Lynch‐like syndrome: Characterization and comparison with EPCAM deletion carriers

Colorectal cancers (CRCs) with microsatellite instability‐high (MSI+) but without detectable germline mutation or hypermethylation in DNA mismatch repair (MMR) genes can be classified as Lynch‐like syndrome (LLS). The underlying mechanism and clinical significances of LLS are largely unknown. We measured MSI and MMR protein expression in 4,765 consecutive CRC cases. Among these, MSI+ cases were further classified based on clinical parameters, germline sequencing of MMR genes or polymerase ε (POLE) and δ (POLD1) and promoter methylation analysis of MLH1 and MSH2. We found that MSI+ and MMR protein‐deficient CRCs comprised 6.3% (N = 302) of this cohort. On the basis of germline sequencing of 124 cases, we identified 54 LS with MMR germline mutation (LS‐MMR), 15 LS with EPCAM deletions (LS‐EPCAM) and 55 LLS patients. Of the 55 LLS patients, six (10.9%) had variants of unknown significance in the genes tested, and one patient had a novel somatic mutation (p.S459P) in POLE. In patients with biallelic deletions of EPCAM, all tumors and their matched normal mucosa showed promoter hypermethylation of MSH2. Finally, we found that patients with LLS and LS‐EPCAM shared clinical features that differed from LS‐MMR patients, including lower frequency of fulfillment of the revised Bethesda guidelines (83.6 and 86.7% vs. 98.1% for LS‐MMR) and older mean age at CRC diagnosis (52.6 and 52.7 years vs. 43.9 years for LS‐MMR). We identified somatic mutation in POLE as a rare underlying cause for MMR deficiency in LLS. The similarity between LLS and LS‐EPCAM suggests LLS as a subset of familial MSI+ CRC.     

Prognosis of microsatellite instability and/or mismatch repair deficiency stage III colon cancer patients after disease recurrence following adjuvant treatment: results of an ACCENT pooled analysis of seven studies

BackgroundMicrosatellite instable/deficient mismatch repair (MSI/dMMR) metastatic colorectal cancers have been reported to have a poor prognosis. Frequent co-occurrence of MSI/dMMR and BRAF^V600E complicates the association.Patients and methodsPatients with resected stage III colon cancer (CC) from seven adjuvant studies with available data for disease recurrence and MMR and BRAF^V600E status were analyzed. The primary end point was survival after recurrence (SAR). Associations of markers with SAR were analyzed using Cox proportional hazards models adjusted for age, gender, performance status, T stage, N stage, primary tumor location, grade, KRAS status, and timing of recurrence.ResultsAmong 2630 patients with cancer recurrence (1491 men [56.7%], mean age, 58.5 [19–85] years), multivariable analysis revealed that patients with MSI/dMMR tumors had significantly longer SAR than did patients with microsatellite stable/proficient MMR tumors (MSS/pMMR) (adjusted hazard ratio [aHR], 0.82; 95% CI [confidence interval], 0.69–0.98; P = 0.029). This finding remained when looking at patients treated with standard oxaliplatin-based adjuvant chemotherapy regimens only (aHR, 0.76; 95% CI, 0.58–1.00; P = 0.048). Same trends for SAR were observed when analyzing MSI/dMMR versus MSS/pMMR tumor subgroups lacking BRAF^V600E (aHR, 0.84; P = 0.10) or those harboring BRAF^V600E (aHR, 0.88; P = 0.43), without reaching statistical significance. Furthermore, SAR was significantly shorter in tumors with BRAF^V600E versus those lacking this mutation (aHR, 2.06; 95% CI, 1.73–2.46; P < 0.0001), even in the subgroup of MSI/dMMR tumors (aHR, 2.65; 95% CI, 1.67–4.21; P < 0.0001). Other factors associated with a shorter SAR were as follows: older age, male gender, T4/N2, proximal primary tumor location, poorly differentiated adenocarcinoma, and early recurrence.ConclusionsIn stage III CC patients recurring after adjuvant chemotherapy, and before the era of immunotherapy, the MSI/dMMR phenotype was associated with a better SAR compared with MSS/pMMR. BRAF^V600E mutation was a poor prognostic factor for both MSI/dMMR and MSS/pMMR patients.Trial identification numbersNCT00079274, NCT00265811, NCT00004931, NCT00004931, NCT00026273, NCT00096278, NCT00112918.     

