Kirsten ras mutations in patients with colorectal cancer: the 'RASCAL II' study

KRAS-mutation status in relation to colorectal cancer survival: the joint impact of correlated tumour markers

Background:

Mutations in the Kirsten Ras (KRAS) oncogene are common in colorectal cancer (CRC). The role of KRAS-mutation status as a prognostic factor, however, is unclear. We evaluated the relationship between KRAS-mutation status and CRC survival, considering heterogeneity in this association by tumour and patient characteristics.

Methods:

The population-based study included individuals diagnosed with CRC between 1998–2007 in Western Washington State. Tumour specimens were tested for KRAS exon 2 mutations, the BRAF p.V600E mutation, and microsatellite instability (MSI). We used Cox regression to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between KRAS-mutation status and disease-specific and overall survival. Stratified analyses were conducted by age, sex, tumour site, stage, and MSI. We conducted additional analyses combining KRAS-mutation, BRAF-mutation, and MSI status.

Results:

Among 1989 cases, 31% had KRAS-mutated CRC. Kirsten Ras (KRAS)-mutated CRC was associated with poorer disease-specific survival (HR=1.37, 95% CI: 1.13–1.66). This association was not evident in cases who presented with distant-stage CRC. Cases with KRAS-wild-type/BRAF-wild-type/MSI-high CRC had the most favourable prognosis; those with CRC exhibiting a KRAS- or BRAF-mutation and no MSI had the poorest prognosis. Patterns were similar for overall survival.

Conclusion:

Kirsten Ras (KRAS)-mutated CRC was associated with statistically significantly poorer survival after diagnosis than KRAS-wild-type CRC.

New and potential clinical applications of KRAS as a cancer biomarker

IMPORTANCE OF THE FIELD

KRAS mutation is the most common oncogenic alteration in various human cancers. Recently, KRAS has emerged as an important predictive biomarker in common malignancies such as metastatic colorectal cancer (mCRC) and non-small cell lung cancer (NSCLC). This work aims to discuss the clinical impact of the KRAS mutation status on state-of-the-art treatment approaches, including epidermal growth factor receptor (EGFR)-targeted therapies.

AREAS COVERED IN THIS REVIEW

This review considers the potential of KRAS to serve as a diagnostic, prognostic or predictive biomarker in various cancers, including those of the lung, colon/rectum, pancreas, ovary and endometrium.

WHAT THE READER WILL GAIN

KRAS mutations in mCRC and NSCLC primary tumors predict resistance to EGFR-targeted therapy. In pancreatic cancer, KRAS may prove useful as a diagnostic biomarker to screen for early neoplasia. Furthermore, quantitative KRAS mutation analysis could have the potential to distinguish pancreatic cancer from other conditions such as chronic pancreatitis. With respect to ovarian and endometrial cancer, further studies should focus on determining reliable biomarkers for predicting response to EGFR-targeted therapy. Besides EGFR inhibition, KRAS may also serve as a diagnostic and predictive biomarker for evolving therapies directed against mutant RAS proteins.

TAKE HOME MESSAGE

KRAS has been recognized as an outstanding predictive biomarker to select mCRC and NSCLC patients for EGFR-targeted therapies; however, multi-determinant approaches including other molecular markers should facilitate the identification of patients likely to respond to such therapies.

KRAS mutations are associated with inferior clinical outcome in patients with metastatic colorectal cancer, but are not predictive for benefit with cediranib

PURPOSE

The prognostic potential of KRAS mutations in advanced colorectal cancer (CRC) patients and the impact of KRAS mutation status on the effectiveness of chemotherapy or vascular endothelial growth factor (VEGF) signalling inhibitor therapy remain unclear. KRAS mutation status was evaluated retrospectively as a potential prognostic/predictive marker of clinical outcomes using tumour samples from patients with metastatic CRC receiving cediranib or placebo plus FOLFOX/XELOX in a Phase III trial (HORIZON II; NCT00399035).

METHODS

KRAS codon 12 and 13 mutation analyses were performed using a commercially available, allele-specific, amplification refractory mutation system (ARMS)-based polymerase chain reaction (PCR) assay. Retrospective analyses of progression-free survival (PFS) and overall survival (OS) according to KRAS mutation status were performed for patients randomised to cediranib 20mg or placebo.

RESULTS

KRAS status was determined in 599/1076 patients (cediranib 20mg, n=285/502; cediranib 30 mg, n=110/216; placebo, n=204/358). Baseline characteristics were similar across KRAS mutant (n=258; 24.0%), wild-type (n=341; 31.7%) and status unknown (n=477; 44.3%) groups. There was a trend towards improved PFS and OS in the wild-type versus mutant subgroups independent of treatment (cediranib 20 mg and placebo: PFS hazard ratio (HR)=0.85 [median PFS: wild-type=8.5 months; mutant=8.3 months]; OS HR=0.71 [median OS: wild-type=20.9 months; mutant=16.9 months]). Treatment effects were similar between KRAS subgroups for cediranib 20mg versus placebo (PFS: wild-type HR=0.78, mutant HR=0.82; OS: wild-type HR=0.92, mutant HR=1.01).

CONCLUSION

Data from this large randomised Phase III study show that KRAS codon 12/13 mutations have negative prognostic value in metastatic CRC patients receiving treatment with FOLFOX/XELOX, but KRAS mutation status is not predictive of treatment benefit with cediranib, using PFS or OS.

EGFR Expression and KRAS and BRAF Mutational Status in Intestinal-Type Sinonasal Adenocarcinoma

Accumulation of molecular alterations, including EGFR overexpression and mutations in KRAS and BRAF, contribute to colorectal carcinogenesis. Since intestinal-type adenocarcinoma (ITAC) of the nasal cavity and paranasal sinus has morphologic and phenotypic features that are usually indistinguishable from colorectal cancer (CRC), it is likely that both tumor types share equivalent genetic alterations. Data from a series of 43 patients treated surgically for ITAC in Montpellier, France between November 1998 and December 2012 were collected. Tumors were characterized for mutations in KRAS and BRAF as well as EGFR overexpression. Kaplan-Meier survival curves were constructed using overall survival as the primary end points. Patient survival was analyzed using the hazards ratio. Twenty seven tumors (63%) showed EGFR positivity and 30% exhibited a high expression level (+2/+3). KRAS mutations were detected in 43% of cases. BRAF mutations were identified in 3.6% of specimens. Patients with age superior to 60 years, metastatic status, and KRAS mutations had significant overall survival values (p = 0.026, p = 0.001 and p = 0.03, respectively). Our results indicate that KRAS mutations and EGFR expression are frequent in ITAC and that KRAS mutations predict good patient prognosis in ITAC. Finally, EGFR directed molecular treatments could be investigated in a subset of patients affected by ITAC.

Worse prognosis of KRAS c.35 G > A mutant metastatic colorectal cancer (MCRC) patients treated with intensive triplet chemotherapy plus bevacizumab (FIr-B/FOx)

BACKGROUND

Prognosis of KRAS wild-type and mutant metastatic colorectal cancer (MCRC) patients (pts) treated with bevacizumab (BEV)-containing chemotherapy is not significantly different. Since specific KRAS mutations confer different aggressive behaviors, the prognostic role of prevalent KRAS mutations was retrospectively evaluated in MCRC pts treated with first line FIr-B/FOx, associating BEV to triplet chemotherapy.

METHODS

Tumor samples were screened for KRAS codon 12, 13 and BRAF V600E mutations by SNaPshot and/or direct sequencing. MCRC pts <75-years-old were consecutively treated with FIr-B/FOx: weekly 12 hour-timed-flat-infusion/5-fluorouracil (900 mg/m(2) on days 1,2, 8, 9, 15, 16,22, 23), irinotecan plus BEV (160 mg/m(2) and 5 mg/kg, respectively, on days 1,15); and oxaliplatin (80 mg/m(2), on days 8,22). Pts were classified as liver-limited (L-L) and other/multiple metastatic (O/MM). Progression-free survival (PFS) and overall survival (OS) were compared using the log-rank test.

