BRAFV600E immunohistochemistry facilitates universal screening of colorectal cancers for Lynch syndrome

Current and Future Trends of Colorectal Cancer Treatment: Exploring Advances in Immunotherapy

Cancer of the colon and rectum (CRC) has been identified among the three most prevalent types of cancer and cancer-related deaths for both sexes. Even though significant progress in surgical and chemotherapeutic techniques has markedly improved disease-free and overall survival rates in contrast to those three decades ago, recent years have seen a stagnation in these improvements. This underscores the need for new therapies aiming to augment patient outcomes. A number of emerging strategies, such as immune checkpoint inhibitors (ICIs) and adoptive cell therapy (ACT), have exhibited promising outcomes not only in preclinical but also in clinical settings. Additionally, a thorough appreciation of the underlying biology has expanded the scope of research into potential therapeutic interventions. For instance, the pivotal role of altered telomere length in early CRC carcinogenesis, leading to chromosomal instability and telomere dysfunction, presents a promising avenue for future treatments. Thus, this review explores the advancements in CRC immunotherapy and telomere-targeted therapies, examining potential synergies and how these novel treatment modalities intersect to potentially enhance each other's efficacy, paving the way for promising future therapeutic advancements.

BRAFV600E immunohistochemistry can reliably substitute BRAF molecular testing in the Lynch syndrome screening algorithm in colorectal cancer

AIMS

The Lynch syndrome (LS) screening algorithm requires BRAF testing as a fundamental step to distinguish sporadic from LS-associated colorectal carcinomas (CRC). BRAF testing by immunohistochemistry (IHC) has shown variable results in the literature. Our aim was to analyse concordance between BRAFV600E IHC and BRAF molecular analysis in a large, mono-institutional CRC whole-slide, case series with laboratory validation.

METHODS AND RESULTS

MisMatch repair (MMR) protein (hMLH1, hPMS2, hMSH2, and hMSH6) and BRAFV600E IHC were performed on all unselected cases of surgically resected CRCs (2018-2023). An in-house validation study for BRAFV600E IHC was performed in order to obtain optimal IHC stains. BRAFVV600E IHC was considered negative (score 0), positive (scores 2-3), and equivocal (score 1). Interobserver differences in BRAFV600E IHC scoring were noted in the first 150 cases prospectively collected. Nine-hundred and ninety CRCs cases (830 proficient (p)MMR/160 deficient (d)MMR) were included and all cases performed BRAFV600E IHC (BRAFV600E IHC-positive 13.5% of all series; 66.3% dMMR cases; 3.4% pMMR cases), while 333 also went to BRAF mutation analysis. Optimal agreement in IHC scoring between pathologists (P < 0.0001) was seen; concordance between BRAFV600E IHC and BRAF molecular analysis was extremely high (sensitivity 99.1%, specificity 99.5%; PPV 99.1%, and NPV 99.5%). Discordant cases were reevaluated; 1 score 3 + IHC/wildtype case was an interpretation error and one score 0 IHC/mutated case was related to heterogenous BRAFV600E IHC expression. Among the 12 IHC-equivocal score 1+ cases (which require BRAF molecular analysis), three were BRAF-mutated and nine BRAF-wildtype.

CONCLUSION

BRAFV600E IHC can be used as a reliable surrogate of molecular testing after stringent in-house validation.

Identifying primary and secondary MLH1 epimutation carriers displaying low-level constitutional MLH1 methylation using droplet digital PCR and genome-wide DNA methylation profiling of colorectal cancers

BACKGROUND

MLH1 epimutation is characterised by constitutional monoallelic MLH1 promoter hypermethylation, which can cause colorectal cancer (CRC). Tumour molecular profiles of MLH1 epimutation CRCs were used to classify germline MLH1 promoter variants of uncertain significance and MLH1 methylated early-onset CRCs (EOCRCs). Genome-wide DNA methylation and somatic mutational profiles of tumours from two germline MLH1: c.-11C > T and one MLH1: c.-[28A > G; 7C > T] carriers and three MLH1 methylated EOCRCs (< 45 years) were compared with 38 reference CRCs. Methylation-sensitive droplet digital PCR (ddPCR) was used to detect mosaic MLH1 methylation in blood, normal mucosa and buccal DNA.

RESULTS

Genome-wide methylation-based Consensus Clustering identified four clusters where the tumour methylation profiles of germline MLH1: c.-11C > T carriers and MLH1 methylated EOCRCs clustered with the constitutional MLH1 epimutation CRCs but not with the sporadic MLH1 methylated CRCs. Furthermore, monoallelic MLH1 methylation and APC promoter hypermethylation in tumour were observed in both MLH1 epimutation and germline MLH1: c.-11C > T carriers and MLH1 methylated EOCRCs. Mosaic constitutional MLH1 methylation in MLH1: c.-11C > T carriers and 1 of 3 MLH1 methylated EOCRCs was identified by methylation-sensitive ddPCR.

CONCLUSIONS

Mosaic MLH1 epimutation underlies the CRC aetiology in MLH1: c.-11C > T germline carriers and a subset of MLH1 methylated EOCRCs. Tumour profiling and ultra-sensitive ddPCR methylation testing can be used to identify mosaic MLH1 epimutation carriers.

Cyclooxygenase and Lipoxygenase Gene Expression in the Inflammogenesis of Colorectal Cancer: Correlated Expression of EGFR, JAK STAT and Src Genes, and a Natural Antisense Transcript, RP11-C67.2.2

We examined the expression of major inflammatory genes, cyclooxygenase-1, 2 (COX1, COX2), arachidonate-5-lipoxygenase (ALOX5), and arachidonate-5-lipoxygenase activating protein (ALOX5AP) among 469 tumor specimens of colorectal cancer in The Cancer Genome Atlas (TCGA). Among 411 specimens without mutations in mismatch repair (MMR) genes, the mean expression of each of the inflammatory genes ranked above the 80th percentile, and the overall mean cyclooxygenase expression (COX1+COX2) ranked in the upper 99th percentile of all genes. Similar levels were observed for 58 cases with MMR mutations. Pearson correlation coefficients exceeding r = 0.70 were observed between COX and LOX mRNA levels with genes of major cell-signaling pathways involved in tumorigenesis (Src, JAK STAT, MAPK, PI3K). We observed a novel association (r = 0.78) between ALOX5 expression and a natural antisense transcript (NAT), RP11-67C2.2, a long non-coding mRNA gene, 462 base pairs in length that is located within the terminal intron of the ALOX5 gene on chromosome 10q11.21. Tumor-promoting genes highly correlated with the expression of COX1, COX2, ALOX5 and ALOX5AP are known to increase mitogenesis, mutagenesis, angiogenesis, cell survival, immunosuppression and metastasis in the inflammogenesis of colorectal cancer. These genes and the novel NAT, RP1167C2.2 are potential molecular targets for chemoprevention and therapy of colorectal cancer.

A Focused Clinical Review of Lynch Syndrome

Lynch syndrome (LS) is an autosomal dominant condition that increases an individual's risk of a constellation of cancers. LS is defined when an individual has inherited pathogenic variants in the mismatch repair genes. Currently, most people with LS are undiagnosed. Early detection of LS is vital as those with LS can be enrolled in cancer reduction strategies through chemoprophylaxis, risk reducing surgery and cancer surveillance. However, these interventions are often invasive and require refinement. Furthermore, not all LS associated cancers are currently amenable to surveillance. Historically only those with a strong family history suggestive of LS were offered testing; this has proved far too restrictive. New criteria for testing have recently been introduced including the universal screening for LS in associated cancers. This has increased the number of people being diagnosed with LS but has also brought about unique challenges such as when to consent for germline testing and questions over how and who should carry out the consent. The results of germline testing for LS can be complicated and the diagnostic pathway is not always clear. Furthermore, by testing only those with cancer for LS we fail to identify these individuals before they develop potentially fatal pathology. This review will outline these challenges and explore solutions. Furthermore, we consider the potential future of LS care and the related treatments and interventions which are the current focus of research.

