Prognostic Value of BRAF, PI3K, PTEN, EGFR Copy Number, Amphiregulin and Epiregulin Status in Patients with KRAS Codon 12 Wild-Type Metastatic Colorectal Cancer Receiving First-Line Chemotherapy with Anti-EGFR Therapy

Colorectal Cancer: From Genetic Landscape to Targeted Therapy

Colorectal cancer (CRC) is the third most common cancer type and the second cause of death worldwide. The advancement in understanding molecular pathways involved in CRC has led to new classifications based on the molecular characteristics of each tumor and also improved CRC management through the integration of targeted therapy into clinical practice. In this review, we will present the main molecular pathways involved in CRC carcinogenesis, the molecular classifications. The anti-VEGF and anti-EGFR therapies currently used in CRC treatment and those under clinical investigation will also be outlined, as well as the mechanisms of primary and acquired resistance to anti-EGFR monoclonal antibodies (cetuximab and panitumumab). Targeted therapy has led to great improvement in the treatment of metastatic CRC. However, there has been variability in CRC treatment outcomes due to molecular heterogeneity in colorectal tumors, which underscores the need for identifying prognostic and predictive biomarkers for CRC-targeted drugs.

Amphiregulin Expression Is a Predictive Biomarker for EGFR Inhibition in Metastatic Colorectal Cancer: Combined Analysis of Three Randomized Trials

PURPOSE

Amphiregulin (AREG) and epiregulin (EREG) are ligands of EGFR. Predictive information for anti-EGFR treatment in metastatic colorectal cancer (mCRC) was observed, but data for other agents is limited.

EXPERIMENTAL DESIGN

Ligand mRNA expression; RAS, BRAF, PIK3CA mutations; and EGFR expression were assessed by qRT-PCR, pyrosequencing, and IHC, respectively, in mCRC tumor tissue of patients participating in the randomized controlled trials FIRE-1, CIOX, and FIRE-3. Normalized mRNA expression was dichotomized using median and third quartile. Overall (OS) and progression-free survival (PFS) were estimated by Kaplan-Meier method including univariate and multivariate Cox regression analyses. Penalized spline regression analysis tested interaction of mRNA expression and outcome.

RESULTS

Of 688 patients with available material, high AREG expression was detected in 343 (>median) and 172 (>3rd quartile) patients. High AREG expression was associated with significantly higher OS [26.2 vs. 21.5 months, HR = 0.80; 95% confidence interval (CI), 0.68-0.94; P = 0.007], PFS (10.0 vs. 8.1 months, HR = 0.74; 95% CI, 0.63-0.86; P = 0.001), and objective response rate (63.1% vs. 51.6%, P = 0.004) compared to low expression at both threshold values. This effect remained significant in multivariate Cox regression analysis (OS: P = 0.01, PFS: P = 0.002). High AREG mRNA expression interacted significantly with the efficacy of cetuximab compared with bevacizumab (OS: P = 0.02, PFS: P = 0.04) in RAS WT mCRC.

CONCLUSIONS

High AREG mRNA expression is a favorable prognostic biomarker for mCRC which interacted significantly with efficacy of anti-EGFR treatment.

Anti-EGFR therapy in metastatic colorectal cancer: mechanisms and potential regimens of drug resistance

Cetuximab and panitumumab, as the highly effective antibodies targeting epidermal growth factor receptor (EGFR), have clinical activity in the patients with metastatic colorectal cancer (mCRC). These agents have good curative efficacy, but drug resistance also exists at the same time. The effects of KRAS, NRAS, and BRAF mutations and HER2 amplification on the treatment of refractory mCRC have been elucidated and the corresponding countermeasures have been put forward. However, the changes in EGFR and its ligands, the mutations or amplifications of PIK3CA, PTEN, TP53, MET, HER3, IRS2, FGFR1, and MAP2K1, the overexpression of insulin growth factor-1, the low expression of Bcl-2-interacting mediator of cell death, mismatch repair-deficient, and epigenetic instability may also lead to drug resistance in mCRC. Although the emergence of drug resistance has genetic or epigenetic heterogeneity, most of these molecular changes relating to it are focused on the key signaling pathways, such as the RAS/RAF/mitogen-activated protein kinase or phosphatidylinositol 3-kinase/Akt/mammalian target of the rapamycin pathway. Accordingly, numerous efforts to target these signaling pathways and develop the novel therapeutic regimens have been carried out. Herein, we have reviewed the underlying mechanisms of the resistance to anti-EGFR therapy and the possible implications in clinical practice.