Lynch Syndrome in Thai Endometrial Cancer Patients

Background: Lynch syndrome increases lifetime risk of endometrial cancer to 40-60%. Screening with molecular tumor testing for mismatch repair (MMR) proteins have been recommended. This study aims to evaluate the incidence of MMR deficiency and germline mutation in endometrial cancer Thai patients. Methods: Immunohistochemistry for MMR proteins, including MLH1, MSH2, MSH6 and PMS2 were tested in 166 surgical specimens. Patients who had MMR deficiencies were offered genetic counseling and a germline testing using gene-panel next generation sequencing. Results: Fifty-eight of 166 patients (34.9%) had one or more MMR deficiencies which were: MLH1 and PMS2 in 42 patients (25.3%), MSH2 and MSH6 in 11 patients (6.6%), and MSH6 in 5 patients (3.0%). Of the 40 patients (24.1%) who met the revised Bethesda guidelines, 19 patients (47.5%) had MMR deficiency. In contrast, MMR deficiency was found in 39 of the 126 patients (31.0%) who did not meet the revised Bethesda guidelines. A total of 27 patients with MMR deficiencies agreed to have germline genetic testing. Germline MMR mutations were detected in 5 patients (18.5%) including MSH6 (n=2), PMS2 (n=2), and MLH1 mutations (n=1). Incidental germline mutations in other genes were detected in 3 patients (1 BRCA1, 1 PTEN, and 1 BARD1). Among 5 Lynch syndrome patients, 2 patients (40%) did not meet the revised Bethesda guidelines. Eight patients who met the revised Bethesda Guidelines but having MMR proficiency had genetic testing, but no germline mutation was detected. Conclusion: MMR deficiencies were detected in 34.9% of the endometrial cancer patients. Germline mutations were diagnosed in 3.0% of this cohort (5/166 patients). Lynch syndrome screening with MMR immunohistochemistry should be considered in all patients regardless of personal or family history of Lynch syndrome-related cancers.     

Clinical and molecular characterisation of hereditary and sporadic metastatic colorectal cancers harbouring microsatellite instability/DNA mismatch repair deficiency

BackgroundPatients treated with chemotherapy for microsatellite unstable (MSI) and/or mismatch repair deficient (dMMR) cancer metastatic colorectal cancer (mCRC) exhibit poor prognosis. We aimed to evaluate the relevance of distinguishing sporadic from Lynch syndrome (LS)-like mCRCs.Patients and methodsMSI/dMMR mCRC patients were retrospectively identified in six French hospitals. Tumour samples were screened for MSI, dMMR, RAS/RAF mutations and MLH1 methylation. Sporadic cases were molecularly defined as those displaying MLH1/PMS2 loss of expression with BRAFV600E and/or MLH1 hypermethylation and no MMR germline mutation.ResultsAmong 129 MSI/dMMR mCRC patients, 81 (63%) were LS-like and 48 (37%) had sporadic tumours; 22% of MLH1/PMS2-negative mCRCs would have been misclassified using an algorithm based on local medical records (age, Amsterdam II criteria, BRAF and MMR statuses when locally tested), compared to a systematical assessment of MMR, BRAF and MLH1 methylation statuses. In univariate analysis, parameters associated with better overall survival were age (P < 0.0001), metastatic resection (P = 0.001) and LS-like mCRC (P = 0.01), but not BRAFV600E. In multivariate analysis, age (hazard ratio (HR) = 3.19, P = 0.01) and metastatic resection (HR = 4.2, P = 0.001) were associated with overall survival, but not LS. LS-like patients were associated with more frequent liver involvement, metastatic resection and better disease-free survival after metastasectomy (HR = 0.28, P = 0.01). Median progression-free survival of first-line chemotherapy was similar between the two groups (4.2 and 4.2 months; P = 0.44).ConclusionsLS-like and sporadic MSI/dMMR mCRCs display distinct natural histories. MMR, BRAF mutation and MLH1 methylation testing should be mandatory to differentiate LS-like and sporadic MSI/dMMR mCRC, to determine in particular whether immune checkpoint inhibitors efficacy differs in these two populations.     