Clinicopathological characteristics of high microsatellite instability/mismatch repair-deficient colorectal cancer: A narrative review

Colorectal cancers (CRCs) with high microsatellite instability (MSI-H) and deficient mismatch repair (dMMR) show molecular and clinicopathological characteristics that differ from those of proficient mismatch repair/microsatellite stable CRCs. Despite the importance of MSI-H/dMMR status in clinical decision making, the testing rates for MSI and MMR in clinical practice remain low, even in high-risk populations. Additionally, the real-world prevalence of MSI-H/dMMR CRC may be lower than that reported in the literature. Insufficient MSI and MMR testing fails to identify patients with MSI-H/dMMR CRC, who could benefit from immunotherapy. In this article, we describe the current knowledge of the clinicopathological features, molecular landscape, and radiomic characteristics of MSI-H/dMMR CRCs. A better understanding of the importance of MMR/MSI status in the clinical characteristics and prognosis of CRC may help increase the rates of MMR/MSI testing and guide the development of more effective therapies based on the unique features of these tumors.

DNA Mismatch Repair Proteins and BRAF V600E Detection by Immunohistochemistry in Colorectal Cancer Demonstrates Concordance with Next Generation Sequencing

Background and Aims: Multiple laboratory methods are used to screen patients with colorectal cancer (CRC) for mismatch repair (MMR) protein deficiency to identify possible Lynch syndrome patients. The goal of this study was to compare the agreement between ready-to-use immunohistochemistry (IHC) assays for MLH-1, PMS-2, MSH-2, MSH-6, and mutated BRAF at V600E and molecular methods in CRC cases. The inclusion of the BRAF V600E mutation testing is important for the identification of patients with sporadic CRC, as the BRAF V600E mutation is very rarely observed in patients with Lynch syndrome tumors. Methods: CRC cases were analyzed by ColoSeqTM tumor sequencing assay and VENTANA MMR IHC Panel that included anti-MLH1, anti-PMS2, anti-MSH2, anti-MSH6, and anti-BRAF V600E antibodies. Additionally, CRC cases with MLH1 IHC loss were evaluated for MLH1 promoter hypermethylation. Results: One hundred and eighteen cases were analyzed. The overall percent agreement (OPA) for each evaluated marker status compared to next-generation sequencing (NGS) exceeded 96%. Twenty-three cases were positive for the BRAF V600E mutation by IHC and NGS, and twenty cases showed loss of MLH1 protein and were positive for MLH1 hypermethylation. Samples with loss of MMR protein expression by IHC demonstrated genetic and/or epigenetic alterations that were consistent with the observed protein expression patterns. Conclusions: The results of this study indicate that ready-to-use IHC assays can correctly identify the loss of MMR proteins and the presence of mutated BRAF V600E protein, supporting the utility of the VENTANA MMR IHC Panel as an aid to stratify patients with sporadic CRC vs. potential Lynch syndrome.

Identifying patients with Lynch syndrome using a universal tumor screening program in an integrated healthcare system

INTRODUCTION

Lynch syndrome (LS) is associated with an increased risk of colorectal (CRC) and endometrial (EC) cancers. Universal tumor screening (UTS) of all individuals diagnosed with CRC and EC is recommended to increase identification of LS. Kaiser Permanente Northwest (KPNW) implemented a UTS program for LS among individuals newly diagnosed with CRC in January 2016 and EC in November 2016. UTS at KPNW begins with immunohistochemistry (IHC) of tumor tissue to determine loss of mismatch repair proteins associated with LS (MLH1, MSH2, MSH6, and PMS2)., IHC showing loss of MLH1 is followed by reflex testing (automatic testing) to detect the presence of the BRAF V600E variant (in cases of CRC) and MLH1 promoter hypermethylation to rule out likely sporadic cases.

MATERIALS AND METHODS

Individuals newly diagnosed with CRC and EC were identified between the initiation of the respective UTS programs and July 2018. Electronic medical records were reviewed to extract patient data related to UTS, including IHC and reflex testing results, date of referrals to the genetics department, and results of germline genetic testing for LS.

RESULTS

313 out of 362 individuals diagnosed with CRC and 61 out of 64 individuals diagnosed with EC who were eligible were screened by IHC for LS. Most (47/52 or 90%, including 46/49 CRC and 1/3 EC) individuals that were not screened by IHC only had a biopsy sample available. Fourteen individuals (3.7% overall, including 13/313 CRC and 1/61 EC) received an abnormal result after reflex testing and were referred for genetic counseling. Of these, 10 individuals (71% overall, including 9/13 CRC and 1/1 EC) underwent germline genetic testing for LS. Five individuals diagnosed with CRC were found to have pathogenic variants. in PMS2 (n = 3), MLH1 (n = 1), and MSH6 (n = 1). No pathogenic variants were identified in individuals diagnosed with EC.

CONCLUSIONS

UTS identified individuals at risk for LS. Most individuals who screened positive for LS had follow-up germline genetic testing for LS. The consistent use of biopsy samples is an opportunity to improve UTS.

Universal Immunohistochemistry for Lynch Syndrome: A Systematic Review and Meta-analysis of 58,580 Colorectal Carcinomas

BACKGROUND & AIMS

Lynch syndrome is a form of hereditary colorectal cancer (CRC) caused by pathogenic germline variants (PV) in DNA mismatch repair (MMR) genes. Currently, many Western countries perform universal immunohistochemistry testing on CRC to increase the identification of Lynch syndrome patients and their relatives. For a clear understanding of health benefits and costs, data on its outcomes are required: proportions of Lynch syndrome, sporadic MMR-deficient (MMRd) cases, and unexplained MMRd cases.

METHODS

Ovid Medline, Embase, and Cochrane CENTRAL were searched for studies reporting on universal MMR immunohistochemistry, followed by MMR germline analysis, until March 20, 2020. Proportions were calculated, subgroup analyses were performed based on age and diagnostics used, and random effects meta-analyses were conducted. Quality was assessed using the Joanna Briggs Critical Appraisal Tool for Prevalence Studies.

RESULTS

Of 2723 identified articles, 56 studies covering 58,580 CRCs were included. In 6.22% (95% CI, 5.08%-7.61%; I² = 96%) MMRd was identified. MMR germline PV was present in 2.00% (95% CI, 1.59%-2.50%; I² = 92%), ranging from 1.80% to 7.27% based on completeness of diagnostics and age restriction. Immunohistochemistry outcomes were missing in 11.81%, and germline testing was performed in 76.30% of eligible patients. In 7 studies, including 6848 CRCs completing all diagnostic stages, germline PV and biallelic somatic MMR inactivation were found in 3.01% and 1.75%, respectively; 0.61% remained unexplained MMRd.

CONCLUSIONS

Age, completeness, and type of diagnostics affect the percentage of MMR PV and unexplained MMRd percentages. Complete diagnostics explain almost all MMRd CRCs, reducing the amount of subsequent multigene panel testing. This contributes to optimizing testing and surveillance in MMRd CRC patients and relatives.

