Prognostic and predictive value of common mutations for treatment response and survival in patients with metastatic colorectal cancer. Br J Cancer. 2009;101:465-472. [PMID: 19603024 PMCID: PMC2720232 DOI: 10.1038/sj.bjc.6605164]

BRAF inhibitors in clinical oncology

Activating mutations of the BRAF oncogene are present in approximately 5-10% of all human malignancies and lead to constitutive activation of the mitogen activated protein kinase (MAPK) pathway. The introduction of BRAF inhibitors has greatly improved the short term prospects of some patients with these tumors, but the tumors tend to become resistant to therapy with time by activating alternative signaling pathways. Consequently, combination strategies with drugs that block not only the primary mutated BRAF kinase but also the alternative pathways implicated in development of resistance may represent a better strategy for improving survival in patients with tumors harboring BRAF mutations.

Molecular pathological epidemiology of epigenetics: emerging integrative science to analyze environment, host, and disease

Epigenetics acts as an interface between environmental/exogenous factors, cellular responses, and pathological processes. Aberrant epigenetic signatures are a hallmark of complex multifactorial diseases (including neoplasms and malignancies such as leukemias, lymphomas, sarcomas, and breast, lung, prostate, liver, and colorectal cancers). Epigenetic signatures (DNA methylation, mRNA and microRNA expression, etc) may serve as biomarkers for risk stratification, early detection, and disease classification, as well as targets for therapy and chemoprevention. In particular, DNA methylation assays are widely applied to formalin-fixed, paraffin-embedded archival tissue specimens as clinical pathology tests. To better understand the interplay between etiological factors, cellular molecular characteristics, and disease evolution, the field of 'molecular pathological epidemiology (MPE)' has emerged as an interdisciplinary integration of 'molecular pathology' and 'epidemiology'. In contrast to traditional epidemiological research including genome-wide association studies (GWAS), MPE is founded on the unique disease principle, that is, each disease process results from unique profiles of exposomes, epigenomes, transcriptomes, proteomes, metabolomes, microbiomes, and interactomes in relation to the macroenvironment and tissue microenvironment. MPE may represent a logical evolution of GWAS, termed 'GWAS-MPE approach'. Although epigenome-wide association study attracts increasing attention, currently, it has a fundamental problem in that each cell within one individual has a unique, time-varying epigenome. Having a similar conceptual framework to systems biology, the holistic MPE approach enables us to link potential etiological factors to specific molecular pathology, and gain novel pathogenic insights on causality. The widespread application of epigenome (eg, methylome) analyses will enhance our understanding of disease heterogeneity, epigenotypes (CpG island methylator phenotype, LINE-1 (long interspersed nucleotide element-1; also called long interspersed nuclear element-1; long interspersed element-1; L1) hypomethylation, etc), and host-disease interactions. In this article, we illustrate increasing contribution of modern pathology to broader public health sciences, which attests pivotal roles of pathologists in the new integrated MPE science towards our ultimate goal of personalized medicine and prevention.

PIK3CA mutation is associated with poor survival among patients with metastatic colorectal cancer following anti-EGFR monoclonal antibody therapy: a meta-analysis

PURPOSE

PIK3CA mutation appears to predict a lack of response to anti-EGFR monoclonal antibody (mAb) treatment in patients with metastatic colorectal cancer (mCRC). However, the predictive value of PIK3CA mutations for survival remains inconclusive. Here, we pooled the data from published studies to estimate the association between PIK3CA mutation and survival outcomes in mCRC patients treated with anti-EGFR mAbs.

METHODS

Studies investigating the association of PIK3CA mutations with clinical survival outcomes of mCRC patients treated with anti-EGFR mAbs were systematically identified. The overall hazard ratio (HR) was estimated by using fixed effect model or random effect model according to heterogeneity between trails.

RESULTS

Eight studies that reported survival outcome in 839 mCRC patients were included. In unselected patients, we found that PIK3CA mutations were significantly associated with poorer PFS [8 studies, 839 patients; HR = 1.53; 95 % confidence interval (CI) 1.28-1.84; P < 0.001] and OS (5 studies; 587 patients; HR = 1.28; 95 % CI 1.05-1.56; P = 0.015). With increased predictive power in KRAS wild-type patients (3 studies; 275 patients), the overall HR for PFS was 2.44 (95 % CI 1.33-4.48; P = 0.004) and was statistically significant. We also observed a worse OS in KRAS wild-type patients with PIK3CA mutations (2 studies; 163 patients; HR = 1.37; 95 % CI 0.80-2.35; P = 0.258), although the result was not statistically significant due to small sample size.

CONCLUSIONS

PIK3CA mutation is a promising predictive biomarker for poor survival in mCRC patients treated with anti-EGFR mAbs, particularly in KRAS wild-type patients.

Combined analysis of KRAS and PIK3CA mutations, MET and PTEN expression in primary tumors and corresponding metastases in colorectal cancer

Metastasis is the main cause of mortality in patients with colorectal cancer. However, most of the targeted therapies and predictive molecular biomarkers were developed based mainly on primary tumors. The current study was conducted to determine the degree of discordance between potential predictive and/or prognostic molecular markers in primary colorectal tumors and corresponding metastases, as this could have an impact on the efficacy of targeted therapies in the advanced colorectal cancer. KRAS, PIK3CA and BRAF mutations were determined by Sanger sequencing and mutant-enriched polymerase chain reaction (PCR) assays in 83 paired samples, MET gene copy number by quantitative PCR in 59, MET expression by immunohistochemistry in 73 and nuclear and cytoplasmic expression of PTEN by immunohistochemistry in 78 and 71 pairs, respectively. A certain degree of discordance between primary tumors and corresponding metastases was demonstrated for all examined biomarkers except BRAF mutations. PIK3CA exon 9 mutations in primary tumors and loss of PTEN nuclear expression in metastases correlated with KRAS mutations. KRAS wild-type status in primary tumors was associated with loss of PTEN cytoplasmic expression and high gene copy number of MET. Survival and clinical data were available for 68 patients. The multiple regression analysis revealed that the right-sided tumor localization and overexpression of MET were associated with shorter overall survival.

Targeted therapies in colorectal cancer-an integrative view by PPPM

In developed countries, colorectal cancer (CRC) is the third most common malignancy, but it is the second most frequent cause of cancer-related death. Clinicians are still faced with numerous challenges in the treatment of this disease, and future approaches which target the molecular features of the disorder will be critical for success in this disease setting. Genetic analyses of many solid tumours have shown that up to 100 protein-encoding genes are mutated. Within CRC, numerous genetic alterations have been identified in a number of pathways. Therefore, understanding the molecular pathology of CRC may present information on potential routes for treatment and may also provide valuable prognostic information. This will be particularly pertinent for molecularly targeted treatments, such as anti-vascular endothelial growth factor therapies and anti-epidermal growth factor receptor (EGFR) monoclonal antibody therapy. KRAS and BRAF mutations have been shown to predict response to anti-EGFR therapy. As EGFR can also signal via the phosphatidylinositol 3-kinase (PI3K) kinase pathway, there is considerable interest in the potential roles of members of this pathway (such as PI3K and PTEN) in predicting treatment response. Therefore, a combined approach of new techniques that allow identification of these biomarkers alongside interdisciplinary approaches to the treatment of advanced CRC will aid in the treatment decision-making process and may also serve to guide future therapeutic approaches.

Massively parallel tumor multigene sequencing to evaluate response to panitumumab in a randomized phase III study of metastatic colorectal cancer

PURPOSE

To investigate whether EGF receptor (EGFR) pathway mutations predicted response to monotherapy with panitumumab, an anti-EGFR monoclonal antibody, in a randomized phase III study of metastatic colorectal cancer.