RESULTS

Fifty-nine pts were evaluated at a median follow-up of 21.5 months. KRAS mutant pts: c.35 G > A, 15 (25.4%); c.35 G > T, 7 (11.8%); c.38 G > A, 3 (5%); other, 3 (5%). KRAS wild-type, 31 pts (52.7%). The objective response rate (ORR), PFS and OS were, respectively: c.35 G > A mutant, 71%, 9 months, 14 months; other than c.35 G > A mutants, 61%, 12 months, 39 months. OS was significantly worse in c.35 G > A pts compared to KRAS wild-type (P = 0.002), KRAS/BRAF wild-type (P = 0.03), other MCRC patients (P = 0.002), other than c.35 G > A (P = 0.05), other codon 12 (P = 0.03) mutant pts. OS was not significantly different compared to c.35 G > T KRAS mutant (P = 0.142).

CONCLUSIONS

KRAS c.35 G > A mutant status may be significantly associated with a worse prognosis of MCRC pts treated with first line FIr-B/FOx intensive regimen compared to KRAS/BRAF wild type and other than c.35 G > A mutant pts.

KRAS mutant tumor subpopulations can subvert durable responses to personalized cancer treatments

KRAS mutations in colorectal and lung cancers predict failure to respond to therapies that target the EGFR. Significant percentages of patients with KRAS wild-type tumors also fail to respond to these therapies. Relapse occurs in patients with KRAS wild-type and mutant tumors, with moderately longer progression-free survival in patients with KRAS wild-type tumors. Colon and lung tumors frequently carry KRAS mutant tumor subpopulations not detected by DNA sequencing. This suggests detected and undetected KRAS mutant subpopulations in colon and lung tumors are undermining the efficacy of anti-EGFR therapies. Therefore, consideration should be given to combining therapies that target KRAS mutant cells with those that downregulate EGFR signaling. As tumors are frequently polyclonal in origin and comprised of distinct clonal populations carrying complementing genetic and/or epigenetic lesions, preclinical models that assess the efficacy of combination therapies in the context of heterogeneous tumor cell populations will be essential for progress in this area.

Monoclonal antibodies in gastrointestinal cancers

INTRODUCTION

Among gastrointestinal cancers, colorectal and gastric neoplasms are the most frequent. The development of new targeted drugs improved the efficacy of systemic therapy in advanced stages of those malignancies.

AREAS COVERED

This review highlights the main biological processes implicated in gastrointestinal cancer development and progression, such as angiogenesis and epidermal growth factor receptor (EGFR) signaling pathway. On these bases, anti-EGFR and anti-vascular endothelial growth factor (VEGF) monoclonal antibodies in colorectal and gastric cancer are discussed. Data about further monoclonal antibodies in development are also reported.

EXPERT OPINION

The use of monoclonal antibodies in colorectal and gastric cancers showed the best outcomes when combined with chemotherapy, even though single agent anti-EGFR antibodies seem active in particular setting of metastatic colorectal cancer (CRC) patients. It is not well defined whether the addition of anti-VEGF and anti-EGFR to chemotherapy could improve outcome in those patients susceptible to CRC-related metastases resection. Little and conflicting data are available about the role of these drugs in adjuvant setting. Tests are available to select patients with higher probability to get benefit from these treatments. Further biomarkers need to be evaluated to improve this selection and achieve "tailorization" of systemic therapy.

Bevacizumab plus chemotherapy in metastatic colorectal cancer patients treated in clinical practice

AIM

The effect of KRAS status on response to bevacizumab plus chemotherapy in metastatic colorectal cancer is still unclear. We aimed to evaluate the overall clinical response to such a therapy in clinical practice and assess the role of KRAS status on therapy response.

PATIENTS & METHODS

This was a retrospective study enrolling 108 metastatic colorectal cancer patients. KRAS mutation analysis was performed by PCR.

RESULTS

Overall, 41.7% of patients had stable disease, 39.8% a partial response, 3.7% a complete response and 14.8% disease progression. Both clinical benefit and objective response rate tended to be higher in patients with only hepatic metastases than those with extrahepatic or multiple metastases. Response to therapy would appear to be independent of KRAS status, but larger studies are needed.

CONCLUSION

Bevacizumab plus chemotherapy provides clinical benefit and objective response rate in patients with metastatic colorectal cancer independently of KRAS expression, especially in those patients with only liver metastases.

Detection of KRAS mutations and their associations with clinicopathological features and survival in Chinese colorectal cancer patients

OBJECTIVE

Mutation of the KRAS (v-Kiras2 Kirsten rat sarcoma viral oncogene homologue) gene plays an important role in colorectal tumorigenesis. This study examined associations between KRAS gene mutations and clinicopathological and survival data in Chinese patients with colorectal cancer (CRC).

METHODS

CRC patients were recruited for the detection of KRAS gene mutations using polymerase chain reaction and DNA sequencing. Data on clinicopathological features and survival times were collected.

RESULTS

The study included 78 CRC patients. The overall mutation frequency of the KRAS gene at codons 12 and 13 was 33.3% (26/78). KRAS gene mutations were significantly associated with poor tumour differentiation and liver metastasis. Patients with the wild-type KRAS gene had significantly higher median survival times than patients with KRAS gene mutations (35.05 months versus 25.72 months). Those with KRAS gene mutations at codons 12 or 13 did not have significantly different median survival times (25.69 months versus 20.67 months, respectively).

CONCLUSIONS

These findings suggest that a high frequency of KRAS gene mutations exists in Chinese patients with CRC, and that such mutations are associated with poor survival, tumour differentiation and liver metastasis in CRC patients.

KRAS p.G13D mutations are associated with sensitivity to anti-EGFR antibody treatment in colorectal cancer cell lines

PURPOSE

Targeted therapies using the anti-EGFR antibodies panitumumab (Pmab) or cetuximab (Cmab) are currently restricted to patients with metastatic colorectal adenocarcinoma whose tumours do not show a mutation in KRAS. However, recent retrospective studies indicated that patients with tumours mutated in codon 13 of KRAS may benefit from treatment with Cmab in contrast to patients with tumours mutated in KRAS codon 12.

METHODS

To study the functional impact of the subtype of KRAS mutations on the efficiency of EGFR-targeted therapies, we correlated the KRAS mutation status of 15 colorectal carcinoma cell lines with the in vitro sensitivity of these cells to Cmab/Pmab. Mutations in the potential predictive biomarkers BRAF and PIK3CA as well as protein expression of EGFR and PTEN were also determined.

RESULTS

Four out of seven KRAS-mutated cell lines were characterised by the p.G13D mutation. Treatment of these cells using Cmab/Pmab induced a significant growth inhibition in contrast to cell lines showing a KRAS mutation at codon 12 or 61. Out of the eight KRAS wild-type cell lines, five were insensitive to Cmab/Pmab. These cell lines were characterised either by BRAF mutation or by absence of EGFR or PTEN protein expression.

CONCLUSIONS

Since KRAS p.G13D-mutated tumour cells may respond to EGFR-targeted therapy, we suggest including subtype analysis of KRAS mutations in prospective clinical trials. In KRAS wild-type tumour cells, BRAF mutations and loss of EGFR or PTEN expression may lead to resistance to EGFR-targeted therapy and should be considered as additional negative predictive biomarkers.