Risk assessment and genetic counseling for Lynch syndrome - Practice resource of the National Society of Genetic Counselors and the Collaborative Group of the Americas on Inherited Gastrointestinal Cancer

Identifying individuals who have Lynch syndrome involves a complex diagnostic workup that includes taking a detailed family history and a combination of various tests such as immunohistochemistry and/or molecular which may be germline and/or somatic. The National Society of Genetic Counselors and the Collaborative Group of the Americas on Inherited Gastrointestinal Cancer have come together to publish this practice resource for the evaluation of Lynch syndrome. The purpose of this practice resource was to provide guidance and a testing algorithm for Lynch syndrome as well as recommendations on when to offer testing. This practice resource does not replace a consultation with a genetics professional. This practice resource includes explanations in support of this and a summary of background data. While this practice resource is not intended to serve as a review of Lynch syndrome, it includes a discussion of background information and cites a number of key publications which should be reviewed for a more in-depth understanding. This practice resource is intended for genetic counselors, geneticists, gastroenterologists, surgeons, medical oncologists, obstetricians and gynecologists, nurses, and other healthcare providers who evaluate patients for Lynch syndrome.

Real-world outcome of universal screening for Lynch syndrome in Japanese patients with colorectal cancer highlights the importance of targeting patients with young-onset disease

Despite the recommendations of the latest guidelines, the practical efficacy of universal screening for identifying Lynch syndrome (LS) among patients with colorectal cancer (CRC) may be limited in the real world due to infrequent referrals and the difficulties of genetic testing. Thus, the present study aimed to retrospectively analyze the results of universal screening of patients with CRC at a referral hospital in Japan. Immunohistochemistry was performed for mismatch repair proteins [including DNA mismatch repair protein MSH6 (MSH6), mismatch repair endonuclease PMS2 (PMS2), DNA mismatch repair protein Msh2 (MSH2) and DNA mismatch repair protein Mlh1 (MLH1)] and BRAF V600E mutation. Tumors that showed the following were considered to indicate LS and patients with such tumors were designated as genetic testing candidates (GTCs): i) Loss of MSH6/MSH2; ii) loss of MSH6 alone; iii) loss of PMS2 alone; and iv) loss of PMS2/MLH1 with negative BRAF V600E. MLH1 methylation and BRAF V600E mutation were analyzed in deficient mismatch repair (dMMR) tumors retrospectively. The frequency of dMMR and GTCs in an independent cohort of patients with young-onset CRC were also investigated. Universal screening revealed dMMR tumors, GTCs and LS probands in 7.3, 3.9 and 0.4%, respectively, of 463 patients with CRC. Although dMMR tumors were observed in both younger (<50 years) and older (≥60 years) patients, the GTCs were enriched in younger individuals. Evaluation of mismatch repair status in an independent cohort confirmed the high rate of GTCs in patients with young-onset CRC. The low detection rate of LS demonstrated in this study questions the implementation of routine universal screening in regions with low prevalence of LS. Considering the enrichment of GTCs in young-onset CRCs, age-restricted strategies may be simple and efficient practical alternatives to universal screening in the real world.

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.

BRAF V600E and Mismatch Repair Proteins Expression in Sporadic Young-onset Colorectal Cancer in Kelantan, Malaysia

Objectives

We sought to determine the immunohistochemistry expression of mismatch repair (MMR) and BRAF V600E proteins in sporadic young-onset colorectal cancer (CRC) and their association with clinicopathological features in the Kelantan population.

Methods

This was a cross-sectional study of sporadic young-onset CRC over 11 years from 1 January 2006 to 31 December 2017 in Kelantan. Formalin-fixed paraffin-embedded tissue blocks were immunohistochemically stained with antibodies for MMR (MLH1, MSH2, MSH6, and PMS2) and BRAF V600E. These expressions were correlated with clinicopathological parameters.

Results

Our patient sample included 31 patients with a mean age of 31.5 years. More than half (61.3%) of the patients were women. The majority presented with abdominal pain (41.9%), and 71.0% had a tumor located on the right side of the colon, with 83.9% being moderately differentiated adenocarcinoma. The majority of patients presented at stage IV (54.8%). The most frequent pattern was all MMR protein expressions, which constituted patients in the microsatellite stable group (64.5%). Nine (29.0%) were microsatellite instability (MSI-high), and two (6.5%) were MSI-low. Positive BRAF V600E expression was observed in 83.9% of patients. Only histopathological subtypes revealed a significant association with BRAF V600E positive expression (p = 0.015).

Conclusions

The majority of sporadic young-onset CRC presented with abdominal pain and advanced cancer stage. Most were microsatellite stable, and most cases showed positive expressions in all MMR markers and BRAF V600E by immunohistochemistry method. This finding will pave the way for further research on this disease.

Predicting survival in colorectal carcinoma after curative resection: a new prognostic nomogram

Several prognostic nomograms designed to predict survival after curative resection for colorectal cancer (CRC) have been proposed. Recently, routine pathological assessment has evolved with subtle changes to the AJCC staging system, and routine screening for mismatch repair deficiency (MMRd). Therefore we sought to develop and validate a new prognostic nomogram. All cause survival data from 4517 consecutive patients with primary CRC were used as independent training and validation cohorts to develop a final model including only: age, sex, tumour stage, nodal status, number of lymph nodes resected, apical node status, distant metastases, thin-walled vascular invasion, and MMR status. Patients were stratified into four risk groups to assess model discrimination and calibration. To assess discrimination, the area-under-the-curve (AUC) of a receiver-operator-curve (ROC), concordance-index (C-index), and D-index were calculated. The model was compared to the Memorial Sloan Kettering Cancer Center (MSKCC) CRC nomogram and the AJCC TNM staging. Based on the 5-year ROC analysis, the AUC for our model was 0.81 (0.79 and 0.74 for MSKCC and AJCC, respectively). Moreover, our model demonstrated a concordance index of 0.77 (95% CI 0.70-0.82) compared to 0.75 (95% CI 0.68-0.81) for MSKCC and 0.73 (95% CI 0.65-0.79) for AJCC. In conclusion, our new prognostic nomogram incorporates a larger number of clinically relevant prognostic markers, including MMR status, and therefore demonstrates improved predictive capability. As these factors are routinely assessed, it is hoped that this model will inform prognostication and difficult management decisions, such as patient selection for adjuvant therapy.

Enhancing the landscape of colorectal cancer using targeted deep sequencing

Targeted next-generation sequencing (NGS) technology detects specific mutations that can provide treatment opportunities for colorectal cancer (CRC) patients. We included 145 CRC patients who underwent surgery. We analyzed the mutation frequencies of common actionable genes and their association with clinicopathological characteristics and oncologic outcomes using targeted NGS. Approximately 97.9% (142) of patients showed somatic mutations. Frequent mutations were observed in TP53 (70%), APC (60%), and KRAS (49%). TP53 mutations were significantly linked to higher overall stage (p = 0.038) and lower disease-free survival (DFS) (p = 0.039). ATM mutation was significantly associated with higher tumor stage (p = 0.012) and shorter overall survival (OS) (p = 0.041). Stage 3 and 4 patients with ATM mutations (p = 0.023) had shorter OS, and FBXW7 mutation was significantly associated with shorter DFS (p = 0.002). However, the OS of patients with or without TP53, RAS, APC, PIK3CA, and SMAD4 mutations did not differ significantly (p = 0.59, 0.72, 0.059, 0.25, and 0.12, respectively). Similarly, the DFS between patients with RAS, APC, PIK3CA, and SMAD4 mutations and those with wild-type were not statistically different (p = 0.3, 0.79, 0.13, and 0.59, respectively). In multivariate Cox regression analysis, ATM mutation was an independent biomarker for poor prognosis of OS (p = 0.043). A comprehensive analysis of the molecular markers for CRC can provide insights into the mechanisms underlying disease progression and help optimize a personalized therapy.