Epidemiological,clinical and molecular characterization of Lynch-like syndrome: A population-based study

Colorectal carcinomas that are mismatch repair (MMR)-deficient in the absence of MLH1 promoter methylation or germline mutations represent Lynch-like syndrome (LLS). Double somatic events inactivating MMR genes are involved in the etiology of LLS tumors. Our purpose was to define the clinical and broader molecular hallmarks of LLS tumors and the population incidence of LLS, which remain poorly characterized. We investigated 762 consecutive colorectal carcinomas operated in Central Finland in 2000–2010. LLS cases were identified by a stepwise protocol based on MMR protein expression, MLH1 methylation and MMR gene mutation status. LLS tumors were profiled for CpG Island Methylator Phenotype (CIMP) and somatic mutations in 578 cancer-relevant genes. Among 107 MMR-deficient tumors, 81 (76%) were attributable to MLH1 promoter methylation and 9 (8%) to germline mutations (Lynch syndrome, LS), leaving 14 LLS cases (13%) (3 remained unclassified). LLS carcinomas were diagnosed at a mean age of 65 years (vs. 44 years in LS, p < 0.001), had a proximal to distal ratio of 1:1, and all were BRAF V600E-negative. Two somatic events in MMR genes were identifiable in 11 tumors (79%). As novel findings, the tumors contained an average of 31 nonsynonymous somatic mutations/Mb and 13/14 were CIMP-positive. In conclusion, we establish the epidemiological, clinical and molecular characteristics of LLS in a population-based study design. Significantly more frequent CIMP-positivity and lower rates of somatic mutations make a distinction to LS. The absence of BRAF V600E mutation separates LLS colorectal carcinomas from MLH1-methylated colorectal carcinomas with CIMP-positive phenotype.     

Molecular subtypes in early colorectal cancer associated with clinical features and patient prognosis

Purpose

After surgical resection, an ample prognosis variability among stages is observed. Multiple prognostic factors are individually studied and some CRC classifiers have been proposed. Not one have been implemented into clinical practice.

Methods/patients

We classified 105 patients with resected CRC (stage I–III) into five molecular subtypes using BRAF^V600E and RAS (KRAS; NRAS) status, and the expression of DNA mismatch repair (MMR) proteins (MLH1 and MSH2). Clinicopathological features and DFS) of distincts groups were evaluated.

Results and conclusions

RAS and BRAF^V600E mutations were detected in 43.8 and 11.4% of patients, respectively. 19% of tumours had lack of expression of any MMR proteins reflecting a system deficiency (dMMR). Patients with any RAS mutation had lower DFS that patients with RAS wild type (wt) (40.23 vs 45.26 months; p value?=?0.035). Of a total of five molecular subtypes, three were MMR proficient (pMMR): RAS mutated (39%), BRAF^V600E mutated (6.7%) and RAS/BRAF^V600E wt (35.2%); and two were dMMR: BRAF^V600E mutated (4.8%) and BRAF^V600E wt (14.3%). Left side tumours were more frequently observed in pMMR/RAS and BRAF^V600E wt subtype, and right side tumours in dMMR subtypes. Among the three pMMR subtypes, a benefit survival was observed for patients without any mutation in BRAF^v600E or RAS oncogenes (median of DFS?=?45.5 vs 40.98 months in RAS mutated group; p?=?0.084 and vs 34.13 in BRAF^v600E mutated group; p?=?0.031). Molecular classification using these biomarkers can be useful to identify groups with differences in prognosis.

     

Evaluation of yield and experiences of age-related molecular investigation for heritable and nonheritable causes of mismatch repair deficient colorectal cancer to identify Lynch syndrome

Universal mismatch repair deficiency (dMMR) testing of colorectal cancer (CRC) is promoted as routine diagnostics to prescreen for Lynch syndrome. We evaluated the yield and experience of age-related molecular investigation for heritable and nonheritable causes of dMMR in CRC below age 70 to identify Lynch Syndrome. In a prospective cohort of 3602 newly diagnosed CRCs below age 70 from 19 hospitals, dMMR, MLH1 promoter hypermethylation, germline MMR gene and somatic MMR gene testing was assessed in daily practice. Yield was evaluated using data from the Dutch Pathology Registry (PALGA) and two regional genetic centers. Experiences of clinicians were evaluated through questionnaires. Participating clinicians were overwhelmingly positive about the clinical workflow. Pathologists routinely applied dMMR-testing in 84% CRCs and determined 10% was dMMR, largely due to somatic MLH1 hypermethylation (66%). Of those, 69% with dMMR CRC below age 70 without hypermethylation were referred for genetic testing, of which 55% was due to Lynch syndrome (hereditary) and 43% to somatic biallelic pathogenic MMR (nonhereditary). The prevalence of Lynch syndrome was 18% in CRC < 40, 1.7% in CRC age 40-64 and 0.7% in CRC age 65-69. Age 65-69 represents most cases with dMMR, in which dMMR due to somatic causes (13%) is 20 times more prevalent than Lynch syndrome. In conclusion, up to age 65 routine diagnostics of (non-)heritable causes of dMMR CRCs effectively identifies Lynch syndrome and reduces Lynch-like diagnoses. Above age 64, the effort to detect one Lynch syndrome patient in dMMR CRC is high and germline testing rarely needed.     