EXPERIMENTAL DESIGN

Using massively parallel multigene sequencing, we analyzed 320 samples for 9 genes, with multigene sequence data from 288 (90%) samples.

RESULTS

Mutation rates were: KRAS (45%), NRAS (5%), BRAF (7%), PIK3CA (9%), PTEN (6%), TP53 (60%), EGFR (1%), AKT1 (<1%), and CTNNB1 (2%). In the randomized study and open-label extension, 22 of 138 (16%) wild-type KRAS (codons 12/13/61) patients versus 0 of 103 mutant KRAS (codons 12/13) patients had objective responses. Of 6 mutant KRAS (codon 61) patients, 1 with a Q61H mutation achieved partial response during the extension. Among wild-type KRAS (codons 12/13/61) patients, 0 of 9 patients with NRAS mutations, 0 of 13 with BRAF mutations, 2 of 10 with PIK3CA mutations, 1 of 9 with PTEN mutations, and 1 of 2 with CTNNB1 mutations responded to panitumumab. No patients responded to best supportive care alone. Panitumumab treatment was associated with longer progression-free survival (PFS) among wild-type KRAS (codons 12/13/61) patients [HR, 0.39; 95% confidence interval (CI), 0.28-0.56]. Among wild-type KRAS patients, a treatment effect for PFS favoring panitumumab occurred in patients with wild-type NRAS (HR, 0.39; 95% CI, 0.27-0.56) and wild-type BRAF (HR, 0.37; 95% CI, 0.24-0.55) but not mutant NRAS (HR, 1.94; 95% CI, 0.44-8.44).

CONCLUSIONS

These results show the feasibility and potential clinical use of next-generation sequencing for evaluating predictive biomarkers.

Optimizing treatment of metastatic colorectal cancer patients with anti-EGFR antibodies: overcoming the mechanisms of cancer cell resistance

INTRODUCTION

A number of anti-EGFR monoclonal antibodies (mAbs) have been recently developed for the treatment of refractory metastatic colorectal cancer (mCRC). These mAbs, blocking ligand/receptor interactions, exert their biological activity via multiple mechanisms, including inhibition of cell cycle progression, potentiation of cell apoptosis, inhibition of angiogenesis, tumor cell invasion and metastasis and, potentially, induction of immunological effector mechanisms.

AREAS COVERED

Cetuximab is an anti-EGFR mAb currently used in mCRC treatment. Despite the evidence of efficacy of cetuximab in the treatment of mCRC patients, the observation of low response rates was the proof of concept of resistance to anti-EGFR mAbs treatment. An increasing number of molecular alterations have been more recently hypothesized to be involved in resistance to anti-EGFR mAbs in CRC: mutations in BRAF, NRAS and PIK3CA, loss of expression of PTEN and, now, activation of HER2 signaling through HER2 gene amplification and/or increased heregulin stimulation.

EXPERT OPINION

This review focuses on the development of new strategies such as combination with other agents blocking alternative escape pathways, cancer cell prioritization hyperactivating EGFR pathway, combination with immune system, development of nanotech devices to increase efficacy of antibody-based therapy and overcome the mechanisms of cancer cell resistance.

Hotspot oncomutations: implications for personalized cancer treatment

Understanding the extent to which specific tumor mutations impact or mediate patient response to particular cancer therapies has become a rapidly increasing area of research. Recent research findings regarding four predominant mutational targets (KRAS, BRAF, EGFR and PIK3CA) show that these tumor mutations have predictive power for identifying which patients are likely to respond to particular therapies, and have prognostic significance irrespective of treatment. However, in this regard, the literature is frequently nuanced and sometimes contradictory. This lack of clarity may be due, at least in part, to the utilization of mutation detection methods with varying sensitivities across studies of different patient populations. Nevertheless, considerable evidence suggests minor tumor subpopulations may be contributing to inappropriate patient stratification, development of resistance to treatment, and the relapse that often follows treatment with molecularly targeted therapies. Consequently, mutant tumor subpopulations need to be considered in order to improve strategies for personalized cancer treatment.

Comparison of KRAS/BRAF mutations between primary tumors and serum in colorectal cancer: Biological and clinical implications

In colorectal cancer (CRC), KRAS and BRAF mutations in primary tumors are associated with resistance to anti-epidermal growth factor receptor (anti-EGFR)-based therapies. However, the correlation between KRAS/BRAF mutation in primary tumors and serum has not been well studied. To evaluate the degree of concordance of KRAS/BRAF mutations between the primary tumors and the matched serum samples in CRC, serum and tumor tissues were collected from 115 patients with CRC and KRAS/BRAF mutations were examined by nested polymerase chain reaction (PCR) and direct sequencing. BRAF mutations were present in 3.5% (4/115) of the primary tumor tissue samples and 0.87% (1/115) of the serum samples. In the 4 primary tumors with BRAF mutations, identical mutations were not observed in the corresponding serum samples (κ=-0.016). KRAS mutations were observed in 32.2% (37/115) of the primary tumors and 11.3% (13/115) of the serum samples. Of the 37 tumor cases with KRAS mutations, 9 had identical mutations in the corresponding serum sample, with a concordance rate of 24.3% (9/37). Discordance was observed in 32 (27.8%) patients. The concordance between KRAS mutations in the primary tumors and KRAS mutations in the matched serums was low (κ=0.231). The results of the present study suggest that the possibility of differences in the mutational status of KRAS/BRAF between primary tumors and matched serum samples should be considered when patients are selected for anti-EGFR-based therapies.

The prognostic value of BRAF mutation in colorectal cancer and melanoma: a systematic review and meta-analysis

BACKGROUND

Mutation of BRAF is a predominant event in cancers with poor prognosis such as melanoma and colorectal cancer. BRAF mutation leads to a constitutive activation of mitogen activated protein kinase pathway which is essential for cell proliferation and tumor progression. Despite tremendous efforts made to target BRAF for cancer treatment, the correlation between BRAF mutation and patient survival is still a matter of controversy.

METHODS/PRINCIPAL FINDINGS

Clinical studies on the correlation between BRAF mutation and patient survival were retrieved from MEDLINE and EMBASE databases between June 2002 and December 2011. One hundred twenty relevant full text studies were categorized based on study design and cancer type. Publication bias was evaluated for each category and pooled hazard ratio (HR) with 95% confidence interval (CI) was calculated using random or fixed effect meta-analysis based on the percentage of heterogeneity. Twenty six studies on colorectal cancer (11,773 patients) and four studies on melanoma (674 patients) were included in our final meta-analysis. The average prevalence of BRAF mutation was 9.6% in colorectal cancer, and 47.8% in melanoma reports. We found that BRAF mutation increases the risk of mortality in colorectal cancer patients for more than two times; HR = 2.25 (95% CI, 1.82-2.83). In addition, we revealed that BRAF mutation also increases the risk of mortality in melanoma patients by 1.7 times (95% CI, 1.37-2.12).

CONCLUSIONS

We revealed that BRAF mutation is an absolute risk factor for patient survival in colorectal cancer and melanoma.

Phosphatase and tensin homolog expression related to cetuximab effects in colorectal cancer patients: A meta-analysis

AIM: To investigate the correlation between expression of phosphatase and tensin homolog (PTEN) and cetuximab effects in colorectal cancer.

