Deficient mismatch repair system in patients with sporadic advanced colorectal cancer

State of the art: Targeting microsatellite instability in gastrointestinal cancers

DNA mismatch repair (MMR) deficiency and the associated microsatellite instability (MSI) phenotype has become a subject of enormous interest in recent years due to the demonstrated efficacy of immune checkpoint inhibitors (ICI) in advanced tumours. Assessing MSI in patients with gastrointestinal tract (GI) cancers is useful to exclude Lynch syndrome, but also to predict benefit for ICI. Following review of the relevant literature, this review article aims to outline the clinicopathologic spectrum of MSI and mismatch repair deficiency (dMMR) in the GI tract, hepatobiliary system and pancreas and discuss the therapeutic consideration in this disease.

State-of-the-Art Management of Colorectal Cancer: Treatment Advances and Innovation

Colorectal cancer (CRC) remains a significant global health challenge, ranking among the leading causes of cancer-related morbidity and mortality worldwide. Recent advancements in molecular characterization have revolutionized our understanding of the heterogeneity within colorectal tumors, particularly in the context of tumor sidedness. Tumor sidedness, referring to the location of the primary tumor in either the right or left colon, has emerged as a critical factor influencing prognosis and treatment responses in metastatic CRC. Molecular underpinnings of CRC, the impact of tumor sidedness, and how this knowledge guides therapeutic decisions in the era of precision medicine have led to improved outcomes and better quality of life in patients. The emergence of circulating tumor DNA as a prognostic and predictive tool in CRC heralds promising advancements in the diagnosis and monitoring of the disease. This innovation facilitates better patient selection for exploration of additional treatment options. As the field progresses, with investigational agents demonstrating potential as future treatments for refractory metastatic CRC, new avenues for enhancing outcomes in this challenging disease are emerging.

PTCH1 mutation as a potential predictive biomarker for immune checkpoint inhibitors in gastrointestinal cancer

Immune checkpoint inhibitors (ICIs) have become prominent therapies for gastrointestinal cancer (GC). However, it is urgent to screen patients who can benefit from ICIs. Protein patched homolog 1 (PTCH1) is a frequently altered gene in GC. We attempt to explore the association between PTCH1 mutation and immunotherapy efficacy. The Memorial Sloan Kettering Cancer Center (MSKCC) cohort (n = 236) with GC (esophageal, gastric and colorectal cancers) patients receiving ICIs was used for discovery and the Peking University Cancer Hospital (PUCH) GC cohort (n = 92) was used for validation. Overall survival (OS) and tumor mutational burden (TMB) of the PTCH1 mutant-type (PTCH1-MUT) and PTCH1 wild-type (PTCH1-WT) groups were compared. Furthermore, GC data were collected from The Cancer Genome Atlas to assess the potential mechanisms. In the MSKCC cohort, PTCH1-MUT group showed significantly better OS (P = 0.017) and higher TMB. Multivariate analysis showed that PTCH1 mutation was associated with better OS. In the PUCH cohort, PTCH1-MUT group showed significantly longer OS (P = 0.036) and progression-free survival, and higher durable clinical benefit and TMB. Immune cell infiltration analysis revealed that PTCH1-MUT group had significantly higher distributions of CD8 T cells, CD4 T cells, NK cells, mast cells and M1 cells. The PTCH1-MUT group showed significantly higher expression of most immune-related genes. Gene set enrichment analysis showed that the PTCH1-MUT group had enriched INF-γ response, INF-α response, glycolysis and reactive oxygen species pathway gene sets. PTCH1 mutation may represent a potential biomarker for predicting ICIs response in GC. Nevertheless, prospective cohort studies should be performed to further validate our results.

Robust best linear weighted estimator with missing covariates in survival analysis

Missing data in covariates can result in biased estimates and loss of power to detect associations. We consider Cox regression in which some covariates are subject to missing. The inverse probability weighted approach is often applied to regression analysis with missing covariates. Inverse probability weighted estimators typically are less efficient than likelihood-based estimators, but in general are more robust against model misspecification. In this article, we propose a robust best linear weighted estimator for Cox regression with missing covariates. Our proposed estimator is the projection of the simple inverse probability weighted estimator onto the orthogonal complement of the score space based on a working regression model of the observed data. The efficiency gain is from the use of the association between the survival outcome variable and the available covariates, which is the working regression model. The asymptotic distribution is derived, and the finite sample performance of the proposed estimator is examined via extensive simulation studies. The methods are applied to a colorectal cancer study to assess the association of the microsatellite instability status with colorectal cancer-specific mortality.

Molecular Landscape and Therapeutic Strategies against Colorectal Cancer

Colorectal cancer (CRC) is the second leading cause of cancer deaths worldwide. Although the overall incidence of CRC is decreasing, the incidence of young-onset CRC, characterized by a diagnosis of CRC before age 50, is increasing. Outcomes for CRC patients are improving, partly due to comprehensive molecular characterization of tumors and novel therapeutic strategies. Advances in genomic and transcriptomic analyses using blood- and tumor-tissue-based sequencing have facilitated identification of distinct tumor subtypes harboring unique biological characteristics and therapeutic vulnerabilities. These insights have led to the development and incorporation of targeted therapies and immunotherapy in CRC treatment. In this review, we discuss the molecular landscape and key oncogenes/tumor suppressors contributing to CRC tumorigenesis, metastasis, and therapeutic resistance. We also discuss personalized therapeutic strategies for subsets of CRC patients and provide an overview of evolving novel treatments being evaluated in clinical trials.

A Case of Medullary Carcinoma of Colon Morphologically Resembling Non-Hodgkin's Lymphoma

Medullary carcinoma of the colon is an unusual and unique histologic subtype of colorectal cancer. It is strongly associated with microsatellite instability, most commonly loss of MLH1 indicative of deficient mismatch repair proteins. Diagnosis is challenging as they do not display the usual histological pattern. Immunohistochemical staining also shows unusual findings like negativity for CD20 and CDX2. Here, we explore an intriguing case of medullary carcinoma of colon which showed loss of MSH2 and MSH6 and a morphology reminiscent of Non-Hodgkin's lymphoma.

Overall Survival, BRAF, RAS, and MSI Status in Patients Who Underwent Cetuximab After Refractory Chemotherapy for Metastatic Colorectal Cancer

PURPOSE

Evaluate overall survival (OS), RAS, BRAF, and MSI frequencies in patients with metastatic colorectal cancer (mCRC), refractory to chemotherapy, and finally treated with cetuximab.

METHODS

A retrospective cohort study to evaluate 211 mCRC patients with wild-type KRAS treated with cetuximab. BRAF V600E, KRAS, NRAS gene mutations, and MSI status were identified using PCR techniques in a population of pre-treated patients who were refractory to fluoropyrimidines, oxaliplatin, and irinotecan. In addition, we evaluated the mutation frequency of the BRAF and NRAS genes and the MSI status of this population. Uni- and multivariate analyses were performed for independent prognostic factors of OS.

RESULTS

The median OS was 10.4 months, 6.6 months for patients with right and 11.5 months for left colon cancers (p = 0.02). The frequencies of mutations were BRAF at 3.9% (median OS of 4.9 months), NRAS at 3.38% (median OS of 6.9 months), and MSI-High status at 3.3% (median OS of 4.6 months). The OS, NRAS, and MSI frequencies were similar to those found in other studies that evaluated cetuximab in poly-treated patients and were associated with lower survival rates in univariate analyses. The frequency of BRAF mutations was lower than that found in previous studies. The only variable that remained significant for OS in the multivariate model was tumour laterality, with patients with right colon cancer presenting a worse prognosis (HR = 2.81).

CONCLUSION

Although BRAF, NRAS mutations, and MSI-High status were associated with shorter OS in univariate analyses, only tumour laterality remained an independent prognostic factor in the multivariate analysis.

Neoadjuvant Immunotherapy With Ipilimumab Plus Nivolumab in Mismatch Repair Deficient/Microsatellite Instability-High Colorectal Cancer: A Preliminary Report of Case Series

BACKGROUND

Although ipilimumab plus nivolumab have significantly improved the survival of metastatic colorectal cancer (CRC) with mismatch repair deficient (dMMR) /microsatellite instability-high (MSI-H), the data on neoadjuvant setting is limited.

PATIENTS AND METHODS

We enrolled 11 patients with advanced dMMR/MSI-H CRC. 10 patients were locally advanced and 1 was metastatic. Ten patients were treated with 1 dose of ipilimumab (1 mg/kg) and 2 doses of nivolumab (3 mg/kg), and 1 patient was treated with 1 dose of ipilimumab (1 mg/kg) and 2 doses of nivolumab (3 mg/kg) with 2 cycles. All the patients underwent surgery after immunotherapy. The aim of the study was to evaluate the safety and short-term efficacy of this strategy.

