Effects of microsatellite instability on recurrence patterns and outcomes in colorectal cancers

Rate of dissemination and prognosis in early and advanced stage colorectal cancer based on microsatellite instability status: systematic review and meta-analysis

INTRODUCTION

For the past two decades, microsatellite instability (MSI) has been reported as a robust clinical biomarker associated with survival advantage attributed to its immunogenicity. However, MSI is also associated with high-risk adverse pathological features (poorly differentiated, mucinous, signet cell, higher grade) and exhibits a double-edged sword phenomenon. We performed a systematic review and meta-analysis to evaluate the rate of dissemination and the prognosis of early and advanced stage colorectal cancer based on MSI status.

METHODS

A systematic literature search of original studies was performed on Ovid searching MEDLINE, Embase, Cochrane Database of Systematic Reviews, American College of Physicians ACP Journal Club, Database of Abstracts of Reviews of Effects DARE, Clinical Trials databases from inception of database to June 2019. Colorectal cancer, microsatellite instability, genomic instability and DNA mismatch repair were used as key words or MeSH terms. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline was followed. Data were pooled using a random-effects model with odds ratio (OR) as the effect size. Statistical analysis was performed using RevMan ver 5.3 Cochrane Collaboration.

RESULTS

From 5288 studies, 136 met the inclusion criteria (n = 92,035; MSI-H 11,746 (13%)). Overall, MSI-H was associated with improved OS (OR, 0.81; 95% CI 0.73-0.90), DFS (OR, 0.73; 95% CI 0.66-0.81) and DSS (OR, 0.69; 95% CI 0.52-0.90). Importantly, MSI-H had a protective effect against dissemination with a significantly lower rate of lymph node and distant metastases. By stage, the protective effect of MSI-H in terms of OS and DFS was observed clearly in stage II and stage III. Survival in stage I CRC was excellent irrespective of MSI status. In stage IV CRC, without immunotherapy, MSI-H was not associated with any survival benefit.

CONCLUSIONS

MSI-H CRC was associated with an overall survival benefit with a lower rate of dissemination. Survival benefit was clearly evident in both stage II and III CRC, but MSI-H was neither a robust prognostic marker in stage I nor stage IV CRC without immunotherapy.

Prevalence of cancer susceptibility variants in patients with multiple Lynch syndrome related cancers

Along with early-onset cancers, multiple primary cancers (MPCs) are likely resulting from increased genetic susceptibility; however, the associated predisposition genes or prevalence of the pathogenic variants genes in MPC patients are often unknown. We screened 71 patients with MPC of the stomach, colorectal, and endometrium, sequencing 65 cancer predisposition genes. A subset of 19 patients with early-onset MPC of stomach and colorectum were further evaluated for variants in cancer related genes using both normal and tumor whole exome sequencing. Among 71 patients with MPCs, variants classified to be pathogenic were observed in 15 (21.1%) patients and affected Lynch Syndrome (LS) genes: MLH1 (n = 10), MSH6 (n = 2), PMS2 (n = 2), and MSH2 (n = 1). All carriers had tumors with high microsatellite instability and 13 of them (86.7%) were early-onset, consistent with LS. In 19 patients with early-onset MPCs, loss of function (LoF) variants in RECQL5 were more prevalent in non-LS MPC than in matched sporadic cancer patients (OR = 31.6, 2.73–1700.6, p = 0.001). Additionally, there were high-confidence LoF variants at FANCG and CASP8 in two patients accompanied by somatic loss of heterozygosity in tumor, respectively. The results suggest that genetic screening should be considered for synchronous cancers and metachronous MPCs of the LS tumor spectrum, particularly in early-onset. Susceptibility variants in non-LS genes for MPC patients may exist, but evidence for their role is more elusive than for LS patients.

Microsatellite Instability in Sporadic Colorectal Malignancy: A Pilot Study from Northern India

BACKGROUND

Three molecular pathways are described as the genetic basis of colorectal tumorigenesis. Among these, microsatellite instability (MSI) has shown greatest promise in serving as a biomarker to determine disease aggression by tumour biology, recurrence, and response to chemotherapy.

METHODOLOGY

This prospective observational pilot study included patients of colorectal cancers, in a population subset coming to a tertiary care hospital in northern India, who were operated with curative or palliative intent over a period of one year and followed up for a maximum of 55 months. The post-operative pathological assessment was done for MSI status using PCR technique, and an attempt was made to evaluate its correlation with conventional clinical and histological parameters, early recurrences, disease-free survival and overall survival in comparison to MSS type tumours in sporadic cases of colorectal malignancies.

RESULTS

Out of 38 patients of colorectal cancer, 26 were included in the study. Male to female ratio was 7:6 (n=14:12). Mean age of presentation was 48±14.2 years. Incidence of MSI was n=4 (15.4%). On subgroup analysis, age of presentation (p=0.044) and evidence of perineural invasion (p=0.017) was found to have significant statistical association with MSI tumour biology. Recurrence was seen in seven of the seventeen patients who previously had no synchronous or metastatic disease (41.2%). The mean disease-free survival for MSS was 21.32 months and was 25.25 months for MSI group which was statistically insignificant (p = 0.277). Out of four MSI tumour biology patients one was alive and without recurrence at 47 months. While the other two were alive and without recurrence till 27 months of follow-up.   Conclusion: Age and perineural invasion showed statistically significant association with MSI tumour biology. Due to the small sample size statistical significance was not established with site, recurrence rate, DFS and OS.

Computed Tomography-Based Radiomics Model to Preoperatively Predict Microsatellite Instability Status in Colorectal Cancer: A Multicenter Study

Objectives

To establish and validate a combined radiomics model based on radiomics features and clinical characteristics, and to predict microsatellite instability (MSI) status in colorectal cancer (CRC) patients preoperatively.

Methods

A total of 368 patients from four hospitals, who underwent preoperative contrast-enhanced CT examination, were included in this study. The data of 226 patients from a single hospital were used as the training dataset. The data of 142 patients from the other three hospitals were used as an independent validation dataset. The regions of interest were drawn on the portal venous phase of contrast-enhanced CT images. The filtered radiomics features and clinical characteristics were combined. A total of 15 different discrimination models were constructed based on a feature selection strategy from a pool of 3 feature selection methods and a classifier from a pool of 5 classification algorithms. The generalization capability of each model was evaluated in an external validation set. The model with high area under the curve (AUC) value from the training set and without a significant decrease in the external validation set was final selected. The Brier score (BS) was used to quantify overall performance of the selected model.

Results

The logistic regression model using the mutual information (MI) dimensionality reduction method was final selected with an AUC value of 0.79 for the training set and 0.73 for the external validation set to predicting MSI. The BS value of the model was 0.12 in the training set and 0.19 in the validation set.

Conclusion

The established combined radiomics model has the potential to predict MSI status in CRC patients preoperatively.

Subcutaneous envafolimab monotherapy in patients with advanced defective mismatch repair/microsatellite instability high solid tumors

Background

Monoclonal antibodies targeting programmed death ligand 1 (PD-L1) signaling currently approved for defective mismatch repair (dMMR)/microsatellite instability high (MSI-H) tumors must be delivered by intravenous infusion. Envafolimab, a humanized single-domain anti-PD-L1 antibody fused to an Fc fragment, represents a potential advance because it can be conveniently administered subcutaneously.

Methods

This open-label, single-arm, phase 2 study evaluated the efficacy and safety of envafolimab in patients with previously treated advanced dMMR/MSI-H tumors from 25 clinical sites across China. Adults with histologically confirmed locally advanced or metastatic malignant dMMR/MSI-H solid tumors received weekly 150 mg subcutaneous envafolimab injections in a 28-day treatment cycle. The primary efficacy endpoint was the objective response rate (assessed by a blinded independent review committee). Secondary efficacy outcomes were disease control rate, duration of response, progression-free survival, and overall survival.

Results

One hundred and three patients (65 with colorectal cancer, 18 with gastric cancer, and 20 with other solid tumors) were enrolled. Median follow-up was 11.5 months. The objective response rate was 42.7% (95% confidence interval [CI] 33.0–52.8), and the disease control rate was 66.0% (95% CI 56.0–75.1). Median duration of response was not reached; the duration of response rate at 12 months was 92.2% (95% CI 77.5–97.4). Median progression-free survival was 11.1 months (95% CI 5.5 to not evaluable). Overall survival at 12 months was 74.6% (95% CI 64.7–82.1). Sixteen patients (16%) had at least one grade 3 or 4 related treatment-emergent adverse event. No grade 5 treatment-emergent adverse events related to envafolimab were reported. Injection site reactions, all grade 1–2, were reported in nine patients (9%), but there were no infusion reactions. Eight patients (8%) had grade 3 or 4 immune-related adverse events.

Conclusions

This is the first pivotal phase 2 study to examine the efficacy and safety of a single-domain immune checkpoint antibody in the treatment of cancer. Envafolimab was effective and had acceptable safety in the treatment of previously treated advanced dMMR/MSI-H solid tumors. As the first single-domain PD-L1-targeting antibody administered by rapid subcutaneous injection, envafolimab has the potential to be a significant advance in the treatment of cancer.

Trial registration ClinicalTrials.gov, NCT03667170. Registered 10 September 2018—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03667170.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-021-01095-1.