Combined analysis of specific KRAS mutation,BRAF and microsatellite instability identifies prognostic subgroups of sporadic and hereditary colorectal cancer

Confounding effects of specific KRAS gene alterations on colorectal cancer (CRC) prognosis stratified by microsatellite instability (MSI) and BRAF^V600E have not yet been investigated. The aim of our study was to evaluate the combined effects of MSI, BRAF^V600E and specific KRAS mutation (Gly → Asp; G12D, Gly → Asp, G13D; Gly → Val; G12V) on prognosis in 404 sporadic and 94 hereditary CRC patients. MSI status was determined according to the Bethesda guidelines. Mutational status of KRAS and BRAF^V600E was assessed by direct DNA sequencing. In sporadic CRC, KRAS G12D mutations had a negative prognostic effect compared to G13D and wild‐type cancers (p = 0.038). With MSI, specific KRAS and BRAF^V600E mutations, 3 distinct prognostic subgroups were observed in univariate (p = 0.006) and multivariable (p = 0.051) analysis: patients with (i) KRAS mutation G12D, G12V or BRAF^V600E mutation, (ii) KRAS/BRAF^V600E wild‐type or KRAS G13D mutations in MSS/MSI‐L and (iii) MSI‐H and KRAS G13D mutations. Moreover, none of the sporadic MSI‐H or hereditary patients with KRAS G13 mutations had a fatal outcome. Specific KRAS mutation is an informative prognostic factor in both sporadic and hereditary CRC and applied in an algorithm with BRAF^V600E and MSI may identify sporadic CRC patients with poor clinical outcome.     

Endometrial cancer in Lynch syndrome

Lynch syndrome (LS) is an autosomal dominant inherited disease caused by germline pathogenic variants (PVs) in mismatch repair (MMR) genes. LS-associated endometrial cancer (LS-EC) is the most common extraintestinal sentinel cancer caused by germline PVs in MMR genes, including MLH1, MSH2, MSH6 and PMS2. The clinicopathologic features of LS-EC include early age of onset, lower body mass index (BMI), endometrioid carcinoma and lower uterine segment involvement. There has been significant progress in screening, diagnosis, surveillance, prevention and treatment of LS-EC. Many studies support universal screening for LS among patients with EC. Screening mainly involves a combination of traditional clinical criteria and molecular techniques, including MMR-immunohistochemistry (MMR-IHC), microsatellite instability (MSI) testing, MLH1 promoter methylation testing and gene sequencing. The effectiveness of endometrial biopsy and transvaginal ultrasound (TVS) for clinical monitoring of asymptomatic women with LS are uncertain yet. Preventive strategies include hysterectomy and bilateral salpingo-oophorectomy (BSO) as well as chemoprophylaxis using exogenous progestin or aspirin. Recent research has revealed the benefits of immunotherapy for LS-EC. The NCCN guidelines recommend pembrolizumab and nivolumab for treating patients with advanced or recurrent microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) EC.     