RESULTS

Pathologic responses were observed in 11/11 (100%) dMMR/MSI-H tumors, with 9/11 (81.8%) achieving complete responses. Among these 9 cases with complete responses, 1 achieved a radiological noncomplete response after treatment with 1 dose of ipilimumab (1 mg/kg) and 2 doses of nivolumab (3 mg/kg), so another cycle of treatment with 1 dose of ipilimumab (1 mg/kg) and 2 doses of nivolumab (3 mg/kg) was administered, followed by surgery. The postoperative pathological evaluation was a complete response. Seven patients (63.6%) developed grade I/II adverse events. No patients developed grade III/IV adverse events or postoperative complications.

CONCLUSION

Neoadjuvant immunotherapy with ipilimumab plus nivolumab induced tumor regression with a major clinical and pathological response in advanced dMMR/MSI-H CRC. Notably, patients do not achieve a complete response to neoadjuvant immunotherapy, additional neoadjuvant immunotherapy may offer benefits. Further research is needed to assess the long-term efficacy of this strategy.

Construction and validation of a colon cancer prognostic model based on tumor mutation burden-related genes

Currently, immunotherapy has entered the clinical diagnosis and treatment guidelines for colon cancer, but existing immunotherapy markers cannot predict the effectiveness of immunotherapy well. This study utilized the TCGA-COAD queue to perform differential gene analysis on high and low-mutation burden samples, and screen differentially expressed genes (DEGs). To explore new molecular markers or predictive models of immunotherapy by using DEGs for NMF classification and prognostic model construction. Through systematic bioinformatics analysis, the TCGA-COAD cohort was successfully divided into high mutation burden subtypes and low mutation burden subtypes by NMF typing using DEGs. The proportion of MSI-H between high mutation burden subtypes was significantly higher than that of low mutation burden subtypes, but there was no significant difference in immunotherapy efficacy between the two subtypes. Drug sensitivity analysis showed significant differences in drug sensitivity between the two subtypes. Subsequently, we constructed a prognostic model using DEGs, which can effectively predict patient survival and immunotherapy outcomes. The prognosis and immunotherapy outcomes of the low-risk group were significantly better than those of the high-risk group. The external dataset validation of the constructed prognostic model using the GSE39582 dataset from the GEO database yielded consistent results. At the same time, we also analyzed the TMB and MSI situation between the high and low-risk groups, and the results showed that there was no significant difference in TMB between the high and low-risk groups, but the proportion of MSI-H in the high-risk group was significantly higher than that in the low-risk group. Finally, we conclude that TMB is not a suitable molecular marker for predicting the efficacy of immunotherapy in colon cancer. The newly constructed prognostic model can effectively differentiate the prognosis of colon cancer patients and predict their immunotherapy efficacy.

The effects of oxaliplatin-based adjuvant chemotherapy in high-risk stage II colon cancer with mismatch repair-deficient: a retrospective study

BACKGROUND

For high-risk stageIImismatch repair deficient (dMMR) colon cancers, the benefit of adjuvant chemotherapy remains debatable. The principal aim of this study was to evaluate the prognostic value of high-risk factors and the effect of oxaliplatin-based adjuvant chemotherapy among dMMR stageIIcolon cancers.

METHODS

Patients with stage II dMMR colon cancers diagnosed between June 2011 and May 2018 were enrolled in the study. Clinicopathological characteristics, treatment, and follow-up data were retrospectively collected. The high-risk group was defined as having one of the following factors: pT4 disease, fewer than twelve lymph nodes harvested (< 12 LNs), poorly differentiated histology, perineural invasion (PNI), lymphatic vascular invasion (LVI), or elevated preoperative carcinoembryonic antigen (CEA). The low-risk group did not have any risk factors above. Factors associated with disease-free survival (DFS) were included in univariate and multivariate Cox analyses.

RESULTS

We collected a total of 262 consecutive patients with stage II dMMR colon cancer. 179 patients (68.3%) have at least one high-risk factor. With a median follow-up of 50.1 months, the low-risk group was associated with a tended to have a better 3-year DFS than the high-risk group (96.4% vs 89.4%; P = 0.056). Both elevated preoperative CEA (HR 2.93; 95% CI 1.26-6.82; P = 0.013) and pT4 disease (HR 2.58; 95% CI 1.06-6.25; P = 0.037) were independent risk factors of recurrence. Then, the 3-year DFS was 92.6% for the surgery alone group and 88.1% for the adjuvant chemotherapy group (HR 1.64; 95% CI 0.67-4.02; P = 0.280). Furthermore, no survival benefit from oxaliplatin-based adjuvant chemotherapy was observed in the high-risk group and in the subgroups with pT4 disease or < 12 LNs.

CONCLUSIONS

These data suggests that not all high-risk factors have a similar impact on stage II dMMR colon cancers. Elevated preoperative CEA and pT4 tumor stage are associated with increased recurrence risk. However, oxaliplatin-based adjuvant chemotherapy shows no survival benefits in stage II dMMR colon cancers, either with or without high-risk factors.

Immunotherapy in mismatch repair-deficient metastatic colorectal cancer - Outcome and novel predictive markers

BACKGROUND

This study aims to assess predictive markers for response to immunotherapy in dMMR/MSI-H metastatic colorectal cancer (mCRC) patients.

MATERIALS AND METHODS

A study using two prospective cohorts from MD Anderson Cancer Center and Sheba Medical Center of consecutive patients with dMMR/MSI-H mCRC that were treated with immunotherapy between 2014-2022. Primary outcome was progression-free survival (PFS) and secondary outcome was overall response rate (ORR). Evaluated predictors included ECOG-PS score, RAS/BRAF status, single-agent versus doublet immunotherapy, metastatic sites, disease burden, and CEA levels prior to treatment initiation. Kaplan-Meier analysis and Cox proportional hazard regression model were used to analyze the effect of exposure variables on PFS.

RESULTS

The study included 153 patients. Median follow-up time was 26 months (IQR 11-48). Median PFS was 51.6 months (95%CI 38.1-NR) and ORR was 58.1%. In a univariate analysis, male sex was associated with worse PFS with a HR of 1.67 (95% CI 1.00-2.79); Right-sided tumors were associated with improved PFS with a HR of 0.56 (95% CI 0.32-0.97); Liver or lung metastasis were associated with worse PFS with HRs of 2.35 (95%CI 1.43-3.88) and 2.30 (95%CI 1.31-4.04), respectively; ECOG-PS score ≥ 2, CEA levels ˃5 μg/L prior to treatment initiation and ≥ 3 metastatic sites were associated with worse PFS with HRs of 2.09 (95%CI 0.98-4.47), 2.23 (95%CI 1.30-3.81) and 3.11 (95%CI 1.61-6.03), respectively. Liver or lung metastasis remained significant in a multivariable model.

CONCLUSIONS

Extent of disease (worse PFS with high CEA, poor ECOG-PS and ≥3 metastatic sites) and disease location (worse PFS with liver or lung metastasis and left sided tumor) were associated with immunotherapy outcome in dMMR/MSI-H mCRC.

Identification of colon cancer subtypes based on multi-omics data-construction of methylation markers for immunotherapy

Background

Being the most widely used biomarker for immunotherapy, the microsatellite status has limitations in identifying all patients who benefit in clinical practice. It is essential to identify additional biomarkers to guide immunotherapy. Aberrant DNA methylation is consistently associated with changes in the anti-tumor immune response, which can promote tumor progression. This study aims to explore immunotherapy biomarkers for colon cancers from the perspective of DNA methylation.

Methods

The related data (RNA sequencing data and DNA methylation data) were obtained from The Cancer Genome Atlas (TCGA) and UCSC XENA database. Methylation-driven genes (MDGs) were identified through the Pearson correlation analysis. Unsupervised consensus clustering was conducted using these MDGs to identify distinct clusters of colon cancers. Subsequently, we evaluated the immune status and predicted the efficacy of immunotherapy by tumor immune dysfunction and exclusion (Tide) score. Finally, The Quantitative Differentially Methylated Regions (QDMR) software was used to identify the specific DNA methylation markers within particular clusters.

Results

A total of 282 MDGs were identified by integrating the DNA methylation and RNA-seq data. Consensus clustering using the K-means algorithm revealed that the optimal number of clusters was 4. It was revealed that the composition of the tumor immune microenvironment (TIME) in Cluster 1 was significantly different from others, and it exhibited a higher level of tumor mutation burdens (TMB) and stronger anti-tumor immune activity. Furthermore, we identified three specific hypermethylation genes that defined Cluster 1 (PCDH20, APCDD1, COCH). Receiver operating characteristic (ROC) curves demonstrated that these specific markers could effectively distinguish Cluster 1 from other clusters, with an AUC of 0.947 (95% CI 0.903-0.990). Finally, we selected clinical samples for immunohistochemical validation.