An Insight Into the Driver Mutations and Molecular Mechanisms Underlying Mucinous Adenocarcinoma of the Rectum

BACKGROUND

Mucinous adenocarcinoma of the rectum accounts for 10% of all rectal cancers and has an impaired response to neoadjuvant chemoradiotherapy and worse overall survival. To date, insufficient genomic research has been performed on this histological subtype.

OBJECTIVE

This study aims to define the mismatch repair deficiency rate and the driver mutations underpinning mucinous adenocarcinoma of the rectum and to compare it with rectal adenocarcinoma not otherwise specified.

DESIGN

Immunohistochemistry and sequencing were performed on tumor samples from our tumor biobank.

SETTINGS

This study was conducted across 2 tertiary referral centers.

PATIENTS

Patients with mucinous adenocarcinoma and rectal adenocarcinoma not otherwise specified who underwent rectal resection between 2008 and 2018 were included.

MAIN OUTCOME MEASURES

Mismatch repair status was performed by immunohistochemical staining. Mutations in the panel of oncogenes and tumor suppressor genes were determined by sequencing on the MiSeq V3 platform.

RESULTS

The study included 33 patients with mucinous adenocarcinoma of the rectum and 100 patients with rectal adenocarcinoma not otherwise specified. Those with mucinous adenocarcinoma had a mismatch repair deficiency rate of 12.1% compared to 2.0% in the adenocarcinoma not otherwise specified cohort (p = 0.04). Mucinous adenocarcinoma and adenocarcinoma not otherwise specified rectal tumors had similar mutation frequencies in most oncogenes and tumor suppressor genes. No difference was found in the KRAS mutation rate (50.0% vs 37.1%, p = 0.29) or BRAF mutation rate (6.7% vs 3.1%, p = 0.34) between the cohorts. No difference was found between the cohorts regarding recurrence-free (p = 0.29) or overall survival (p = 0.14).

LIMITATIONS

The major limitations of this study were the use of formalin-fixed, paraffin-embedded tissue over fresh-frozen tissue and the small number of patients included, in particular, in the mucinous rectal cohort.

CONCLUSIONS

Most mucinous rectal tumors develop and progress along the chromosomal instability pathway. Further research in the form of transcriptomics, proteomics, and analysis of the effects of the mucin barrier may yield valuable insights into the mechanisms of resistance to chemoradiotherapy in this cohort. See Video Abstract at http://links.lww.com/DCR/B464.

UNA PERCEPCIN SOBRE MUTACIONES IMPULSORAS Y MECANISMOS MOLECULARES SUBYACENTES AL ADENOCARCINOMA MUCINOSO DEL RECTO

ANTECEDENTES:El adenocarcinoma mucinoso del recto, representa el 10% de todos los cánceres rectales y tiene una respuesta deficiente a la quimioradioterapia neoadyuvante y una peor supervivencia en general. A la fecha, se han realizado muy pocas investigaciones genómicas sobre este subtipo histológico.OBJETIVO:Definir la tasa de deficiencia en la reparación de desajustes y mutaciones impulsoras, que sustentan el adenocarcinoma mucinoso del recto y compararlo con el adenocarcinoma rectal no especificado de otra manera.DISEÑO:Se realizaron inmunohistoquímica y secuenciación en muestras tumorales de nuestro biobanco de tumores.AJUSTE:El estudio se realizó en dos centros de referencia terciarios.PACIENTES:Se incluyeron pacientes con adenocarcinoma mucinoso y adenocarcinoma no especificado de otra manera, sometidos a resección rectal entre 2008 y 2018.PRINCIPALES MEDIDAS DE RESULTADO:El estado de reparación de desajustes se realizó mediante tinción inmunohistoquímica. Las mutaciones en el panel de oncogenes y genes supresores de tumores, se determinaron mediante secuenciación en la plataforma MiSeq V3.RESULTADOS:El estudio incluyó a 33 pacientes con adenocarcinoma mucinoso del recto y 100 pacientes con adenocarcinoma del recto no especificado de otra manera. Aquellos con adenocarcinoma mucinoso, tenían una tasa de deficiencia de reparación de desajustes del 12,1% en comparación con el 2,0% en la cohorte de adenocarcinoma no especificado de otra manera (p = 0,04). El adenocarcinoma mucinoso y el adenocarcinoma no especificado de otra manera, tuvieron frecuencias de mutación similares en la mayoría de los oncogenes y genes supresores de tumores. No se encontraron diferencias en la tasa de mutación de KRAS (50,0% frente a 37,1%, p = 0,29) o la tasa de mutación de BRAF (6,7% frente a 3,1%, p = 0,34) entre las cohortes. No se encontraron diferencias entre las cohortes con respecto a la supervivencia libre de recurrencia (p = 0,29) o la supervivencia global (p = 0,14).LIMITACIONES:Las mayores limitaciones de este estudio, fueron el uso de tejido embebido en parafina y fijado con formalina, sobre el tejido fresco congelado y el pequeño número de pacientes incluidos, particularmente en la cohorte mucinoso rectal.CONCLUSIONES:La mayoría de los tumores rectales mucinosos se desarrollan y progresan a lo largo de la vía de inestabilidad cromosómica. La investigación adicional en forma transcriptómica, proteómica y análisis de los efectos de la barrera de la mucina, puede proporcionar información valiosa sobre los mecanismos de resistencia a la quimioradioterapia, en esta cohorte. Consulte Video Resumen en http://links.lww.com/DCR/B464.

Importance of lymph node immune responses in MSI-H/dMMR colorectal cancer

Patients with colorectal cancers (CRCs) generally exhibit improved survival through intensive lymph node (LN) dissection. However, recent progress in cancer immunotherapy revisits the potential importance of regional LNs, where T cells are primed to attack tumor cells. To elucidate the role of regional LN, we investigated the immunological status of nonmetastatic regional LN lymphocytes (LNLs) in comparison with those of the tumor microenvironment (tumor-infiltrating lymphocytes; TILs) using flow cytometry and next-generation sequencing. LNLs comprised an intermediate level of the effector T cell population between peripheral blood lymphocytes (PBLs) and TILs. Significant overlap of the T cell receptor (TCR) repertoire was observed in microsatellite instability–high/mismatch repair–deficient (MSI-H/dMMR) CRCs with high tumor mutation burden (TMB), although limited TCRs were shared between nonmetastatic LNs and primary tumors in microsatellite stable/MMR proficient (MSS/pMMR) CRC patients with low TMB. In line with the overlap of the TCR repertoire, an excessive LN dissection did not provide a positive impact on long-term prognosis in our MSI-H/dMMR CRC cohort (n = 130). We propose that regional LNs play an important role in antitumor immunity, particularly in MSI-H/dMMR CRCs with high TMB, requiring care to be taken regarding excessive nonmetastatic LN dissection in MSI-H/dMMR CRC patients.

Molecular Oncology in Management of Colorectal Cancer

Colorectal cancers are the third most common cancers in the world. Management of both primary and metastatic colorectal cancers has evolved over the last couple of decades. Extensive research in molecular oncology has helped us understand and identify these complex intricacies in colorectal cancer biology and disease progression. These advances coupled with improved knowledge on various mutations have helped develop targeted chemotherapeutics and has allowed planning an effective treatment regimen in this era of immunotherapy with precision. The diverse chemotherapeutic and biological agents at our disposal can make decision making a very complex process. Molecular profile, including CIN, RAS, BRAF mutations, microsatellite instability, ctDNA, and consensus molecular subtypes, are some of the important factors which are to be considered while planning an individualized treatment regimen. This article summarizes the current status of molecular oncology in the management of colorectal cancer and should serve as a practical guide for the clinical team.

Genomic and epigenomic biomarkers in colorectal cancer: From diagnosis to therapy

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the United States. Despite ongoing efforts aimed at increasing screening for CRC and early detection, and development of more effective therapeutic regimens, the overall morbidity and mortality from this malignancy remains a clinical challenge. Therefore, identifying and developing genomic and epigenomic biomarkers that can improve CRC diagnosis and help predict response to current therapies are of paramount importance for improving survival outcomes in CRC patients, sparing patients from toxicity associated with current regimens, and reducing the economic burden associated with these treatments. Although efforts to develop biomarkers over the past decades have achieved some success, the recent availability of high-throughput analytical tools, together with the use of machine learning algorithms, will likely hasten the development of more robust diagnostic biomarkers and improved guidance for clinical decision-making in the coming years. In this chapter, we provide a systematic and comprehensive overview on the current status of genomic and epigenomic biomarkers in CRC, and comment on their potential clinical significance in the management of patients with this fatal malignancy, including in the context of precision medicine.

Analysis of the Clinicopathological Characteristics of Stage I-III Colorectal Cancer Patients Deficient in Mismatch Repair Proteins

Purpose

To investigate the clinicopathological characteristics of stage I–III colorectal cancer (CRC) patients with deficient mismatch repair (dMMR) protein.

Patients and Methods

A retrospective analysis of 61 patients with stage I–III CRC confirmed by immunohistochemistry as dMMR after radical resection at Shenjing Hospital of China Medical University from May 2017 to June 2019 was performed. A total of 183 stage I–III CRC patients with proficient mismatch repair (pMMR) protein from the same period were randomly selected as a control group. The clinicopathological data of the two groups were investigated.