METHODS: We searched PubMed, EMBASE and ASCO to identify eligible studies. Finally, 8 randomized control studies were included in the meta-analysis. STATA 10.0 Software was used to investigate heterogeneity among individual studies and to summarize all the studies. Risk ratios (RRs) and hazard ratios (HRs) with 95% confidence intervals (CIs) were used to assess the strength of the association.

RESULTS: Compared with 20 of 266 patients with loss of PTEN, 206 of 496 patients with intact PTEN protein expression had a better objective response rate to cetuximab-based therapy (RR, 4.75; 95% CI, 2.59-8.72; P < 0.001). PTEN positivity was associated with better progression-free survival (PFS) (HR, 0.675; 95% CI, 0.473-0.964; P = 0.031) but not with better overall survival (OS) (HR, 0.608; 95% CI, 0.411-0.899; P = 0.013). In patients with KRAS wild-type status, PTEN positivity did not predict a longer PFS or OS (PFS: HR, 0.707; 95% CI, 0.440-1.138; P = 0.154; OS: HR, 0.943; 95% CI, 0.646-1.377; P = 0.761).

CONCLUSION: Expression of PTEN is related to the effect of cetuximab in colorectal cancer patients and should be considered in treatment with cetuximab.

Prognostic and predictive biomarkers for epidermal growth factor receptor-targeted therapy in colorectal cancer: beyond KRAS mutations

The advent of the epidermal growth factor receptor (EGFR)-targeted monoclonal antibodies (mAbs), cetuximab and panitumumab has expanded the range of treatment options for metastatic colorectal cancer (CRC). Despite these agents have paved the way to individualized therapy, our understanding why some patients respond to treatment whereas others do not remain poor. The realization that detection of positive EGFR expression by IHC does not reliably predict clinical outcome of EGFR-targeted treatment has led to an intense search for alternative predictive biomarkers. Data derived from multiple phase III trials have indicated that KRAS mutations can be considered a highly specific negative biomarker of benefit to anti-EGFR mAbs. Oncologists are now facing emerging issues in the treatment of metastatic CRC, including the identification of additional genetic determinants of primary resistance to EGFR-targeted therapy for further improving selection of patients, the explanation of rare cases of patients carrying KRAS-mutated tumours who have been reported to respond to cetuximab and panitumumab and the discovery of mechanisms of secondary resistance to EGFR-targeted therapy. Current data suggest that, together with KRAS mutations, the evaluation of EGFR gene copy number (GCN), BRAF, NRAS, PIK3CA mutations or loss of PTEN expression could also be useful for selecting patients with reduced chance to benefit from anti-EGFR mAbs. This review aims to provide an updated of the most recent data on predictive and prognostic biomarkers within the EGFR pathway, the challenges this emerging field presents and the future role of these molecular markers in CRC treatment.

A simple immunohistochemical algorithm predicts the risk of distant metastases in right-sided colon cancer

AIMS

A test predicting distant metastases would be valuable for prognostication in colon cancer (CC). In previous studies, CC with microsatellite instability (MSI) showed a reduced risk of distant metastases. High expression of CD133 and β-catenin, both related to cancer stem cell phenotypes, might be predictive markers for metastasis. The aim of this study was to develop a simple and robust test for risk assessment of distant metastases in CC.

METHODS AND RESULTS

In a case-control study, 57 cases of right-sided CC specimens with synchronous distant metastases were matched with 57 CC without distant metastases. Immunohistochemistry for MLH1, CD133 and nuclear β-catenin was carried out. To define the diagnostic algorithm the tumours were first stratified according to their MLH1 expression. Loss of MLH1 expression was correlated significantly with a very low risk of distant metastases (5.3%; P = 0.00003). In MLH1-positive cases, combined high scores of CD133 and β-catenin were associated with a very high rate of distant metastases (94.4%), whereas the risk was intermediate for carcinomas with either low CD133 and/or low β-catenin expression (P = 0.0007). A validation study using an independent set of 68 right-sided CC specimens showed a clear trend towards risk stratification according to the algorithm; however, sample sizes were small, and associations were not statistically significant.

CONCLUSIONS

By the use of three markers, this algorithm allowed identification of subgroups of right-sided CC patients with extremely high and extremely low risk of distant metastases.

Predictive role of multiple gene alterations in response to cetuximab in metastatic colorectal cancer: a single center study

Background

KRAS mutations negatively affect outcome after treatment with cetuximab in metastatic colorectal cancer (mCRC) patients. As only 20% of KRAS wild type (WT) patients respond to cetuximab it is possible that other mutations, constitutively activating the EGFR pathway, are present in the non-responding KRAS WT patients. We retrospectively analyzed objective tumor response rate, (ORR) progression-free (PFS) and overall survival (OS) with respect to the mutational status of KRAS, BRAF, PIK3CA and PTEN expression in mCRC patients treated with a cetuximab-based regimen.

Methods

67 mCRC patients were enrolled onto the study. DNA was extracted from paraffin-embedded sections derived from primary or metastatic lesions. Exon 2 of KRAS and exon 15 of BRAF were analyzed by direct sequencing, PIK3CA was evaluated by pyrosequencing and PTEN expression by immunohistochemistry.

Results

BRAF and PIK3CA mutations were independently associated with worse PFS (p = 0.006 and p = 0.028, respectively) and OS (p = 0.008 and p = 0.029, respectively). No differences in clinical outcome were found between patients who were positive or negative for PTEN expression. Conversely, patients negative for KRAS, BRAF and PIK3CA mutations were characterized by significantly better ORR, PFS and OS than patients with at least one of these mutations.

Conclusions

BRAF and PIK3CA mutations would seem to be independent predictors of anti-EGFR therapy effectiveness and could be taken into consideration during treatment decision making.

Where now for anti-EGF receptor therapies in colorectal cancer?

Current US FDA-approved monoclonal antibodies targeting the EGF receptor (EGFR) include cetuximab and panitumumab. In this article, we discuss the clinical evidence concerning the use of monoclonal antibodies targeting the EGFR in the setting of advanced colorectal cancer and the emergence of predictive molecular biomarkers. In addition, we also consider the evidence surrounding the evolution of anti-EGFR-resistance mechanisms evoked by targeted anti-EGFR therapy and potential therapeutic strategies that may counteract resistant tumor growth.

Omics Screening for Pharmaceutical Efficacy and Safety in Clinical Practice

As molecular techniques have improved, investigators have attempted to improve pharmaceutical efficacy and safety by making trait associations with genomic, epigenomic, transcriptomic, proteomic, and metabolomic polymorphisms. The 'omics era has seen screening assays for pharmaceutical efficacy and safety translated into clinical practice. This manuscript will discuss each 'omic field and the screening assays available to the clinician. While success has been demonstrated in each 'omic field, many challenges remain. Assays need wider availability, predictive values remain low, and costs remain high. In order for clinicians to realize improved efficacy and safety due 'omic screens, development of improved techniques, combining of 'omic assays, and increased clinical utilization is necessary. This is an exciting time for investigators and clinicians that desire improved pharmaceutical therapy.

Prognostic role of PIK3CA mutation in colorectal cancer: cohort study and literature review

PURPOSE

Mutations in PIK3CA [the gene encoding the p110α catalytic subunit of phosphatidylinositide-3-kinase (PI3K)] play an important role in colorectal carcinogenesis. Experimental evidence suggests that PIK3CA exon 9 and exon 20 mutations trigger different biologic effects, and that concomitant mutations in both exons 9 and 20 synergistically enhance tumorigenic effects. Thus, we hypothesized that PIK3CA exon 9 and exon 20 mutations might have differential effects on clinical outcome in colorectal cancer, and that concomitant PIK3CA exon 9 and 20 mutations might confer aggressive tumor behavior.