Diagnosis of Lynch Syndrome and Strategies to Distinguish Lynch-Related Tumors from Sporadic MSI/dMMR Tumors

Simple Summary

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific, as most of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Therefore, the identification of MSI/dMMR requires additional diagnostic tools to identify LS. In this review, we address the hallmarks of LS and present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with current strategies, which should be taken into account in order to improve the diagnosis of LS.

Abstract

Microsatellite instability (MSI) is a hallmark of Lynch syndrome (LS)-related tumors but is not specific to it, as approximately 80% of MSI/mismatch repair-deficient (dMMR) tumors are sporadic. Methods leading to the diagnosis of LS have considerably evolved in recent years and so have tumoral tests for LS screening and for the discrimination of LS-related to MSI-sporadic tumors. In this review, we address the hallmarks of LS, including the clinical, histopathological, and molecular features. We present recent advances in diagnostic and screening strategies to identify LS patients. We also discuss the pitfalls associated with the current strategies, which should be taken into account to improve the diagnosis of LS and avoid inappropriate clinical management.

Frequency and coexistence of KRAS, NRAS, BRAF and PIK3CA mutations and occurrence of MMR deficiency in Danish colorectal cancer patients

The MAPK signalling genes KRAS, NRAS and BRAF and the PIK3CA gene are routinely investigated for mutations in the diagnostic routine of colorectal cancer. Few studies have reported co-existing mutations in these genes with clinical relevance, while some have been previously regarded as mutually exclusive. We set to investigate the frequency and co-occurrent mutations in these targets, and the occurrence of mismatch repair deficiency (dMMR) in a large cohort of Danish colorectal cancers. 1000 colorectal tumours were sequenced as part of our diagnostic workflow for KRAS, NRAS, BRAF and PIK3CA mutations using next-generation sequencing (NGS) and analysed by immunohistochemistry (IHC) for loss of the MMR proteins, MLH1, PMS2, MSH2 and MSH6. Co-existing mutations in 12 patients (1.2%) occurred as multiple mutations in the same gene or spread across several genes (KRAS, NRAS and/or BRAF). The frequency of single mutations in the genes occurred with a frequency similar to previously reported, except for a higher frequency of BRAF mutations (18.0%). We found dMMR in 14.6% of the cases with a majority lacking expression of both MLH1 and PMS2. BRAF mutations were only present in dMMR cases involving MLH1 and/or PMS2. Our findings suggest that co-existing mutations occur, except for the hotspot BRAF V600E, which is mutually exclusive with KRAS/NRAS mutations. Therefore, instead of single gene alterations from the MAPK signalling, assessing co-occurrence of mutations within one or more of those genes should also be accounted. This may impact future oncological treatments and should be considered in the diagnostic workflow.

Multiplex detection of ctDNA mutations in plasma of colorectal cancer patients by PCR/SERS assay

Molecular diagnostic testing of KRAS and BRAF mutations has become critical in the management of colorectal cancer (CRC) patients. Some progress has been made in liquid biopsy detection of mutations in circulating tumor DNA (ctDNA), which is a fraction of circulating cell-free DNA (cfDNA), but slow analysis for DNA sequencing methods has limited rapid diagnostics. Other methods such as quantitative PCR and more recently, droplet digital PCR (ddPCR), have limitations in multiplexed capacity and the need for expensive specialized equipment. Hence, a robust, rapid and facile strategy is needed for detecting multiple ctDNA mutations to improve the management of CRC patients. To address this significant problem, herein, we propose a new application of multiplex PCR/SERS (surface-enhanced Raman scattering) assay for the detection of ctDNA in CRC, in a fast and non-invasive manner to diagnose and stratify patients for effective treatment.

Methods: To discriminate ctDNA mutations from wild-type cfDNA, allele-specific primers were designed for the amplification of three clinically important DNA point mutations in CRC including KRAS G12V, KRAS G13D and BRAF V600E. Surface-enhanced Raman scattering (SERS) nanotags were labelled with a short and specific sequence of oligonucleotide, which can hybridize with the corresponding PCR amplicons. The PCR/SERS assay was implemented by firstly amplifying the multiple mutations, followed by binding with multicolor SERS nanotags specific to each mutation, and subsequent enrichment with magnetic beads. The mutation status was evaluated using a portable Raman spectrometer where the fingerprint spectral peaks of the corresponding SERS nanotags indicate the presence of the mutant targets. The method was then applied to detect ctDNA from CRC patients under a blinded test, the results were further validated by ddPCR.

Results: The PCR/SERS strategy showed high specificity and sensitivity for genotyping CRC cell lines and plasma ctDNA, where as few as 0.1% mutant alleles could be detected from a background of abundant wild-type cfDNA. The blinded test using 9 samples from advanced CRC patients by PCR/SERS assay was validated with ddPCR and showed good consistency with pathology testing results.

Conclusions: With ddPCR-like sensitivity yet at the convenience of standard PCR, the proposed assay shows great potential in sensitive detection of multiple ctDNA mutations for clinical decision-making.

Assessment of Tumor-infiltrating Lymphocytes Using International TILs Working Group (ITWG) System Is a Strong Predictor of Overall Survival in Colorectal Carcinoma: A Study of 1034 Patients

The presence of increased tumor-infiltrating lymphocytes (TILs) is established as a positive prognostic factor in many malignancies including colorectal carcinoma (CRC). However, multiple different approaches have been used to assess TILs. In 2014, the International TILs Working Group (ITWG) proposed a standardized methodology for evaluating TILs, initially in the context of breast cancer, but subsequently expanded to other malignancies. To date, the efficacy of the ITWG system has not been investigated in a large cohort of all-stage CRC. We, therefore, sought to validate this system in CRC. We used the ITWG system to assess the density of stromal TILs in an unselected cohort of 1034 CRC patients undergoing primary tumor resection at our institution. The percentage TILs' score was categorized into 3 groups: low (0% to 10%), intermediate (15% to 50%), and high (55% to 100%). The mean survival was 53, 67, and 75 months, respectively (P=0.0001). This survival benefit remained statistically significant in multivariate analyses (P=0.0001) and subgroup analyses of mismatch repair-proficient CRCs (P=0.0001), mismatch repair-deficient CRCs (P=0.031), BRAFV600E-mutant CRCs (P=0.0001), and BRAF wild-type CRCs (P=0.001). The predictive value of TILs assessed using the ITWG system was superior to the assessment of intraepithelial lymphocyte performed prospectively using a standard system requiring ≥5 lymphocytes per high-powered field in direct contact with tumor cells or between tumor clusters. We conclude that the ITWG system for assessing TILs is a powerful predictor of all-cause survival in CRC independent of many prognostic factors and superior to the assessment of intraepithelial lymphocytes using a traditional system.