Results

There were significant differences between the two groups in age, sex, site of onset, maximum diameter of tumor, T stage, tumor differentiation, and histological type (P < 0.05). No significant difference was detected in nerve vessel invasion, cancer nodules, the N stage or the TNM stage. In the dMMR group, 41 patients (66.13%) showed PMS2/MLH1 deletion, and the number of MSH2/MSH6 deletion is 21 patients (33.87%). Among them, 34 patients (54.84%) had PMS2 and MLH1 deficiency. In total, 16 patients (25.81%) had MSH2 and MSH6 deficiency. A total of 5 patients (8.06%) showed simply PMS2 deletion and 5 patients (8.06%) showed simply MSH6 deletion. In total, 2 patients (3.23%) showed concurrent loss of PMS2, MLH1 and MSH2. No significant difference were found (P > 0.05) in the above factors among dMMR CRC patients with different MMR proteins deletions.

Conclusion

Our results show that dMMR status may be more likely exist in female and younger (≤55 years) patients with a greater tumor burden (>5cm), right colon, T4 stage disease, poor differentiation and mucinous adenocarcinoma. Loss of PMS2 and MLH1 is the most common pattern of MMR protein expression deficiency, followed by concurrent deletion of MSH2 and MSH6.

A review of the sensitivity of metastatic colorectal cancer patients with deficient mismatch repair to standard-of-care chemotherapy and monoclonal antibodies, with recommendations for future research

In 5% of metastatic colorectal cancer (mCRC) patients, tumours display a deficient mismatch repair (dMMR) system. Immunotherapy is beneficial in dMMR mCRC patients and has recently been approved by the Food and Drug Administration for patients with unresectable or metastatic dMMR CRC. Although dMMR and proficient MMR (pMMR) CRC tumours are biologically distinct, they are commonly treated with the same chemotherapy and monoclonal antibodies. This includes dMMR mCRC patients who did not respond to immunotherapy (20-30%). However, it is unclear if these treatments are equally beneficial in dMMR mCRC. Of note, dMMR mCRC patients have a worse prognosis compared to pMMR, which may in part be caused by a lower response to treatment. To avoid unnecessary exposure to ineffective treatments and their associated toxicity, it is important to identify which systemic treatments are most beneficial in dMMR mCRC patients, thus improving their outcome. Indeed, future treatment strategies are likely to involve combinations of immunotherapy, chemotherapy and monoclonal antibodies. In this evidence-based review, we summarize clinical trials reporting treatment efficacy of different types of chemotherapy and monoclonal antibodies in dMMR mCRC patients. We also review the biological rationale behind a potential differential benefit of chemotherapy with or without monoclonal antibodies in dMMR mCRC patients. A barrier in the interpretation of preclinical results is the choice of model systems. They largely comprise traditional models, including cell lines and xenografts, rather than more representative models, such as patient-derived organoids. We provide concrete recommendations for clinical investigators and fundamental researchers to accelerate research regarding which systemic therapy is most effective in dMMR mCRC patients.

Reg4 and its downstream transcriptional activator CD44ICD in stage II and III colorectal cancer

Reg4 is highly expressed in gastrointestinal malignancies and acts as a mitogenic and pro-invasive factor. Our recent works suggest that Reg4 binds with CD44 and induces its proteolytic cleavage to release intra-cytoplasmic domain of CD44 (CD44ICD). The goal of this study is to demonstrate clinical significance of the Reg4-CD44/CD44ICD pathway in stage II/III colon cancer and its association with clinical parameters of aggression. We constructed a tissue microarray (TMA) of 93 stage II/III matched colon adenocarcinoma patients, 23 with recurrent disease. The TMA was immunohistochemically stained for Reg4, CD44, and CD44ICD proteins and analyzed to identify associations with tumor characteristics, recurrence and overall survival. The TMA data analysis showed a significant correlation between Reg4 and CD44 (r² = 0.23, P = 0.028), CD44 and CD44ICD (r² = 0.36, p = 0.0004), and Reg4 and CD44ICD (r² = 0.45, p ≤ 0.0001). Reg4 expression was associated with larger tumor size (r² = 0.23, p = 0.026). Although, no association was observed between Reg4, CD44, or CD44ICD expression and disease recurrence, Reg4-positive patients had a median survival of 4 years vs. 7 years for Reg4-negative patients (p = 0.04) in patients who recurred. Inhibition of the Reg4-CD44/CD44ICD pathway may be a future therapeutic target for colon cancer patients.

Clinical Significance of Preoperative Inflammatory Markers in Prediction of Prognosis in Node-Negative Colon Cancer: Correlation between Neutrophil-to-Lymphocyte Ratio and Poorly Differentiated Clusters

Although stage I and II colon cancers (CC) generally show a very good prognosis, a small proportion of these patients dies from recurrent disease. The identification of high-risk patients, who may benefit from adjuvant chemotherapy, becomes therefore essential. We retrospectively evaluated 107 cases of stage I (n = 28, 26.2%) and II (n = 79, 73.8%) CC for correlations among preoperative inflammatory markers, histopathological factors and long-term prognosis. A neutrophil-to-lymphocyte ratio greater than 3 (H-NLR) and a platelet-to-lymphocyte ratio greater than 150 (H-PLR) were significantly associated with the presence of poorly differentiated clusters (PDC) (p = 0.007 and p = 0.039, respectively). In addition, H-NLR and PDC proved to be significant and independent survival prognosticators for overall survival (OS; p = 0.007 and p < 0.001, respectively), while PDC was the only significant prognostic factor for cancer-specific survival (CSS; p < 0.001,). Finally, the combination of H-NLR and PDC allowed an optimal stratification of OS and CSS in our cohort, suggesting a potential role in clinical practice for the identification of high-risk patients with stage I and II CC.

High frequency of microsatellite instability and its substantial co-existence with KRAS and BRAF mutations in Vietnamese patients with colorectal cancer

Tumor heterogeneity and resistance to chemotherapy have been recognized as two major obstacles in the diagnosis and treatment of colorectal cancer (CRC). Microsatellite instability (MSI) and KRAS and BRAF mutations are common diagnostic factors that have been widely used to classify CRC for therapeutics. In the present study, 151 patients with CRC were analyzed from the two most populous ethnic groups of Vietnam, Kinh and Muong, for their MSI status, frequency of KRAS and BRAF mutations, and their clinical implications. MSI-high (MSI-H) was detected in 45.0% (68/151), while mutated KRAS and BRAF were identified in 37.1% (56/151) and 2.6% (4/151) of the cases, respectively. There was a substantial co-existence of MSI-H with KRAS (27/56; 48.2%) and BRAF (3/4; 75.0%) mutations. Statistical analysis showed that MSI-H tumors were significantly associated with colon location (P=0.011) and more advanced T stages (P=0.016). KRAS exon 2 mutations were significantly more likely to be detected in patients who belonged to the Muong ethnic group (P=0.013) or those with no/fewer lymph node metastasis (P=0.048) as compared with their counterparts. In summary, the data revealed typical molecular features of Vietnamese patients with CRC, including a strikingly high rate of MSI-H and its high co-existence with KRAS and BRAF mutations, which should be carefully considered in the future therapeutics for this type of cancer.

The transition from primary colorectal cancer to isolated peritoneal malignancy is associated with an increased tumour mutational burden

Colorectal Peritoneal metastases (CPM) develop in 15% of colorectal cancers. Cytoreductive surgery and heated intraperitoneal chemotherapy (CRS & HIPEC) is the current standard of care in selected patients with limited resectable CPM. Despite selection using known prognostic factors survival is varied and morbidity and mortality are relatively high. There is a need to improve patient selection and a paucity of research concerning the biology of isolated CPM. We aimed to determine the biology associated with transition from primary CRC to CPM and of patients with CPM not responding to treatment with CRS & HIPEC, to identify those suitable for treatment with CRS & HIPEC and to identify targets for existing repurposed or novel treatment strategies. A cohort of patients with CPM treated with CRS & HIPEC was recruited and divided according to prognosis. Molecular profiling of the transcriptome (n = 25), epigenome (n = 24) and genome (n = 21) of CPM and matched primary CRC was performed. CPM were characterised by frequent Wnt/ β catenin negative regulator mutations, TET2 mutations, mismatch repair mutations and high tumour mutational burden. Here we show the molecular features associated with CPM development and associated with not responding to CRS & HIPEC. Potential applications include improving patient selection for treatment with CRS & HIPEC and in future research into novel and personalised treatments targeting the molecular features identified here.

Survival of patients with deficient mismatch repair metastatic colorectal cancer in the pre-immunotherapy era

Background

Metastatic colorectal cancer patients with deficient mismatch repair (dMMR mCRC) benefit from immunotherapy. Interpretation of the single-arm immunotherapy trials is complicated by insignificant survival data during systemic non-immunotherapy. We present survival data on a large, comprehensive cohort of dMMR mCRC patients, treated with or without systemic non-immunotherapy.

Methods

Two hundred and eighty-one dMMR mCRC patients (n = 54 from three prospective Phase 3 CAIRO trials; n = 227 from the Netherlands Cancer Registry). Overall survival was analysed from diagnosis of mCRC (OS), from initiation of first-line (OS1) and second-line (OS2) systemic treatment. Cox regression analysis examined prognostic factors. As comparison for OS 2746 MMR proficient mCRC patients were identified.

Results

Of 281 dMMR patients, 62% received first-line and 26% second-line treatment. Median OS was 16.0 months (13.8–19.6) with antitumour therapy and 2.5 months (1.8–3.5) in untreated patients. OS1 was 12.8 months (10.7–15.2) and OS2 6.2 months (5.4–8.9) in treated dMMR patients. Treated dMMR patients had a 7.6-month shorter median OS than pMMR patients.