Lynch-like syndrome is as frequent as Lynch syndrome in early-onset nonfamilial nonpolyposis colorectal cancer

Early-onset (<50 years-old) nonpolyposis nonfamilial colorectal cancer (EO NP NF CRC) is a common clinical challenge. Although Lynch syndrome (LS) is associated with EO CRC, the frequency of this syndrome in the EO NF cases remains unknown. Besides, mismatch repair deficient (MMRd) CRCs with negative MMR gene testing have recently been described in up to 60% of cases and termed “Lynch-like syndrome” (LLS). Management and counseling decisions of these patients are complicated because of unconfirmed suspicions of hereditary cancer. To define the prevalence of MMR deficient CRCs, LS and LLS in patients with EO NP NF CRC, we recruited 102 patients with a first diagnosis of NP NF CRC ≤ 50 years old during 2003–2009 who underwent genetic counseling at our institution in Argentina. Tumor immunohistochemical (IHC) MMR for protein expression and microsatellite instability (MSI) status were evaluated, and in those with loss of MLH1 expression by IHC, somatic BRAF V600E mutation and both somatic and germline MLH1 methylation levels were studied. Tumors characterized as MMRd without somatic BRAF mutation nor MLH1 methylation were sent for germline analysis. Twenty one (20.6%) tumors were MMRd. Fourteen of 16 putative LS cases underwent germline testing: 6 pathogenic mutations were identified and 8 cases had no identifiable pathogenic mutations. The prevalence of LS and LLS in this cohort was 5.8% (6/102) and 7.8% (8/102), respectively. As a conclusion we found that 20% of patients with EO NP NF CRC have MMRd tumors, and at least half of these are likely to have LLS.     

Incorporation of somatic <Emphasis Type="Italic">BRAF</Emphasis> mutation testing into an algorithm for the investigation of hereditary non-polyposis colorectal cancer

Patients suspected on clinical grounds to have hereditary non-polyposis colorectal cancer (HNPCC) may be offered laboratory testing in order to confirm the diagnosis and to facilitate screening of pre-symptomatic family members. Tumours from an affected family member are usually pre-screened for microsatellite instability (MSI) and/or loss of immunohistochemical expression of mismatch repair (MMR) genes prior to germline MMR gene mutation testing. The efficiency of this triage process is compromised by the more frequent occurrence of sporadic colorectal cancer (CRC) showing high levels of MSI (MSI-H) due to epigenetic loss of MLH1 expression. Somatic BRAF mutations, most frequently V600E, have been described in a significant proportion of sporadic MSI-H CRC but not in HNPCC-associated cancers. BRAF mutation testing has therefore been proposed as a means to more definitively identify and exclude sporadic MSI-H CRC cases from germline MMR gene testing. However, the clinical validity and utility of this approach have not been previously evaluated in a familial cancer clinic setting. Testing for the V600E mutation was performed on MSI-H CRC samples from 68 individuals referred for laboratory investigation of suspected HNPCC. The V600E mutation was identified in 17 of 40 (42%) tumours showing loss of MLH1 protein expression by immunohistochemistry but in none of the 28 tumours that exhibited loss of MSH2 expression (P < 0.001). The assay was negative in all patients with an identified germline MMR gene mutation. Although biased by the fact that germline testing was not pursued beyond direct sequencing in many cases lacking a high clinical index of suspicion of HNPCC, BRAF V600E detection was therefore considered to be 100% specific and 48% sensitive in detecting sporadic MSI-H CRC amongst those cases showing loss of MLH1 protein expression, in a population of patients with MSI-H CRC and clinical features suggestive of HNPCC. Accordingly, we recommend the incorporation of BRAF V600E mutation testing into the laboratory algorithm for pre-screening patients with suspected HNPCC, whose CRCs show loss of expression of MLH1. In such tumours, the presence of a BRAF V600E mutation indicates the tumour is not related to HNPCC and that germline testing of MLH1 in that individual is not warranted. We also recommend that in families where the clinical suspicion of HNPCC is high, germline testing should not be performed on an individual whose CRC harbours a somatic BRAF mutation, as this may compromise identification of the familial mutation.     