Prognostic value of molecular biomarkers in patients with metastatic colorectal cancer: a real-world study

PURPOSE

Outcomes for patients with metastatic colorectal cancer (mCRC) have been improved by the identification of biomarkers predictive and prognostic of clinical outcome. The present retrospective analysis was undertaken to assess the utility of key biomarkers and clinical parameters in predicting outcomes in Spanish patients with mCRC.

METHODS

We retrospectively analyzed tumor samples from a series of patients aged > 18 years with mCRC who were treated at the Hospital General Universitario Gregorio Marañón Spain. Real-time polymerase chain reaction was used to detect KRAS, NRAS, BRAF, and PIK3CA mutations. The key outcome of interest was overall survival (OS). Survival curves were estimated using the Kaplan-Meier method and stratified by the variables of greatest clinical interest. Differences were tested using the log-rank test.

RESULTS

Median OS in the overall population was 24.4 months. Triple WT patients (WT KRAS, NRAS, and BRAF) and quadruple WT patients (WT KRAS, NRAS, BRAF, and PIK3CA) had significantly better OS than those who did not have triple or quadruple WT tumors. OS was significantly better in patients with left- vs. right-sided tumors, patients with resected primary tumors and metastases vs. those without resection, and patients with isolated hepatic and isolated pulmonary metastases.

CONCLUSIONS

This retrospective, observational study has confirmed the prognostic value of the location and resection status of the primary tumor and metastases in Spanish patients with mCRC. Triple WT status, in particular, was prognostic in this patient population, with PIK3CA adding to the prognostic value in the quadruple WT population.

Consecutive and automatic detection of multi-gene mutations from colorectal cancer samples by coupling droplet array-based capillary electrophoresis and PCR-RFLP

The efficacy of targeted therapy is associated with multi-gene mutation status. Carrying out effective multi-genotyping analysis in combination has been a challenge in clinical settings. We therefore developed a droplet-based capillary electrophoresis (CE) system coupled with PCR-restriction fragment length polymorphism (PCR-RFLP) technology to detect multi-gene mutations from a small volume of samples. A 16 × 16 200-nL droplet array for sample encapsulation was constructed on a glass chip. The electrophoresis system consisted of a tapered vertical capillary filled with polyvinylpyrrolidone, a laser-induced fluorescence detector, and a high voltage power supply. Notably, a droplet-based electrokinetic sample introduction method and a "∩" shape capillary were developed to facilitate consecutive droplet sampling using a home-made automatic control module. The DL2000 DNA marker was consecutively separated, achieving high migration time and plate number reproducibility. The system was further applied to detect PCR-RFLP products. For colorectal cancer (CRC) cell lines, KRAS, BRAF, and PIK3CA were genotyped with a sensitivity of 0.25%. For CRC patient specimens, 30 samples were consecutively and automatically multi-genotyped without inter-sample contamination, with a lowest mutation frequency of 0.37%. For the first time, we developed a droplet-based CE system for consecutive DNA analysis with low sample consumption. This automated CE system could be further developed to integrate the full process of gene mutation detection, serving as a more effective platform for individualised therapy.