Conclusion

Available data from immunotherapy trials lack a control arm with standard systemic treatment. Given the poor outcome compared to the immunotherapy results, our data strongly suggest a survival benefit of immunotherapy in dMMR mCRC patients.

The tumor microenvironment of colorectal cancer metastases: opportunities in cancer immunotherapy

About a fifth of individuals with colorectal cancer (CRC) present with disease metastasis at the time of diagnosis. While the role of the tumor microenvironment (TME) in governing CRC progression is undeniable, the role of the TME in either establishing or suppressing the formation of distant metastases of CRC is less well established. Despite advances in immunotherapy, many individuals with metastatic CRC do not respond to standard-of-care therapy. Therefore, understanding the role of the TME in establishing distant metastases is essential for developing new immunological agents. Here, we summarize our current understanding of the TME of CRC metastases, describe differences between the TME of primary tumors and their distant metastases, and discuss advances in the design and combinations of immunotherapeutic agents.

DNA mismatch repair is not disrupted in stage 0 colorectal cancer resected using endoscopic submucosal dissection

The frequency of deficient mismatch repair (dMMR) or microsatellite instability-high colorectal cancer (CRC) is estimated to be ~15% of all patients with CRC; however, the patients reported are limited to surgical cases, and the frequency of patients exhibiting stage 0 disease is not considered, despite the currently increasing use of endoscopic techniques to cure a number of these patients. In the present study, the DNA MMR status for stage 0 patients with CRC treated using endoscopic submucosal dissection or endoscopic mucosal resection was analyzed via immunohistochemical staining of four types of proteins, namely MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MSH6 and PMS1 homolog 2 MMR system component, in adenocarcinoma specimens. Notably, none of the endoscopically resected specimens exhibited dMMR among the 41 patients diagnosed with stage 0 CRC. Since tumors harboring dMMR progress more rapidly than tumors with chromosomal instability, the present results highlight the importance of tumor resection during very early phases that exist before the promoter region of MLH1 becomes hypermethylated, resulting in a loss of DNA MMR function.

Genome-wide cell-free DNA mutational integration enables ultra-sensitive cancer monitoring

In many areas of oncology, we lack sensitive tools to track low-burden disease. Although cell-free DNA (cfDNA) shows promise in detecting cancer mutations, we found that the combination of low tumor fraction (TF) and limited number of DNA fragments restricts low-disease-burden monitoring through the prevailing deep targeted sequencing paradigm. We reasoned that breadth may supplant depth of sequencing to overcome the barrier of cfDNA abundance. Whole-genome sequencing (WGS) of cfDNA allowed ultra-sensitive detection, capitalizing on the cumulative signal of thousands of somatic mutations observed in solid malignancies, with TF detection sensitivity as low as 10-5. The WGS approach enabled dynamic tumor burden tracking and postoperative residual disease detection, associated with adverse outcome. Thus, we present an orthogonal framework for cfDNA cancer monitoring via genome-wide mutational integration, enabling ultra-sensitive detection, overcoming the limitation of cfDNA abundance and empowering treatment optimization in low-disease-burden oncology care.

Node negative colorectal cancer patients: assesment of high-risk features on recurrence

BACKGROUND

The introduction of population-based screening programs for colorectal cancer (CRC) results in less patients with advanced disease. There is an increase in the amount of node negative CRC, which makes adequate risk stratification for this particular group of patients necessary. The addition of more risk factors to the conventional histological high-risk factors is investigated in this retrospective study.

PATIENTS AND METHODS

A cohort of 227 node negative (stage I and II) CRC patients who were not treated with adjuvant chemotherapy were selected from two previously conducted cohort studies. Detailed histopathological examination was performed by two independent observers and molecular background (BRAF/RAS mutations, microsatellite status (MSI)) was studied. Univariate analyses were used to analyse differences in histological and mutational characteristics between patients with and without recurrence. P-values below 0.05 were considered statistically significant.

RESULTS

Poorly differentiated histology (p:0.002), BRAF mutation (p:0.002) and MSI status (p:0.006) were found significant relevant risk factors that were related to recurrent disease. Poorly differentiated histology was associated with intermediate/high tumor budding (TB) (p:0.001), a BRAF mutation (p:0.001) and MSI status (p:0.001). A combination of all three features (poorly differentiated histology, BRAF and MSI) was more often present in the recurrence group.

CONCLUSIONS

Recurrence in node negative CRC patients could be better predicted when molecular features such as, BRAF mutation and MSI status are incorporated into a model with poorly differentiated CRC. Therefore, these features might help in the selection of patients who possibly will benefit from adjuvant treatment.

The Role of Palliative Surgery for Malignant Bowel Obstruction and Perforation in Advanced Microsatellite Instability-High Colorectal Carcinoma in the Era of Immunotherapy: Case Report

The role of palliative surgery in the management of acute complications in patients with disseminated malignancy remains controversial given the complexity of assessing acute surgical risk and long-term oncologic outcome. With the emergence of checkpoint blockade immunotherapy, there appears to be an increasing role for historically palliative procedures as a bridge to systemic immunotherapy. This is especially evident in advanced microsatellite instability-high (MSI-H) colorectal cancer where malignant obstruction and fistula formation are more common and where immunotherapy with checkpoint blockade (anti-PD-1/PD-L1, anti-CTLA-4) has a high response rate with potential for favorable oncologic outcomes. We present a series of three patients with MSI-H metastatic colorectal cancer complicated by malignant bowel obstruction and fistula formation, who having progressed on standard chemotherapy, underwent palliative intervention as a bridge to immune checkpoint blockade with durable and clinically meaningful anti-cancer responses. These cases highlight the need to re-evaluate the role of historically palliative operations in the setting of disease progression for immunotherapy-responsive tumors.

Prognostic implications of EGFR protein expression in sporadic colorectal tumors: Correlation with copy number status, mRNA levels and miRNA regulation

Sporadic colorectal cancer (sCRC) is the third most frequent cancer worldwide and the second most common cause of cancer-related deaths (mainly due metastatic dissemination). We investigated the immunohistochemical expression of frequently altered proteins in primary tumors from 51 patients (25 liver metastatic and 26 non-metastatic cases) with a median 103 months follow-up (103 months). We evaluated EGFR copy number (using SNP arrays and FISH) and its expression and regulation (by mRNA and miRNA arrays). We found differences between metastatic and non-metastatic sCRCs for MLH1 (p = 0.05), PMS2 (p = 0.02), CEA (p < 0.001) and EGFR (p < 0.001) expression. EGFR expression was associated with lymph node metastases (p = 0.001), liver metastases at diagnosis (p < 0.001), and advanced stage (p < 0.001). There were associations between EGFR expression-, EGFR gene copy number- and EGFR mRNA levels. We found potential interactions of two miRNAs targeting EGFR expression, (miR-134 and miR-4328, in non-metastatic and metastatic tumors, respectively). EGFR expression was associated with a worse outcome (p = 0.005). Multivariate analysis of prognostic factors for overall survival identified that, the expression of EGFR expression (p = 0.047) and pTNM stage (p < 0.001) predicted an adverse outcome. EGFR expression could be regulated by amplification or polysomies (in metastatic tumors), or miRNAs (miRNA-134, in non-metastatic tumors). EGFR expression in sCRC appears to be related to metastases and poor outcome.

Peritoneal Metastases in Colorectal Cancer: Biology and Barriers

BACKGROUND

Advances in the molecular biology of tumor metastasis have paralleled the evolution in the management of metastatic disease from colorectal cancer. In this review, we summarize the current understanding of the mechanism of colorectal cancer metastases, in particular that of peritoneal metastases, as well as clinical data on the treatment of this disease.

METHODS

A review of relevant English literature using MEDLINE/PubMed on the biology of colorectal cancer metastases, determinants of oligometastasis, and use of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in the treatment of metastatic colorectal cancer is presented.

RESULTS

Recognition of oligometastasis in the evolution of colorectal peritoneal metastases provides the theoretical framework for which cytoreductive surgery with or without hyperthermic intraperitoneal chemotherapy is considered. Clearly, a subset of patients benefit from peritoneal metastasectomy.

CONCLUSION

Advances in cancer biology and clinical imaging promise to expand the role of cytoreductive surgery with or without intraperitoneal chemotherapy in the management of peritoneal metastases from colorectal cancer.

Prognostic and predictive significance of microsatellite instability in stage II colorectal carcinoma: An 8-year study from a tertiary center in South India

BACKGROUND

Microsatellite instability (MSI) accounts for 15-20% of colorectal cancer (CRC) and is considered to have favorable stage-adjusted prognosis compared to Microsatellite stable (MSS) CRCs. Determination of MSI in stage II CRC is important for management decisions regarding adjuvant chemotherapy administration. The aim of this study was to determine the prognostic and predictive significance of MSI in stage 2 CRC in the Indian scenario.

MATERIALS AND METHODS

A total of 195 patients who underwent curative surgery for stage II CRC from 2010 to 2017 were included. MSI testing by immunohistochemistry (DNA MisMatch Repair proteins) was performed in all. Various clinicopathological factors and disease-free survival and overall survival were assessed between MSI and MSS groups. The effect of treatment in terms of survival benefits with adjuvant therapy in the MSI group was also assessed.