Comparisons of screening strategies for identifying Lynch syndrome among patients with MLH1-deficient colorectal cancer

BRAF and MLH1 promoter methylation testings have been proven effective prescreens for Lynch Syndrome. We aimed to compare different screening strategies for Lynch Syndrome in patients with MLH1(-) CRC. Patients with MLH1(-) CRC who had been tested for BRAF mutation and germline variants of DNA mismatch repair genes were included. We compared the sensitivities and specificities for identifying Lynch Syndrome and the cost-effectiveness of four screening approaches that used the following tests as prescreens: BRAF testing, MLH1 methylation testing, MLH1 methylation & BRAF testing, and MLH1 methylation testing & Revised Bethesda Criteria. Of 109 patients included, 23 (21.1%) were Lynch Syndrome patients. BRAF mutation and MLH1 methylation occurred in 6 (5.5%) and 40 (36.7%) patients, respectively. The sensitivity for identifying Lynch syndrome of BRAF testing was 100%, but the specificity was only 7%. MLH1 methylation testing had a lower sensitivity than BRAF testing (97.5% vs 100%), but had a markedly higher specificity (45.3% vs 7%). The combination of the two testings had a slightly higher specificity than MLH1 methylation testing alone (47.7% vs 45.3%). The MLH1 methylation testing approach had a 10% lower cost of identifying MLH1(-) Lynch syndrome carriers per case than universal genetic testing, but it missed 4.5% of patients. BRAF and MLH1 promoter methylation testings as prescreens for Lynch syndrome are less effective in Chinese patients with MLH1(-) CRC than in their Western counterparts. Universal genetic testing could be considered an up-front option for this population.

NTRK gene rearrangements are highly enriched in MLH1/PMS2 deficient, BRAF wild-type colorectal carcinomas-a study of 4569 cases

NTRK gene rearrangements are important to identify as predictors of response to targeted therapy in many malignancies. Only 0.16-0.3% of colorectal carcinomas (CRCs) harbor these fusions making universal screening difficult. We therefore investigated whether pan-Trk immunohistochemistry (IHC), mismatch repair deficiency (MMRd), and BRAFV600E mutation status could be used to triage molecular testing for NTRK gene rearrangements in CRC. CRCs from 4569 unselected patients underwent IHC in TMA format with two different anti-pan-Trk rabbit monoclonal antibodies. All positive cases were confirmed on whole sections and underwent RNA-sequencing. Pan-Trk IHC was positive in 0.2% of CRCs (9/4569). Both antibodies demonstrated similar staining characteristics with diffuse positive staining in all neoplastic cells. Of note 8/9 (89%) IHC positive cases were both MMRd (all showing MLH1/PMS2 loss) and lacked BRAFV600E mutation. That is, IHC was positive in 5.3% (8/152) MLH1/PMS2/BRAFV600E triple negative CRCs, but only 0.02% (1/4417) not showing this phenotype. All nine IHC positive CRCs demonstrated gene rearrangements (LMNA-NTRK1 in 5 CRCs, TPR-NTRK1, STRM-NTRK1, MUC2-NTRK2, and NTRK1 with an unknown partner in one each), suggesting close to 100% specificity for IHC in this sub-population. NTRK fusions were associated with right sided (p = 0.02), larger tumors (p = 0.029) with infiltrative growth (p = 0.021). As a part of universal Lynch syndrome screening many institutions routinely test all CRCs for MMRd, and then proceed to reflex BRAFV600E mutation testing in MLH1/PMS2 negative CRCs. We conclude that performing pan-Trk IHC on this preselected subgroup of MLH1/PMS2/BRAFV600E triple negative CRCs (only 3.3% of all CRC patients) is a resource effective approach to identify the overwhelming majority of CRC patients with NTRK gene fusions.

Ameloblastic fibrosarcoma: clinicopathological and molecular analysis of seven cases highlighting frequent BRAF and occasional NRAS mutations

AIMS

Ameloblastic fibrosarcoma (AFS) is an aggressive odontogenic neoplasm featuring malignant mesenchymal stroma in addition to an ameloblastic epithelial component, and is hence considered to be the malignant counterpart of ameloblastic fibroma (AF). AFS is exceedingly rare, with <110 cases having been reported so far. Although BRAF mutations are recognised driver mutations in ameloblastoma, the molecular pathogenesis of AFS remains elusive.

METHODS AND RESULTS

We herein describe seven AFSs that were analysed, for the first time, for mutations in the BRAF-NRAS pathway. The patients were four females and three males aged 23-57 years (median, 26 years). Three tumours developed after one or multiple recurrences of AF (4-20 years after initial diagnosis), two showed transition from AF-like bland areas, and two developed de novo. All patients were treated with surgery; adjuvant chemotherapy was given to one patient. At the last follow-up, five patients were alive and well (19-344 months). The remainder were lost to follow-up. Histological examination showed variable sarcomatous overgrowth with varying degrees of atypia and increased mitotic activity. The epithelial component varied greatly according to the degree of sarcomatous overgrowth. Molecular testing revealed BRAF V600E mutations in five cases and NRAS p.Gln61Lys mutation in one case. One tumour was wild-type.

CONCLUSION

To our knowledge, this is the first study on BRAF/NRAS mutations in AFS. Given the activity of RAF and MEK inhibitors across different cancers harbouring V600E mutations, our data strongly suggest that all AFS cases should be genetically tested, and that targeted treatment approaches for this extremely rare sarcoma subtype should be clinically investigated.

MSI status is associated with distinct clinicopathological features in BRAF mutation colorectal cancer: A systematic review and meta-analysis

BACKGROUND

Microsatellite stable (MSS) BRAF p.V600E mutation colorectal cancer (BRAF-CRC) has a poor prognosis, whereas microsatellite instability (MSI) in BRAF-CRC is associated with a favorable prognosis. Although usually considered a single clinical entity, the MSI BRAF-CRC subtype shows some distinct characteristics in comparison with the MSS BRAF-CRC subtype.

METHODS

We conducted a meta-analysis to investigate the influence of clinicopathological features on MSI status in BRAF-CRC. We searched publications up to March 2019 from PubMed, Embase, and the Cochrane Library. The effect of MSI status on outcome parameters was assessed using odds ratios (ORs) with 95% confidence intervals (CIs) and fixed- or random-effects models according to the heterogeneity.

RESULTS

After reviewing 2839 reports, 16 eligible studies including 1381 patients with BRAF-CRC met the criteria. The MSI BRAF-CRC subtype was associated with older age, female sex (OR = 1.70; 95% CI = 1.35-2.14; P < 0.00001), proximal tumor location (OR = 5.10; 95% CI = 3.70-7.03; P < 0.00001), early TNM stage (OR = 5.28; 95% CI = 3.93-7.09; P < 0.00001), and poor differentiation (OR = 2.29; 95% CI = 1.60-3.28; P < 0.00001).

CONCLUSIONS

MSI was significantly correlated with distinct favorable clinicopathological characteristics in BRAF-CRC. These results suggest that MSI status should be considered as a stratification factor for better management of the BRAF-CRC.

Immunohistochemistry in screening for heritable colorectal cancer: what to do with an abnormal result

Recent developments in our understanding of molecular genetics have transformed screening and diagnostic practices for Lynch syndrome. The current standard involves universal tumour analysis of resected colorectal cancer (and ideally polypectomy) specimens using immunohistochemistry and molecular techniques. Patients with abnormal immunohistochemical findings are subsequently referred for definitive mutational testing. This review relates the molecular pathogenesis of Lynch syndrome to current immunohistochemistry-based screening strategies and discusses the interpretation and clinical implications of screening results.