Epidermal growth factor receptor ligands: targets for optimizing treatment of metastatic colorectal cancer

The discovery of epidermal growth factor (EGF) and its receptor (EGFR) revealed the connection between EGF-like ligands, signaling from the EGFR family members and cancer. Over the next fifty years, analysis of EGFR expression and mutation led to the use of monoclonal antibodies to target EGFR in the treatment of metastatic colorectal cancer (mCRC) and this treatment has improved outcomes for patients. The use of the RAS oncogene mutational status has helped to refine patient selection for EGFR antibody therapy, but an effective molecular predictor of likely responders is lacking. This review analyzes the potential utility of measuring the expression, levels and activation of EGF-like ligands and associated processes as prognostic or predictive markers for the identification of patient risk and more effective mCRC therapies.

A predictive computational model reveals that GIV/girdin serves as a tunable valve for EGFR-stimulated cyclic AMP signals

Cellular levels of the versatile second messenger cyclic (c)AMP are regulated by the antagonistic actions of the canonical G protein → adenylyl cyclase pathway that is initiated by G-protein–coupled receptors (GPCRs) and attenuated by phosphodiesterases (PDEs). Dysregulated cAMP signaling drives many diseases; for example, its low levels facilitate numerous sinister properties of cancer cells. Recently, an alternative paradigm for cAMP signaling has emerged in which growth factor–receptor tyrosine kinases (RTKs; e.g., EGFR) access and modulate G proteins via a cytosolic guanine-nucleotide exchange modulator (GEM), GIV/girdin; dysregulation of this pathway is frequently encountered in cancers. In this study, we present a network-based compartmental model for the paradigm of GEM-facilitated cross-talk between RTKs and G proteins and how that impacts cellular cAMP. Our model predicts that cross-talk between GIV, Gα_s, and Gα_i proteins dampens ligand-stimulated cAMP dynamics. This prediction was experimentally verified by measuring cAMP levels in cells under different conditions. We further predict that the direct proportionality of cAMP concentration as a function of receptor number and the inverse proportionality of cAMP concentration as a function of PDE concentration are both altered by GIV levels. Taking these results together, our model reveals that GIV acts as a tunable control valve that regulates cAMP flux after growth factor stimulation. For a given stimulus, when GIV levels are high, cAMP levels are low, and vice versa. In doing so, GIV modulates cAMP via mechanisms distinct from the two most often targeted classes of cAMP modulators, GPCRs and PDEs.

The Role of M3 Muscarinic Receptor Ligand-Induced Kinase Signaling in Colon Cancer Progression

Despite a reduction in incidence over the past decade, colon cancer remains the second most common cause of cancer death in the United States; recent demographics suggest this disease is now afflicting younger persons. M₃ muscarinic receptor (M₃R) mRNA and protein are over-expressed in colon cancer, and M₃R can be activated by both traditional (e.g., acetylcholine) and non-traditional (e.g., bile acids) muscarinic ligands. In this review, we weigh the data supporting a prominent role for key protein kinases downstream of M₃R activation in promoting colon cancer progression and dissemination. Specifically, we explore the roles that downstream activation of the mitogen activated protein kinase/extracellular signal-related kinase (MAPK/ERK), protein kinase C, p38 MAPK, and phosphatidylinositol 3-kinase/Akt (PI3K/Akt) pathways play in mediating colon cancer cell proliferation, survival, migration and invasion. We assess the impact of M₃R-stimulated induction of selected matrix metalloproteinases germane to these hallmarks of colon cancer progression. In this context, we also critically review the reproducibility of findings derived from a variety of in vivo and in vitro colon cancer models, and their fidelity to human disease. Finally, we summarize the therapeutic potential of targeting various steps from ligand-M₃R interaction to the activation of key downstream molecules.

Oncologic Outcomes in Metastatic Colorectal Cancer with Regorafenib with FOLFIRI as a Third- or Fourth-Line Setting

BACKGROUND

To evaluate the efficacy and toxicities of regorafenib plus irinotecan, dose-escalated on the basis of uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) genotyping, in previously heavily treated metastatic colorectal cancer (mCRC) and the prognostic values of EGFR expression, KRAS mutations, and tumor sidedness.