RESULTS

27.1% of the CRCs' showed MSI. Younger age (<50 years), family history of cancer, synchronous/metachronous malignancies, proximal (right sided) location, poor morphological tumour differentiation, mucin production, and presence of peritumoral (Crohn's-like) lymphocytic response showed statistically significant association with MSI. Majority (56%) of our patients showed combined loss of MLH1 and PMS2. Overall, survival among the MSI patients was significantly higher (76.6 ± 4.149 months) than the MSS patients (65.05 ± 3.555)P= 0.04. MSI patients did not show any differences in survival with or without treatment.

CONCLUSION

This study highlights the distinct clinicopathological features of MSI-related CRC and the relevance of MSI testing of stage II CRC for management decisions and prognostication.

Microsatellite instability in Costa Rican patients with colorectal adenocarcinoma and its association with overall survival and response to fluoropyrimidine-based chemotherapy

BACKGROUND

Microsatellite instability (MSI) is a prognostic and predictive factor in colorectal cancer (CRC). Previous trials have acknowledged that MSI prevalence varies according to ethnicity. The aim of this study was to determine the prevalence of MSI among CRC patients from Costa Rica and to analyze its influence on overall survival (OS) and response to fluoropyrimidine-based chemotherapy.

METHODS

We conducted a retrospective cohort study with all diagnosed CRC cases from 2010 to 2015 in a referral center in San José, Costa Rica. MSI was determined by immunohistochemical analysis. Clinical and epidemiological variables were retrieved from medical records. An univariate and multivariate COX regression analysis was performed to evaluate the association between MSI and mortality in the overall population and in those patients treated or not with fluoropyrimidine-based chemotherapy.

RESULTS

553 CRC patients were identified during the study timeframe, and 165 of them were diagnosed with MSI (29.84 %; 95 % Confidence Interval CI: 26.02-33.65%). MSI was associated with M1 disease, and right-sided tumor location. After adjusting for potential confounders, MSI was an independent prognostic factor for OS (Hazard Ratio (HR): 0.56; 95 %CI: 0.43-0.67; Log-rankp = 0.03). MSI status did not modify the response to fluoropyrimidine-based chemotherapy (HR: 0.56; 95 %CI: 0.18-1.80; Log-rank: p = 0.33).

CONCLUSIONS

MSI was detected in a higher proportion of CRC patients than previously reported for other non-Hispanic populations. MSI was an independent prognostic factor for OS, but did not predict the efficacy of cytotoxic treatment with Fluoropyrimidine-based chemotherapy.

Analysis of mismatch repair (MMR) proteins expression in a series of malignant pleural mesothelioma (MPM) patients

BACKGROUND

Promising results have been reported with immune checkpoint inhibitors (ICI) in a small proportion of MPM patients. MMR deficiency (dMMR) has been well described in several malignancies and was approved as a biomarker for anti-PD-1 inhibitors. Next generation sequencing (NGS) data demonstrated that 2% of MPM harbor microsatellite instability. The aim of this study is to characterize MMR by immunohistochemistry (IHC) in a series of MPM including a subset of patients treated with immunotherapy.

METHODS

Tumors of 159 MPM p diagnosed between 2002 and 2017 were reviewed. Formalin-fixed, paraffin-embedded tissue was stained for MLH1, MSH2, MSH6 and PMS2 and tumors were classified as dMMR (MMR protein expression negative) and MMR intact (all MMR proteins positively expressed). We retrospectively collected clinical outcomes under standard chemotherapy and experimental immunotherapy in the entire cohort.

RESULTS

MMR protein expression was analyzed in 158 samples with enough tissue and was positive in all of the cases. Twenty two patients received ICI with anti-CTLA4 or anti-PD-1 blockade in clinical trials, 58% had a response or stable disease for more than 6 m, with median progression-free survival (PFS) of 5.7 m (2.1-26.1 m). The median overall survival (mOS) in all population was 15 months (m) (13.5-18.8 m). In a multivariable model factors associated to improved mOS were PS 0, neutrophil-lymphocyte ratio (NLR) < 5 and epithelioid histology (p < 0.001).

CONCLUSIONS

In our series we were unable to identify any MPM patient with dMMR by IHC. Further studies are needed to elucidate potential predictive biomarkers of ICI benefit in MPM.

Outcomes for Metastatic Colorectal Cancer Based on Microsatellite Instability: Results from the South Australian Metastatic Colorectal Cancer Registry

BACKGROUND

Microsatellite instability (MSI) is the molecular marker for DNA mismatch repair deficiency (dMMR) in colorectal cancer (CRC) and has been associated with better survival outcomes in early stage disease. In metastatic CRC (mCRC), outcomes for patients with MSI are less clear. There is evolving evidence that treatment pathways for MSI CRC should include programmed-death 1 (PD-1) antibodies.

OBJECTIVE

An analysis was performed to explore the impact of MSI status on overall survival (OS) in mCRC.

PATIENTS AND METHODS

South Australian Metastatic CRC Registry data were analysed to assess patient characteristics and survival outcomes, comparing patients with MSI CRC with those whose tumours were microsatellite stable (MSS). Kaplan-Meier survival analysis was used to assess OS. Cox regression analysis was undertaken to assess the independence of MSI as a prognostic factor.

RESULTS

Of 4359 patients registered on the database, 598 (14%) had been tested for, and 62 (10.1%) of these patients had, demonstrable MSI. There were significantly higher rates of right-sided primary (p < 0.001), poorly differentiated pathology (p = 0.002), and BRAF V600E mutation (p < 0.001) in the MSI group. The MSI group were also less likely to receive chemotherapy (p < 0.001) or to have liver surgery, but more likely to be diagnosed at an early stage. The median overall survival was 9.5 months for those with MSI CRC versus 21.3 months for MSS CRC patients (p = 0.052). Cox regression analysis indicated that MSI was not an independent predictor of OS. Independent predictors of better OS included having liver surgery for metastasis, having chemotherapy, and being initially diagnosed at an early stage.

CONCLUSIONS

Only 14% of patients with mCRC were tested for MSI, and 1 in 10 were found to be MSI high. The clinical characteristics of MSI mCRC are in keeping with those previously reported. MSI in this population-based registry was associated with a numerically lower survival which did not attain statistical significance.

Biomarker-guided therapy for colorectal cancer: strength in complexity

The number of molecularly stratified treatment options available to patients with colorectal cancer (CRC) is increasing, with a parallel rise in the use of biomarkers to guide prognostication and treatment decision-making. The increase in both the number of biomarkers and their use has resulted in a progressively complex situation, evident both from the extensive interactions between biomarkers and from their sometimes complex associations with patient prognosis and treatment benefit. Current and emerging biomarkers also reflect the genomic complexity of CRC, and include a wide range of aberrations such as point mutations, amplifications, fusions and hypermutator phenotypes, in addition to global gene expression subtypes. In this Review, we provide an overview of current and emerging clinically relevant biomarkers and their role in the management of patients with CRC, illustrating the intricacies of biomarker interactions and the growing treatment opportunities created by the availability of comprehensive molecular profiling.

Clinicopathological features of Egyptian colorectal cancer patients regarding somatic genetic mutations especially in KRAS gene and microsatellite instability status: a pilot study

Background

Colorectal cancer (CRC) is the third most common cause of cancer-related deaths which contributes to a significant public health problem worldwide with 1.8 million new cases and almost 861,000 deaths in 2018 according to the World Health Organization. It exhibits 7.4% of all diagnosed cancer cases in the region of the Middle East and North Africa. Molecular changes that happen in CRCs are chromosomal instability, microsatellite instability (MSI), and CpG island methylator phenotype. The human RAS family (KRAS, NRAS, and HRAS) is the most frequently mutated oncogenes in human cancer appearing in 45% of colon cancers. Determining MSI status across CRCs offers the opportunity to identify patients who are likely to respond to targeted therapies such as anti-PD-1. Therefore, a method to efficiently determine MSI status for every cancer patient is needed.

Results

KRAS mutations were detected in 31.6% of CRC patients, namely in older patients (p = 0.003). Codons 12 and 13 constituted 5/6 (83.3%) and 1/6 (16.7%) of all KRAS mutations, respectively. We found three mutations G12D, G12C, and G13D which occur as a result of substitution at c.35G>A, c.34G>T, and c.38G>A and have been detected in 4/6 (66.6%), 1/6 (16.7%), and 1/6 (16.7%) patients, respectively. Eleven (57.9%) patients had microsatellite instability-high (MSI-H) CRC. A higher percentage of MSI-H CRC was detected in female patients (p = 0.048). Eight patients had both MSI-H CRC and wild KRAS mutation with no statistical significance was found between MSI status and KRAS mutation in these studied patients.

Conclusion

In conclusion, considering that KRAS mutations confer resistance to EGFR inhibitors, patients who have CRC with KRAS mutation could receive more tailored management by defining MSI status. MSI-high patients have enhanced responsiveness to anti-PD-1 therapies. Thus, the question arises as to whether it is worth investigating this association in the routine clinical setting or not. Further studies with a larger number of patients are needed to assess the impact of MSI status on Egyptian CRC care.

Elevated Microsatellite Alterations at Selected Tetranucleotides (EMAST) in Colorectal Cancer is Associated with an Elderly, Frail Phenotype and Improved Recurrence-Free Survival

BACKGROUND

Elevated microsatellite alterations at selected tetranucleotides (EMAST) is a poorly investigated form of microsatellite instability (MSI) in colorectal cancer (CRC).

OBJECTIVE

The aim of this study was to investigate the clinicopathological features of EMAST in CRC and its relation to outcome.