Non-V600E BRAF mutations and EGFR signaling pathway in colorectal cancer

The Raf murine sarcoma viral oncogene homolog B (BRAF^V600E) mutation (MT) in metastatic colorectal cancer (CRC) is a well-known prognostic indicator and a negative predictive biomarker for antiepidermal growth factor receptor (EGFR) treatment. However, the clinical characteristics and significance of BRAF^non-V600E MTs remain unclear. Here, we evaluated the clinical characteristics of BRAF^non-V600E MTs vs. those of other MTs in the EGFR signaling pathway, including BRAF^V600E. Consecutive CRC patients in our institute from June 2012 to November 2013 were enrolled in our study. Multiplex genotyping of the EGFR pathway was performed with archival samples using a Luminex Assay for BRAF^V600E/BRAF^non-V600E, KRAS/NRAS exons 2–4, and phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA). We analyzed correlations among the MT profiles, clinical data and primary tumor locations in CRC. All statistical analyses were performed using R software. CRC samples (824) from 374 (45.4%) male and 450 (54.6%) female patients were analyzed, of which 154 (18.7%), 202 (24.5%), 270 (32.8%) or 198 (24.0%) had Stages I, II, III or IV or recurrent CRC, respectively. The frequencies of BRAF^V600E/BRAF^non-V600E, KRAS (including exons 2–4), NRAS and PIK3CA MTs were 5.3/1.7, 41.4, 3.3 and 9.6%, respectively. The characteristics of patients with the BRAF^V600E MT were an age of ≥65 years old, a right-sided primary tumor location, poorly differentiated histology and an advanced disease stage. In contrast, the characteristics of patients with BRAF^non-V600E MTs were a left-sided primary tumor location and well-differentiated histology. BRAF^non-V600E MTs were relatively rare and showed different characteristics compared to the BRAF^V600E MT. These results may contribute to future precision medicine.     

New Therapeutic Opportunities Based on DNA Mismatch Repair and <Emphasis Type="Italic">BRAF</Emphasis> Status in Metastatic Colorectal Cancer

Recently, colorectal cancer (CRC) subtyping consortium identified four consensus molecular subtypes (CMS1–4). CMS1 is enriched for deficient mismatch repair (dMMR) and BRAF ^V600E tumors. Intriguingly, this subtype has better relapse-free survival but worse overall survival after relapse compared with the other subtypes. Growing evidence is accumulating on the benefit of specific therapeutic strategies such as immune checkpoint inhibition therapy in dMMR tumors and mitogen-activated protein kinase (MAPK) pathway targeted therapy in tumors harboring BRAF ^V600E mutation. After reviewing dMMR prognostic value, immune checkpoints as major targets for dMMR carcinomas will be highlighted. Following, BRAF ^V600E prognostic impact will be reviewed and therapeutic strategies with the combination of cytotoxic agents and especially the combinations of BRAF and MAPK inhibitors will be discussed.     

Optimizing targeted therapeutic development: Analysis of a colorectal cancer patient population with the BRAFV600E mutation

BRAF^V600E mutations are found in 10% of colorectal cancers (CRCs). The low frequency of this mutation therefore makes it a challenging target for drug development, unless subsets of patients with higher rates of BRAF^V600E can be defined. Knowledge of the concordance between primary–metastasis pairs and the impact of BRAF^V600E on outcome would also assist in optimal drug development. We selected primary CRCs from 525 patients (stages I–IV) evenly matched for age (<70 and ≥70), gender and tumor location (right, left and rectum), and 81 primary–metastasis pairs. BRAF^V600E, KRAS mutation and microsatellite instability (MSI) were determined and correlated with clinical features and patient outcomes. In multivariate analyses, increasing patient age (p = 0.04), female gender (p = 0.0005) and right‐sided tumor location (p < 0.0001) were independently associated with BRAF^V600E. The prevalence of BRAF^V600E was considerably higher in older (age > 70) females with KRAS wild‐type right‐sided colon cancers (50%) compared to the unselected cohort (10%). BRAF^V600E was associated with inferior overall survival in metastatic CRC (HR = 2.02; 95% CI 1.26–3.26), particularly evident in patients treated with chemotherapy, and is independent of MSI status. BRAF status was concordant in all primary tumors and matched metastases (79 wild‐type pairs and two mutant pairs). Clinicopathological and molecular features can identify CRC patients with a higher prevalence of BRAF^V600E. Patients with BRAF^V600E wild‐type primary tumor do not appear to acquire the mutation in their metastases, and BRAF^V600E is associated with poorer outcomes in metastatic patients. Our findings are timely and will help inform the rational development of BRAF^V600E inhibitors in CRC.     

Advances in the therapy of BRAFV600E metastatic colorectal cancer

ABSTRACT

Introduction: BRAF^V600E metastatic colorectal cancer (CRC) is an aggressive tumor subset with an approximate 8% incidence. In these patients, standard chemotherapy has limited efficacy, and the recent development of novel-targeted treatment regimens may significantly improve clinical outcome.