Report from the 20th annual Western Canadian Gastrointestinal Cancer Consensus Conference; Saskatoon, Saskatchewan; 28-29 September 2018

The 20th annual Western Canadian Gastrointestinal Cancer Consensus Conference was held in Saskatoon, Saskatchewan, 28-29 September 2018. This interactive multidisciplinary conference is attended by health care professionals from across Western Canada (British Columbia, Alberta, Saskatchewan, and Manitoba) who are involved in the care of patients with gastrointestinal cancers. In addition, invited speakers from other provinces participate. Surgical, medical, and radiation oncologists, and allied health care professionals participated in presentations and discussion sessions for the purpose of developing the recommendations presented here. This consensus statement addresses current issues in the management of colorectal cancers.

A Longitudinal Investigation of Inflammatory Markers in Colorectal Cancer Patients Perioperatively Demonstrates Benefit in Serial Remeasurement

OBJECTIVE

To characterize the longitudinal course of the systemic inflammatory response (SIR) throughout the perioperative period. To investigate whether postoperative changes in the neutrophil-to-lymphocyte ratio (NLR) or lymphocyte-to-monocyte ratio (LMR) when compared with preoperative levels ('conversion') are associated with survival differences in colorectal cancer patients undergoing resection.

BACKGROUND

Recent evidence suggests that preoperative measurements of markers of the SIR including the NLR and LMR are prognostic. However, a few data exist evaluating longitudinal changes in the SIR especially in regards to their association with surgical interventions, optimal timing of assessment, and their effect on patient survival.

METHODS

Data from 6 hospitals from January 1998 to December 2012 were retrospectively collected. We examined 2280 patients with complete data. For the subgroup analysis investigating conversion, we examined 587 patients with full preoperative and postoperative data from 21 to 56 days postoperative. Patients were stratified into 4 groups for analysis of conversion in a multivariate Cox-regression model.

RESULTS

A longitudinal profile for the perioperative NLR and LMR was clearly characterized identifying an optimal period of remeasurement at 21 to 56 days postoperation. In multivariate analysis both NLR change group (P < 0.001) and LMR change group (P < 0.001) were independently associated with overall survival. For both biomarkers, patients with both a low preoperative and postoperative inflammatory state had the best survival. A change from the preoperative to postoperative inflammatory state was associated with a survival difference.

CONCLUSIONS

This study characterizes the perioperative SIR profile and provides evidence for the remeasurement of SIR biomarkers postoperatively at 21 to 56 days for further prognostication.

Off-label use of common predictive biomarkers in gastrointestinal malignancies: a critical appraisal

The use of immunohistochemistry (IHC) as a companion diagnostic is an increasingly important part of the case workup by pathologists and is often central to clinical decision making. New predictive molecular markers are constantly sought for to improve treatment stratification parallel to drug development. Unfortunately, official biomarker guidelines lag behind, and pathologists are often left hesitating when medical oncologists request off-labelled biomarker testing. We performed a literature review of five commonly requested off-label IHC predictive biomarkers in gastrointestinal tract (GIT) malignancies: HER2, mismatch repair (MMR), PD-L1, BRAF V600E and ROS1. We found that HER2 amplification is rare and poorly associated to IHC overexpression in extracolonic and extragastric GIT cancers; however in KRAS wild type colorectal cancers, which fail conventional treatment, HER2 IHC may be useful and should be considered. For MMR testing, more evidence is needed to recommend reflex testing in GIT cancers for treatment purposes. MMR testing should not be discouraged in patients considered for second line checkpoint inhibitor therapy. With the exception of gastric tumors, PD-L1 IHC is a weak predictor of checkpoint inhibitor response in the GIT and should be replaced by MMR in this context. BRAF inhibitors showed activity in BRAF V600E mutated cholangiocarcinomas and pancreatic carcinomas in non-first line settings. ROS1 translocation is extremely rare and poorly correlated to ROS1 IHC expression in the GIT; currently there is no role for ROS1 IHC testing in GIT cancers. Overall, the predictive biomarker literature has grown exponentially, and official guidelines need to be updated more regularly to support pathologists’ testing decisions.

Clinicopathological Significance of BRAFV600E Mutation in Colorectal Cancer: An Updated Meta-Analysis

Background and Aims: Numerous studies have identified BRAF^V600E mutation as a predictive factor of anti-EGFR antibodies in colorectal cancer (CRC). However, the association between BRAF^V600E mutation and clinicopathological features remains unclear. Therefore, we aimed to conduct an updated and comprehensive meta-analysis to evaluate the above issues. Methods: We performed a systematic literature search from PubMed, Web of Science, Embase, and PMC database examining the association between BRAF^V600E mutation and clinicopathological features in CRC patients. Odds ratio with 95% confidence interval were used to estimate the effects of BRAF^V600E mutation on each clinicopathological parameter with fixed-effect model or random-effect model. Results: Sixty-one studies published, including 32407 CRC patients from multiple countries, were included in the meta-analysis. The overall BRAF^V600E mutation rate was 11.38%, and BRAF^V600E mutation was positively related to high disease stage (OR=0.81; 95% CI=0.72-0.92; P=0.001), high T stage (OR=0.51; 95% CI=0.40-0.65; P<0.00001), proximal colon (OR=4.76; 95% CI=3.81-5.96; P<0.00001) or right colon (OR=5.15; 95% CI=4.35-6.10, P<0.00001) tumor location, poor tumor differentiation (OR=0.27; 95% CI=0.21-0.34; P<0.00001), mucinous histology (OR=2.97; 95% CI=2.37-3.72; P<0.00001), K-ras-wild type (OR=0.04; 95% CI=0.02-0.07; P<0.00001), TP53-wild type (OR=0.50; 95% CI=0.31-0.78; P=0.003), deficient DNA mismatch repair (OR=2.93; 95% CI=1.78-4.82; P<0.00001), high microsatellite instability (OR=11.15; 95% CI=8.51-14.61; P<0.00001) and high CpG island methylator phenotype (OR=0.04; 95% CI=0.03-0.08; P<0.00001). Conclusions: Our updated meta-analysis demonstrated that BRAF^V600E mutation was related to poor prognosis of CRC and associated with the distinct molecular phenotypes.

Mismatch repair deficiency assessment by immunohistochemistry: for Lynch syndrome screening and beyond

While mismatch repair (MMR) deficiency has been studied extensively, the assessment of MMR status in colorectal and other cancers remains highly relevant, particularly in light of recent data demonstrating that MMR deficiency is a strong predictor for treatment benefit with immune checkpoint inhibitors across multiple tumor types. In colorectal cancer, there is a growing consensus in support of routine MMR testing for Lynch syndrome screening, to inform prognosis and adjuvant chemotherapy use in early stage disease, and to predict response to immunotherapy in advanced disease. Here, we provide a review of the Ventana MMR Immunohistochemistry Panel, which was recently approved by the US FDA for use in Lynch syndrome screening.

Clinical significance of the BRAFV600E mutation in Asian patients with colorectal cancer

BACKGROUND

To investigate the clinicopathological features and prognostic significance of the BRAFV600E mutation in Asian patients with colorectal cancer.

METHODS

We retrospectively reviewed the medical records of 1969 patients with colorectal cancer admitted to Taipei Veterans General Hospital for surgical treatment between 2000 and 2013. The measured endpoint was overall survival after surgery. The prognostic value of the BRAFV600E mutation was analyzed using the log-rank test and Cox regression analysis.

RESULTS

The BRAFV600E mutation was detected in 106 (5.4%) patients and associated with female gender, abnormal cancer antigen (CA)19-9 at diagnosis, microsatellite status, right-sided primary tumors, mucinous histology, poor differentiation, and lymphovascular invasion. Metastatic patterns were more common in non-regional lymph node metastasis (20.8 vs. 7.4%, p = 0.06) and peritoneal seeding (41. vs. 21.2%, p = 0.04). Mutations were not prognostic in the overall survival of the entire study group but only in specific patients: age < 65, normal carcinoembryonic antigen at diagnosis, and stage IV disease.