Conclusion

In conclusion, through the analysis of DNA methylation, consensus clustering of colon cancer could effectively identify the cluster that benefit from immunotherapy along with specific methylation biomarkers.

Multi-omics of the gut microbial ecosystem in patients with microsatellite-instability-high gastrointestinal cancer resistant to immunotherapy

Despite the encouraging efficacy of anti-PD-1/PD-L1 immunotherapy in microsatellite-instability-high/deficient mismatch repair (MSI-H/dMMR) advanced gastrointestinal cancer, many patients exhibit primary or acquired resistance. Using multi-omics approaches, we interrogate gut microbiome, blood metabolome, and cytokines/chemokines of patients with MSI-H/dMMR gastrointestinal cancer (N = 77) at baseline and during the treatment. We identify a number of microbes (e.g., Porphyromonadaceae) and metabolites (e.g., arginine) highly associated with primary resistance to immunotherapy. An independent validation cohort (N = 39) and mouse model are used to further confirm our findings. A predictive machine learning model for primary resistance is also built and achieves an accuracy of 0.79 on the external validation set. Furthermore, several microbes are pinpointed that gradually changed during the process of acquired resistance. In summary, our study demonstrates the essential role of gut microbiome in drug resistance, and this can be utilized as a preventative diagnosis tool and therapeutic target in the future.

Challenging case of deficient mismatch repair right-sided locally advanced adenocarcinoma of the ascending colon with duodenal involvement: A case report including step-by-step video of operation

INTRODUCTION AND IMPORTANCE

Irresectable colon cancer presents a complex clinical challenge. Neoadjuvant immunotherapy has shown potential in improving resectability. Additionally, advancements in surgical techniques, including complete mesocolic excision (CME) with central vascular ligation (CVL), have contributed to better outcomes for right-sided colon cancer. This case report aims to demonstrate the successful laparoscopic resection of initial appearing irresectable colon cancer with suspected duodenal involvement.

CASE PRESENTATION

A 70-year-old female presented with an irresectable mismatch repair deficient (dMMR) adenocarcinoma of the ascending colon with suspected duodenal ingrowth. Neoadjuvant treatment with pembrolizumab and ataluren resulted in a significant response, allowing for surgical resection. A laparoscopic right hemicolectomy with CME, including CVL, intracorporeal anastomosis and extraction through a Pfannenstiel incision, was performed. Additionally, the serosal layer of the duodenum was shaved after observing the absence of intraluminal invasion. Postoperatively, transient gastroparesis occurred, but overall outcomes were favourable.

CLINICAL DISCUSSION

This case emphasizes the potential of immunotherapy in improving resectability for irresectable dMMR colon cancer with suspected involvement of surrounding organs. The combination of neoadjuvant therapy and advanced surgical techniques, such as CME with CVL, shows promise in achieving favourable clinical outcomes. However, further studies are needed to validate the effectiveness and safety of this combined approach in a larger cohort of patients.

CONCLUSION

The successful laparoscopic resection of initially irresectable dMMR colon cancer with duodenal involvement, following neoadjuvant immunotherapy, demonstrated promising outcomes. This case advocates for further exploration of neoadjuvant treatments' efficacy, coupled with advanced surgical techniques, in managing locally advanced right-sided colon cancer.

Leveraging a KRAS-based signature to predict the prognosis and drug sensitivity of colon cancer and identifying SPINK4 as a new biomarker

KRAS is one of the leading mutations reported in colon cancer. However, there are few studies on the application of KRAS related signature in predicting prognosis and drug sensitivity of colon cancer patient. We identified KRAS related differentially expressed genes (DEGs) using The Cancer Genome Atlas (TCGA) database. A signature closely related to overall survival was recognized with Kaplan-Meier survival analysis and univariate cox regression analysis. Then we validated this signature with overall expression score (OE score) algorithm using both scRNA-seq and bulk RNA-seq data. Based on this signature, we performed LASSO cox regression to establish a prognostic model, and corresponding scores were calculated. Differences in genomic alteration, immune microenvironment, drug sensitivity between high- and low-KRD score groups were investigated. A KRAS related signature composed of 80 DEGs in colon cancer were recognized, among which 19 genes were selected to construct a prognostic model. This KRAS related signature was significantly correlated with worse prognosis. Furthermore, patients who scored lower in the prognostic model presented a higher likelihood of responding to chemotherapy, targeted therapy and immunotherapy. Furthermore, among the 19 selected genes in the model, SPINK4 was identified as an independent prognostic biomarker. Further validation in vitro indicated the knockdown of SPINK4 promoted the proliferation and migration of SW48 cells. In conclusion, a novel KRAS related signature was identified and validated based on clinical and genomic information from TCGA and GEO databases. The signature was proved to regulate genomic alteration, immune microenvironment and drug sensitivity in colon cancer, and thus might serve as a predictor for individual prognosis and treatment.

Unique characteristics of the tumor immune microenvironment in young patients with metastatic colorectal cancer

Introduction

Metastatic colorectal cancer (mCRC) remains a common and highly morbid disease, with a recent increase in incidence in patients younger than 50 years. There is an acute need to better understand differences in tumor biology, molecular characteristics, and other age-related differences in the tumor microenvironment (TME).

Methods

111 patients undergoing curative-intent resection of colorectal liver metastases were stratified by age into those <50 years or >65 years old, and tumors were subjected to multiplex fluorescent immunohistochemistry (mfIHC) to characterize immune infiltration and cellular engagement.

Results

There was no difference in infiltration or proportion of immune cells based upon age, but the younger cohort had a higher proportion of programmed death-ligand 1 (PD-L1)+ expressing antigen presenting cells (APCs) and demonstrated decreased intercellular distance and increased cellular engagement between tumor cells (TCs) and cytotoxic T lymphocytes (CTLs), and between TCs and APCs. These trends were independent of microsatellite instability in tumors.

Discussion

Age-related differences in PD-L1 expression and cellular engagement in the tumor microenvironment of patients with mCRC, findings which were unrelated to microsatellite status, suggest a more active immune microenvironment in younger patients that may offer an opportunity for therapeutic intervention with immune based therapy.

Heterogeneity and Adjuvant Therapeutic Approaches in MSI-H/dMMR Resectable Gastric Cancer: Emerging Trends in Immunotherapy

Gastric cancer (GC) remains one of the world's most common and fatal malignant tumors. With a refined understanding of molecular typing in recent years, microsatellite instability (MSI) has become a major molecular typing approach for gastric cancer. MSI is well recognized for its important role during the immunotherapy of advanced GC. However, its value remains unclear in resectable gastric cancer. The reported incidence of microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) in resectable gastric cancer varies widely, with no consensus reached on the value of postoperative adjuvant therapy in patients with MSI-H/dMMR resectable GC. It has been established that MSI-H/dMMR tumor cells can elicit an endogenous immune antitumor response and ubiquitously express immune checkpoint ligands such as PD-1 or PD-L1. On the basis of these considerations, MSI-H/dMMR resectable GCs are responsive to adjuvant immunotherapy, although limited research has hitherto been conducted. In this review, we comprehensively describe the differences in geographic distribution and pathological stages in patients with MSI-H/dMMR with resectable gastric cancer and explore the value of adjuvant chemotherapy and immunotherapy on MSI-H/dMMR to provide a foothold for the individualized treatment of this patient population.

[Novel Treatment Concepts in Patients with Colorectal Carcinomas and High Microsatellite Instability]

Approximately 15% of patients with colorectal cancer show high microsatellite instability (MSI-high) in their tumour tissue. For one third of these patients, there is a hereditary cause for this finding - that leads to the diagnosis of Lynch Syndrome. In combination with clinical findings such as the Amsterdam or the revised Bethesda criteria, MSI-high status has been used as a tool in identifying patients at risk. Today, MSI-status has gained much more importance, due to its impact on treatment decisions. Patients with UICC II cancers should not receive adjuvant treatment. For patients with distant metastases and MSI-high status, immune checkpoint inhibitors can be given as first line therapy - with tremendous success. Novel data show a deep response for immune checkpoint antibodies in patients with locally advanced colon as well as rectal cancer in a neoadjuvant setting. Especially for patients with MSI-high rectal cancer, there might be a novel therapeutic regimen utilising immune checkpoint inhibitors without neoadjuvant radio-chemotherapy and even without surgery. This could lead to a relevant reduction in morbidity in this patient cohort. In conclusion, universal MSI-testing is essential for identifying patients at risk for Lynch syndrome and for optimal decision making in treatment planning.