EXPERIMENTAL DESIGN

We sequenced PIK3CA by pyrosequencing in 1,170 rectal and colon cancers in two prospective cohort studies, and found 189 (16%) PIK3CA mutated tumors. Mortality HR according to PIK3CA status was computed using Cox proportional hazards model, adjusting for clinical and molecular features, including microsatellite instability, CpG island methylator phenotype, LINE-1 methylation, and BRAF and KRAS mutations.

RESULTS

Compared with PIK3CA wild-type cases, patients with concomitant PIK3CA mutations in exons 9 and 20 experienced significantly worse cancer-specific survival [log-rank P = 0.031; multivariate HR = 3.51; 95% confidence interval (CI): 1.28-9.62] and overall survival (log-rank P = 0.0008; multivariate HR = 2.68; 95% CI: 1.24-5.77). PIK3CA mutation in either exon 9 or 20 alone was not significantly associated with patient survival. No significant interaction of PIK3CA mutation with BRAF or KRAS mutation was observed in survival analysis.

CONCLUSION

Coexistence of PIK3CA (the PI3K p110α subunit) exon 9 and 20 mutations, but not PIK3CA mutation in either exon 9 or 20 alone, is associated with poor prognosis of colorectal cancer patients.

Prognostic role of PIK3CA mutation in colorectal cancer: cohort study and literature review

PURPOSE

Mutations in PIK3CA [the gene encoding the p110α catalytic subunit of phosphatidylinositide-3-kinase (PI3K)] play an important role in colorectal carcinogenesis. Experimental evidence suggests that PIK3CA exon 9 and exon 20 mutations trigger different biologic effects, and that concomitant mutations in both exons 9 and 20 synergistically enhance tumorigenic effects. Thus, we hypothesized that PIK3CA exon 9 and exon 20 mutations might have differential effects on clinical outcome in colorectal cancer, and that concomitant PIK3CA exon 9 and 20 mutations might confer aggressive tumor behavior.

EXPERIMENTAL DESIGN

We sequenced PIK3CA by pyrosequencing in 1,170 rectal and colon cancers in two prospective cohort studies, and found 189 (16%) PIK3CA mutated tumors. Mortality HR according to PIK3CA status was computed using Cox proportional hazards model, adjusting for clinical and molecular features, including microsatellite instability, CpG island methylator phenotype, LINE-1 methylation, and BRAF and KRAS mutations.

RESULTS

Compared with PIK3CA wild-type cases, patients with concomitant PIK3CA mutations in exons 9 and 20 experienced significantly worse cancer-specific survival [log-rank P = 0.031; multivariate HR = 3.51; 95% confidence interval (CI): 1.28-9.62] and overall survival (log-rank P = 0.0008; multivariate HR = 2.68; 95% CI: 1.24-5.77). PIK3CA mutation in either exon 9 or 20 alone was not significantly associated with patient survival. No significant interaction of PIK3CA mutation with BRAF or KRAS mutation was observed in survival analysis.

CONCLUSION

Coexistence of PIK3CA (the PI3K p110α subunit) exon 9 and 20 mutations, but not PIK3CA mutation in either exon 9 or 20 alone, is associated with poor prognosis of colorectal cancer patients.

Are KRAS/BRAF mutations potent prognostic and/or predictive biomarkers in colorectal cancers?

KRAS and BRAF mutations lead to the constitutive activation of EGFR signaling through the oncogenic Ras/Raf/Mek/Erk pathway. Currently, KRAS is the only potential biomarker for predicting the efficacy of anti-EGFR monoclonal antibodies (mAb) in colorectal cancer (CRC). However, a recent report suggested that the use of cetuximab was associated with survival benefit among patients with p.G13D-mutated tumors. Furthermore, although the presence of mutated BRAF is one of the most powerful prognostic factors for advanced and recurrent CRC, it remains unknown whether patients with BRAF-mutated tumors experience a survival benefit from treatment with anti-EGFR mAb. Thus, the prognostic or predictive relevance of the KRAS and BRAF genotype in CRC remains controversial despite several investigations. Routine KRAS/BRAF screening of pathological specimens is required to promote the appropriate clinical use of anti-EGFR mAb and to determine malignant phenotypes in CRC. The significance of KRAS/BRAF mutations as predictive or prognostic biomarkers should be taken into consideration when selecting a KRAS/BRAF screening assay. This article will review the spectrum of KRAS/BRAF genotype and the impact of KRAS/BRAF mutations on the clinicopathological features and prognosis of patients with CRC, particularly when differentiating between the mutations at KRAS codons 12 and 13. Furthermore, the predictive role of KRAS/BRAF mutations in treatments with anti-EGFR mAb will be verified, focusing on KRAS p.G13D and BRAF mutations.

BRAF mutations in colorectal cancer are associated with distinct clinical characteristics and worse prognosis

BACKGROUND

Colorectal cancer is a heterogeneous disease with multiple underlying genetic mutations causing different clinical phenotypes. Mutation in the BRAF oncogene is a key step in malignant transformation within the methylator pathway to colorectal cancer. However, there is a paucity of information about BRAF mutant colorectal tumors.

OBJECTIVE

This study defines the clinical characteristics and oncologic outcome associated with colorectal cancer BRAF mutations.

DESIGN

Colorectal adenocarcinomas from a single-institution frozen-tumor biobank were studied. Genomic DNA was isolated and analyzed for mutations in the BRAF oncogene by polymerase chain reaction amplification followed by direct sequencing. A sample was classified as mutant if any of the tested loci were mutated. Patient and tumor characteristics were recorded including patient age, sex, tumor location, tumor differentiation, and microsatellite instability.

MAIN OUTCOME MEASURES

Statistical associations with BRAF mutant tumors were determined by the Fisher exact probability test, χ test, or Wilcoxon analysis. Kaplan-Meier estimates and multivariate Cox regression analysis were performed for overall survival.

RESULTS

Four hundred seventy-five colorectal adenocarcinomas were included in the study population; 56 samples harbored a BRAF mutation (12%). There were significant differences between BRAF wild-type and mutant tumors in age (66 vs 75 years, p = 0.004), female sex (44% vs 71%, p < 0.001), proximal tumor location (44% vs 95%, p < 0.001), and frequency of microsatellite instability (16% vs 76%, p < 0.001). There was no difference in cancer stage between BRAF mutant and wild-type populations. Survival data were analyzed for 322 patients with stage I to III disease, and patients with a BRAF mutation had decreased overall survival than those without a mutation (p = 0.018). With the use of Cox regression analysis, BRAF mutation conferred a worse overall survival (HR 1.79, CI 1.05-3.05, p = 0.03) independent of microsatellite instability status.

CONCLUSIONS

BRAF mutations in colorectal cancers are associated with distinct clinical characteristics and worse prognosis.

Predictive and prognostic roles of BRAF mutation in stage III colon cancer: results from intergroup trial CALGB 89803

PURPOSE

Alterations in the RAS-RAF-MAP2K (MEK)-MAPK signaling pathway are major drivers in colorectal carcinogenesis. In colorectal cancer, BRAF mutation is associated with microsatellite instability (MSI), and typically predicts inferior prognosis. We examined the effect of BRAF mutation on survival and treatment efficacy in patients with stage III colon cancer.

METHODS

We assessed status of BRAF c.1799T>A (p.V600E) mutation and MSI in 506 stage III colon cancer patients enrolled in a randomized adjuvant chemotherapy trial [5-fluorouracil and leucovorin (FU/LV) vs. irinotecan (CPT11), FU and LV (IFL); CALGB 89803]. Cox proportional hazards model was used to assess the prognostic role of BRAF mutation, adjusting for clinical features, adjuvant chemotherapy arm, and MSI status.