Area covered: This review provides an overview of available data regarding advances in the first–line treatment of BRAF^V600E metastatic CRC including patient tumors with microsatellite instability. The implications of BRAF^V600E in earlier stage CRC are also discussed.

Expert opinion: Recently, significant progress has been achieved in improving tumor response rates using a novel-targeted regimen in patients with BRAF^V600E metastatic CRC. The implications of BRAF^V600E in non-metastatic CRC are also becoming more evident and remains an area of ongoing investigation. The majority of CRCs with microsatellite instability high are sporadic and frequently harbor BRAF^V600E. All patients with microsatellite instability high metastatic CRCs, irrespective of BRAF^V600E, are candidates for immune checkpoint inhibitors. The optimal sequencing of treatment regimens for patients with BRAF^V600E metastatic CRCs is an important area for future research.     

Possible role of Cdx2 in the serrated pathway of colorectal cancer characterized by BRAF mutation,high‐level CpG Island methylator phenotype and mismatch repair‐deficiency

Colorectal cancer is a heterogeneous disease at the histomorphological, clinical and molecular level. Approximately 20% of cases may progress through the “serrated” pathway characterized by BRAF mutation and high‐level CpG Island Methylator Phenotype (CIMP). A large subgroup are additionally microsatellite instable (MSI) and demonstrate significant loss of tumor suppressor Cdx2. The aim of this study is to determine the specificity of Cdx2 protein expression and CpG promoter hypermethylation for BRAF^V600E and high‐level CIMP in colorectal cancer. Cdx2, Mlh1, Msh2, Msh6, and Pms2 were analyzed by immunohistochemistry using a multi‐punch tissue microarray (TMA; n = 220 patients). KRAS and BRAF^V600E mutation analysis, CDX2 methylation and CIMP were investigated. Loss of Cdx2 was correlated with larger tumor size (P = 0.0154), right‐sided location (P = 0.0014), higher tumor grade (P < 0.0001), more advanced pT (P = 0.0234) and lymphatic invasion (P = 0.0351). Specificity was 100% for mismatch repair (MMR)‐deficiency (P < 0.0001), 92.2% (P < 0.0001) for BRAF^V600E and 91.8% for CIMP‐high. Combined analysis of BRAF^V600E/CIMP identified Cdx2 loss as sensitive (80%) and specific (91.5%) for mutation/high status. These results were validated on eight well‐established colorectal cancer cell lines. CDX2 methylation correlated with BRAF^V600E (P = 0.0184) and with Cdx2 protein loss (P = 0.0028). These results seem to indicate that Cdx2 may play a role in the serrated pathway to colorectal cancer as underlined by strong relationships with BRAF^V600E, CIMP‐high and MMR‐deficiency. Whether this protein can only be used as a “surrogate” marker, or is functionally involved in the progression of these tumors remains to be elucidated.     

Demographic trends and KRAS/BRAFV600E mutations in colorectal cancer patients of South China: A single-site report

The incidence of colorectal cancer (CRC) is increasing in China. Here, we aimed to evaluate the latest demographic trends and KRAS/BRAF mutations status of Chinese CRC. Five thousand five hundred and forty-six CRC patients diagnosed from 2010 to 2017 were involved. KRAS exon 2 and BRAF^V600E mutations were detected by Sanger sequencing and high-resolution melting analysis or allelic-specific probe method. Gene mutation profiles and clinicopathologic characteristics of 5495 patients were analyzed. The joinpoint regression model was used to predict the demographic data in 2018. We found KRAS exon 2 and BRAF^V600E mutation rates were 37.7 and 2.8% in CRC patients. Tumors with KRAS exon 2 mutations were more likely to be present in female and patients aged older than 75 years, right colon and have well-differentiated histology. Tumors with BRAF^V600E mutations were more likely to be present in the female, right colon and have poorly differentiated histology. From 2010 to 2017, the percentage of colon cancer and tubular adenocarcinoma in CRC increased substantially (from 39.3 to 51.8%, from 78.6 to 93.4%, respectively). The percentage of right colon cancer increased from 18.3 to 20.5%, which predictively may keep at 22.6% in 2018. The rise trends for patients with moderate differentiation tumor or KRAS exon 2 mutated tumor were apparent (from 50.3 to 78.6%, from 32.8 to 39.7%, respectively). In conclusion, in recent 8 years, there is a shift to the colon, especially right colon in the incidence of Chinese CRC. Moreover tubular adenocarcinoma is becoming the primary histology type.     