Current progress of immune checkpoint inhibitors for advanced colorectal cancer: concentrating on the efficacy improvement

Immune checkpoint inhibitors (ICIs) have paved a new pathway and revolutionized cancer treatment. Currently, ICIs have been extensively used for patients with advanced colorectal cancer (CRC), especially those harboring microsatellite instability (MSI). However, the efficacy of ICIs varies tremendously in different individuals, and some patients may not benefit from ICIs, which limits their clinical application. How to improve the efficacy of ICIs is an important issue to be solved. On the one hand, it is urgent to discover the predictive biomarkers to accurately screen the patients who gain benefit from ICIs, like microsatellite stability, tumor mutation burden (TMB), DNA polymerase ε/DNA polymerase δ1 mutations, and the expression of programmed death-ligand 1 (PD-L1). The rational use of these biomarkers will help clinicians identify suitable candidates who will benefit from ICI treatment, thereby improving therapeutic efficiency. Additionally, it is vital to design combination therapeutic strategies for optimizing the therapeutic effectiveness of ICIs. Nowadays, treatment strategies like chemotherapy, radiotherapy, targeted therapy along with ICIs, have helped improve the therapeutic effectiveness of ICIs. In this review, we have focused on the recent advancements in the predictive biomarkers and combination therapeutic strategies with ICIs for colorectal cancer.

Mismatch Repair Deficiency Is a Prognostic Factor Predicting Good Survival of Opisthorchis viverrini-Associated Cholangiocarcinoma at Early Cancer Stage

BACKGROUND

The mismatch repair (MMR) system prevents DNA mutation; therefore, deficient MMR protein (dMMR) expression causes genetic alterations and microsatellite instability (MSI). dMMR is correlated with a good outcome and treatment response in various cancers; however, the situation remains ambiguous in cholangiocarcinoma (CCA). This study aims to evaluate the prevalence of dMMR and investigate the correlation with clinicopathological features and the survival of CCA patients after resection.

MATERIALS AND METHODS

Serum and tissues were collected from CCA patients who underwent resection from January 2005 to December 2017. Serum OV IgG was examined using ELISA. The expression of MMR proteins MLH1, MSH2, MSH6 and PMS2 was investigated by immunohistochemistry; subsequently, MMR assessment was evaluated as either proficient or as deficient by pathologists. The clinicopathological features and MMR status were compared using the Chi-square test. Univariate and multivariate analyses were conducted to identify prognostic factors.

RESULTS

Among the 102 CCA patients, dMMR was detected in 22.5%. Survival analysis revealed that dMMR patients had better survival than pMMR (HR = 0.50, p = 0.008). In multivariate analysis, dMMR was an independent factor for a good prognosis in CCA patients (HR = 0.58, p = 0.041), especially at an early stage (HR = 0.18, p = 0.027). Moreover, subgroup analysis showed dMMR patients who received adjuvant chemotherapy had better survival than surgery alone (HR = 0.28, p = 0.012).

CONCLUSION

This study showed a high prevalence of dMMR in cholangiocarcinoma with dMMR being the independent prognostic factor for good survival, especially in early-stage CCA and for patients who received adjuvant chemotherapy. dMMR should be the marker for selecting patients to receive a specific adjuvant treatment after resection for CCA.

Avelumab vs Standard Second-Line Chemotherapy in Patients With Metastatic Colorectal Cancer and Microsatellite Instability: A Randomized Clinical Trial

Importance

Only 1 randomized clinical trial has shown the superiority of immune checkpoint inhibitors in patients with deficient mismatch repair and/or microsatellite instability (dMMR/MSI) metastatic colorectal cancer (mCRC) in the first-line setting.

Objectives

To determine whether avelumab (an anti-programmed cell death ligand 1 antibody) improves progression-free survival (PFS) compared with standard second-line chemotherapy in patients with dMMR/MSI mCRC.

Design, Setting, and Participants

The SAMCO-PRODIGE 54 trial is a national open-label phase 2 randomized clinical trial that was conducted from April 24, 2018, to April 29, 2021, at 49 French sites. Patients with dMMR/MSI mCRC who experienced progression while receiving standard first-line therapy were included in the analysis.

Interventions

Patients were randomized to receive standard second-line therapy or avelumab every 2 weeks until progression, unacceptable toxic effects, or patient refusal.

Main Outcome and Measures

The primary end point was PFS according to RECIST (Response Evaluation Criteria in Solid Tumours), version 1.1, evaluated by investigators in patients with mCRC and confirmed dMMR and MSI status who received at least 1 dose of treatment (modified intention-to-treat [mITT] population).

Results

A total of 122 patients were enrolled in the mITT population. Median age was 66 (IQR, 56-76) years, 65 patients (53.3%) were women, 100 (82.0%) had a right-sided tumor, and 52 (42.6%) had BRAF V600E-mutated tumors. There was no difference in patients and tumor characteristics between treatment groups. No new safety concerns in either group were detected, with fewer treatment-related adverse events of at least grade 3 in the avelumab group than in the chemotherapy group (20 [31.7%] vs 34 [53.1%]; P = .02). After a median follow-up of 33.3 (95% CI, 28.3-34.8) months, avelumab was superior to chemotherapy with or without targeted agents with respect to PFS (15 [24.6%] vs 5 [8.2%] among patients without progression; P = .03). Rates of PFS rates at 12 months were 31.2% (95% CI, 20.1%-42.9%) and 19.4% (95% CI, 10.6%-30.2%) in the avelumab and control groups, respectively, and 27.4% (95% CI, 16.8%-39.0%) and 9.1% (95% CI, 3.2%-18.8%) at 18 months. Objective response rates were similar in both groups (18 [29.5%] vs 16 [26.2%]; P = .45). Among patients with disease control, 18 (75.7%) in the avelumab group compared with 9 (19.1%) in the control group had ongoing disease control at 18 months.

Conclusions

The SAMCO-PRODIGE 54 phase 2 randomized clinical trial showed, in patients with dMMR/MSI mCRC, better PFS and disease control duration with avelumab over standard second-line treatment, with a favorable safety profile.

Trial Registration

ClinicalTrials.gov Identifier: NCT03186326.

Survival of Patients with Deficient Mismatch Repair Versus Proficient Mismatch Repair Metastatic Colorectal Cancer Receiving Curative-Intent Local Treatment of Metastases in a Nationwide Cohort

BACKGROUND

It is unclear whether curative-intent local therapy of metastases is of similar benefit for the biological distinct subgroup of patients with deficient mismatch repair (dMMR) metastatic colorectal cancer (mCRC) compared with proficient mismatch repair (pMMR) mCRC.

PATIENTS AND METHODS

In this nationwide study, recurrence-free (RFS) and overall survival (OS) were analyzed in patients with dMMR versus pMMR mCRC who underwent curative-intent local treatment of metastases between 2015 and 2018. Subgroup analyses were performed for resection of colorectal liver metastases (CRLM) and cytoreductive surgery ± hyperthermic intraperitoneal chemotherapy (CRS ± HIPEC). Multivariable regression was conducted.

RESULTS

Median RFS was 11.1 months [95% confidence interval (CI) 8.5-41.1 months] for patients with dMMR tumors compared with 8.9 months (95% CI 8.1-9.8 months) for pMMR tumors. Two-year RFS was higher in patients with dMMR versus pMMR (43% vs. 21%). Results were similar within subgroups of local treatment (CRLM and CRS ± HIPEC). Characteristics differed significantly between patients with dMMR and pMMR mCRC; however, multivariable analysis continued to demonstrate dMMR as independent factor for improved RFS [hazard ratio (HR): 0.57, 95% CI 0.38-0.87]. Median OS was 33.3 months for dMMR mCRC compared with 43.5 months for pMMR mCRC, mainly due to poor survival of patients with dMMR in cases of recurrence in the preimmunotherapy era.

CONCLUSION

Patients with dMMR eligible for curative-intent local treatment of metastases showed a comparable to more favorable RFS compared with patients with pMMR, with a clinically relevant proportion of patients remaining free of recurrence. This supports local treatment as a valuable treatment option in patients with dMMR mCRC and can aid in shared decision-making regarding upfront local therapy versus immunotherapy.

Advanced Appendiceal Cancer with Systematic Metastasis without Gastrointestinal Symptoms Found by Subcutaneous Tumor

An 86-year-old woman with a subcutaneous nodule in her left axilla visited our hospital. She had no gastrointestinal symptoms, but contrast-enhanced computed tomography revealed a cecal mass and systemic metastasis, including cutaneous, bone, peritoneal dissemination and ascites. Colonoscopy revealed a circumferential, elevated cecal lesion. She underwent right hemicolectomy to prevent colon obstruction. The pathological diagnosis was poorly differentiated adenocarcinoma (por1>tub2>muc) arising from the appendix with a BRAFV600E mutation and microsatellite instability-high. Chemotherapy was administered, and she is currently still alive and undergoing chemotherapy. We describe a rare case of advanced appendiceal cancer without gastrointestinal symptoms diagnosed due to cutaneous metastasis.