METHODS

Forty-one patients with mCRC with disease progression after treatment with fluoropyrimidines, oxaliplatin, irinotecan, anti-VEGF, and anti-EGFR MoAbs were subjected to UGT1A1 genotyping and received regorafenib combined with FOLFIRI with dose-escalated irinotecan.

RESULTS

The median follow-up period was 10.0 months (1.3-23.5 months). The overall disease control rate was 58.5%, whereas the median progression-free survival (PFS) and overall survival (OS) were 6.0 months and 12.0 months, respectively. KRAS mutations were significantly associated with positive EGFR expression (P = .026). KRAS mutations significantly correlated with a shorter OS than KRAS wild-type (6.0 vs. 14.4 months, P = .014) but had no significant association with PFS. Positive EGFR expression had an inverse correlation with PFS (2.5 vs. 14.0 months, P = .039) and OS (9.6 vs. 19.7 months, P = .044). Moreover, left-sided tumors associated with superior PFS (2.0 vs. 7.0 months, P < .0001) and OS (4.0 vs. 13.0 months, P < .0001), and tumor sidedness was an independent prognostic factor by the multivariate analysis.

CONCLUSION

Regorafenib and FOLFIRI concomitant therapy with dose-escalated irinotecan seemed to be potentially practicable with satisfactory oncological results. KRAS mutations and EGFR expression might be predictors of poor oncological outcomes; however, left-sided mCRCs would be more beneficial for concomitant regorafenib and FOLFIRI therapy.

How the BRAF V600E Mutation Defines a Distinct Subgroup of Colorectal Cancer: Molecular and Clinical Implications

The BRAF oncogene is an integral component of the MAP kinase pathway, and an activating V600E mutation occurs in 15% of sporadic colorectal cancer. This is an early event in serrated pathway tumourigenesis, and the BRAF V600E has been commonly associated with the CpG island methylator phenotype, microsatellite instability (MSI), and a consistent clinical presentation including a proximal location and predilection for elderly females. A proportion of the BRAF mutant lesions remain as microsatellite stable (MSS), and in contrast to the MSI cancers, they have an aggressive phenotype and correlate with poor patient outcomes. Recent studies have found that they have clinical and molecular features of both the BRAF mutant/MSI and the conventional BRAF wild-type cancers and comprise a distinct colorectal cancer subgroup. This review highlights the importance of the BRAF mutation occurring in colorectal cancer stratified for molecular background and discusses its prognostic and clinical significance.

Molecular characterization of ERBB2-amplified colorectal cancer identifies potential mechanisms of resistance to targeted therapies: a report of two instructive cases

ERBB2 amplification has been identified in ∼5% of KRAS wild-type colorectal cancers (CRCs). A recent clinical trial showed response to HER2-directed therapy in a subset of ERBB2-amplified metastatic CRCs resistant to chemotherapy and EGFR-directed therapy. With the aim of better understanding mechanisms of resistance to HER2-directed and EGFR-directed therapies, we report the complete molecular characterization of two cases of ERBB2-amplified CRC. PCR-free whole-genome sequencing was used to identify mutations, copy-number alterations, structural variations, and losses of heterozygosity. ERBB2 copy number was also measured by fluorescence in situ hybridization. Single-stranded mRNA sequencing was used for gene expression profiling. Immunohistochemistry and protein mass spectrometry were used to quantify HER2 protein expression. The cases showed ERBB2 copy number of 86 and 92, respectively. Both cases were immunohistochemically positive for HER2 according to CRC-specific scoring criteria. Fluorescence in situ hybridization and protein mass spectrometry corroborated significantly elevated ERBB2 copy number and abundance of HER2 protein. Both cases were microsatellite stable and without mutation of RAS pathway genes. Additional findings included altered expression of PTEN, MET, and MUC1 and mutation of PIK3CA The potential effects of the molecular alterations on sensitivity to EGFR and HER2-directed therapies were discussed. Identification of ERBB2 amplification in CRC is necessary to select patients who may respond to HER2-directed therapy. An improved understanding of the molecular characteristics of ERBB2-amplified CRCs and their potential mechanisms of resistance will be useful for future research into targeted therapies and may eventually inform therapeutic decision-making.