Clinicopathologic features and prognostic value of KRAS,NRAS and BRAF mutations and DNA mismatch repair status: A single-center retrospective study of 1,834 Chinese patients with Stage I–IV colorectal cancer

Mutations of KRAS, NRAS, BRAF and DNA mismatch repair (MMR) status have become an important part of the assessment of patients with colorectal cancer (CRC), while respective clinicopathologic features and prognostic significance in specific stages and related detection strategies remain unclear. We retrospectively analyzed clinicopathologic features and prognosis of 1,834 patients with Stage I–IV colorectal adenocarcinoma. Mutations in KRAS, NRAS and BRAF and DNA MMR status were determined. The mutation rates of KRAS, NRAS and BRAF were 46.4, 3.2 and 3.5%, respectively, and the mismatch repair gene deletion (dMMR) rate was 5.6%. In a multivariate analysis, female, advanced age, tumor type histology, mucinous carcinoma and positive tumor deposits were associated with a high KRAS mutation rate. A high BRAF mutation rate was associated with female, poor differentiation, lymphovascular invasion and positive tumor deposits. Factors associated with high dMMR rates included low age, large tumor size, poor differentiation, Stages I–III. Tumor site was independently associated with KRAS mutation, BRAF mutation and dMMR. KRAS and BRAF mutations were independent risk factors for shorter overall survival (OS) in Stage IV tumors but not in Stage I–III tumors. NRAS mutation was an independent risk factor for shorter OS in Stage I–II tumors. dMMR was independently associated with longer OS in Stage III tumors.     

Japanese Society of Medical Oncology Clinical Guidelines: Molecular Testing for Colorectal Cancer Treatment,Third Edition

The Japanese Society of Medical Oncology (JSMO) previously published 2 editions of the clinical guidelines: “Japanese guidelines for testing of KRAS gene mutation in colorectal cancer” in 2008 and “Japanese Society of Medical Oncology Clinical Guidelines: RAS (KRAS/NRAS) mutation testing in colorectal cancer patients” in 2014. These guidelines have contributed to the proper use of KRAS and RAS mutation testing, respectively. Recently, clinical utility, particularly for colorectal cancer (CRC) patients with BRAF V600E mutation or DNA mismatch‐repair (MMR) deficiency, has been established. Therefore, the guideline members decided these genetic alterations should also be involved. The aim of this revision is to properly carry out testing for BRAF V600E mutation and MMR deficiency in addition to RAS mutation. The revised guidelines include the basic requirements for testing for these genetic alterations based on recent scientific evidence. Furthermore, because clinical utility of comprehensive genetic testing using next‐generation sequencing and somatic gene testing of analyzing circulating tumor DNA has increasingly evolved with recent advancements in testing technology, we noted the current situation and prospects for these testing technologies and their clinical implementation in the revised guidelines.     

Population‐based screening for Lynch syndrome in Western Australia

We showed earlier that routine screening for microsatellite instability (MSI) and loss of mismatch repair (MMR) protein expression in colorectal cancer (CRC) led to the identification of previously unrecognized cases of Lynch syndrome (LS). We report here the results of screening for LS in Western Australia (WA) during 1994–2012. Immunohistochemistry (IHC) for loss of MMR protein expression was performed in routine pathology laboratories, while MSI was detected in a reference molecular pathology laboratory. Information on germline mutations in MMR genes was obtained from the state's single familial cancer registry. Prior to the introduction of routine laboratory‐based screening, an average of 2–3 cases of LS were diagnosed each year amongst WA CRC patients. Following the implementation of IHC and/or MSI screening for all younger (<60 years) CRC patients, this has increased to an average of 8 LS cases diagnosed annually. Based on our experience in WA, we propose three key elements for successful population‐based screening of LS. First, for all younger CRC patients, reflex IHC testing should be carried out in accredited pathology services with ongoing quality control. Second, a state‐ or region‐wide reference laboratory for MSI testing should be established to confirm abnormal or suspicious IHC test results and to exclude sporadic cases by carrying out BRAF mutation or MLH1 methylation testing. Finally, a state or regional LS coordinator is essential to ensure that all appropriate cases identified by laboratory testing are referred to and attend a Familial Cancer Clinic for follow‐up and germline testing.