Targeted therapy in metastatic colorectal cancer -- an example of personalised medicine in action

In metastatic colorectal cancer (mCRC), an improved understanding of the underlying pathology and molecular biology has successfully merged with advances in diagnostic techniques and local/systemic therapies as well as improvements in the functioning of multidisciplinary teams, to enable tailored treatment regimens and optimized outcomes. Indeed, as a result of these advancements, median survival for patients with mCRC is now in the range of 20-24months, having approximately tripled in the last 20years. The identification of KRAS as a negative predictive marker for activity of epidermal growth factor receptor (EGFR)-targeted monoclonal antibodies (mAbs), such as panitumumab (Amgen, Thousand Oaks, USA) and cetuximab (ImClone, Branchburg, USA), has perhaps had the greatest impact on patient management. This meant that, for the first time, mCRC patients unlikely to respond to a targeted therapy could be defined ahead of treatment. Ongoing controversies such as whether patients with KRAS G13D- (or BRAF V600-) mutated tumours can still respond to EGFR-targeted mAbs and the potential impact of inter- and intra-tumour heterogeneity on tumour sampling show that the usefulness of KRAS as a biomarker has not yet been exhausted, and that other downstream biomarkers should be considered. Conversely, a predictive biomarker for anti-angiogenic agents such as bevacizumab (Genentech, San Francisco, USA) in the mCRC setting is still lacking. In this review we will discuss the discovery and ongoing investigation into predictive biomarkers for mCRC as well as how recent advances have impacted on clinical practice and ultimately the overall cost of treatment for these patients.

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.

KRAS Testing: A Tool for the Implementation of Personalized Medicine

Activating point mutations in codons 12, 13, and 61 of the KRAS proto-oncogene are common in colorectal, non-small cell lung, pancreatic, and thyroid cancers. Constitutively activated KRAS mutations are strongly associated with a resistance to anti-epidermal growth factor receptor (EGFR) therapies, such as panitumumab and cetuximab used for treating metastatic colorectal carcinoma and EGFR tyrosine inhibitors used for advanced non-small cell lung cancers. Since anti-EGFR therapies are costly and may exert deleterious effects on individuals without activating mutations, KRAS mutation testing is recommended prior to the initiation of anti-EGFR therapy for these malignancies. The goal of this review is to summarize the KRAS mutation testing methods. Testing is now routinely requested in the clinical practice to provide data to assign the most appropriate anticancer chemotherapy for each given patient. Review of the most relevant literature was performed. Several areas were considered: ordering of the test, selection of the sample to be tested, and review of the testing methodologies. We found that several different methods are used for clinical KRAS mutation testing. Each of the methodologies is described, and information is provided about their performance, cost, turnaround times, detection limits, sensitivities, and specificities. We also provided "tips" for the appropriate selection and preparation of the sample to be tested. This is an important aspect of KRAS testing for clinical use, as the results of the test will affect clinical decisions with consequences for the patient.

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.

KRAS mutations and subtyping in colorectal cancer in Jordanian patients

Colorectal cancer (CRC) is one of the most common malignancies in the Western world and Jordan. v-Ki-ras2 Kirsten rat sarcoma (KRAS) mutations represent an early event in the development and progression of CRC. Previous studies have demonstrated that KRAS mutations serve as a predictor of response to EGFR-targeted therapies for patients with metastatic CRC. The aim of this study was to determine the portion of CRC patients with wildtype KRAS status and molecular subtypes of KRAS mutations in Jordan as compared with other countries. DNA was isolated from 100 consecutive colorectal carcinoma specimens from patients who underwent surgical resection or colonoscopic biopsies of colorectal tumors and had developed metastatic disease. KRAS mutations were detected by hybridization-based strip assay as well as RT-PCR-based assay and confirmed by standard Sanger sequencing of codon 12 and 13 of exon 1 of the KRAS gene. Among 100 tested patients, 56% had a wt-KRAS genotype and 44% had a mutated KRAS genotype. The pGly12Asp was the most commonly detected mutation (54.5%). KRAS mutations were independently associated with patient age, gender and tumoral variables. The ratio of mutated versus wt-KRAS patients in this study is similar to those reported in Western countries but contrasts to neighboring Middle Eastern countries. Colorectal carcinoma cases from Jordan had higher KRAS mutation frequencies compared with other Middle Eastern countries which is likely to reflect different molecular pathogenesis and environmental exposures.

Mutant KRAS codon 12 and 13 alleles in patients with metastatic colorectal cancer: assessment as prognostic and predictive biomarkers of response to panitumumab

PURPOSE

Panitumumab, a fully human monoclonal antibody targeting the epidermal growth factor receptor (EGFR), has demonstrated significant improvements in progression-free survival (PFS) in patients with wild-type KRAS metastatic colorectal cancer (mCRC) in studies 20050203 (first line), 20050181 (second line), and 20020408 (monotherapy). Mutations in KRAS codons 12 and 13 are recognized biomarkers that predict lack of response to anti-EGFR antibody therapies. This retrospective analysis of three randomized phase III studies assessed the prognostic and predictive impact of individual mutant KRAS codon 12 and 13 alleles.

PATIENTS AND METHODS

Patients were randomly assigned 1:1 to FOLFOX4 (infusional fluorouracil, leucovorin, and oxaliplatin) in study 20050203, FOLFIRI (fluorouracil, leucovorin, and irinotecan) in study 20050181, or best supportive care in study 20020408 with or without panitumumab 6.0 mg/kg once every 2 weeks. In all, 441 (20050203), 486 (20050181), and 126 (20020408) patients with mutant KRAS codon 12 or 13 alleles were included in the analysis.

RESULTS

No mutant KRAS allele in patients treated on the control arm emerged as a consistent prognostic factor for PFS or overall survival (OS). In addition, no mutant KRAS allele was consistently identified as a predictive factor for PFS or OS in patients receiving panitumumab treatment. Significant interactions for individual mutant KRAS alleles were observed only in study 20050203 with G13D negatively and G12V positively associated with OS in the panitumumab-containing arm. Pooled analysis indicated that only G12A was associated with a negative predictive effect on OS.

CONCLUSION

In this retrospective analysis, results across three treatment regimens suggest that patients with mutant KRAS codon 12 or 13 mCRC tumors are unlikely to benefit from panitumumab therapy. Currently, panitumumab therapy should be limited to patients with wild-type KRAS mCRC.

Frequent epigenetic silencing of the folate-metabolising gene cystathionine-beta-synthase in gastrointestinal cancer

Background

Both gastric and colorectal cancers (CRC) are the most frequently occurring malignancies worldwide with the overall survival of these patients remains unsatisfied. Identification of tumor suppressor genes (TSG) silenced by promoter CpG methylation uncovers mechanisms of tumorigenesis and identifies new epigenetic biomarkers for early cancer detection and prognosis assessment. Cystathionine-beta-synthase (CBS) functions in the folate metabolism pathway, which is intricately linked to methylation of genomic DNA. Dysregulation of DNA methylation contributes substantially to cancer development.

Methodology/Principal Findings

To identify potential TSGs silenced by aberrant promoter methylation in CRC, we analyzed tumor and adjacent tissues from CRC cases using the Illumina Human Methylation45 BeadChip. We identified hypermethylation of the CBS gene in CRC samples, compared to adjacent tissues. Methylation and decreased mRNA expression of CBS were detected in most CRC cell lines by methylation-specific PCR and semiquantitative RT-PCR, as well as in gastric cancer. Treatment with 5-aza-2'-deoxycytidine and/or trichostatin A reversed methylation and restored CBS mRNA expression indicating a direct effect. Aberrant methylation was further detected in 31% of primary CRCs (29 of 96) and 55% of gastric tumors (11 of 20). In contrast, methylation was seldom found in normal tissues adjacent to the tumor. CBS methylation was associated with KRAS mutations in primary CRCs (P = 0.04, by χ²-test). However, no association was found between CBS methylation or KRAS mutations with cancer relapse/metastasis in Stage II CRC patients.