RESULTS

Compared with 431 BRAF wild-type patients, 75 BRAF-mutated patients experienced significantly worse overall survival [OS; log-rank P = 0.015; multivariate HR = 1.66; 95% CI: 1.05-2.63]. By assessing combined status of BRAF and MSI, it seemed that BRAF-mutated MSS (microsatellite stable) tumor was an unfavorable subtype, whereas BRAF wild-type MSI-high tumor was a favorable subtype, and BRAF-mutated MSI-high tumor and BRAF wild-type MSS tumor were intermediate subtypes. Among patients with BRAF-mutated tumors, a nonsignificant trend toward improved OS was observed for IFL versus FU/LV arm (multivariate HR = 0.52; 95% CI: 0.25-1.10). Among patients with BRAF wild-type cancer, IFL conferred no suggestion of benefit beyond FU/LV alone (multivariate HR = 1.02; 95% CI: 0.72-1.46).

CONCLUSIONS

BRAF mutation is associated with inferior survival in stage III colon cancer. Additional studies are necessary to assess whether there is any predictive role of BRAF mutation for irinotecan-based therapy.

Targeted therapies and predictive markers in epithelial malignancies of the gastrointestinal tract

CONTEXT

In recent years, there has been a tremendous amount of interest in the development of targeted therapies for the treatment of human cancers. Increased understanding of the specific molecular pathways and driver mutations critical to cancer cell growth have allowed the development of these advanced therapeutics. Among these, inhibitors of the epidermal growth factor receptor and HER2/neu pathways now play a major role in the management of gastrointestinal cancers in addition to other solid malignancies. In colorectal and gastric cancers, the use of epidermal growth factor receptor inhibitors and HER2/neu inhibitors has increased the available treatment options for patients with advanced disease.

OBJECTIVE

To focus on the current targeted therapies and predictors of response in malignancies of the gastrointestinal tract.

DATA SOURCES

Medical literature searchable on PubMed (US National Library of Medicine) as well as older studies revealed by the literature review were used as the source of data.

CONCLUSION

Gene testing of critical elements of the pathways targeted by these agents (such as KRAS mutational analysis in colorectal tumors and HER2/neu testing in gastric cancers) allows the ability to predict which patients will respond to these treatments. As the molecular profiling of tumors and our understanding of cancer genomics and epigenetic alterations continues to grow, it is expected that these personalized targeted therapies will form one of the mainstays of gastrointestinal cancer treatment.

Review of biomarkers in colorectal cancer

AIM

Advances in molecular technology have resulted in the discovery of many putative biomarkers relevant to colorectal cancer (CRC).

METHOD

Literature searches were performed on PubMed and EMBASE using the words 'colorectal cancer', AND 'biomarkers OR markers'. Biomarkers that are either currently in clinical use or have potential clinical use were identified.

RESULTS

Most potential markers are in the discovery phase waiting to undergo clinical validation. Hypermethylation of the plasma septin-9 gene shows promise as a nonstool-based screening tool. Hypermethylation of the DYPD gene (encodes the enzyme dihydropyrimidine dehydrogenase) and variation of the uridine diphosphate-glucuronosyltransferase 1A (UGT1A1) gene have predictive value for side effects and the efficacy of 5-fluoruracil and irinotecan, respectively. Mismatch repair protein immunohistochemistry is able to predict response to 5-fluorouracil, and the KRAS (Kirsten rat sarcoma viral oncogene) and B-RAF (v-RAF murine sarcoma viral oncogene homolog B1) somatic gene mutation status can predict the response to anti-epidermal growth factor receptor therapy.

CONCLUSION

Recent advances indicate that the widespread use of biomarkers may herald the next major advance in the diagnosis and management of CRC.

Differences in the frequencies of K-ras c12-13 genotypes by gender and pathologic phenotypes in colorectal tumors measured using the allele discrimination method

The frequencies of different genotypes of the K-ras oncogene in colorectal cancer (CRC) reveal complex relationships among gender, age, and tumor aggression, however, differences among these studies could also be attributed to a lack of standardization of the detection methods used. We developed the allele discrimination assay, which uses dual-color real-time polymerase chain reaction (qPCR) as a fast K-ras genotyping method, and demonstrated higher sensitivity and specificity than DNA sequencing with formalin-fixed paraffin tissues. The assay detected K-ras mutations among 83 of 204 patients with CRC (40.7%); 20.6% of these mutations were G12D (GAT) mutations, 7.4% were G13D (GAC) and G12V (GTT), and 5.3% were other types. A higher proportion of females was observed overall in tumors with K-ras mutations (60.2%, P = 0.01), codon 12 mutations (63.2%, P = 0.005), and transversions (69.6%, P = 0.02), which reflected the higher prevalence of females among the well- to moderately differentiated tumors (29% in males vs. 53% in females; interaction P = 0.03). The opposite was observed for poorly differentiated tumors (47% in males vs. 35% in females). No significant influence of age was found on the prevalence of K-ras mutation. Males with pathological changes and females with poorly differentiated tumors displayed GAT as a less common genotype compared with most other prevalence studies. In conclusion, allele discrimination, with no additional amplification step, is a fast and reliable genotyping method for detecting K-ras c12-13 mutations. Using this method, we demonstrate differences in the frequencies of K-ras genotypes by gender and pathologic phenotypes of CRC.

Targeting oncogenic serine/threonine-protein kinase BRAF in cancer cells inhibits angiogenesis and abrogates hypoxia

Carcinomas are comprised of transformed epithelial cells that are supported in their growth by a dedicated neovasculature. How the genetic milieu of the epithelial compartment influences tumor angiogenesis is largely unexplored. Drugs targeted to mutant cancer genes may act not only on tumor cells but also, directly or indirectly, on the surrounding stroma. We investigated the role of the BRAF(V600E) oncogene in tumor/vessel crosstalk and analyzed the effect of the BRAF inhibitor PLX4720 on tumor angiogenesis. Knock-in of the BRAF(V600E) allele into the genome of human epithelial cells triggered their angiogenic response. In cancer cells harboring oncogenic BRAF, the inhibitor PLX4720 switches off the ERK pathway and inhibits the expression of proangiogenic molecules. In tumor xenografts harboring the BRAF(V600E), PLX4720 extensively modifies the vascular network causing abrogation of hypoxia. Overall, our results provide a functional link between oncogenic BRAF and angiogenesis. Furthermore, they indicate how the tumor vasculature can be "indirectly" besieged through targeting of a genetic lesion to which the cancer cells are addicted.

PIK3CA exon 20 mutations as a potential biomarker for resistance to anti-EGFR monoclonal antibodies in KRAS wild-type metastatic colorectal cancer: a systematic review and meta-analysis

BACKGROUND

We conducted a systematic review and meta-analysis to dissect the association between PIK3CA mutations and resistance to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs) according to PIK3CA exon of mutations in metastatic colorectal cancer (mCRC).

METHODS

We systematically identified studies exploring the association between PIK3CA mutations and clinical outcomes of mCRC patients treated with anti-EGFR MoAbs. The primary clinical outcomes included objective response rate (ORR), progression-free survival (PFS), and overall survival (OS). The pooled relative risk (RR) or hazard ratio (HR) was estimated by using fixed effect model or random effect model according to heterogeneity between studies.