Final Analysis of Outcomes and RAS/BRAF Status in a Randomized Phase 3 Study of Panitumumab and Best Supportive Care in Chemorefractory Wild Type KRAS Metastatic Colorectal Cancer

INTRODUCTION

Tumor rat sarcoma gene (RAS) status is a negative predictive biomarker for anti-epidermal growth factor receptor (EGFR) therapy in metastatic colorectal cancer (mCRC). We analyzed outcomes according to RAS and v-Raf murine sarcoma viral oncogene homolog B (BRAF) mutational status, and evaluated early tumor shrinkage (ETS) and depth of response (DpR) for patients with wild type RAS.

PATIENTS AND METHODS

Patients with confirmed metastatic colon or rectum adenocarcinoma, wild type Kristen rat sarcoma gene tumor exon 2 status, clinical/radiologic disease progression or toxicity during irinotecan or oxaliplatin treatment, and no previous anti-EGFR therapy were randomized 1:1 to receive best supportive care (BSC) with or without panitumumab (6.0 mg/kg, intravenously, on day 1 of each 14-day cycle) in this open-label, multicenter, phase III study (20100007). RAS and BRAF mutation status were determined using Sanger sequencing. ETS was evaluated as maximum percentage change from baseline to week 8; DpR was calculated as the percentage change for tumor shrinkage at nadir versus baseline.

RESULTS

Overall, 270 patients had RAS wild type mCRC (panitumumab with BSC, n = 142; BSC, n = 128). For patients with wild type RAS tumors, median overall survival (OS; hazard ratio [HR], 0.72; P = .015) and progression-free survival (PFS; HR, 0.45; P < .0001) were improved with panitumumab with BSC versus BSC. Similar improvements were seen for patients with wild type RAS, and wild type BRAF tumors (OS: HR, 0.75; P = .04; PFS: HR, 0.45; P < .0001). Median DpR was 16.9% for the evaluable panitumumab with BSC wild type RAS population. Overall, 69.5% experienced any type of tumor shrinkage at week 8; 38.2% experienced ≥ 20% shrinkage. Similar improvements in OS and PFS were seen with stratification according to ETS.

CONCLUSION

This analysis showed that panitumumab improved outcomes in wild type RAS mCRC and indicated that ETS and DpR could be used as additional efficacy markers.

The impact of co-expression of wild-type EGFR and its ligands determined by immunohistochemistry for response to treatment with cetuximab in patients with metastatic colorectal cancer

Anti-EGFR mAbs cetuximab and panitumumab are routinely used for the treatment of patients with KRAS-wild type metastatic colorectal cancer (mCRC). However, in some patients their efficacy remains modest and with no clear association between the EGFR protein expression determined by PharmDx™ kit, and response to anti-EGFR therapies. Therefore, we investigated the relative expression and predictive value of wild-type EGFR (wtEGFR), mutated EGFRvIII and EGFR ligand proteins in mCRC patients treated with cetuximab. The expression levels of wtEGFR, EGFRvIII, and EGFR ligand were determined by immunohistochemistry (IHC) in 60 tumour specimens using specific antibodies. Sections were scored according to the percentage of positive tumour cells, intensity and cellular location of staining, and these were associated with response, overall survival (OS) and progression-free survival (PFS). At cut-off value > 5%, wtEGFR, and EGFRvIII were present in 44%, and 41%, betacellulin (BTC) in 72%, followed by epigen (67%), TGFα (58%), amphiregulin (34%), EGF (31%) of the cases, respectively and 96% of the wtEGFR positive cases had co-expression of at least one ligand. We found a significant association between the expression of wtEGFR and poor response to cetuximab. In addition, the co-expression of wtEGFR with one ligand at a cut-off value of > 5% and > 10% was associated with worse response to cetuximab (P = 0.021, and P = 0.005 respectively). We found a 3-fold and 5-fold increased risk of shorter OS with expression of BTC and epigen. Interestingly, the expression of wtEGFR and its co-expression with one or two ligands was associated with shorter PFS but not with OS. The relative expression of wtEGFR and its competing ligands, which is the target for therapeutic interventions with anti-EGFR antibodies, could serve as a more reliable predictive biomarker of response to therapy with anti-EGFR mAbs in mCRC patients and warrants further investigation in large prospective studies.