Conclusion

A novel finding from this study is that the folate metabolism enzyme CBS mRNA levels are frequently downregulated through CpG methylation of the CBS gene in gastric cancer and CRC, suggesting that CBS functions as a tumor suppressor gene. These findings warrant further study of CBS as an epigenetic biomarker for molecular diagnosis of gastrointestinal cancers.

Prognostic value of KRAS genotype in metastatic colorectal cancer (MCRC) patients treated with intensive triplet chemotherapy plus bevacizumab (FIr-B/FOx) according to extension of metastatic disease

BACKGROUND

Bevacizumab (BEV) plus triplet chemotherapy can increase efficacy of first-line treatment of metastatic colorectal cancer (MCRC), particularly integrated with secondary liver surgery in liver-limited (L-L) patients. The prognostic value of the KRAS genotype in L-L and other or multiple metastatic (O/MM) MCRC patients treated with the FIr-B/FOx regimen was retrospectively evaluated.

METHODS

Tumoral and metastatic samples were screened for KRAS codon 12 and 13 and BRAF mutations by SNaPshot and/or direct sequencing. Fit MCRC patients <75 years were consecutively treated with FIr-B/FOx regimen: weekly 12-h timed flat-infusion/5-fluorouracil (TFI 5-FU) 900 mg/m2, days 1, 2, 8, 9, 15, 16, 22 and 23; irinotecan (CPT-11) 160 mg/m2 plus BEV 5 mg/kg, days 1, 15; oxaliplatin (OXP) 80 mg/m2, days 8, 22; every 4 weeks. MCRC patients were classified as L-L and O/MM. Activity and efficacy were evaluated and compared using log-rank test.

RESULTS

In all, 59 patients were evaluated: 31 KRAS wild-type (53%), 28 KRAS mutant (47%). At 21.5 months median follow-up, objective response rate (ORR), progression-free survival (PFS) and overall survival (OS) were, respectively: KRAS wild-type 90%, 14 months, 38 months; KRAS mutant 67%, 11 months, 20 months. PFS and OS were not significantly different. PFS and OS were significantly different in L-L compared to O/MM evaluable patients. In KRAS wild-type patients, clinical outcome of 12 L-L compared to 18 O/MM was significantly different: PFS 21 versus 12 months and OS 47 versus 28 months, respectively. In KRAS mutant patients, the clinical outcome of 13 L-L compared to 14 O/MM was not significantly different: PFS 11 months equivalently and OS 39 versus 19 months, respectively.

CONCLUSIONS

The KRAS genotype wild-type and mutant does not significantly affect different clinical outcomes for MCRC patients treated with the first-line FIr-B/FOx intensive regimen. KRAS wild-type patients with L-L disease may achieve a significantly prolonged clinical outcome due to integration with secondary liver surgery, with respect to KRAS mutant patients.

Role of Kras status in patients with metastatic colorectal cancer receiving first-line chemotherapy plus bevacizumab: a TTD group cooperative study

BACKGROUND

In the MACRO study, patients with metastatic colorectal cancer (mCRC) were randomised to first-line treatment with 6 cycles of capecitabine and oxaliplatin (XELOX) plus bevacizumab followed by either single-agent bevacizumab or XELOX plus bevacizumab until disease progression. An additional retrospective analysis was performed to define the prognostic value of tumour KRAS status on progression-free survival (PFS), overall survival (OS) and response rates.

METHODOLOGY/PRINCIPAL FINDINGS

KRAS data (tumour KRAS status and type of mutation) were collected by questionnaire from participating centres that performed KRAS analyses. These data were then cross-referenced with efficacy data for relevant patients in the MACRO study database. KRAS status was analysed in 394 of the 480 patients (82.1%) in the MACRO study. Wild-type (WT) KRAS tumours were found in 219 patients (56%) and mutant (MT) KRAS in 175 patients (44%). Median PFS was 10.9 months for patients with WT KRAS and 9.4 months for patients with MT KRAS tumours (p=0.0038; HR: 1.40; 95% CI:1.12-1.77). The difference in OS was also significant: 26.7 months versus 18.0 months for WT versus MT KRAS, respectively (p=0.0002; HR: 1.55; 95% CI: 1.23-1.96). Univariate and multivariate analyses showed that KRAS was an independent variable for both PFS and OS. Responses were observed in 126 patients (57.5%) with WT KRAS tumours and 76 patients (43.4%) with MT KRAS tumours (p=0.0054; OR: 1.77; 95% CI: 1.18-2.64).

CONCLUSIONS/SIGNIFICANCE

This analysis of the MACRO study suggests a prognostic role for tumour KRAS status in patients with mCRC treated with XELOX plus bevacizumab. For both PFS and OS, KRAS status was an independent factor in univariate and multivariate analyses.

Mutation profiling and microsatellite instability in stage II and III colon cancer: an assessment of their prognostic and oxaliplatin predictive value

PURPOSE

The purpose of this study was to examine the prognostic and oxaliplatin predictive value of mismatch repair (MMR) status and common hot spot mutations, which we previously identified in stage II and III colon cancer.

EXPERIMENTAL DESIGN

Mutations in BRAF, KRAS, NRAS, MET, and PIK3CA were profiled in 2,299 stage II and III colon tumors from National Surgical Adjuvant Breast and Bowel Project (NSABP) clinical trials C-07 (n = 1,836) and C-08 (n = 463) with Type Plex chemistry and mass spectrometry. C-07 tested the worth of adding oxaliplatin to 5-fluorouracil plus leucovorin, and C-08 tested the worth of adding bevacizumab to FOLFOX. Cox proportional hazard models were used to assess prognostic or oxaliplatin predictive value of mutations for tumor recurrence, overall survival (OS), and survival after recurrence (SAR).

RESULTS

BRAF mutations were associated with MMR-deficient tumors (P < 0.0001), poor OS [HR, 1.46; 95% confidence interval (CI), 1.20-1.79; P ≤ 0.0002], and poor SAR (HR, 2.31; 95% CI, 1.83-2.95; P < 0.0001). Mutations in KRAS, NRAS, MET, and PIK3CA were not associated with recurrence, OS, or SAR. MMR-deficient tumors were associated with an improved prognosis based on recurrence (HR, 0.48; 95% CI, 0.33-0.70; P < 0.0001). Mutations and MMR status were not predictive for oxaliplatin benefit.

CONCLUSIONS

This study shows that BRAF mutations profiled from stage II and III colon cancer tumors were associated with poor SAR and validates and explains, at least in part, previous observations associating it with poor OS. Profiling of all of these mutations is warranted for future clinical trials testing new targeted therapies that block relevant signaling pathways. Such clinical trials are under development at NSABP.

KRAS mutation testing in metastatic colorectal cancer

The KRAS oncogene is mutated in approximately 35%-45% of colorectal cancers, and KRAS mutational status testing has been highlighted in recent years. The most frequent mutations in this gene, point substitutions in codons 12 and 13, were validated as negative predictors of response to anti-epidermal growth factor receptor antibodies. Therefore, determining the KRAS mutational status of tumor samples has become an essential tool for managing patients with colorectal cancers. Currently, a variety of detection methods have been established to analyze the mutation status in the key regions of the KRAS gene; however, several challenges remain related to standardized and uniform testing, including the selection of tumor samples, tumor sample processing and optimal testing methods. Moreover, new testing strategies, in combination with the mutation analysis of BRAF, PIK3CA and loss of PTEN proposed by many researchers and pathologists, should be promoted. In addition, we recommend that microsatellite instability, a prognostic factor, be added to the abovementioned concomitant analysis. This review provides an overview of KRAS biology and the recent advances in KRAS mutation testing. This review also addresses other aspects of status testing for determining the appropriate treatment and offers insight into the potential drawbacks of mutational testing.