METHODS

A population-based, consecutive cohort of surgically treated stage I-III CRC patients investigated for high-frequency MSI (MSI-H) and EMAST. Clinicopathological differences were reported as odds ratios (OR) and survival was presented as hazard ratios (HR) with 95% confidence intervals (CIs).

RESULTS

Of 161 patients included, 25% were aged > 79 years. There was a large overlap in the prevalence of EMAST (31.7%) and MSI-H (27.3%) [82.4% of EMAST were also MSI-H]. EMAST had the highest prevalence in the proximal colon (OR 15.9, 95% CI 5.6-45.1; p < 0.001) and in women (OR 4.1, 95% CI 1.9-8.6; p < 0.001), and were poorly differentiated (OR 5.0, 95% CI 2.3-10.7; p < 0.001). Compared with EMAST-negative patients, EMAST-positive patients were older (median age 77 vs. 69 years; p < 0.001), leaner (median weight 67.5 vs. 77 kg; p = 0.001), had significantly higher rates of hypoalbuminemia (24% vs. 6%; OR 2.3, 95% CI 1.5-3.6; p = 0.002) and anemia (45% vs. 20%; OR 3.3, 95% CI 1.6-6.8; p = 0.001), and had elevated preoperative C-reactive protein (CRP) levels (51% vs. 34%; OR 1.9, 95% CI 1.0-3.9; p = 0.046). Improved recurrence-free survival was found in both MSI-H and EMAST subtypes. In multivariable analysis, node status (pN +), together with elevated CRP and MSI-positive, were the strongest prognostic factors for recurrence-free survival.

CONCLUSIONS

EMAST in CRC is associated with an older, leaner, and frailer phenotype with a lower risk of recurrence. The relevance of, and putative mechanisms to, EMAST warrants further investigation.

Is microsatellite instability-high really a favorable prognostic factor for advanced colorectal cancer? A meta-analysis

Background

Stage II colorectal cancer with microsatellite instability-high (MSI-H) has been proven to have a better prognosis. However, in advanced stage, this trend remains controversial. This study aimed to explore the prognostic role of MSI-H in stage III and IV colorectal cancer (CRC) through meta-analysis.

Methods

A comprehensive search was performed in PubMed, Cochrane Central Library, and Embase databases. All randomized clinical trials and non-randomized studies were included based on inclusion and exclusion criteria and on survival after a radical operation with or without chemotherapy. The adjusted log hazard ratios (HRs) were used to estimate the prognostic value between MSI-H and microsatellite-stable CRCs. The random-effects model was used to estimate the pooled effect size.

Results

Thirty-six studies were included. Randomized controlled trials (RCT) and non-RCT were analyzed separately. For stage III CRCs, pooled HR for overall survival (OS) was 0.96 (95% confidence interval [CI] 0.75–.123) in the RCT subgroup and 0.89 (95% CI 0.62–1.28) in the non-RCT subgroup. For disease-free survival (DFS), the HR for the RCT group was 0.83 (95% CI 0.65–1.07), similar to the non-RCT subgroup (0.83, 95% CI 0.65–1.07). Disease-specific survival (DSS) was also calculated, which had an HR of 1.07 (95% CI 0.68–1.69) in the non-RCT subgroup. All these results showed that MSI-H has no beneficial effects in stage III CRC. For stage IV CRC, the HR for OS in the RCT subgroup was 1.23 (95% CI 0.92–1.64) but only two RCTs were included. For non-RCT study, the combined HR for OS and DFS was 1.10 (95% CI 0.77–1.51) and 0.72 (95% CI 0.53–0.98), respectively, suggesting the beneficial effect for DFS and non-beneficial effect for OS.

Conclusion

For stage III CRC, MSI-H had no prognostic effect for OS, DFS, and DSS. For stage IV CRC, DFS showed a beneficial result, whereas OS did not; however, the included studies were limited and needed further exploration.

Chromatin remodeling and mismatch repair: Access and excision

DNA mismatch repair (MMR) increases replication fidelity and genome stability by correcting DNA polymerase errors that remain after replication. Defects in MMR result in the accumulation of mutations and lead to human tumor development. Germline mutations in MMR cause the hereditary cancer syndrome, Lynch syndrome. After replication, DNA is reorganized into its chromatin structure and wrapped around histone octamers. DNA MMR is thought to be less efficient in recognizing and repairing mispairs packaged in chromatin, in which case MMR must either compete for access to naked DNA before histone deposition or actively move nucleosomes to access the mispair. This article reviews studies into the mechanistic and physical interactions between MMR and various chromatin-associated factors, including the histone deposition complex CAF1. Recent Xenopus and Saccharomyces cerevisiae studies describe a physical interaction between Msh2 and chromatin-remodeling ATPase Fun30/SMARCAD1, with potential mechanistic roles for SMARCAD1 in moving histones for both mispair access and excision tract elongation. The RSC complex, another histone remodeling complex, also potentially influences excision tract length. Deletion mutations of RSC2 point to mechanistic interactions with the MMR pathways. Together, these studies paint a picture of complex interactions between MMR and the chromatin environment that will require numerous additional genetic, biochemical, and cell biology experiments to fully understand. Understanding how these pathways interconnect is essential in fully understanding eukaryotic MMR and has numerous implications in human tumor formation and treatment.

Correlations between microsatellite instability and the biological behaviour of tumours

Purpose

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

Methods

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

Results

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

Conclusion

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

Development and Validation of a Prediction Model for Organ-Specific Recurrences After Curative Resection of Colon Cancer

BACKGROUND

Early detection of postoperative recurrence is beneficial for patients with cancer; however, optimal surveillance remains an issue. To optimize the follow-up plan, the estimation of an individual patient's risk of recurrence is indispensable.

OBJECTIVE

This study aimed to establish a statistical model for predicting the risk of organ-specific recurrence after curative resection of colon cancer.

DESIGN

This was a retrospective cohort study at a tertiary referral hospital.

SETTINGS

This study included 1720 patients with colon cancer treated at the University of Tokyo Hospital between 1997 and 2015. Data were retrospectively retrieved from patient medical charts. The risk score was developed using a competing risk model in a derivation cohort (973 patients treated in 1997-2009) and then validated in a validation cohort (747 patients treated in 2010-2015).

PATIENTS

Patients who underwent curative resection for stage I to III colon cancer were included.

MAIN OUTCOME MEASURES

The prediction of the incidence of postoperative liver and lung metastasis of colon cancer was measured.

RESULTS

The factors selected for the prediction model for liver metastasis included differentiation, T category, venous invasion, N category, and preoperative CEA level. The model for lung metastasis included sex, lymphatic invasion, venous invasion, N category, preoperative CEA level, and malignant bowel obstruction. During external validation, the area under the curve at 60 months was 0.78 (95% CI, 0.71-0.84) for liver metastasis and 0.72 (95% CI, 0.64-0.81) for lung metastasis.

LIMITATIONS

The generalizability of the model to different healthcare settings remains to be elucidated.

CONCLUSIONS

We developed a prediction model to estimate the risk of recurrence in the liver and lung after curative resection of colon cancer, which demonstrated good discrimination ability in the external validation cohort. Our model can aid clinicians and patients in customizing postoperative surveillance according to an individual patient's risk of organ-specific recurrence. See Video Abstract at http://links.lww.com/DCR/A977. DESARROLLO Y VALIDACIÓN DE UN MODELO DE PREDICCIÓN PARA RECURRENCIAS ESPECÍFICAS DESPUÉS DE RESECCIÓN CURATIVA DE UN CÁNCER DE COLON: La detección temprana de una recidiva postoperatoria es beneficiosa para los pacientes afectados de cáncer. Sin embargo, la mejor vigilancia sigue siendo un problema. Para optimizar el plan de seguimiento, la estimación del riesgo individual de recurrencia de un paciente es indispensable.

OBJETIVO

Establecer un modelo estadístico para predecir el riesgo de recurrencia en un organo específico luego de la resección curativa de un cáncer de colon. DISEÑO:: Estudio retrospectivo de cohortes en un hospital de referencia terciaria.

AJUSTES

Este estudio incluyó 1720 pacientes con cáncer de colon tratados en el Hospital de la Universidad de Tokio entre 1997 y 2015. Los datos se recuperaron retrospectivamente de las historias clinicas de los pacientes. La puntuación de riesgo fué desarrollada utilizando un modelo de riesgo competitivo en cohortes de derivación (973 pacientes tratados en 1997-2009) y luego se lo validó en cohortes de validación (747 pacientes tratados en 2010-2015).

PACIENTES

Todos aquellos casos que se sometieron a una resección curativa de cáncer de colon en estadio I-III RESULTADOS PRINCIPLES:: La predicción de la incidencia de metástasis hepáticas y pulmonares postoperatorias del cáncer de colon.

RESULTADOS

Los factores seleccionados para el modelo de predicción de metástasis hepáticas incluyeron diferenciación tumoral, categoría T, invasión venosa, categoría N y nivel de antígeno carcinoembrionario preoperatorio. El modelo de predicción de metástasis pulmonar incluyó el sexo del paciente, la invasión linfática, la invasión venosa, la categoría N, el nivel de antígeno carcinoembrionario preoperatorio y la obstrucción intestinal maligna. Durante la validación externa, el área inferior de la curva a 60 meses fue de 0,78 (intervalo de confianza del 95%: 0,71 a 0,84) para las metástasis hepáticas y de 0,72 (intervalo de confianza del 95%: 0,64 a 0,81) para las metástasis pulmonares.