Prognostic value of amphiregulin and epiregulin mRNA expression in metastatic colorectal cancer patients

Epidermal growth factor receptor (EGFR) and its ligands amphiregulin (AREG) and epiregulin (EREG) play a central role in the development of colorectal cancer, but the prognostic values of AREG and EREG are controversial. We conducted a meta-analysis of studies that investigated AREG and/or EREG mRNA levels in primary tumors to determine their prognostic value in metastatic colorectal cancer (mCRC). In addition, RAS status was assessed. Relevant articles were identified by searching the EMBASE, PubMed, and Cochrane Library databases. Hazard ratios (HR) with 95% confidence intervals (CIs) were calculated using a random-effects model. Nine studies involving 2167 patients were included in this meta-analysis. High AREG expression was associated with longer overall survival (OS) and progression-free survival (PFS). High EREG expression was also associated with prolonged OS and PFS. In RAS wild-type (WT) patients who received anti-EGFR therapy, high AREG and EREG expression was associated with longer OS. Our results indicate that high AREG and EREG mRNA expression are independent favorable prognostic biomarkers in mCRC. The expression of these ligands should be considered when evaluating prognoses in RAS-WT patients receiving anti-EGFR therapy.

Expression of P-EGFR and P-Akt protein in esophageal squamous cell carcinoma and its prognosis

The phosphorylated epidermal growth factor receptor (P-EGFR) and phosphorylated Akt (P-Akt) protein in esophageal squamous cell carcinoma (ESCC) were studied, and its significance in clinical prognosis of patients was assessed. The expression of P-EGFR and P-Akt protein in 83 cases of ESCC and 83 normal esophageal tissues was determined by immunohistochemical staining. Log-rank test and correlation analysis were used to analyze the prognosis of ESCC. The positive expression of P-EGFR in ESCC was 88% (73/83 cases) compared with 41% in normal esophageal mucosa (34/83 cases) (P<0.05). The rate of P-Akt protein expression in ESCC was 90.4% (75/83 cases), compared with 27.7% seen in normal esophageal mucosa (23/83 cases) (P<0.05). The expression of P-EGFR and P-Akt protein was positively correlated with lymph node metastasis and degree of differentiation (P<0.05) irrespective of sex, age, tumor diameter and TNM stage (P>0.05). The expression of P-EGFR was positively correlated with that of P-Akt protein (r=0.674, P<0.01). P-EGFR expression was negatively correlated with survival time of patients with ESCC (r=−0.526, P<0.01). The Kaplan-Meier survival curves showed that the cumulative survival rate of P-EGFR-positive cases was significantly lower than that of the P-EGFR-negative cases (P<0.01). The expression of P-Akt was negatively correlated with survival in patients with ESCC (r=−0.473, P<0.01). The Kaplan-Meier survival curves showed that the cumulative survival rate of the P-Akt-positive cases was significantly lower than that of the P-Akt-negative cases (P<0.01). In conclusion, P-EGFR and P-Akt protein expression is closely related to the incidence of ESCC and mediates the development of invasive cancer and metastasis. It is used to determine the prognosis of ESCC, and may represent a new therapeutic target for the disease.