KRAS status and outcome of liver resection after neoadjuvant chemotherapy including bevacizumab

Background

The prognostic value of KRAS mutation in patients with colorectal cancer liver metastases (CLM) receiving neoadjuvant chemotherapy including bevacizumab before liver resection is unclear.

Methods

The KRAS and BRAF status of resected CLM was assessed in prospectively studied patients. Mutations were correlated with recurrence-free and overall survival. Only patients with remaining vital tumour cells in the resected specimen and those without disease progression were analysed; those with progressive disease did not undergo resection.

Results

A total of 60 patients were enrolled. Fifteen (25 per cent) had a KRAS mutation, but none of the 60 patients had a BRAF mutation. The radiological response to neoadjuvant chemotherapy including bevacizumab, assessed according to the Response Evaluation Criteria In Solid Tumours, was partial in 52 patients (87 per cent) and the remaining eight had stable disease. The partial response rate was similar in patients with a KRAS mutation and those with the wild-type gene (12 of 15 versus 40 of 45 patients; P = 0·400). KRAS mutation had a negative prognostic effect on recurrence-free survival (hazard ratio (HR) 2·48, 95 per cent confidence interval 1·26 to 4·89; P = 0·009) and overall survival (HR 3·51, 1·30 to 9·45; P = 0·013).

Conclusion

This study provided further evidence for the prognostic importance of KRAS status in terms of recurrence-free and overall survival. Neoadjuvant chemotherapy including bevacizumab elicited a response, irrespective of KRAS status, in this selected group of patients with CLM.

Prognostic and predictive roles of KRAS mutation in colorectal cancer

The RAS gene family is among the most studied and best characterized of the known cancer-related genes. Of the three human ras isoforms, KRAS is the most frequently altered gene, with mutations occurring in 17%-25% of all cancers. In particular, approximately 30%-40% of colon cancers harbor a KRAS mutation. KRAS mutations in colon cancers have been associated with poorer survival and increased tumor aggressiveness. Additionally, KRAS mutations in colorectal cancer lead to resistance to select treatment strategies. In this review we examine the history of KRAS, its prognostic value in patients with colorectal cancer, and evidence supporting its predictive value in determining appropriate therapies for patients with colorectal cancer.

Prognostic value of circulating cytokines for stage III colon cancer

BACKGROUND

This study was to determine preoperative serum levels of epidermal growth factor (EGF), interleukin-6 (IL-6), and C-reactive protein (CRP) in stage III colon cancer and correlate them with disease status and prognosis. The circulating EGF in correlation with primary site epidermal growth factor receptor (EGFR) was also evaluated.

METHODS

Seventy-seven patients with curatively resected stage III colon cancer were selected for analysis. Enzyme-linked immunosorbent assay was used to determine EGF and IL-6 serum levels, and serum CRP levels were measured via immunoturbidimetry. EGFR expression was observed with immunohistochemical studies.

RESULTS

The median levels of EGFR, IL-6, and CRP were 189.4 pg/mL, 9.09 pg/mL, and 1.4 mg/mL, respectively. The factors related to recurrence with statistical significance included positive node status (P = 0.041), lymphovascular invasion (P = 0.001), and preoperative IL-6 level ≥9 pg/mL (P = 0.020). CRP and EGF levels were not significantly associated with disease-free survival rates (P = 0.438 and P = 0.309, respectively). Multivariate analysis using Cox's proportion model revealed that lymph node status was the single independent prognostic factor for predicting time until recurrence (odds ratio, 4.99; 95% confidence interval, 1.09-22.91; P = 0.038).

CONCLUSION

IL-6 expression in stage III colon cancer patients appears to be a prognostic marker of tumor behavior. No correlations between serum EGF concentrations and tumor EGFR positivity were found in this study.

HSP27 expression in primary colorectal cancers is dependent on mutation of KRAS and PI3K/AKT activation status and is independent of TP53

Colorectal adenomas display features of senescence, but these are often lost upon progression to carcinoma, indicating that oncogene induced senescence (OIS) could be a roadblock in colorectal cancer (CRC) development. Heat shock proteins (HSPs) have been implicated in the prognosis of CRC and HSP based therapy is a current interest for drug development. Recent cell culture studies have suggested that in the absence of a TP53 mutation, OIS mediated by PI3K/AKT activation can be circumvented by high expression of HSPs. Furthermore, while PI3K/AKT activation and KRAS mutations are independent inducers of OIS, PI3K/AKT activation can suppress KRAS-induced OIS when both are present in cultured cells. As KRAS mutations, PI3K/AKT activation and TP53 mutations are all common features of CRC, it is possible that the requirement for HSP to inhibit OIS in CRC is dependent on the mutation spectrum of a tumour. However, work on HSP that utilised mutation profiled human tumour tissues has been limited. Here, we characterised the expression of two major HSP proteins (HSP27 and 72) by immunohistochemistry (IHC), the mutation status of TP53, KRAS and PIK3CA genes by direct sequencing and the activation status of AKT by IHC in a cohort of unselected primary CRC (n=74). We compare our data with findings generated from cell-based studies. Expression of HSP27 and HSP72 was correlated to clinicopathological and survival data but no significant association was found. We also established the mutation status of TP53, KRAS and PIK3CA genes and the activation status of AKT in our CRC panel. We did not detect any associations between HSP27 or HSP72 expression with TP53 mutation status. However, HSP27 expression in CRCs was strongly associated with the co-presence of wildtype KRAS and activated PI3K/AKT (p=0.004), indicating a possible role of HSP27 in overcoming PI3K/AKT induced OIS in tumours. Our studies suggest a role for using archival tissues in validating hypotheses generated from cell culture based investigations.

Recent approaches to identifying biomarkers for high-risk stage II colon cancer

The use of adjuvant chemotherapy for stage II colon cancer remains controversial. The accurate assessment of the risk factors associated with recurrence in patients with stage II disease is the key to identifying the patients that are most likely to benefit from adjuvant chemotherapy. Recent guidelines advocate that adjuvant chemotherapy for high-risk stage II colon cancer should take into account factors such as the T stage, number of lymph nodes examined, tumor differentiation, and tumor perforation. In addition to these clinicopathological factors, there has also been intense interest in the identification of new prognostic or predictive biomarkers that can improve outcomes through better patient classification and selection for adjuvant chemotherapy. Recent advances in the field of molecular genetics have led to the identification of specific biomarkers involved in colorectal cancer progression, whereas gene expression microarray technology has led to the identification of molecular profiles able to predict recurrence or benefit from adjuvant chemotherapy. However, none of these has yet been validated in large prospective clinical trials. In this article, we review the current status of prognostic and predictive biomarkers for stage II colon cancer and provide an update on the most recent developments.

Specific mutations in KRAS codons 12 and 13, and patient prognosis in 1075 BRAF wild-type colorectal cancers

PURPOSE

To assess prognostic roles of various KRAS oncogene mutations in colorectal cancer, BRAF mutation status must be controlled for because BRAF mutation is associated with poor prognosis, and almost all BRAF mutants are present among KRAS wild-type tumors. Taking into account experimental data supporting a greater oncogenic effect of codon 12 mutations compared with codon 13 mutations, we hypothesized that KRAS codon 12-mutated colorectal cancers might behave more aggressively than KRAS wild-type tumors and codon 13 mutants.

EXPERIMENTAL DESIGN

Using molecular pathological epidemiology database of 1,261 rectal and colon cancers, we examined clinical outcome and tumor biomarkers of KRAS codon 12 and 13 mutations in 1,075 BRAF wild-type cancers (i.e., controlling for BRAF status). Cox proportional hazards model was used to compute mortality HR, adjusting for potential confounders, including stage, PIK3CA mutations, microsatellite instability, CpG island methylator phenotype, and LINE-1 methylation.