The impact of time to surgery on oncological outcomes in stage I-III dMMR colon cancer - A nationwide cohort study

INTRODUCTION

One of the considerations when investigating neoadjuvant interventions is the prolonging of time from diagnosis to curative surgery (i.e. the treatment interval [TI]). The aim of this study was to investigate the association between the length of TI and overall survival and disease-free survival in patients with deficient mismatch repair (dMMR) colon cancer.

MATERIALS AND METHODS

This retrospective propensity score-adjusted study included all patients of ≥18 years of age undergoing elective curative surgery for stage I-III, dMMR colon cancer. Data were extracted from four Danish patient databases. Outcomes were investigated in groups with TIs of ≤14 days versus >14 days. Propensity scores were computed using all demographics, diagnoses and measurements. Matching was done in a 1:1 ratio.

RESULTS

A total of 4130 patients were included in the study with a mean age of 73.8 years and a median follow-up time of 43.9 months. After matching, 2794 patients were included in the analysis of overall survival. No significant difference in overall survival was seen between patients with TIs of ≤14 days versus >14 days (hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.81-1.17; p = 0.78). In the analysis of disease-free survival, 1798 patients were included after matching. This showed no significant difference between patients with TIs of ≤14 days versus >14 days (HR, 0.85; 95% CI, 0.69-1.06; p = 0.14).

CONCLUSION

No associations were found between TI and overall survival and disease-free survival in patients with stage I-III, dMMR colon cancer undergoing elective curative surgery.

Prognostic value of Lynch syndrome, BRAFV600E , and RAS mutational status in dMMR/MSI-H metastatic colorectal cancer in a pooled analysis of Dutch and French cohorts

BACKGROUND

Current knowledge on prognostic biomarkers (especially BRAFV600E /RAS mutations) in metastatic colorectal cancer (mCRC) is mainly based on mCRC patients with proficient mismatch repair (pMMR) tumors. It is uncertain whether these biomarkers have the same prognostic value in mCRC patients with deficient mismatch repair (dMMR) tumors.

METHODS

This observational cohort study combined a population-based Dutch cohort (2014-2019) and a large French multicenter cohort (2007-2017). All mCRC patients with a histologically proven dMMR tumor were included.

RESULTS

In our real-world data cohort of 707 dMMR mCRC patients, 438 patients were treated with first-line palliative systemic chemotherapy. Mean age of first-line treated patients was 61.9 years, 49% were male, and 40% had Lynch syndrome. BRAFV600E mutation was present in 47% of tumors and 30% harbored a RAS mutation. Multivariable regression analysis on OS showed significant hazard rates (HR) for known prognostic factors as age and performance status, however showed no significance for Lynch syndrome (HR: 1.07, 95% CI: 0.66-1.72), BRAFV600E mutational status (HR: 1.02, 95% CI: 0.67-1.54), and RAS mutational status (HR: 1.01, 95% CI: 0.64-1.59), with similar results for PFS.

CONCLUSION

BRAFV600E and RAS mutational status are not associated with prognosis in dMMR mCRC patients, in contrast to pMMR mCRC patients. Lynch syndrome is also not an independent prognostic factor for survival. These findings underline that prognostic factors of patients with dMMR mCRC are different of those with pMMR, which could be taken into consideration when prognosis is used for clinical decision-making in dMMR mCRC patients and underline the complex heterogeneity of mCRC.

Cost-effectiveness analysis of pembrolizumab in patients with treatment-refractory metastatic colorectal cancer in Japan

OBJECTIVE

The immune checkpoint inhibitor pembrolizumab has recently been recognized as a standard treatment regimen for patients with metastatic colorectal cancer and the microsatellite-instability-high/mismatch repair-deficient mutation. However, its cost-effectiveness in late-line treatment remains unclear. The aim of this study was to assess the cost-effectiveness of pembrolizumab for patients with microsatellite-instability-high/mismatch repair-deficient metastatic colorectal cancer.

METHODS

Markov decision modeling using treatment costs, disease-free survival and overall survival was performed to examine the cost-effectiveness of pembrolizumab monotherapy compared with chemotherapy, and best supportive care. The Japanese healthcare payer's perspective was adopted. The outcomes were modeled on the basis of published literature. The primary outcome was the incremental cost-effectiveness ratio between the strategies. Sensitivity analyses were performed and the effects of uncertainty on the model parameters were investigated.

RESULTS

Pembrolizumab monotherapy had incremental cost-effectiveness ratios of $408204.3 per quality-adjusted life-year gained compared with best supportive care and $489123.4 per quality-adjusted life-year gained compared with chemotherapy. Given a Japanese willingness-to-pay threshold of $69560.38 per quality-adjusted life-year, the base case results suggested that pembrolizumab monotherapy was not cost-effective. The sensitivity analysis results were in line with the base case results.

CONCLUSION

Pembrolizumab monotherapy is not a cost-effective option in late-line treatment for patients with metastatic colorectal cancer and microsatellite-instability-high/mismatch repair-deficient mutation in the Japanese healthcare system. Further studies on its cost-effectiveness in first-line treatment are warranted.

Combination of Immunotherapy and Radiation Therapy in Gastrointestinal Cancers: An Appraisal of the Current Literature and Ongoing Research

Oncological outcomes are improving in gastrointestinal cancer with advancements in systemic therapies, and there is notable potential in combining immunotherapy and radiation therapy (RT) to allow for further improvements. Various preclinical and early phase II studies have shown promising synergy with immunotherapy and RT in gastrointestinal cancer. A few recent phase III studies have shown improved survival with the addition of immunotherapy to standard treatment for gastrointestinal cancer. The timing, duration, sequencing, and integration with other anti-cancer treatments are still areas of ongoing research. We have reviewed the published and ongoing studies of the combinations of immunotherapy and RT in gastrointestinal cancers.

Case report: long-term sustained remission in a case of metastatic colon cancer with high microsatellite instability and KRAS exon 2 p.G12D mutation treated with fruquintinib after local radiotherapy: a case report and literature review

To demonstrate the efficacy of fruquintinib administration after local radiotherapy in a patient with metastatic colon cancer with high microsatellite instability and the KRAS exon 2 p. G12D mutation. The patient was administered four cycles of pembrolizumab intravenous infusion and achieved stable disease as the best outcome. He was then underwent follow-up concurrent radiochemical therapy (local DT4600cGy/23f/32d radiotherapy, and S-1 to increase sensitivity to radiotherapy), but this had little efficacy. Following this, he was administered fruquintinib and achieved sustained partial remission. At the time of last follow-up, the patient was in continuous remission for 30 months. Administration of fruquintinib after local radiotherapy may be an effective treatment for specific populations with metastatic colorectal cancer.

Evaluating the efficacy and safety of neoadjuvant pembrolizumab in patients with stage I-III MMR-deficient colon cancer: a national, multicentre, prospective, single-arm, phase II study protocol

INTRODUCTION

Within the last two decades, major advances have been made in the surgical approach for patients with colorectal cancer. However, to this day we face considerable challenges in reducing surgery-related complications and improving long-term oncological outcomes. Unprecedented response rates have been achieved in studies investigating immunotherapy in patients with mismatch repair deficient (dMMR) colorectal cancer. This has raised the question of whether neoadjuvant immunotherapy may change the standard of care for localised dMMR colon cancer and pave the way for organ-sparing treatment.

METHODS AND ANALYSIS

This is an investigator-initiated, multicentre, prospective, single-arm, phase II study in patients with stage I-III dMMR colon cancer scheduled for intended curative surgery. Eighty-five patients will be treated with one dose of pembrolizumab (4 mg/kg) and within 5 weeks will undergo a re-evaluation with an endoscopy and a CT scan-to assess tumour response-before standard resection of the tumour. The primary endpoint is the number of patients with pathological complete response, and secondary endpoints include safety (number and severity of adverse events) and postoperative surgical complications. In addition, we aspire to identify predictive biomarkers that can point out patients that achieve pathological complete response.

ETHICS AND DISSEMINATION

The Regional Committee for Health Research and Ethics and the Danish Medicines Agency have approved this study. The study will be performed according to the Helsinki II declaration. Written informed consent will be obtained from all participants. The results of the study will be submitted to peer-reviewed journals for publication and presented at international congresses.

TRIAL REGISTRATION NUMBER

NCT05662527.

Molecular and genetic targets within metastatic colorectal cancer and associated novel treatment advancements

Colorectal cancer results in the deaths of hundreds of thousands of patients worldwide each year, with incidence expected to rise over the next two decades. In the metastatic setting, cytotoxic therapy options remain limited, which is reflected in the meager improvement of patient survival rates. Therefore, focus has turned to the identification of the mutational composition inherent to colorectal cancers and development of therapeutic targeted agents. Herein, we review the most up to date systemic treatment strategies for metastatic colorectal cancer based on the actionable molecular alterations and genetic profiles of colorectal malignancies.