RESULTS

Thirteen studies were considered eligible, with 576 mCRC patients included. In KRAS wild-type mCRC patients, we observed a lower ORR in patients with PIK3CA exon 20 mutations [3 studies, 377 patients; ORR = 0% versus 37%; RR = 0.25; 95% confidence interval (CI) 0.05-1.19; P = 0.082], although the result was not statistically significant because of the small sample size. Only one study provided survival data according to the PIK3CA exon of the mutations, in which PIK3CA exon 20 mutations were statistically significantly associated with shorter PFS (HR = 2.52; 95% CI 1.33-4.78; P = 0.013) and OS (HR = 3.29; 95% CI 1.60-6.74; P = 0.006) in KRAS wild-type mCRC patients treated with anti-EGFR MoAbs. The predictive power of exon 20 mutation is greater than exon 9 mutations and all exons mutations in terms of ORR, PFS, and OS.

CONCLUSION

These analyses suggest that PIK3CA exon 20 mutations may be a potential biomarker for resistance to anti-EGFR MoAbs in KRAS wild-type mCRC.

What can the molecular pathologist offer for optimal decision making?

As a consequence of new innovative therapies and therapeutic combinations, the treatment of advanced colorectal cancer is becoming increasingly complex. Validated molecular biomarkers could contribute to patient management, but until recently, none has been routinely used. With the recognition that activating mutations of the KRAS oncogene can predict resistance to anti-epidermal growth factor receptor agents, the clinical value of biomarkers in advanced colorectal cancer has been brought to the fore. Prognostic and predictive biomarkers that reflect the molecular and therapeutic complexities of advanced colorectal cancer may provide valuable information regarding likely clinical outcome and therapeutic response and thus may improve patient management and therapeutic agent selection. Such biomarkers are discussed herein.

Impact of BRAF mutation and microsatellite instability on the pattern of metastatic spread and prognosis in metastatic colorectal cancer

BACKGROUND

It is hypothesized that BRAF mutant cancers represent a discrete subset of metastatic colorectal cancer (CRC) defined by poorer survival. This study investigates whether BRAF mutant CRC is further defined by a distinct pattern of metastatic spread and explores the impact of BRAF mutation and microsatellite instability (MSI) on prognosis in metastatic CRC.

METHODS

By using prospective clinical data and molecular analyses from 2 major centers (Royal Melbourne Hospital and The University of Texas MD Anderson Cancer Center), patients with known BRAF mutation status were analyzed for clinical characteristics, survival, and metastatic sites.

RESULTS

The authors identified 524 metastatic CRC patients where BRAF mutation status was known; 57 (11%) were BRAF mutant tumors. BRAF mutant tumors were significantly associated with right-sided primary tumor, MSI, and poorer survival (median, 10.4 months vs 34.7 months, P < .001). A distinct pattern of metastatic spread was observed in BRAF mutant tumors, namely higher rates of peritoneal metastases (46% vs 24%, P = .001), distant lymph node metastases (53% vs 38%, P = .008), and lower rates of lung metastases (35% vs 49%, P = .049). In additional survival analyses, MSI tumors had significantly poorer survival compared with microsatellite stable tumors (22.1 months vs 11.1 months, P = .017), but this difference was not evident in the BRAF mutant population.

CONCLUSIONS

The pattern of metastatic spread observed in this study further defines BRAF mutant CRC as a discrete disease subset. The authors demonstrated that, unlikely early stage disease, MSI is associated with poorer survival in metastatic CRC, although this is driven by its association with BRAF mutation.

Whole cancer genome sequencing by next-generation methods

Traditional approaches to sequence analysis are widely used to guide therapy for patients with lung and colorectal cancer and for patients with melanoma, sarcomas (eg, gastrointestinal stromal tumor), and subtypes of leukemia and lymphoma. The next-generation sequencing (NGS) approach holds a number of potential advantages over traditional methods, including the ability to fully sequence large numbers of genes (hundreds to thousands) in a single test and simultaneously detect deletions, insertions, copy number alterations, translocations, and exome-wide base substitutions (including known "hot-spot mutations") in all known cancer-related genes. Adoption of clinical NGS testing will place significant demands on laboratory infrastructure and will require extensive computational expertise and a deep knowledge of cancer medicine and biology to generate truly useful "clinically actionable" reports. It is anticipated that continuing advances in NGS technology will lower the overall cost, speed the turnaround time, increase the breadth of genome sequencing, detect epigenetic markers and other important genomic parameters, and become applicable to smaller and smaller specimens, including circulating tumor cells and circulating free DNA in plasma.

Biomarker-based selection of therapy for colorectal cancer

Colorectal cancer (CRC) has been re-classified based on molecular analyses of various genes and proteins capable of separating morphologic types of tumors into molecular categories. The diagnosis and management of CRC has evolved with the discovery and validation of a wide variety of biomarkers designed to facilitate a personalized approach for the treatment of the disease. In addition, a number of new prognostic and predictive individual genes and proteins have been discovered that are designed to reflect the sensitivity and/or resistance of CRC to existing therapies. Multigene predictors have also been developed to predict the risk of relapse for intermediate-stage CRC after completion of surgical resection. Finally, a number of biomarkers have been proposed as specific predictors of chemotherapy and radiotherapy response and, in some instances, drug toxicity. In this article, a series of novel biomarkers are considered and compared with standard-of-care markers for their potential use as pharmacogenomic and pharmacogenetic predictors of disease outcome.

Comprehensive next-generation cancer genome sequencing in the era of targeted therapy and personalized oncology

DNA sequence analysis has become a significant laboratory test in oncology, permitting treatment to become increasingly personalized for both solid tumors and hematologic malignancies. Traditional approaches to sequence analysis, including Sanger sequencing, pyrosequencing and allele-specific PCR, are now widely used to guide therapy for patients diagnosed with lung and colorectal cancer as well as for melanoma, sarcomas (e.g., gastrointestinal stromal tumors) and subtypes of leukemia and lymphoma. Traditional sequence analysis has been limited in bandwidth and throughput and as a result, has been focused exclusively on testing the most common aberrations in key genes or fully sequencing single genes. The massively parallel or next-generation sequencing (NGS) approach to DNA analysis holds a number of potential advantages over the traditional methods, including the ability to fully sequence large numbers of genes (hundreds to thousands) in a single test. Furthermore, NGS can simultaneously detect deletions, insertions, copy number alterations, translocations and exome-wide base substitutions (including known hot-spot mutations) in all known cancer-related genes. However, significant challenges, particularly with respect to demands on expertise and infrastructure, will have to be overcome to translate NGS to the bedside of the cancer patient. Extensive computational expertise is required to bring NGS into clinical context, and a deep knowledge of cancer medicine and cancer biology will be required to generate truly useful, so-called 'clinically actionable' reports for clinicians. While NGS is on the cusp of being launched as a clinical test, it may be expected that the near future will continue to bring major advances in the technology that will lower the overall cost, speed up the turnaround time, increase the breadth of genome sequencing, and detect epigenetic markers and other important genomic parameters, while becoming applicable to smaller and smaller specimens, including circulating tumor cells and circulating free DNA in plasma.