CONCLUSION

The BRAFV600E mutation was associated with distinct clinicopathological features and metastatic patterns. The overall survival rate was lower in selected colorectal patients with the BRAFV600E mutation.

Improving diagnosis, prognosis and prediction by using biomarkers in CRC patients (Review)

Colorectal cancer (CRC) is among the most common cancers. In fact, it is placed in the third place among the most diagnosed cancer in men, after lung and prostate cancer, and in the second one for the most diagnosed cancer in women, following breast cancer. Moreover, its high mortality rates classifies it among the leading causes of cancer‑related death worldwide. Thus, in order to help clinicians to optimize their practice, it is crucial to introduce more effective tools that will improve not only early diagnosis, but also prediction of the most likely progression of the disease and response to chemotherapy. In that way, they will be able to decrease both morbidity and mortality of their patients. In accordance with that, colon cancer research has described numerous biomarkers for diagnostic, prognostic and predictive purposes that either alone or as part of a panel would help improve patient's clinical management. This review aims to describe the most accepted biomarkers among those proposed for use in CRC divided based on the clinical specimen that is examined (tissue, faeces or blood) along with their restrictions. Lastly, new insight in CRC monitoring will be discussed presenting promising emerging biomarkers (telomerase activity, telomere length and micronuclei frequency).

Concomitant KIT/BRAF and PDGFRA/BRAF mutations are rare events in gastrointestinal stromal tumors

AIM

The BRAF mutation is a rare pathogenetic alternative to KIT/PDGFRA mutation in GIST and causes Imatinib resistance. A recent description of KIT and BRAF mutations co-occurring in an untreated GIST has challenged the concept of their being mutually exclusive and may account for ab initio resistance to Imatinib, even in the presence of Imatinib-sensitive KIT mutations. BRAF sequencing is generally limited to KIT/PDGFRA wild-type cases. Hence, the frequency of concomitant mutations may be underestimated.

METHODS

We screened for KIT (exon 9, 11, 13, 17), PDGFRA (exon 12,14, 18) and BRAF (exon 15) mutations a series of 407 GIST. Additionally, we evaluated the BRAF V600E mutation-specific antibody, VE1, as a surrogate for V600E mutation, on a series of 313 GIST (24 on whole sections, 288 cases on tissue array), including 6 cases molecularly ascertained to carry the BRAF V600E mutation.

RESULTS

No concomitant KIT/BRAF or PDGFRA/BRAF mutations were detected. BRAF mutation was detected only in one case, wild-type for KIT/PDGFRA. All the 6 BRAF-mutant cases stained positive with the VE1 antibody. A weak VE1 expression was observed in 14/287 (4.9%) BRAF wild-type cases, as observed also in 2/6 BRAF-mutant cases. Overall in our series, sensitivity and specificity of the VE1 antobody were 100% and 95.1%, respectively.

CONCLUSION

The concomitance of BRAF mutation with either KIT or PDGFRA mutation is rare in GIST. In these tumors, moderate/strong VE1 immunoreactivity is a valuable surrogate for molecular analysis. Instead, genotyping is warranted in the presence of weak VE1 staining.

Immunohistochemistry with Anti-BRAF V600E (VE1) Mouse Monoclonal Antibody is a Sensitive Method for Detection of the BRAF V600E Mutation in Colon Cancer: Evaluation of 120 Cases with and without KRAS Mutation and Literature Review

The major aim of this study was to evaluate the performance of anti-BRAF V600E (VE1) antibody in colorectal tumors with and without KRAS mutation. KRAS and BRAF are two major oncogenic drivers of colorectal cancer (CRC) that have been frequently described as mutually exclusive, thus the BRAF V600E mutation is not expected to be present in the cases with KRAS mutation. In addition, a review of 25 studies comparing immunohistochemistry (IHC) using the anti-BRAF V600E (VE1) antibody with BRAF V600E molecular testing in 4041 patient samples was included. One-hundred and twenty cases with/without KRAS or BRAF mutations were acquired. The tissue were immunostained with anti-BRAF V600E (VE1) antibody with OptiView DAB IHC detection kit. The KRAS mutated cases with equivocal immunostaining were further evaluated by Sanger sequencing for BRAF V600E mutation. Thirty cases with BRAF V600E mutation showed unequivocal, diffuse, uniform, positive cytoplasmic staining and 30 cases with wild-type KRAS and BRAF showed negative staining with anti-BRAF V600E (VE1) antibody. Out of 60 cases with KRAS mutation, 56 cases (93.3%) were negative for BRAF V600E mutation by IHC. Four cases showed weak, equivocal, heterogeneous, cytoplasmic staining along with nuclear staining in 25-90% of tumor cells. These cases were confirmed to be negative for BRAF V600E mutation by Sanger sequencing. Overall, IHC with anti-BRAF V600E (VE1) antibody using recommended protocol with OptiView detection is optimal for detection of BRAF V600E mutation in CRC. Our data are consistent with previous reports indicating that KRAS and BRAF V600E mutation are mutually exclusive.

Current Tissue Molecular Markers in Colorectal Cancer: A Literature Review

BACKGROUND

Colorectal cancer (CRC) is one of the most spread neoplasia types all around the world, especially in western areas. It evolves from precancerous lesions and adenomatous polyps, through successive genetic and epigenetic mutations. Numerous risk factors intervene in its development and they are either environmental or genetic.

AIM OF THE REVIEW

Alongside common screening techniques, such as fecal screening tests, endoscopic evaluation, and CT-colonography, we have identified the most important and useful biomarkers and we have analyzed their role in the diagnosis, prevention, and prognosis of CRC.

CONCLUSION

Biomarkers can become an important tool in the diagnostic and therapeutic process for CRC. But further studies are needed to identify a noninvasive, cost-effective, and highly sensible and specific screening test for their detection and to standardize their use in clinical practice.

Associations of alcohol intake, smoking, physical activity and obesity with survival following colorectal cancer diagnosis by stage, anatomic site and tumor molecular subtype

The influence of lifestyle factors on survival following a diagnosis of colorectal cancer (CRC) is not well established. We examined associations between lifestyle factors measured before diagnosis and CRC survival. The Melbourne Collaborative Cohort Study collected data on alcohol intake, cigarette smoking and physical activity, and body measurements at baseline (1990-1994) and wave 2 (2003-2007). We included participants diagnosed to 31 August 2015 with incident stages I-III CRC within 10-years post exposure assessment. Information on tumor characteristics and vital status was obtained. Tumor DNA was tested for microsatellite instability (MSI) and somatic mutations in oncogenes BRAF (V600E) and KRAS. We estimated hazard ratios (HRs) for associations between lifestyle factors and overall and CRC-specific mortality using Cox regression. Of 724 eligible CRC cases, 339 died (170 from CRC) during follow-up (average 9.0 years). Exercise (non-occupational/leisure-time) was associated with higher CRC-specific survival for stage II (HR = 0.25, 95% CI: 0.10-0.60) but not stages I/III disease (p for interaction = 0.01), and possibly for colon and KRAS wild-type tumors. Waist circumference was inversely associated with CRC-specific survival (HR = 1.25 per 10 cm increment, 95% CI: 1.08-1.44), independent of stage, anatomic site and tumor molecular status. Cigarette smoking was associated with lower overall survival, with suggestive evidence of worse survival for BRAF mutated CRC, but not with CRC-specific survival. Alcohol intake was not associated with survival. Survival did not differ by MSI status. We have identified pre-diagnostic predictors of survival following CRC that may have clinical and public health relevance.