Immune checkpoint inhibition in advanced colorectal cancer with inherited and acquired microsatellite instability: Current state and future directions

OBJECTIVE

This paper reviews comprehensively the most relevant data on single-agent and combination therapies for advanced colorectal cancer with inherited and acquired microsatellite instability (MSI).

DATA SOURCES

We performed a systematic search on PubMed and MEDLINE articles published from inception to December 2022. We have also searched independent websites including U.S. Food and Drug Administration and ClinicalTrials.gov.

DATA SUMMARY

Performing microsatellite stability testing, tumor mutational burden (TMB), and germline mutation analysis could identify patients with metastatic colorectal cancer that benefit from immune checkpoint inhibitor (ICI) therapy. Single-agent pembrolizumab has proven superiority over traditional chemotherapy in these patients. The nivolumab-ipilimumab is the only combination ICI therapy approved in this space. Recently, the anti-PD-1 antibody dostarlimab was granted Food and Drug Administration approval in refractory tissue-agnostic advanced solid cancers with deficient mismatch repair (dMMR). ICIs are also being studied in the adjuvant/neoadjuvant setting in colon cancer patients with dMMR. Newer agents are being scrutinized in this space as well. More solid data on biomarkers predicting responses in patients with MSI-high or TMB-H to various therapies are needed. Given its both clinical and financial toxicity, it is imperative to determine the optimal duration of ICI therapy in individual patients.

CONCLUSIONS

Overall, the outlook in advanced colorectal cancer patients with MSI appears optimistic as new and efficacious ICI drugs and combinations are being added to the existing therapeutic armamentarium.

Molecular testing of DNA damage response pathways in prostate cancer patients

PURPOSE OF REVIEW

Personalizing prostate cancer therapy requires germline and tumor molecular tests that predict who will respond to specific treatments and who may not. The review covers molecular testing of DNA damage response pathways, the first biomarker-driven precision target with clinical utility for treatment selection in patients with castration resistant prostate cancer (CRPC).

RECENT FINDINGS

Recurrent somatic and germline variants cause deficiency of the mismatch repair (MMR) or homologous recombination (HR) pathways in about a quarter of CRPC patients. In prospective clinical trials, patients with deleterious variants in the MMR pathway more frequently experience a therapeutic response to immune checkpoint inhibitors (ICI). Similarly, somatic and germline events affecting HR predict response to poly(ADP) ribose polymerase inhibitor (PARPi) therapy. Molecular testing of these pathways currently involves assaying for loss of function variants in individual genes and for the genome-wide consequences of repair deficiency.

SUMMARY

DNA damage response pathways are the first major area of molecular genetic testing in CRPC settings and offer insights into this new paradigm. Our hope is that eventually an arsenal of molecularly-guided therapies will be developed across many pathways to enable precision medicine options for most men with prostate cancer.

Spontaneous regression of advanced transverse colon cancer with deficient mismatch repair: a case report

BACKGROUND

Spontaneous regression (SR) of cancer occurs in 1 in 60,000-100,000 patients. This phenomenon has been reported in almost all cancer types, most commonly neuroblastoma, renal cell carcinoma, malignant melanoma, and lymphoma/leukemia. However, SR in colorectal cancer (CRC) is extremely rare, particularly in advanced cases. Hence, this report describes a very rare case of spontaneous regression of advanced transverse colon cancer.

CASE PRESENTATION

A 76-year-old female with anemia was diagnosed with a type II well-differentiated adenocarcinoma in the middle transverse colon. Two months later, a second colonoscopy examination was performed for preoperative marking, and it revealed tumor shrinkage and a shift to type 0-IIc morphology. Endoscopic tattooing was then performed, followed by a laparoscopic partial resection of the transverse colon with D3 lymph node dissection. However, the resected specimen contained no tumor, and colonoscopy showed no tumor remnants in the remaining colon. Histopathological examination revealed mucosal regeneration and a mucus nodule in between the submucosal and muscular layers, with no cancer cells detected. Immunohistochemical analysis revealed the loss of MutL homolog 1 (MLH1) and postmeiotic segregation increased 2 (PMS2) expression in the cancer cells of biopsied specimens, suggesting deficient mismatch repair (dMMR). The patient continues to be followed up until 6 years postoperatively, and no recurrence has been observed. In this study, we also reviewed similar reported cases of spontaneous regression of cancer involving dMMR.

CONCLUSION

This study presents a rare case of spontaneous regression of advanced transverse colon cancer wherein dMMR is strongly involved. However, further accumulation of similar cases is needed to elucidate this phenomenon and to develop new treatment strategies for CRC.

Microsatellite Instability with BRAF V600E Associated with Delayed Presentation but Poor Survival in Stage III Colorectal Cancer

Colorectal cancer (CRC) has tremendous molecular and genetic heterogeneity, making it a difficult cancer to treat. Two of the key prognostic indicators of CRC include microsatellite instability (MSI) and BRAF V600E mutation. Here, we performed a retrospective survival analysis on 145 stage II and III CRC patients treated at the University of Kansas Cancer Center between 2009 and 2020. Of the 145 patients, BRAF V600E was observed in 15% patients and MSI in 28% patients. Median survival was not reached for stage II. For stage III, patients with BRAF V600E showed poor overall survival, which worsened with concurrent presence of MSI [χ2=6.4, p=0.01]. Eighty-five percent of this group was found to have right-sided CRC. For stage III, overall survival (OS) was 27 months, 37 months, 87 months and not reached for MSI-H/BRAF V600E, MSS/BRAF V600E, MSS/BRAF WT and MSI-H/BRAF WT, respectively. Although associated with poor prognosis, presence of MSI in BRAF V600E patients was associated with delayed disease presentation (mean age 77) compared to those with stable microsatellite (mean age 63) [p=0.01]. Although median survival between the groups could not be assessed for stage II due to very few deaths and/or inadequate length of study, comparison of survival trend suggests that BRAF V600E, rather than MSI, is what drives prognosis in stage II CRC. Our findings suggest that prognostic value of MSI is more relevant for stage III than stage II CRC. Patients with MSI-H and BRAF V600E have advantage of late presentation, although at the cost of poor overall prognosis.

Current Strategy to Treat Immunogenic Gastrointestinal Cancers: Perspectives for a New Era

Since pembrolizumab, an anti-programmed death-1 (PD-1) antibody, showed a dramatic response to immunogenic cancers with microsatellite instability-high (MSI-H) and/or deficient mismatch repair (dMMR) in the pilot clinical trial KEYNOTE-016, subsequent studies have confirmed durable responses of anti-PD-1 inhibitors for MSI-H/dMMR solid tumors. As immunotherapy is described as a "game changer," the therapeutic landscape for MSI-H/dMMR solid tumors including gastrointestinal cancers has changed considerably in the last decade. An MSI/MMR status has been established as the predictive biomarker for immune checkpoint blockades, playing an indispensable role in the clinical practice of patients with MSI-H/dMMR tumors. Immunotherapy is also now investigated for locally advanced MSI-H/dMMR gastrointestinal cancers. Despite this great success, a few populations with MSI-H/dMMR gastrointestinal cancers do not respond to immunotherapy, possibly due to the existence of intrinsic or acquired resistance mechanisms. Clarifying the underlying mechanisms of resistance remains a future task, whereas attempts to overcome resistance and improve the efficacy of immunotherapy are currently ongoing. Herein, we review recent clinical trials with special attention to MSI-H/dMMR gastrointestinal cancers together with basic/translational findings, which provide their rationale, and discuss perspectives for the further therapeutic development of treatment in this field.

Developments in Checkpoint Inhibitor Therapy for the Management of Deficient Mismatch Repair (dMMR) Rectal Cancer

Deficient mismatch repair (dMMR)/microsatellite instability-high (MSIH) colorectal cancer is resistant to conventional chemotherapy but responds to immune checkpoint inhibition (ICI). We review the standard of care in locally advanced dMMR rectal cancer with a focus on ICI. We also present a case report to highlight the treatment complexities and unique challenges of this novel treatment approach. ICI can lead to immune related adverse events (irAEs), resulting in early treatment discontinuation as well as new challenges to surveillance and surgical management. Overall, neoadjuvant ICI can lead to robust treatment responses, but its impact on durable response and organ preservation requires further study.