Panitumumab in combination with cytotoxic chemotherapy for the treatment of metastatic colorectal carcinoma

The fully human anti-epidermal growth factor receptor (EGFR) monoclonal antibody panitumumab has been shown to improve progression-free survival when administered as a monotherapy for patients with chemotherapy-refractory metastatic colorectal cancer (mCRC) and is approved in this setting. Two large randomized clinical trials have investigated panitumumab in combination with 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) as a first-line therapy for mCRC and 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) as a second-line therapy for mCRC. In these studies, the combination of panitumumab with FOLFOX or FOLFIRI resulted in improved progression-free survival compared with FOLFOX or FOLFIRI alone. Improved tumor response was also observed with the addition of panitumumab to FOLFIRI. As in monotherapy trials, the clinical benefits associated with panitumumab treatment were confined to patients with wild-type KRAS tumors, further showing the validity of KRAS mutational status as a predictive biomarker in mCRC. In addition to KRAS mutational status, a number of other potential predictive biomarkers are currently being investigated in mCRC and may eventually help identify patients who are likely to benefit from treatment with anti-EGFR monoclonal antibodies. Toxicities observed during treatment with panitumumab combined with FOLFOX or FOLFIRI were generally manageable and commonly included skin toxicities and gastrointestinal toxicities. Because it can lead to dose delays, dose reductions, and discontinuation, physicians and patients should carefully manage skin toxicity. Overall, the results of these two studies show that panitumumab improves outcomes when added to FOLFOX or FOLFIRI among patients with mCRC with wild-type KRAS.

Cancer immunology--analysis of host and tumor factors for personalized medicine

Immune cells in the tumor microenvironment have an important role in regulating tumor progression. Therefore, stimulating immune reactions to tumors can be an attractive therapeutic and prevention strategy. Cancer cells and host cells constantly interact with each other in the tumor microenvironment; thus, cancer immunology is an interdisciplinary area where integrated analysis of both host and tumor factors is needed. Cancer represents a heterogeneous group of diseases with different genetic and epigenetic alterations; therefore, molecular classification of cancer (for example lung, prostate and breast cancers) is an important component in clinical decision making. However, most studies on antitumor immunity and clinical outcome lack analysis of tumor molecular biomarkers. In this Review, we discuss colorectal cancer as a prototypical example of cancer. Common molecular classifiers of colon cancer include KRAS, BRAF and PIK3CA mutations, microsatellite instability, LINE-1 methylation, and CpG island methylator phenotype. Since tumor molecular features and immune reactions are inter-related, a comprehensive assessment of these factors is critical. Examining the effects of tumor-host interactions on clinical outcome and prognosis represents an evolving interdisciplinary field of molecular pathological epidemiology. Pathological immunity evaluation may provide information on prognosis and help identify patients who are more likely to benefit from immunotherapy.

KRAS and BRAF mutation analysis in metastatic colorectal cancer: a cost-effectiveness analysis from a Swiss perspective

PURPOSE

Monoclonal antibodies against the epidermal growth factor receptor (EGFR), such as cetuximab, have led to significant clinical benefits for metastatic colorectal cancer (mCRC) patients but have also increased treatment costs considerably. Recent evidence associates KRAS and BRAF mutations with resistance to EGFR antibodies. We assessed the cost-effectiveness of predictive testing for KRAS and BRAF mutations, prior to cetuximab treatment of chemorefractory mCRC patients.

EXPERIMENTAL DESIGN

A life-long Markov simulation model was used to estimate direct medical costs (€) and clinical effectiveness [quality-adjusted life-years (QALY)] of the following strategies: KRAS testing, KRAS testing with subsequent BRAF testing of KRAS wild-types (KRAS/BRAF), cetuximab treatment without testing. Comparison was against no cetuximab treatment (reference strategy). In the testing strategies, cetuximab treatment was initiated if no mutations were detected. Best supportive care was given to all patients. Survival times/utilities were derived from published randomized clinical trials. Costs were assessed from the perspective of the Swiss health system.

RESULTS

Average remaining lifetime costs ranged from €3,983 (no cetuximab) to €38,662 (no testing). Cetuximab treatment guided by KRAS/BRAF achieved gains of 0.491 QALYs compared with the reference strategy. The KRAS testing strategy achieved an additional gain of 0.002 QALYs compared with KRAS/BRAF. KRAS/BRAF testing was the most cost-effective approach when compared with the reference strategy (incremental cost-effectiveness ratio: €62,653/QALY).

CONCLUSION

New predictive tests for KRAS and BRAF status are currently being introduced in pathology. Despite substantial costs of predictive testing, it is economically favorable to identify patients with KRAS and BRAF wild-type status.

Molecular predictors of response to chemotherapy in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer mortality worldwide. In the last decade, median overall survival has increased significantly with the introduction of new cytotoxics and biologic therapies. Notably, the definition of molecular markers predicting benefit with epidermal growth factor receptor (EGFR)-targeted agents has led to important advances in the personalized treatment of CRC. Data derived from multiple phase III trials have indicated that KRAS mutations can be considered a highly specific negative biomarker of response to anti-EGFR monoclonal antibodies. The predictive value of additional mutations and deregulations of the signaling pathways downstream of the EGFR such as BRAF, NRAS, PIK3CA, or PTEN is under intensive investigation. In addition, status of microsatellite instability and molecular markers related to the metabolism of chemotherapy agents has shown promising ability to select patients with higher chances of response to cytotoxic agents. Although attempts to identify predictive factors for efficacy to antiangiogenic therapies have been disappointing, further research on this field will maximize their therapeutic index. Determination of molecular predictive factors before selection of chemotherapy is rapidly approaching us to the paradigm of individualized treatment of CRC.

Concordance of predictive markers for EGFR inhibitors in primary tumors and metastases in colorectal cancer: a review

BACKGROUND

Currently, only Kirsten rat sarcoma 2 viral oncogene homolog (KRAS) mutational status is used as a decisional marker for epidermal growth factor receptor (EGFR) inhibitor therapy in colorectal cancer (CRC) patients. Concordance of KRAS status between primary tumors and metastases has always been considered to be close to perfect; however, cases of discordance have been reported. The actual rate of concordance of KRAS status remains unclear, as is the same for v-raf murine sarcoma viral oncogene homolog B1 (BRAF), phosphatidylinositol 3-kinase CA subunit (PIK3CA), and loss of phosphatase and tensin homologue deleted on chromosome ten (PTEN). Therefore, it is unknown whether it is necessary to perform mutational analysis on metastases instead of on (or in addition to) primary tumors.

DESIGN

A systematic literature search was conducted to collect all studies testing concordance of KRAS in CRC, and also of BRAF, PIK3CA, and loss of PTEN.

RESULTS

Twenty-one studies have reported concordance of KRAS, with an overall concordance rate of 93% (range, 76%-100%). Overall concordance rates of studies testing concordance of BRAF status and loss of PTEN were 98% and 68%, respectively. Three studies reported concordance of PIK3CA status (range, 89%-94%).

CONCLUSION

Though discordance of KRAS status does occur, it is uncommon. When considering the downsides of testing metastatic tissue in all patients along with the low incidence of discordance, we conclude that that testing the primary tumor (or whatever tissue available) is sufficient for clinical decision making on EGFR inhibitor therapy.

Cetuximab and panitumumab in KRAS wild-type colorectal cancer: a meta-analysis

BACKGROUND

Anti-epidermal growth factor receptor monoclonal antibodies (panitumumab [P] and cetuximab [C]) are approved and effective only in KRAS wild-type patients with advanced colorectal cancer. The purpose of our meta-analysis is to evaluate the real effects of C and P in KRAS wild-type patients treated in randomized trials.

PATIENTS AND METHODS

Eligible studies included prospective, randomized, and controlled trials in which either C or P had been added to standard antineoplastic therapy or best supportive care and data for KRAS wild-type patients only had been calculated. Six thousand three hundred ninety-five patients' tumor samples have been analyzed (total wild-type n = 3,254; experimental arm n = 1,608; control arm n = 1,646). Relative risks (RRs) with 95% confidence intervals (CIs) for response rate were calculated, as well as hazard ratios (HRs)for progression-free survival (PFS) and overall survival.