Co-targeting of EGFR and autophagy signaling is an emerging treatment strategy in metastatic colorectal cancer

The epidermal growth factor receptor (EGFR) and its associated pathway is a critical key regulator of CRC development and progression. The monoclonal antibodies (MoAbs) cetuximab and panitumumab, directed against EGFR, represent a major step forward in the treatment of metastatic colorectal cancer (mCRC), in terms of progression-free survival and overall survival in several clinical trials. However, the activity of anti-EGFR MoAbs appears to be limited to a subset of patients with mCRC. Studies have highlighted that acquired-resistance to anti-EGFR MoAbs biochemically converge into Ras/Raf/Mek/Erk and PI3K/Akt/mTOR pathways. Recent data also suggest that acquired-resistance to anti-EGFR MoAbs is accompanied by inhibition of EGFR internalization, ubiqutinization, degradation and prolonged downregulation. It is well established that autophagy, a self-cannibalization process, is considered to be associated with resistance to the anti-EGFR MoAbs therapy. Additionally, autophagy induced by anti-EGFR MoAbs acts as a protective response in cancer cells. Thus, inhibition of autophagy after treatment with EGFR MoAbs can result in autophagic cell death. A combination therapy comprising of anti-EGFR MoAbs and autophagy inhibitors would represent a multi-pronged approach that could be evolved into an active therapeutic strategy in mCRC patients.

On-treatment markers as predictors to guide anti-EGFR MoAb treatment in metastatic colorectal cancer: a systematic review with meta-analysis

PURPOSE

Skin toxicity (ST) and early tumor shrinkage (ETS) are early phenomenon during the anti-epidermal growth factor receptor (EGFR) monoclonal antibody (MoAb) treatment. We conducted a meta-analysis and included relevant studies that reported the impact of ST and ETS on survival- and life quality-based outcome of metastatic colorectal cancer (mCRC) patients treated with anti-EGFR MoAb.

METHODS

Relevant studies were identified from PubMed and Embase reporting the correlation of ST and ETS with the clinical outcome of mCRC patients treated with anti-EGFR MoAb. We also collected evidences on the impact of ST and ETS on absolute benefit acquired from additional anti-EGFR treatment and quality of life (ST only). Pooled hazard ratio and rate difference were all estimated by using random-effects model.

RESULTS

Pooled data revealed that the occurrence of ST and ETS ≥20% (v < 20%) during anti-EGFR MoAb treatment were both associated with better OS, PFS and ORR. This association could not be disturbed by KRAS status. Mean changes in safety follow-up life health state from baseline appeared unaffected by ST. Only mCRC patients with wild-type KRAS tumor who suffered grade 2+ ST could benefit from additional anti-EGFR treatment to chemotherapy or best supportive care (BSC) alone. ETS was also a predictor for absolute survival benefit acquired from additional anti-EGFR treatment for patients with wild-type KRAS tumors, and the more early shrinkage the tumor was, the much benefit was observed.

CONCLUSION

ST and ETS are predictive of absolute benefit acquired from anti-EGFR treatment in mCRC patients with wild-type KRAS tumors. These two on-treatment markers can be used for clinical decision-making if no adequate biological markers from tissues are provided.

EGFR gene copy number predicts response to anti-EGFR treatment in RAS wild type and RAS/BRAF/PIK3CA wild type metastatic colorectal cancer

Anti-EGFR antibodies are used for the treatment of RAS wild type metastatic colorectal cancer. We previously showed that EGFR gene copy number (GCN) predicts response to anti-EGFR therapy in KRAS exon 2 wild type metastatic colorectal cancer. The aim of our study was to analyse the predictive role of EGFR GCN in RAS/BRAF/PIK3CA wild type metastatic colorectal cancer. The material included 102 patients with KRAS exon 2 wild type metastatic colorectal cancer treated with anti-EGFR ± cytotoxic therapy. Next generation sequencing was used for KRAS, NRAS, BRAF and PIK3CA gene mutation analyses. EGFR GCN was analysed by EGFR immunohistochemistry guided automated silver in situ hybridisation. Increased EGFR GCN (≥4.0) predicted a better response and prolonged progression free survival in anti-EGFR treated RAS/BRAF/PIK3CA wild type patients (Log-rank test, p = 0.0004). In contrast, survival of RAS/BRAF/PIK3CA wild type, EGFR GCN below 4.0 patients did not differ from patients with mutant RAS, BRAF or PIK3CA. Our study indicates that EGFR GCN predicts anti-EGFR treatment efficacy in patients with RAS/BRAF/PIK3CA wt metastatic CRC. Tumours with EGFR GCN below 4.0 appear to be as refractory to anti-EGFR treatment as tumours with mutation in any of the RAS/RAF/PIK3CA pathway genes.