RESULTS

Compared with patients with KRAS wild-type/BRAF wild-type cancers (N = 635), those with KRAS codon 12 mutations (N = 332) experienced significantly higher colorectal cancer-specific mortality [log-rank P = 0.0001; multivariate HR, 1.30; 95% confidence interval (CI), 1.02-1.67; P = 0.037], whereas KRAS codon 13-mutated cases (N = 108) were not significantly associated with prognosis. Among the seven most common KRAS mutations, c.35G>T (p.G12V; N = 93) was associated with significantly higher colorectal cancer-specific mortality (log-rank P = 0.0007; multivariate HR, 2.00; 95% CI, 1.38-2.90, P = 0.0003) compared with KRAS wild-type/BRAF wild-type cases.

CONCLUSIONS

KRAS codon 12 mutations (in particular, c.35G>T), but not codon 13 mutations, are associated with inferior survival in BRAF wild-type colorectal cancer. Our data highlight the importance of accurate molecular characterization in colorectal cancer.

Impact of the specific mutation in KRAS codon 12 mutated tumors on treatment efficacy in patients with metastatic colorectal cancer receiving cetuximab-based first-line therapy: a pooled analysis of three trials

PURPOSE

This study investigated the impact of specific mutations in codon 12 of the Kirsten-ras (KRAS) gene on treatment efficacy in patients with metastatic colorectal cancer (mCRC).

PATIENTS

Overall, 119 patients bearing a KRAS mutation in codon 12 were evaluated. All patients received cetuximab-based first-line chemotherapy within the Central European Cooperative Oncology Group (CECOG), AIO KRK-0104 or AIO KRK-0306 trials.

RESULTS

Patients with KRAS codon 12 mutant mCRC showed a broad range of outcome when treated with cetuximab-based first-line regimens. Patients with tumors bearing a KRAS p.G12D mutation showed a strong trend to a more favorable outcome compared to other mutations (overall survival 23.3 vs. 14-18 months; hazard ratio 0.66, range 0.43-1.03). An interaction model illustrated that KRAS p.G12C was associated with unfavorable outcome when treated with oxaliplatin plus cetuximab.

CONCLUSION

The present analysis suggests that KRAS codon 12 mutation may not represent a homogeneous entity in mCRC when treated with cetuximab-based first-line therapy.

KRAS status and clinical outcome in metastatic colorectal cancer patients treated with first-line FOLFOX chemotherapy

BACKGROUND

Two previous first-line studies showed an improved trend in response rate (RR) and progression free survival (PFS) in metastatic colorectal cancer (CRC) patients with KRAS mutation. Others have reported a worsened outlook for metastatic CRC patients with KRAS mutation and a higher likelihood of metastatic disease to the lungs. In this study, we aimed to address the impact of KRAS on the pattern of metastatic disease at presentation and on RR and PFS with first-line 5-fluorouracil, leucovorin, and oxaliplatin (FOLFOX) chemotherapy.

METHODS

Patients with CRC who underwent KRAS testing using DxS assay at Roswell Park Cancer Institute (RPCI) were identified. Patients with metastatic CRC treated with first-line FOLFOX +/- bevacizumab were assessed for response and survival using RECIST 1.1 guidelines. A two-sided Fisher's exact test was used to determine the statistical significance.

RESULTS

181 patients with metastatic CRC and KRAS testing were identified. 83/181 patients were treated with FOLFOX (+/- bevacizumab) in the first-line setting at RPCI and were evaluable as per study guidelines. KRAS mutation (MT) occurred in 40.31% cases. There was no difference in organ-metastases distribution, RR (56.60% in KRAS wild-type (WT) and 50% in KRAS mutant) or PFS (9.3 months KRAS WT and 8.7 months in KRAS MT) based on KRAS status.

CONCLUSION

In this single institute study, our findings do not support any predictive role for KRAS-MT in terms of response to FOLFOX first-line chemotherapy, or in terms of sites of metastatic disease at mCRC presentation.

Management of colorectal cancer patients after resection of liver metastases: can we offer a tailored treatment?

Surgical resection remains the only option of cure for patients with colorectal liver metastases, and no patient should be precluded from surgery. There is much controversy not only regarding the most appropriate therapeutic approach in the neoadjuvant setting but also after surgery is performed. Many patients will experience early relapses but others will be long survivors. We need to establish reliable prognostic and predictive factors to offer a tailored treatment. Several prognostic factors after metastasectomy have been identified: high C-reactive protein levels, a high neutrophil-lymphocyte ratio, elevated neutrophil count and low serum albumin are related to a worst outcome. Elevated CEA and Ki 67 levels, intrahepatic and perihepatic lymph node invasion are also some of the markers related to a worst outcome. In contrast, the administration of preoperative chemotherapy has been associated with a better prognosis after hepatectomy. The administration of adjuvant chemotherapy should be done taking in consideration these factors. Regarding predictive factors, determination of ERCC1, TS, TP and DPD and UGT1 polymorphisms assessment could be considered prior to chemotherapy administration. This would avoid treatment related toxicities and increase this population quality of life.

The prognostic value of KRAS mutations in patients with colorectal cancer

Our aim was to evaluate the KRAS genotypes of Japanese colorectal cancer (CRC) patients and to assess the effect of these genotypes on clinical outcome. A total of 99 patients with stage I-IV CRC who underwent resection were prospectively studied for KRAS mutations by direct sequencing. KRAS mutations were found in 37 (37.4%) of 99 patients. Of these, 11.1% were the KRAS p.G13D mutation and the remaining 26.2% were other KRAS mutations. The cumulative 5-year survival rates for patients with wild-type KRAS, KRAS 12 and KRAS p.G13D mutations were 81.4, 61.4 and 42.0%, respectively (P=0.0397). The KRAS genotype had no effect on stage IV patient prognosis without anti-epithelial growth factor receptor (EGFR) antibody therapy. However, in stage I-III patients significant or trends in prognostic factors for disease-free survival (DFS) were pathological T stage, lymphatic vessel involvement and KRAS p.G13D. Multivariate analysis identified T4 pathological stage (P=0.0076) and the KRAS p.G13D mutation (P=0.0499) as the most significant independent prognostic factors associated with DFS. In Japanese CRC patients KRAS p.G13D had prognostic impact on DFS in stage I-III disease, while the prognosis of stage IV patients without anti-EGFR antibody therapy was unaffected by KRAS status.

Influence of anatomical subsite on the incidence of microsatellite instability, and KRAS and BRAF mutation rates in patients with colon carcinoma

There is a growing amount of data supporting the concept that cancers originating from the proximal and distal colon are distinct clinicopathological entities. The incidence of MSI and BRAF mutation is strongly associated with right sided tumor location, whereas there are conflicting results for KRAS mutation rates. However, to date, no data exist whether and to what extent defined colonic subsites influence MSI status, KRAS and BRAF mutation rates. We selected primary colon cancer from 171 patients operated on at our institution between 2007 and 2010. BRAF, KRAS mutation rates and microsatellite instability were determined and correlated with clinicopathological features and tumor location. MSI-h cancers were significantly associated with poor histological grade but a lower rate of distant metastases. KRAS-mutated tumors were linked to lower T-stage and better differentiation. Colon carcinomas with BRAF mutation were significantly associated with distant metastatic spread and poor histological grade. Furthermore, we found that MSI-h status, KRAS and BRAF mutation rates varied remarkably among the colonic subsites irrespective of right- and left-sided origin, respectively. The results of the current study provide further evidence that a simple classification into right- and left-sided colon carcinoma does not represent the complexity of this tumor entity.

Different metastatic pattern according to the KRAS mutational status and site-specific discordance of KRAS status in patients with colorectal cancer

Background

We evaluated the association between a KRAS mutational status and various clinicopathologic features including the metastatic pattern in patients with metastatic or recurrent colorectal cancer (MRCRC). The concordance rates of the KRAS status between primary tumor sites and paired metastatic organs were also analyzed.