CDX-2 expression correlates with clinical outcomes in MSI-H metastatic colorectal cancer patients receiving immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) showed efficacy in metastatic colorectal cancer (mCRC) with mismatch-repair deficiency or high microsatellite instability (dMMR-MSI-H). Unfortunately, a patient's subgroup did not benefit from immunotherapy. Caudal-related homeobox transcription factor 2 (CDX-2) would seem to influence immunotherapy's sensitivity, promoting the chemokine (C-X-C motif) ligand 14 (CXCL14) expression. Therefore, we investigated CDX-2 role as a prognostic-predictive marker in patients with mCRC MSI-H. We retrospectively collected data from 14 MSI-H mCRC patients treated with ICIs between 2019 and 2021. The primary endpoint was the 12-month progression-free-survival (PFS) rate. The secondary endpoints were overall survival (OS), PFS, objective response rate (ORR), and disease control rate (DCR). The PFS rate at 12 months was 81% in CDX-2 positive patients vs 0% in CDX-2 negative patients (p = 0.0011). The median PFS was not reached (NR) in the CDX-2 positive group versus 2.07 months (95%CI 2.07-10.8) in CDX-2 negative patients (p = 0.0011). Median OS was NR in CDX-2-positive patients versus 2.17 months (95% Confidence Interval [CI] 2.17-18.7) in CDX2-negative patients (p = 0.026). All CDX-2-positive patients achieved a disease response, one of them a complete response. Among CDX-2-negative patients, one achieved stable disease, while the other progressed rapidly (ORR: 100% vs 0%, p = 0.0005; DCR: 100% vs 50%, p = 0.02). Twelve patients received 1st-line pembrolizumab (11 CDX-2 positive and 1 CDX-2 negative) not reaching median PFS, while two patients (1 CDX-2 positive and 1 CDX-2 negative) received 3rd-line pembrolizumab reaching a median PFS of 10.8 months (95% CI, 10.8-12.1; p = 0.036). Although our study reports results on a small population, the prognostic role of CDX-2 in CRC seems confirmed and could drive a promising predictive role in defining the population more sensitive to immunotherapy treatment. Modulating the CDX-2/CXCL14 axis in CDX-2-negative patients could help overcome primary resistance to immunotherapy.

Case report: A case of complete clinical response in a patient experiencing high microsatellite instability unresectable colon cancer being treated with a PD-L1 inhibitor after interstitial pneumonia

Immune checkpoint inhibitors (ICI) have dramatically transformed the treatment landscape for metastatic colorectal cancer (mCRC) with deficient DNA mismatch repair (dMMR) or high microsatellite instability (MSI-H). Envafolimab, a novel programmed death-1 ligand 1 (PD-L1) inhibitor, has been reported to be efficient and safe for the management of advanced MSI-H/dMMR solid tumors. Here, we report the case of a 35-year-old female patient with MSI-H/dMMR mCRC who was treated with envafolimab following mFOLFOX6 (oxaliplatin, leucovorin, and fluorouracil) plus bevacizumab. While suffering from interstitial pneumonia after chemotherapy, the patient achieved a complete clinical response with the use of envafolimab without additional adverse events. Thus, PD-L1 inhibitors may be potential candidates for treating patients with MSI-H/dMMR mCRC.

Emerging evidence of immunotherapy for colorectal cancer

Since the advent of immune checkpoint inhibitors, which modulate the interplay between the tumor cell and immune system, immunotherapy has become widely recognized as a new standard treatment for cancers including microsatellite instability-high (MSI-H) colorectal cancer. Immune checkpoint inhibitors such as pembrolizumab and nivolumab (anti-PD-1 antibodies) that act in the effector phase of T cells and ipilimumab (anti-CTLA-4 antibody) that acts mainly in the priming phase are now in clinical use. These antibodies have shown therapeutic efficacy in MSI colorectal cancer patients who have failed to respond to existing standard therapies. Pembrolizumab is also strongly recommended as first-line therapy for MSI-H metastatic colorectal cancer. Therefore, the MSI status and tumor mutation burden of the tumor should be clarified before starting treatment. Because many patients do not respond to immune checkpoint inhibitors, combination therapies with immune checkpoint inhibitors, including chemotherapy, radiotherapy, or molecularly targeted agents, are being investigated. Furthermore, treatment methods for preoperative adjuvant therapy for rectal cancer are being developed.

METTL14-dependent maturation of pri-miR-17 regulates mitochondrial homeostasis and induces chemoresistance in colorectal cancer

miR-17-5p has been found to be involved in the proliferation and metastasis of colorectal cancer (CRC), and N⁶-methyladenosine (m⁶A) modification is the most common RNA modification in eukaryotes. However, whether miR-17-5p contributes to chemotherapy sensitivity in CRC via m⁶A modification is unclear. In this study, we found that overexpression of miR-17-5p led to less apoptosis and lower drug sensitivity in vitro and in vivo under the 5-fluorouracil (5-FU) treatment, which indicated miR-17-5p led to 5-FU chemotherapy resistance. Bioinformatic analysis suggested that miR-17-5p-mediated chemoresistance was associated with mitochondrial homeostasis. miR-17-5p directly bound to the 3' untranslated region of Mitofusin 2 (MFN2), leading to decreased mitochondrial fusion and enhanced mitochondrial fission and mitophagy. Meanwhile, methyltransferase-like protein 14 (METTL14) was downregulated in CRC, resulting in lower m⁶A level. Moreover, the low level of METTL14 promoted the expression of pri-miR-17 and miR-17-5p. Further experiments suggested that m⁶A mRNA methylation initiated by METTL14 inhibits pri-miR-17 mRNA decay via reducing the recognition of YTHDC2 to the "GGACC" binding site. The METTL14/miR-17-5p/MFN2 signaling axis may play a critical role in 5-FU chemoresistance in CRC.

Challenges and Therapeutic Opportunities in the dMMR/MSI-H Colorectal Cancer Landscape

About 5 to 15% of all colorectal cancers harbor mismatch repair deficient/microsatellite instability-high status (dMMR/MSI-H) that associates with high tumor mutation burden and increased immunogenicity. As a result, and in contrast to other colorectal cancer phenotypes, a significant subset of dMMR/MSI-H cancer patients strongly benefit from immunotherapy. Yet, a large proportion of these tumors remain unresponsive to any immuno-modulating treatment. For this reason, current efforts are focused on the characterization of resistance mechanisms and the identification of predictive biomarkers to guide therapeutic decision-making. Here, we provide an overview on the new advances related to the diagnosis and definition of dMMR/MSI-H status and focus on the distinct clinical, functional, and molecular cues that associate with dMMR/MSI-H colorectal cancer. We review the development of novel predictive factors of response or resistance to immunotherapy and their potential application in the clinical setting. Finally, we discuss current and emerging strategies applied to the treatment of localized and metastatic dMMR/MSI-H colorectal tumors in the neoadjuvant and adjuvant setting.

Helicobacter pylori and Gastric Cancer: Pathogenetic Mechanisms

Gastric cancer is the sixth most commonly diagnosed cancer and the fourth leading cause of cancer death worldwide. Helicobacter pylori (H. pylori) is one of the main risk factors for this type of neoplasia. Carcinogenetic mechanisms associated with H. pylori are based, on the one hand, on the onset of chronic inflammation and, on the other hand, on bacterial-specific virulence factors that can damage the DNA of gastric epithelial cells and promote genomic instability. Here, we review and discuss the major pathogenetic mechanisms by which H. pylori infection contributes to the onset and development of gastric cancer.

Blockade of interleukin 10 potentiates antitumour immune function in human colorectal cancer liver metastases

OBJECTIVE

Programmed cell death protein 1 (PD-1) checkpoint inhibition and adoptive cellular therapy have had limited success in patients with microsatellite stable colorectal cancer liver metastases (CRLM). We sought to evaluate the effect of interleukin 10 (IL-10) blockade on endogenous T cell and chimeric antigen receptor T (CAR-T) cell antitumour function in CRLM slice cultures.

DESIGN

We created organotypic slice cultures from human CRLM (n=38 patients' tumours) and tested the antitumour effects of a neutralising antibody against IL-10 (αIL-10) both alone as treatment and in combination with exogenously administered carcinoembryonic antigen (CEA)-specific CAR-T cells. We evaluated slice cultures with single and multiplex immunohistochemistry, in situ hybridisation, single-cell RNA sequencing, reverse-phase protein arrays and time-lapse fluorescent microscopy.

RESULTS

αIL-10 generated a 1.8-fold increase in T cell-mediated carcinoma cell death in human CRLM slice cultures. αIL-10 significantly increased proportions of CD8⁺ T cells without exhaustion transcription changes, and increased human leukocyte antigen - DR isotype (HLA-DR) expression of macrophages. The antitumour effects of αIL-10 were reversed by major histocompatibility complex class I or II (MHC-I or MHC-II) blockade, confirming the essential role of antigen presenting cells. Interrupting IL-10 signalling also rescued murine CAR-T cell proliferation and cytotoxicity from myeloid cell-mediated immunosuppression. In human CRLM slices, αIL-10 increased CEA-specific CAR-T cell activation and CAR-T cell-mediated cytotoxicity, with nearly 70% carcinoma cell apoptosis across multiple human tumours. Pretreatment with an IL-10 receptor blocking antibody also potentiated CAR-T function.