Prognostic and predictive biomarkers in metastatic colorectal cancer anti-EGFR therapy

AIM: To reviewing genetic and epigenetic make-up of metastatic colorectal cancers (mCRCs) addicted to epidermal growth factor receptor (EGFR) signalling.

METHODS: The present study summarizes the potential value of prognostic and predictive biomarkers in selecting mCRC patients treated with anti-EGFR therapy. A meta-analysis was performed using a systematic search of PubMed, Medline and Web of Science to identify eligible papers until March 21^st, 2016 using these following terms: ‘‘colorectal cancer’’, “predictive biomarkers’’, “anti-EGFR therapy”, “KRAS”, “NRAS’’, “PIK3CA”, “TP53”, “PTEN”, ‘‘EGFR”, “MET”, “HER2”, “epiregulin”, “amphiregulin”, “prognostic biomarkers”, “BRAF”, “miRNA” and “antibody-dependent cell-mediated cytotoxicity (ADCC) activity”. Two investigators independently evaluated and extracted data from each identified studies based on selected criteria of inclusion and exclusion.

RESULTS: The introduction of agents targeting EGFR such as cetuximab and panitumumab increased overall survival of mCRCs. Nevertheless, it has firstly became evident that response rates to cetuximab regimens in unselected patient populations were typically lower than 30%. Clinical data confirmed the predictive value of RAS mutations for resistance to cetuximab and panitumumab leading to the license of these monoclonal antibodies exclusively for the management of patients with RAS-wild type colorectal cancers. So far the identification of predictive biomarkers have generated interesting, though preliminary and, at times, conflicting data on the importance of tumour mRNA levels of EGFR ligands, of activating mutations in other genes such as NRAS and PIK3CA. The prognostic value of selected microRNAs level and ADCC activity is under investigation, while the prognostic impact of BRAF status remains controversial.

CONCLUSION: This review focuses on the personalized treatment of mCRC and discusses the potential of new prognostic and predictive biomarkers in selecting patients treated with anti-EGFR therapy.

Potential biomarkers for anti-EGFR therapy in metastatic colorectal cancer

Anti-epidermal growth factor receptor (EGFR) therapy has established efficacy in metastatic colorectal cancer, but a significant number of patients do not respond to such treatment. Recently, various biomarkers were reported to be useful in predicting resistance to anti-EGFR. All the potential biomarkers predicting resistance to anti-EGFR are reviewed herein from five aspects. First, upstream molecules, including epiregulin (EREG) and amphiregulin (AREG), might play different roles according to their abnormal levels in tumor tissue and serum. Second, the EGFR amplification and distinct polymorphisms may have roles in identifying patients for initial anti-EGFR mAbs therapy, while rare EGFR mutations have limited predictive values. Third, among the downstream molecularly related factors, rat sarcoma viral oncogene (Ras) has been identified as a successful predictor, while B-Raf proto-oncogene (BRAF) is considered as a prognostic factor rather than a predictor. Fourth, among the molecular bypass pathway components, phosphatidylinositol 3-kinase (PI3K) and phosphatase and tensin homolog (PTEN) may be potential biomarkers in the future, while activation of hepatocyte growth factor (HGF)/c-Met signaling confers resistance to anti-EGFR therapy. Fifth, many microRNAs and additional molecular biomarkers are promising in predicting the efficacy of anti-EGFR therapy. Applications of multiple biomarkers are more effective than the use of a single biomarker in selecting patients who might benefit from cetuximab- or panitumumab-based treatments. Comprehensive molecular analyses of the EGFR signaling pathways should be considered in the future. Subsequent prospective trials will be required to further confirm the clinical utility of these biomarkers.