Methods

The KRAS mutational status in codons 12, 13, and 61 from formalin-fixed sections of both primary tumors and related metastases was determined by sequencing analysis. One hundred forty-three Korean patients with MRCRC with available tissues (resection or biopsy) from both primary tumors and related metastatic sites were consecutively enrolled.

Results

The KRAS mutation rate was 52.4% (75/143) when considering both the primary and metastatic sites. When the relationship between the KRAS status and initial metastatic sites at the time of diagnosis of MRCRC was analyzed, lung metastasis was more frequent as the initial metastatic site in patients with the KRAS mutation than in patients without the KRAS mutation (45.3% vs. 22.1%; P = 0.003). However, liver (37.3% vs. 70.6%; P < 0.001) or distant lymph node metastases (6.7% vs. 19.1%; P = 0.025) were less frequent as the initial metastatic organ in patients with the KRAS mutation than in patients without the KRAS mutation. The discordance rate of KRAS mutational status between primary and paired metastatic sites other than the lung was 12.3% (13/106). Compared with primary tumor sites, the KRAS discordance rate was significantly higher in matched lung metastases [32.4% (12/37)] than in other matched metastatic organs (P = 0.005).

Conclusions

Organs initially involved by distant metastasis were different according to the KRAS mutational status in MRCRC patients. The concordance rate (87.7%) of the KRAS mutation status at metastatic sites other than the lung was generally high compared with primary tumor sites; however, lung metastasis had a high rate of KRAS discordance (32.4%).

Pharmacogenetics and pharmacogenomics: role of mutational analysis in anti-cancer targeted therapy

The goal of cancer pharmacogenomics is to obtain benefit from personalized approaches of cancer treatment and prevention. Recent advances in genomic research have shed light on the crucial role of genetic variants, mainly involving genes encoding drug-metabolizing enzymes, drug transporters and targets, in driving different treatment responses among individuals, in terms of therapeutic efficacy and safety. Although a considerable amount of new targeted agents have been designed based on a finely understanding of molecular alterations in cancer, a wide gap between pharmacogenomic knowledge and clinical application still persists. This review focuses on the relevance of mutational analyses in predicting individual response to antitumor therapy, in order to improve the translational impact of genetic information on clinical practice.

BRAF-mutated, microsatellite-stable adenocarcinoma of the proximal colon: an aggressive adenocarcinoma with poor survival, mucinous differentiation, and adverse morphologic features

The association of BRAF V600E mutation and the presence of the CpG island methylator phenotype (CIMP) and microsatellite instability (MSI) often confound analysis of BRAF mutation status and survival in colorectal carcinoma. We evaluated a consecutive series of proximal colonic adenocarcinomas for mismatch repair protein abnormalities/MSI, BRAF V600E mutation, and KRAS mutations in an attempt to determine the prognostic significance of these abnormalities and to correlate histopathologic features with molecular alterations. Of the 259 proximal colon adenocarcinomas analyzed for mismatch repair protein abnormalities and/or MSI, 181 proximal colonic adenocarcinomas demonstrated proficient DNA mismatch repair using either MSI PCR (n=78), mismatch repair protein immunohistochemistry (n=91), or both MSI PCR and mismatch repair immunohistochemistry (n=12); these were tested for the BRAF V600E mutation and KRAS mutations. Compared with BRAF wild-type adenocarcinomas, BRAF-mutated adenocarcinomas more frequently demonstrated adverse histologic features such as lymphatic invasion (16/20, 80% vs. 75/161, 47%; P=0.008), mean number of lymph node metastases (4.5 vs. 2.2; P=0.01), perineural invasion (8/20, 40% vs. 13/161, 8%; P=0.0004), and high tumor budding (16/20, 80% vs. 83/161, 52%; P=0.02). BRAF-mutated adenocarcinomas frequently contained areas with mucinous histology (P=0.0002) and signet ring histology (P=0.03), compared with KRAS-mutated and KRAS/BRAF wild-type adenocarcinomas. Clinical follow-up data were available for 173 proximal colonic adenocarcinomas with proficient DNA mismatch repair. Patients with BRAF-mutated adenocarcinomas had a median survival of 12.3 months with a 1-year probability of survival of 54% and a 1-year disease-free survival of 56%. Patients with KRAS-mutated and KRAS/BRAF wild-type adenocarcinomas had significantly improved overall survival (unadjusted log-rank P=0.03 and unadjusted log-rank P=0.0002, respectively) and disease-free survival (unadjusted log-rank P=0.02 and unadjusted log-rank P=0.02, respectively) compared with patients with BRAF-mutated adenocarcinomas. When adjusting for tumor stage, survival analysis demonstrated that patients with BRAF-mutated adenocarcinoma had a significantly poor overall survival and disease-free survival (hazard ratios 6.63, 95% CI, 2.60-16.94; and 6.08, 95% CI, 2.11-17.56, respectively) compared with patients with KRAS/BRAF wild-type adenocarcinomas. No significant difference in overall or disease-free survival was identified between patients with KRAS-mutated and KRAS/BRAF wild-type adenocarcinomas. Our results demonstrate that BRAF-mutated proximal colon adenocarcinomas with proficient DNA mismatch repair have a dismal prognosis with an aggressive clinical course and often display mucinous differentiation, focal signet ring histology, and other adverse histologic features such as lymphatic and perineural invasion and high tumor budding.

KRAS mutation is present in a small subset of primary urinary bladder adenocarcinomas

AIMS

To determine whether KRAS mutations occur in primary bladder adenocarcinoma.

METHODS AND RESULTS

Twenty-six cases of primary urinary bladder adenocarcinoma were analysed. DNA was extracted from formalin-fixed, paraffin-embedded tissue and amplified with shifted termination assay technology, which recognizes wild-type or mutant target sequences and selectively extends detection primers with labelled nucleotides. A mutation in KRAS was found in three (11.5%) of 26 primary bladder adenocarcinomas. Two of these three cases exhibited a G13D mutation, whereas the remaining case contained a mutation in G12V. None of the ten cases of urothelial carcinoma with glandular differentiation displayed KRAS mutation. Colonic adenocarcinoma contained a KRAS mutation in 18 (33%) of 55 cases. There was no distinct difference with regard to grade, stage or outcome according to the limited clinicopathological data available. However, the two youngest patients, aged 32 and 39 years, in our study group, with a mean population age of 61 years, were found to have mutations in KRAS.

CONCLUSIONS

KRAS mutations are present in a small subset of primary urinary bladder adenocarcinomas. Future clinical trials for treatment of bladder adenocarcinoma, employing targeted therapies similar to those used for treatment of colon cancer, may also benefit from the predictive implications of KRAS mutational testing.

Relationship between expression of ras p21 oncoprotein and mutation status of the K-ras gene in sporadic colorectal cancer patients in Tunisia

INTRODUCTION

The K-ras proto-oncogene encodes a protein (p21-ras) belonging to the family of GTP/GDP-binding proteins with GTPase activity. The activation of ras family genes plays an important role in colorectal tumorigenesis. Frequency of K-ras mutations and overexpression of the protein in colorectal cancer (CRC) vary between 14% and 50% and between 29% and 76%, respectively.

AIMS

We investigated the clinicopathologic characteristics of patients with CRC and their relationship with point mutations of K-ras oncogene codons 12/13 and ras p21 expression.

MATERIALS AND METHODS

K-ras codons 12 and 13 point mutations were examined by direct sequence analysis, whereas the ras p21 expression was evaluated using immunohistochemistry.