LIMITACIONES

La generalización del presente modelo a diferentes entornos de atención en salud aún no ha podido ser dilucidado.

CONCLUSIONES

Desarrollamos un modelo de predicción para estimar el riesgo de recurrencia en el hígado y el pulmón después de resección curativa de cáncer de colon, éste modelo demostró una buena capacidad de discriminación en las cohortes de validación externa. El modelo puede ayudar a médicos y pacientes a personalizar la vigilancia postoperatoria de acuerdo con el riesgo individual de recurrencia específica en un órgano específico. Vea el Resumen del Video en http://links.lww.com/DCR/A977.

Transcriptome and Network Dissection of Microsatellite Stable and Highly Instable Colorectal Cancer

Background:

Colorectal cancer (CRC) is one of the most common cancers worldwide with high number of mortality every year. Microsatellite instability (MSI) is a considerable feature of CRC which affects prognosis and treatment. High level of MSI or MSI-high (MSI-H) colorectal cancer has better prognosis and immunotherapy response, while microsatellite stable (MSS) CRC has better response to 5-fluorouracil (5-FU)-based chemotherapy. More studies are needed, specifically on MSS CRC which has worse prognosis, to further reveal biological differences and similarities between MSS and MSI colorectal cancer, which may equip us with the knowledge to develop more promising therapeutic approaches to target both types or be more effective for each type.

Methods:

We aimed to find affected biological processes and their regulators in both type, MSS and MSI-H, of CRC; as well as reveal specific ones in each type. We applied meta- and network analysis on freely available transcriptome data in MSS and MSI-H colorectal cancer from gene expression omnibus (GEO) database to detect common differentially expressed genes (DEGs) and critical biological processes and predict their most significant regulators.

Results:

Our results demonstrate considerable up and downregulation in cell cycle and lipid catabolism processes, respectively; and introduced MYC and FOXM1 as two central and up-stream regulators of DEGs in both type of CRC. Chemokine-mediated processes displayed up-regulation in MSI-H type, while metastasis-related processes showed more activation in MSS CRC. Additionally, DACH1 and TP53 were detected as two important transcription factors that differentially expressed just in MSS and MSI-H, respectively.

Conclusion:

Our results can explain why MSI and MSS CRC display different immunotherapy response, prognosis, and metastasis feature. Moreover, our predicted up-stream regulators in the regulatory networks may be promising therapeutic targets.

Colorectal peritoneal metastases: Optimal management review

The peritoneum is a common site of dissemination for colorrectal cancer, with a poorer prognosis than other sites of metastases. In the last two decades, it has been considered as a locoregional disease progression and treated as such with curative intention treatments. Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) is the actual reference treatment for these patients as better survival results have been reached as compared to systemic chemotherapy alone, but its therapeutic efficacy is still under debate. Actual guidelines recommend that the management of colorectal cancer with peritoneal metastases should be led by a multidisciplinary team carried out in experienced centers and consider CRS + HIPEC for selected patients. Accumulative evidence in the last three years suggests that this is a curative treatment that may improve patients disease-free survival, decrease the risk of recurrence, and does not increase the risk of treatment-related mortality. In this review we aim to gather the latest results from referral centers and opinions from experts about the effectiveness and feasibility of CRS + HIPEC for treating peritoneal disease from colorectal malignancies.

The Molecular Hallmarks of the Serrated Pathway in Colorectal Cancer

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. It includes different subtypes that differ in their clinical and prognostic features. In the past decade, in addition to the conventional adenoma-carcinoma model, an alternative multistep mechanism of carcinogenesis, namely the “serrated pathway”, has been described. Approximately, 15 to 30% of all CRCs arise from neoplastic serrated polyps, a heterogeneous group of lesions that are histologically classified into three morphologic categories: hyperplastic polyps, sessile serrated adenomas/polyps, and the traditional serrated adenomas/polyps. Serrated polyps are characterized by genetic (BRAF or KRAS mutations) and epigenetic (CpG island methylator phenotype (CIMP)) alterations that cooperate to initiate and drive malignant transformation from normal colon mucosa to polyps, and then to CRC. The high heterogeneity of the serrated lesions renders their diagnostic and pathological interpretation difficult. Hence, novel genetic and epigenetic biomarkers are required for better classification and management of CRCs. To date, several molecular alterations have been associated with the serrated polyp-CRC sequence. In addition, the gut microbiota is emerging as a contributor to/modulator of the serrated pathway. This review summarizes the state of the art of the genetic, epigenetic and microbiota signatures associated with serrated CRCs, together with their clinical implications.

Impact of tumor sidedness on survival and recurrence patterns in colon cancer patients

Purpose

Previous studies have reported conflicting results regarding the prognostic value of tumor sidedness in colon cancer. We investigated the oncologic impact of tumor location and examined whether recurrence patterns were related to tumor sidedness in colon cancer patients.

Methods

We identified stage I-III colon adenocarcinoma patients from a prospective colorectal cancer registry at Severance Hospital, Seoul, Korea, who underwent complete mesocolic excision between 2005 and 2012. Adjusted hazard ratios (HRs) and 95% confidence intervals (CI) for predictors of cancer-specific survival (CSS), recurrence-free survival (RFS), and cumulative recurrence at specific anatomic sites were examined using Cox proportional hazard regression analysis.

Results

Overall, 1,912 patients, 1,077 (56.3%) with left-sided colon cancer (LCC), and 835 (43.7%) with right-sided colon cancer (RCC), at a median follow-up of 59 months, were eligible and included in the study. In univariate analysis, similar 5-year CSS and RFS were observed for LCC and RCC in the total patient population, and when stratified by stage for stage I and II patients. For stage III patients, an adjusted Cox regression analysis indicated that RCC patients had a higher risk of cancer-specific mortality (HR, 1.75; 95% CI, 1.07-2.86; P = 0.024) and recurrence (HR, 1.78; 95% CI, 1.22-2.60; P = 0.003). Furthermore, RCC was an independent predictor of peritoneal recurrence (HR, 1.86; 95% CI, 1.05-3.29; P = 0.031) in stage III patients.

Conclusion

RCC correlated with worse CSS and RFS than LCC. In stage III patients, RCC correlated with increased risk of peritoneal recurrence. The reasons for these differences remain to be investigated.

Consequences of a high incidence of microsatellite instability and BRAF-mutated tumors: A population-based cohort of metastatic colorectal cancer patients

Background

Immunotherapy for patients with microsatellite‐instable (MSI‐H) tumors or BRAF‐inhibitors combination treatment for BRAF‐mutated (mutBRAF) tumors in metastatic colorectal cancer (mCRC) is promising, but the frequency of these molecular changes in trial patients are low. Unselected population‐based studies of these molecular changes are warranted.

Methods

A population‐based cohort of 798 mCRC patients in Scandinavia was studied. Patient and molecular tumor characteristics, overall survival (OS) and progression‐free survival (PFS) were estimated.

Results

Here, 40/583 (7%) tumor samples were MSI‐H and 120/591 (20%) were mutBRAF; 87% of MSI‐H tumors were mutBRAF (non‐Lynch). Elderly (>75 years) had more often MSI‐H (10% vs 6%) and MSI‐H/mutBRAF (9% vs 4%) tumors. Response rate (5% vs 44%), PFS (4 vs 8 months), and OS (9 vs 18 months) after first‐line chemotherapy was all significantly lower in patients with MSI‐H compared to patients with microsatellite stable tumors. MSI‐H and mutBRAF were both independent poor prognostic predictors for OS (P = 0.049, P < 0.001) and PFS (P = 0.045, P = 0.005) after first‐line chemotherapy. Patients with MSI‐H tumors received less second‐line chemotherapy (15% vs 37%, P = 0.005).

Conclusions

In unselected mCRC patients, MSI‐H and mutBRAF cases were more common than previously reported. Patients with MSI‐H tumors had worse survival, less benefit from chemotherapy, and they differed considerably from recent third‐line immunotherapy trial patients as they were older and most had mutBRAF tumor (non‐Lynch).

Involvement of MAF1 homolog, negative regulator of RNA polymerase III in colorectal cancer progression

Polymerase (Pol) III‑dependent transcription controls the abundance of transfer RNAs, 5S ribosomal RNA and small non‑coding RNAs within cells, and is known to serve an essential role in the maintenance of intracellular homeostasis. However, its contribution to cancer progression has not been extensively explored. The present study demonstrated that the evolutionarily conserved MAF1 homolog, negative regulator of RNA Pol III (MAF1) may be closely associated with malignant potential and poor prognosis in colorectal cancer (CRC). Notably, immunohistochemical analysis of 146 CRC surgical specimens revealed that high expression levels of MAF1 were associated with advanced tumor depth, lymph node metastasis, distant metastasis and poor prognosis. In vitro loss‑of‑function assays revealed that MAF1 knockdown suppressed chemoresistance and migration of CRC cancer cells. Furthermore, detailed analysis of an independent CRC dataset (n=615) demonstrated that the prognostic impact of MAF1 gene expression was particularly marked in microsatellite instability (MSI)‑positive patients, who benefit from immune checkpoint blockade. High expression levels of MAF1 were revealed to be an independent prognostic indicator in MSI‑positive CRC. These findings suggested that MAF1 may have an essential role in CRC progression, particularly in MSI‑positive cases.

