets in MSS patients with colorectal cancer.