CONCLUSION

Neutralising the effects of IL-10 in human CRLM has therapeutic potential as a stand-alone treatment and to augment the function of adoptively transferred CAR-T cells.

The Prognostic Impact of Microsatellite Instability on the Outcome of Appendiceal Adenocarcinoma: a National Cancer Database Analysis

BACKGROUND

Microsatellite instability (MSI) is recognized as a favorable outcome predictor in colorectal cancer. However, its impact on overall survival (OS) of appendiceal carcinoma has not been thoroughly studied. This study aimed to assess the impact of MSI on OS of patients with appendiceal adenocarcinoma, stratified by disease stage, tumor histology, and patients' demographics.

METHODS

This was a retrospective cohort analysis of the colon cancer National Cancer Database (NCDB) between 2005 and 2019. Patients with appendiceal adenocarcinoma with known MSI status were included and subdivided according to MSI status into positive and negative. Primary outcome was OS stratified by MSI status.

RESULTS

The study included 1681 (50.1% male) patients with a mean age of 58.9 ± 14.2 years; 211 (12.5%) had MSI-positive tumors (69 MSI low, 53 MSI high, and 89 not specified). Mean 5-year OS of patients with MSI-positive and MSI-negative carcinomas was similar (81.9 versus 78.6 months, p = 0.747). Patients with stage IV MSI-positive carcinomas had significantly longer OS than patients with MSI-negative carcinomas of the same stage (41.3 vs 26.5 months, p = 0.02). Differences in OS for patients with stages I-III were not statistically significant. Compared to MSI-negative/low carcinomas, MSI-high tumors had more advanced pathologic TNM stage (stage III: 23.9% vs 17.8%-stage IV: 41.3% vs 35.4%, p = 0.003), received more chemotherapy (56% vs 41%, p = 0.04), yet had similar OS (81.9 vs 78.9 months, p = 0.357).

CONCLUSIONS

MSI status of appendiceal adenocarcinomas did not significantly impact survival, except for stage IV disease in which a survival benefit of MSI was noted.

Immunotherapy combined with radiotherapy to reverse immunosuppression in microsatellite stable colorectal cancer

In recent years, the exploration of immune checkpoint inhibitors (ICIs) has resulted in substantial progress and has changed the pattern of cancer treatment. ICIs have revolutionized the treatment landscape of microsatellite instable colorectal cancer while the efficacy is very limited in patients with microsatellite stable colorectal cancer. Therefore, sensitizing MSS CRC to immunotherapy is a major challenge in the field of CRC immunotherapy. Immunotherapy-based combination therapy is an effective strategy. This review of radiotherapy (RT) as a local treatment has dramatically changed in recent years, and it is now widely accepted that RT can deeply reshape the tumor environment by modulating the immune response. Such evidence gives a strong rationale for the synergism of radiotherapy and immunotherapy, introducing the era of 'immunoradiotherapy'. How to give full play to the synergistic effect of radiotherapy and immunotherapy to improve the therapeutic effect of MSS CRC and bring good prognosis is a hot problem to be solved in the field of cancer treatment.This article reviews the development of CRC immunotherapy, the immune resistance mechanism of MSS CRC, and the impact and potential value of immunotherapy combined with radiotherapy on the immune environment of CRC.

Treatment of Metastatic Colorectal Cancer: ASCO Guideline

PURPOSE

To develop recommendations for treatment of patients with metastatic colorectal cancer (mCRC).

METHODS

ASCO convened an Expert Panel to conduct a systematic review of relevant studies and develop recommendations for clinical practice.

RESULTS

Five systematic reviews and 10 randomized controlled trials met the systematic review inclusion criteria.

RECOMMENDATIONS

Doublet chemotherapy should be offered, or triplet therapy may be offered to patients with previously untreated, initially unresectable mCRC, on the basis of included studies of chemotherapy in combination with anti-vascular endothelial growth factor antibodies. In the first-line setting, pembrolizumab is recommended for patients with mCRC and microsatellite instability-high or deficient mismatch repair tumors; chemotherapy and anti-epidermal growth factor receptor therapy is recommended for microsatellite stable or proficient mismatch repair left-sided treatment-naive RAS wild-type mCRC; chemotherapy and anti-vascular endothelial growth factor therapy is recommended for microsatellite stable or proficient mismatch repair RAS wild-type right-sided mCRC. Encorafenib plus cetuximab is recommended for patients with previously treated BRAF V600E-mutant mCRC that has progressed after at least one previous line of therapy. Cytoreductive surgery plus systemic chemotherapy may be recommended for selected patients with colorectal peritoneal metastases; however, the addition of hyperthermic intraperitoneal chemotherapy is not recommended. Stereotactic body radiation therapy may be recommended following systemic therapy for patients with oligometastases of the liver who are not considered candidates for resection. Selective internal radiation therapy is not routinely recommended for patients with unilobar or bilobar metastases of the liver. Perioperative chemotherapy or surgery alone should be offered to patients with mCRC who are candidates for potentially curative resection of liver metastases. Multidisciplinary team management and shared decision making are recommended. Qualifying statements with further details related to implementation of guideline recommendations are also included.Additional information is available at www.asco.org/gastrointestinal-cancer-guidelines.

Therapeutic landscape and future direction of metastatic colorectal cancer

In the era of targeted therapy based on genomic alterations, the treatment strategy for metastatic colorectal cancer (mCRC) has been changing. Before systemic treatment initiation, determination of tumour genomic status for KRAS and NRAS, BRAF^V600E mutations, ERBB2, and microsatellite instability and/or mismatch repair (MMR) status is recommended. In patients with deficient MMR and BRAF^V600E mCRC, randomized phase III trials have established the efficacy of pembrolizumab as first-line therapy and the combination of encorafenib and cetuximab as second-line or third-line therapy. In addition, new agents have been actively developed in other rare molecular fractions such as ERBB2 alterations and KRAS^G12C mutations. In March 2022, the combination of pertuzumab and trastuzumab for ERBB2-positive mCRC was approved in Japan, thereby combining real-world evidence from the SCRUM-Japan Registry. As the populations are highly fragmented owing to rare genomic alterations, various strategies in clinical development are expected. Clinical development of a tumour-agnostic approach, such as NTRK fusion and tumour mutational burden, has successfully introduced corresponding drugs to clinical practice. Considering the difficulty of randomized trials owing to cost-benefit and rarity, a promising solution could be real-world evidence utilized as an external control from the molecular-based disease registry.

Oncotherapeutic Strategies in Early Onset Colorectal Cancer

Early onset colorectal cancer (EOCRC), defined as colorectal cancers in patients aged less than 50 years, is becoming an increasingly common issue, globally. Since 1994, the incidence of this condition has been rising by 2% annually. Approximately one in five patients under 50 years of age diagnosed with colorectal cancer have an underlying genetic predisposition syndrome. The detection of cancer among the other 80% of patients poses a considerable task, as there is no family history to advocate for commencing early screening in this group. Patients with EOCRC have distinct social, spiritual, fertility, and financial needs from their older counterparts that need to be addressed. This review discusses the risk factors associated with the development of EOCRC and current best practice for the management of this disease.

MAP7D2 reduces CD8+ cytotoxic T lymphocyte infiltration through MYH9-HMGB1 axis in colorectal cancer

Immune checkpoint inhibitors (ICIs) represent a new paradigm in cancer immunotherapy, but can be largely restricted by the limited presence of CD8+ cytotoxic T lymphocytes (CTLs) in colorectal cancer (CRC) patients with microsatellite stable (MSS) tumors. Here, through next-generation sequencing, we identify microtubule-associated protein 7 domain 2 (MAP7D2) as an exploitable therapeutic maneuver to improve the efficacy of ICIs for MSS CRC therapy. In human CRC tissues, MAP7D2 expression is significantly increased in MSS CRC, and MAP7D2 adversely correlates with the presence of antitumor T lymphocytes. In vitro and in vivo experiments demonstrate that MAP7D2 knockdown significantly increases the infiltration of CD8+ CTLs, thereby inhibiting tumor progression and improving the efficacy of ICIs in MSS CRC murine models. Mechanistically, MAP7D2 interacts with MYH9 and protects it from ubiquitin-mediated degradation, subsequently decreasing the secretion of HMGB1, which suppresses the infiltration of CD8+ CTLs in MSS CRC. These findings highlight the importance of MAP7D2 in determining the infiltration of CD8+ CTLs and indicate that targeting MAP7D2 in MSS CRC may present a novel antitumor immunotherapy.