Metastatic Profile of Colorectal Cancer: Interplay Between Primary Tumor Location and KRAS Status

BACKGROUND

Mutant KRAS tumors are purported to metastasize differently than wild-type KRAS tumors. The biological heterogeneity of tumors from different parts of the colon are also reported to affect metastasis. This study aims to characterize the metastatic profile by evaluating these factors in unison.

METHODS

Retrospective analysis of 899 patients with metastatic colorectal cancers treated from January 2010 to December 2014 was conducted. KRAS mutation status and primary tumors location were correlated with single-site metastasis (liver, lung, and peritoneum) and dual-site metastases (liver-peritoneum, liver-lung, and lung-peritoneum). Patients without KRAS analyses were excluded.

RESULTS

Right-sided tumors had highest frequency of peritoneal metastasis as compared to left-sided or rectal tumors (34.7% versus 15.8% versus 8.8%, P = 0.00) regardless of KRAS status (32.6% versus 38.5%, P = 0.62). Left-sided tumors with wild-type KRAS had greater proportion of liver metastasis (78.6% versus 53.5%, P = 0.00), whereas those with mutant KRAS had greater proportion of lung metastasis (23.3% versus 8.7%, P = 0.02). Rectal tumors with wild-type KRAS tend to spread to the liver (81.4% versus 48.0%, P = 0.00) and not to the peritoneum (2.3% versus 20.0%, P = 0.01). In dual-site metastases, left-sided tumors with wild-type KRAS had more liver-peritoneal metastases (75.0% versus 29.4%, P = 0.00), whereas mutant KRAS had greater lung-liver metastases (64.7% versus 20.8%, P = 0.01). Rectal tumors had the predilection for lung-liver metastases as compared to right-sided and left-sided tumors (92.3% versus 40.0% versus 39.0%, P = 0.00) regardless of KRAS status (100% versus 75%, P = 0.12).

CONCLUSIONS

Our results may streamline surveillance programs based on primary tumor location and KRAS mutational status.

Outcome of chemotherapy with or without targeted agents in metastatic colorectal cancer patients with deficient DNA mismatch repair: A single center, cohort study

AIMS

Metastatic colorectal cancer (mCRC) with deficient DNA mismatch repair (dMMR) is a rare disease accounting only for 4-5% of the whole mCRC and its optimal treatment still remains unclear. We conducted a retrospective study to evaluate the outcome of chemotherapy with or without bevacizumab or cetuximab in this setting.

METHODS

A total of 729 colorectal cancer patients with dMMR status were screened for eligibility. The Kaplan-Meier method, the log-rank test and Cox analysis were utilized for survival analyses.

RESULTS

A total of 43 patients met the inclusion criteria and enrolled in the study. The median overall survival (OS) of entire cohort was 21.7 months. Chemotherapy plus bevacizumab group exhibited a tendency of substantially higher overall response rate (ORR) than chemotherapy alone group (63.6% vs. 23.8%, P = 0.053), whereas the ORR between chemotherapy plus cetuximab group and chemotherapy alone group were similar (28.6% vs. 23.8%, P = 1.000). Compared with chemotherapy alone group, bevacizumab combined group achieved a significantly longer progression-free survival (10.0 months vs. 4.8 months, P = 0.028), whereas cetuximab combined group was not (6.8 months vs. 4.8 months, P = 0.158). Although the median OS seemed to favor bevacizumab combined group, no significant differences were detected between the three arms (33.7, 21.7 and 15.3 months, respectively; P = 0.345). Prognostic analysis showed that primary tumor resection was the positive prognostic factor of OS (hazards ratio: 0.438; P = 0.041).

CONCLUSION

dMMR mCRC seems resistant to chemotherapy and cetuximab. Bevacizumab combined therapy shows a sign of potentially favorable outcome in this subtype.

MSI-L/EMAST is a predictive biomarker for metastasis in colorectal cancer patients

BACKGROUND

Microsatellite instability (MSI) is a prognostic marker in colorectal cancer (CRC). The biological significance of MSI-low (MSI-L) phenotype and its differences with microsatellite stable (MSS) phenotype remains unclear. The aim of this study is indicating the role of mononucleotide repeat in identifying MSI-L and revealing the association of MSI-L with elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) and oncologic outcome in CRC patients.

METHODS

MSI and EMAST status were analyzed using three quasimonomorphic panel (BAT-25, BAT-26, and NR-27) and five tetranucleotide repeats (D20S82, D20S85, D9S242, D8S321, and MYCL1), respectively, by capillary electrophoresis method without the need to fluorescent primers. The associations of MSI status with clinicopathological features, EMAST status, metastasis, and overall survival (OS) were investigated.

RESULTS

Among 159 CRC patient 22.0% were MSI-H, 40.3% were MSS, 37.7% were MSI-L, and 41.5% showed EMAST + phenotype. MSI-L were associated with advanced stages, EMAST⁺ tumors and worse OS ( p ≤ 0.001). Metastasis was relatively common in MSI-L/EMAST ⁺ CRCs and BAT-25 were the most unstable marker in these tumors.

CONCLUSIONS

MSI-L tumors have different clinicopathological features from MSS and MSI-H tumors. The MSI-L phenotype is a worse prognostic biomarker in CRC and when accompanied by EMAST could be a predictor for metastasis.

Spatial and phenotypic immune profiling of metastatic colon cancer

Paramount to the efficacy of immune checkpoint inhibitors is proper selection of patients with adequate tumor immunogenicity and a robust but suppressed immune infiltrate. In colon cancer, immune-based therapies are approved for patients with DNA mismatch repair (MMR) deficiencies, in whom accumulation of genetic mutations results in increased neoantigen expression, triggering an immune response that is suppressed by the PD-L1/PD-1 pathway. Here, we report that characterization of the microenvironment of MMR-deficient metastatic colorectal cancer using multiplex fluorescent immunohistochemistry (mfIHC) identified increased infiltration of cytotoxic T lymphocytes (CTLs), which were more often engaged with epithelial cells (ECs) and improved overall survival. A subset of patients with intact MMR but a similar immune microenvironment to MMR-deficient patients was identified and found to universally express high levels of PD-L1, suggesting that they may represent a currently untreated, checkpoint inhibitor-responsive population. Further, PD-L1 expression on antigen-presenting cells (APCs) in the tumor microenvironment (TME) resulted in impaired CTL/EC engagement and enhanced infiltration and engagement of Tregs. Characterization of the TME by mfIHC highlights the interconnection between immunity and immunosuppression in metastatic colon cancer and may better stratify patients for receipt of immunotherapies.

Influence of MSI and 18q LOH markers on capecitabine adjuvant monotherapy in colon cancer patients

PURPOSE

The aim of this study was to evaluate whether pretreatment analysis of selected molecular markers can be used for the prediction of disease-free survival (DFS)/overall survival (OS) of capecitabine adjuvant monotherapy in colon cancer patients.

PATIENTS AND METHODS

A total of 126 patients enrolled in a capecitabine Phase IV clinical trial were analyzed for microsatellite instability (MSI), 18q loss of heterozygosity (LOH), thymidylate synthase (TYMS) 5' variable number of tandem repeat (VNTR), and methylene tetrahydrofolate reductase (MTHFR) C677T variants. The significance in predicting 5-year DFS/OS was assessed by Kaplan-Meier and Cox regression analyses.

RESULTS

The MSI-high (MSI-H) genotype was significantly associated with DFS (HR 0.205, 95% CI 0.05-0.88, P=0.033) and OS (HR 0.208, 95% CI 0.05-0.89, P=0.035) compared to the microsatellite stable genotype. In models stratified according to clinicopathologic characteristics, the MSI-H genotype remained a positive predictive factor for DFS/OS only in patients with stage III (P=0.023) and patients with tumors localized proximally to the splenic flexure (P=0.004). Distal colon cancers with 18q LOH have a greater survival rate when treated with capecitabine than patients with stable tumors (81.3% vs 50.0%, HR for relapse 0.348, 95% CI 0.13-0.97, P=0.043). TYMS 5'VNTR and MTHFR C677T variants were not associated with DFS or OS.

CONCLUSION

MSI and 18q LOH markers have the potential to be utilized in the selection of colon cancer patients eligible for capecitabine adjuvant monotherapy.

Microsatellite instability in colorectal cancer: overview of its clinical significance and novel perspectives

Microsatellite instability (MSI) is a key biomarker in colorectal cancer (CRC), with crucial diagnostic, prognostic, and predictive implications. Testing for mismatch repair deficiency (MMR-D)/MSI is recommended during screening for Lynch syndrome, an autosomal-dominant hereditary disease that is characterized by germline mutations in the MMR genes and associated with an increased risk for several types of cancer. Additionally, MSI-high (MSI-H) status is associated with a better prognosis in early-stage CRC and a lack of benefit from adjuvant treatment with 5-fluorouracil in stage II disease. More recently, MSI has emerged as a predictor of sensitivity to immunotherapy-based treatments. The groundbreaking success of checkpoint inhibitors in MMR-D metastatic CRC has opened a new therapeutic scenario for patients with these tumors. MSI-H CRC, in both the sporadic and hereditary settings, is characterized by distinctive molecular and clinicopathologic features and represents a unique subset of CRC that is the object of growing interest and fervent research efforts. This article, an overview of the expanding role of MSI in CRC, covers its clinical significance, the available data on molecular profiling, novel perspectives on MSI testing, biomarkers in MSI-H CRC, immunotherapy resistance, and novel immunotherapy strategies.