RESULTS

The overall RR of response rate is 1.69 (p = 0.003) in all trials. The overall HRs for PFS and survival are 0.65 (p = 0.0006) and 0.84 (p = 0.03), respectively, and both are significant. The HRs for PFS and survival in C trials are 0.64 and 0.79, respectively, and 0.65 and 0.87, respectively, in P trials, although only the results achieved in P trials are significant (p = 0.0007 and p = 0.03). Both response rate (RR = 10.94) and PFS (HR = 0.51) have increased more in pretreated patients than in first-line trials.

CONCLUSION

The addition of anti-EGFR monoclonal antibodies to standard anticancer therapy in KRAS wild-type colorectal cancer showed an overall significantly increased risk of objective response rate and increased progression-free and overall survival. Only the results achieved in P randomized trials are significant, and the strongest results have been achieved in pretreated patients.

Targeting PI3K signaling as a therapeutic approach for colorectal cancer

Survival times of patients with colorectal cancer (CRC) have increased over the past decade, primarily as a result of treatment with combinations of conventional cytotoxic agents. Because CRC is commonly associated with mutations in genes that control growth factor signaling, therapies are being developed to target the products of these genes; individualized treatment might also be guided by specific mutations in tumors and by new biomarkers. Currently, targeted therapies confer limited clinical benefit; better drugs are therefore needed. Genomic studies indicate that phosphoinositide 3-kinase (PI3K) signaling is one of the most frequently deregulated pathways in several human cancers, including CRC. PI3K signaling has an important role in cancer cell proliferation, survival, motility, and metabolism and therefore could be an attractive therapeutic target. We review PI3K signaling in CRC and discuss current therapeutic approaches.

Review of histopathological and molecular prognostic features in colorectal cancer

Prediction of prognosis in colorectal cancer is vital for the choice of therapeutic options. Histopathological factors remain paramount in this respect. Factors such as tumor size, histological type and subtype, presence of signet ring morphology and the degree of differentiation as well as the presence of lymphovascular invasion and lymph node involvement are well known factors that influence outcome. Our understanding of these factors has improved in the past few years with factors such as tumor budding, lymphocytic infiltration being recognized as important. Likewise the prognostic significance of resection margins, particularly circumferential margins has been appreciated in the last two decades. A number of molecular and genetic markers such as KRAS, BRAF and microsatellite instability are also important and correlate with histological features in some patients. This review summarizes our current understanding of the main histopathological factors that affect prognosis of colorectal cancer.

Low frequency of PIK3CA gene mutations in hepatocellular carcinoma in Chinese population

PI3K/AKT constitutes an important pathway regulating the signaling of multiple biological processes and plays a critical role in carcinogenesis. PIK3CA gene missense mutations have been reported in many human cancer types. The mutation of it in hepatocellular carcinoma cases varies with different races and regions. In this study, we investigated PIK3CA mutation in Chinese hepatocellular carcinoma patients. A total 90 Chinese patients of hepatocellular carcinoma were recruited in this study. Exons 9 and 20 hotspots mutations of PIK3CA gene were detected by PCR-based DNA sequencing. Two point mutations (E542K and D549H) in exon 9 were found in only one patient (1/90; 1.11%), no mutation was found in exon 20 in any cases. 57 patients are associated with HBV infection (57/90; 63.3%), and 8 patients with HCV infection (8/90; 8.9%). The frequency of the PIK3CA mutations in hepatocellular carcinoma seems to be lower in Chinese hepatocellular carcinoma patients. These findings suggest that PI3K mutations may not play a major role in hepatic carcinogenesis in Chinese. HBV infection has close relationship with HCC in Chinese.

Impact of KRAS and BRAF Gene Mutation Status on Outcomes From the Phase III AGITG MAX Trial of Capecitabine Alone or in Combination With Bevacizumab and Mitomycin in Advanced Colorectal Cancer

PURPOSE

Mutations affecting the KRAS gene are established predictive markers of outcome with anti-epithelial growth factor receptor (EGFR) antibodies in advanced colorectal cancer (CRC). The relevance of these markers for anti-vascular endothelial growth factor (VEGF) therapy is controversial. This analysis was performed to assess the predictive and prognostic impact of KRAS and BRAF gene mutation status in patients receiving capecitabine with bevacizumab (CG) or capecitabine without bevacizumab in the phase III AGITG MAX (Australasian Gastrointestinal Trials Group MAX) study.

PATIENTS AND METHODS

Mutation status was determined for 315 (66.9%) of the original 471 patients. Mutation status was correlated with efficacy outcomes (response rate, progression-free survival [PFS], and overall survival [OS]), and a predictive analyses was undertaken.

RESULTS

Mutations in KRAS and BRAF genes were observed in 28.8% and 10.6% of patients, respectively. KRAS gene mutation status (wild type [WT] v mutated [MT]) had no prognostic impact for PFS (hazard ratio [HR], 0.89; CI, 0.69 to 1.14) or OS (HR, 0.97; CI, 0.73 to 1.28). BRAF mutation status (WT v MT) was not prognostic for PFS (HR, 0.80; CI, 0.54 to 1.18) but was prognostic for OS (HR, 0.49; CI, 0.33 to 0.73; P = .001). By using the comparison of capecitabine versus capecitabine and bevacizumab (CB) and CB plus mitomycin (CBM), KRAS gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .95 and 0.43, respectively). Similarly, BRAF gene mutation status was not predictive of the effectiveness of bevacizumab for PFS or OS (test for interaction P = .46 and 0.32, respectively).

CONCLUSION

KRAS gene mutation status was neither prognostic for OS nor predictive of bevacizumab outcome in patients with advanced CRC. BRAF gene mutation status was prognostic for OS but was not predictive of outcome with bevacizumab.

Cetuximab Plus Irinotecan, Fluorouracil, and Leucovorin As First-Line Treatment for Metastatic Colorectal Cancer: Updated Analysis of Overall Survival According to Tumor KRAS and BRAF Mutation Status

Purpose

The addition of cetuximab to irinotecan, fluorouracil, and leucovorin (FOLFIRI) as first-line treatment for metastatic colorectal cancer (mCRC) was shown to reduce the risk of disease progression and increase the chance of response in patients with KRAS wild-type disease. An updated survival analysis, including additional patients analyzed for tumor mutation status, was undertaken.

Patients and Methods

Patients were randomly assigned to receive FOLFIRI with or without cetuximab. DNA was extracted from additional slide-mounted tumor samples previously used to assess epidermal growth factor receptor expression. Clinical outcome according to the tumor mutation status of KRAS and BRAF was assessed in the expanded patient series.

Results

The ascertainment rate of patients analyzed for tumor KRAS status was increased from 45% to 89%, with mutations detected in 37% of tumors. The addition of cetuximab to FOLFIRI in patients with KRAS wild-type disease resulted in significant improvements in overall survival (median, 23.5 v 20.0 months; hazard ratio [HR], 0.796; P = .0093), progression-free survival (median, 9.9 v 8.4 months; HR, 0.696; P = .0012), and response (rate 57.3% v 39.7%; odds ratio, 2.069; P < .001) compared with FOLFIRI alone. Significant interactions between KRAS status and treatment effect were noted for all key efficacy end points. KRAS mutation status was confirmed as a powerful predictive biomarker for the efficacy of cetuximab plus FOLFIRI. BRAF tumor mutation was a strong indicator of poor prognosis.

Conclusion

The addition of cetuximab to FOLFIRI as first-line therapy improves survival in patients with KRAS wild-type mCRC. BRAF tumor mutation is an indicator of poor prognosis.