Recent developments in the treatment of metastatic colorectal cancer

Over the past decade there have been significant advances in the molecular characterization of colorectal cancer (CRC) that are driving treatment decisions. Expanded RAS testing beyond KRAS exon 2 was established as crucial for identifying patients who will respond to anti-epidermal growth factor receptor (EGFR) therapies and low-frequency mutations in RAS/tumor heterogeneity are gaining recognition as potential mechanisms of resistance. Despite this progress, the fact that we do not understand why left-sided but not right-sided tumors have improved outcomes following anti-EGFR therapy highlights our superficial understanding of this disease. Even with few new targeted agents receiving approval in CRC, the incorporation of next-generation sequencing into clinical decision making represents an important step forward. Biomarkers such as BRAF mutations, microsatellite instability, and HER2 amplification represent promising molecular aberrations with therapies in various stages of development, and highlight the importance of companion diagnostics in supporting targeted agents. In this review, we will discuss the importance of incorporating biomarkers into clinical decision making and regimen selection in CRC. We will particularly focus on the recent evidence suggesting an important role for tumor location in selecting first-line therapy, the importance of recent advances in biomarker development and molecular subtyping, as well as recently approved agents (regorafenib and TAS-102) and promising targeted agents that have the potential to change the standard of care.

Prognostic implication of CD274 (PD-L1) protein expression in tumor-infiltrating immune cells for microsatellite unstable and stable colorectal cancer

In this study, we investigated the clinical relevance of CD274 (PD-L1) protein expression by tumor cells and tumor-infiltrating immune cells in colorectal cancer (CRC). To this end, 186 microsatellite instability-high (MSI-H) and 153 microsatellite stable (MSS) CRCs were subjected to immunohistochemistry (IHC) analysis for the expression of CD274 and mismatch repair proteins. CD274 expression was evaluated in tumor cells at the center (TC) and periphery (TP), and immune cells at the center (IC) and periphery (IP) of CRC. IHC slides stained for CD3 and CD8 were scanned using an Aperio ScanScope for precise calculation of tumor-infiltrating T cell density. Additionally, samples were screened for the B-Raf (BRAF)-V600E mutation using a Cobas 4800 System and IHC. In total, CD274TC, CD274TP, CD274IC, and CD274IP were observed in 43 (23.1%), 47 (25.3%), 107 (57.5%), and 102 (54.8%) of the MSI-H CRCs examined, and in three (2.0%), four (2.6%), 47 (30.7%), and 56 (36.6%) of the 153 MSS CRCs tested. Meanwhile, intratumoral heterogeneity of CD274 expression in tumor cells and immune cells was detected in 24 (12.9%) and 47 (25.3%) MSI-H CRCs, respectively. Notably, in both MSI-H and MSS CRC, CD274IC and CD274IP were independently associated with improved prognosis (P < 0.05), while BRAF mutation was associated with CD274TP, poor differentiation, sporadic type, and hMLH1(-)/hMSH2(+)/hMSH6(+)/PMS2(-) in MSI-H CRC (P < 0.006). In conclusion, CD274 expression in tumor-infiltrating immune cells was an independent factor for improved prognosis in CRC patients. A deeper understanding of CD274 status may yield improved responses to future CRC immunotherapies.

Lessons learnt from implementation of a Lynch syndrome screening program for patients with gynaecological malignancy

Despite a trend towards universal testing, best practice to screen patients presenting with gynaecological malignancy for Lynch syndrome (LS) is uncertain. We report our institutional experience of a co-ordinated gynaecological LS screening program. All patients with endometrial carcinoma or carcinosarcoma, or gynaecological endometrioid or clear cell carcinomas undergo reflex four panel immunohistochemistry (IHC) for MLH1, PMS2, MSH2 and MSH6 followed by cascade somatic hypermethylation analysis of the MLH1 promoter locus for dual MLH1/PMS2 negative tumours. On the basis of these results, genetic counselling and targeted germline mutation testing is then offered to patients considered at high risk of LS. From 1 August 2013 to 31 December 2015, 124 patients were screened (mean age 64.6 years). Thirty-six (29.0%) demonstrated abnormal MMR IHC: 26 (72.2%) showed dual loss of MLH1/PMS2, five (13.9%) dual loss of MSH2/MSH6, three (8.3%) isolated loss of MSH6, and two (5.6%) isolated loss of PMS2. Twenty-five of 26 (96.1%) patients with dual MLH1/PMS2 loss demonstrated MLH1 promoter methylation. Therefore, 11 (8.9%) patients screened were classified as high risk for LS, of whom nine (81.8%) accepted germline mutation testing. Three (2.4% of total screened) were confirmed to have LS, two with germline PMS2 and one with germline MSH2 mutation. Massive parallel sequencing of tumour tissue demonstrated somatic mutations which were concordant with the IHC results in the remainder. Interestingly, the one MLH1/PMS2 IHC negative but not hypermethylated tumour harboured only somatic MLH1 mutations, indicating that universal cascade methylation testing in MLH1/PMS2 IHC negative tumours is very low yield and could be reconsidered in a resource-poor setting. In conclusion, universal screening for LS in patients presenting with gynaecological malignancy using the algorithm described above identified LS in three of 124 (2.4%) of our population. Only three of nine (33.3%) patients considered at high risk for LS by combined IHC and hypermethylation analysis were proven to have LS. Only one of the LS patients was less than 50 years of age and none of these patients would have been identified had more restrictive Amsterdam or Bethesda criteria been applied.

The Lymphocyte-to-Monocyte Ratio is a Superior Predictor of Overall Survival in Comparison to Established Biomarkers of Resectable Colorectal Cancer

Objective:

The study aims to investigate the prognostic value of the lymphocyte-to-monocyte ratio (LMR) in patients with colorectal cancer (CRC) undergoing curative resection and to compare it to established biomarkers including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), modified Glasgow prognostic score (mGPS), and combined BRAF-mismatch repair (MMR) status.

Background:

The prognostic significance of systemic inflammatory markers in CRC such as the NLR, PLR, and mGPS has been well defined. Commonly used genetic markers such as combined BRAF-MMR status have also been found to be prognostic. Recent evidence, although limited, suggests that the preoperative LMR may be prognostic in CRC.

Methods:

Data from the Northern Sydney Local Health District from January 1998 to December 2012 were retrospectively collected. Of 3281 consecutive patients identified, 1623 patients who underwent curative resection were deemed eligible for inclusion. The relation between the LMR, clinicopathologic variables, and other biomarkers were analyzed in Kaplan-Meier log-rank survival analysis and then multivariate Cox regression models looking for association with overall survival (OS).

Results:

In multivariate analysis of all patients, elevated LMR was associated with better OS (hazard ratio 0.569, 95% confidence interval: 0.478–0.677, P < 0.001) independent of age (P < 0.001), T stage (P < 0.001), N stage (P < 0.001), and grade (P = 0.049). The NLR, PLR, and combined BRAF-MMR status were not independently significant. In multivariate subgroup analysis of 389 patients with mGPS, LMR remained the only independently significant biomarker (hazard ratio 0.620, 95% confidence interval: 0.437–0.880, P = 0.007).

Conclusions:

The LMR is an independent predictor of OS in patients with CRC undergoing curative resection and appears to be superior to pre-existing biomarkers.