RESULTS

Statistical analysis of immunohistochemical results showed that the expression of ras p21 was correlated with the advanced age of patients (P=0.0001), whereas loss of signal was associated with mucinous histotype (P=0.0001). Mutations in the K-ras gene were detected in 12 of the patients with CRC. Mutations in K-ras gene were found in 12 of 52 tumors (23.07%), and 7 mutations were G→A transitions (58.33% of all mutations), 4 were G→T transversions (33.33%), and only 1 was G→C transversion (8.33%). A total of 83.33% of the mutation occurred at codon 12 and 16.67% at codon 13. Moreover, K-ras mutations were associated with the sex of patients (P=0.017).

CONCLUSIONS

Genetic K-ras alterations were rather low in the Tunisian population, but further study is necessary to unravel the molecular background of CRC.

KRAS mutations and subtyping in colorectal cancer in Jordanian patients

Colorectal cancer (CRC) is one of the most common malignancies in the Western world and Jordan. v-Ki-ras2 Kirsten rat sarcoma (KRAS) mutations represent an early event in the development and progression of CRC. Previous studies have demonstrated that KRAS mutations serve as a predictor of response to EGFR-targeted therapies for patients with metastatic CRC. The aim of this study was to determine the portion of CRC patients with wildtype KRAS status and molecular subtypes of KRAS mutations in Jordan as compared with other countries. DNA was isolated from 100 consecutive colorectal carcinoma specimens from patients who underwent surgical resection or colonoscopic biopsies of colorectal tumors and had developed metastatic disease. KRAS mutations were detected by hybridization-based strip assay as well as RT-PCR-based assay and confirmed by standard Sanger sequencing of codon 12 and 13 of exon 1 of the KRAS gene. Among 100 tested patients, 56% had a wt-KRAS genotype and 44% had a mutated KRAS genotype. The pGly12Asp was the most commonly detected mutation (54.5%). KRAS mutations were independently associated with patient age, gender and tumoral variables. The ratio of mutated versus wt-KRAS patients in this study is similar to those reported in Western countries but contrasts to neighboring Middle Eastern countries. Colorectal carcinoma cases from Jordan had higher KRAS mutation frequencies compared with other Middle Eastern countries which is likely to reflect different molecular pathogenesis and environmental exposures.

Association of KRAS G13D tumor mutations with outcome in patients with metastatic colorectal cancer treated with first-line chemotherapy with or without cetuximab

PURPOSE

We investigated in the first-line setting our previous finding that patients with chemorefractory KRAS G13D-mutated metastatic colorectal cancer (mCRC) benefit from cetuximab treatment.

METHODS

Associations between tumor KRAS mutation status (wild-type, G13D, G12V, or other mutations) and progression-free survival (PFS), survival, and response were investigated in pooled data from 1,378 evaluable patients from the CRYSTAL and OPUS studies. Multivariate analysis correcting for differences in baseline prognostic factors was performed.

RESULTS

Of 533 patients (39%) with KRAS-mutant tumors, 83 (16%) had G13D, 125 (23%) had G12V, and 325 (61%) had other mutations. Significant variations in treatment effects were found for tumor response (P = .005) and PFS (P = .046) in patients with G13D-mutant tumors versus all other mutations (including G12V). Within KRAS mutation subgroups, cetuximab plus chemotherapy versus chemotherapy alone significantly improved PFS (median, 7.4 v 6.0 months; hazard ratio [HR], 0.47; P = .039) and tumor response (40.5% v 22.0%; odds ratio, 3.38; P = .042) but not survival (median, 15.4 v 14.7 months; HR, 0.89; P = .68) in patients with G13D-mutant tumors. Patients with G12V and other mutations did not benefit from this treatment combination. Patients with KRAS G13D-mutated tumors receiving chemotherapy alone experienced worse outcomes (response, 22.0% v 43.2%; odds ratio, 0.40; P = .032) than those with other mutations. Effects were similar in the separate CRYSTAL and OPUS studies.

CONCLUSION

The addition of cetuximab to first-line chemotherapy seems to benefit patients with KRAS G13D-mutant tumors. Relative treatment effects were similar to those in patients with KRAS wild-type tumors but with lower absolute values.

Novel prognostic biomarkers in colorectal cancer

The main predictor of outcome of patients with colorectal cancer (CRC) remains the TNM staging system. Biomarkers, i.e. biological indicators of disease progression or of responsiveness to a pharmacological intervention, are expected to be of help in the management of CRC. Despite high expectations, biomarkers have not entered into clinical practice due to contradictory results of large-scale studies and to some complexity in data interpretation. Here we briefly review the main genetic and immunological changes that have been considered potential CRC biomarkers and that might be considered for further testing aimed at clinical use, at least in specific disease settings.

A comparison of three methods for detecting KRAS mutations in formalin-fixed colorectal cancer specimens

BACKGROUND

KRAS mutation testing is required to select patients with metastatic colorectal cancer (CRC) to receive anti-epidermal growth factor receptor antibodies, but the optimal KRAS mutation test method is uncertain.

METHODS

We conducted a two-site comparison of two commercial KRAS mutation kits - the cobas KRAS Mutation Test and the Qiagen therascreen KRAS Kit - and Sanger sequencing. A panel of 120 CRC specimens was tested with all three methods. The agreement between the cobas test and each of the other methods was assessed. Specimens with discordant results were subjected to quantitative massively parallel pyrosequencing (MPP). DNA blends were tested to determine detection rates at 5% mutant alleles.

RESULTS

Reproducibility of the cobas test between sites was 98%. Six mutations were detected by cobas that were not detected by Sanger, and five were confirmed by MPP. The cobas test detected eight mutations which were not detected by the therascreen test, and seven were confirmed by MPP. Detection rates with 5% mutant DNA blends were 100% for the cobas and therascreen tests and 19% for Sanger.

CONCLUSION

The cobas test was reproducible between sites, and detected several mutations that were not detected by the therascreen test or Sanger. Sanger sequencing had poor sensitivity for low levels of mutation.

Influence of KRAS mutation status in metachronous and synchronous metastatic colorectal adenocarcinoma

BACKGROUND

Mutations in the v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) are present in approximately 30% to 40% of colorectal adenocarcinomas. Wild-type (WT) KRAS mutation status is predictive of tumor response with epidermal growth factor receptor-directed therapies, but the results from studies evaluating the prognostic value of KRAS status in localized disease have been contradictory. The prognostic value of KRAS in metastatic disease, specifically according to whether patients have synchronous or metachronous disease at presentation, is less understood.

METHODS

One-hundred ten consecutive patients with metastatic colorectal adenocarcinoma underwent testing for KRAS exon 2 mutations by polymerase chain reaction amplification and direct nucleotide sequencing. The clinical characteristics, treatments, and outcomes of these patients were then analyzed retrospectively, stratified according to whether patients presented with synchronous or metachronous metastasis and according to KRAS mutation status (WT or mutated).

RESULTS

For the entire cohort, the median overall survival from the date of diagnosis of metastatic disease was 34.3 months (95% confidence interval, 28.3-49.4 months) for patients with WT KRAS (n = 70). The median overall survival for patients with mutated KRAS (n = 40) was 40.3 months (95% confidence interval, 27.9-51.1 months; log-rank P = .91). Kaplan-Meier survival analysis indicated that 3-year overall survival and 5-year overall survival were not statistically different. Within the subgroups of patients with synchronous and metachronous metastatic disease, no significant differences were observed in median overall survival, 3-year overall survival, or 5-year overall survival between the WT KRAS and mutated KRAS groups.

CONCLUSIONS

In this study, KRAS mutation status did not influence overall survival in either synchronous or metachronous metastatic colorectal adenocarcinoma and, as such, had no prognostic role in this disease setting.

Molecular testing in colorectal cancer: diagnosis of Lynch syndrome and personalized cancer medicine

Currently, molecular testing in colorectal cancer (CRC) is aimed at detecting Lynch syndrome and predicting response to anti-epidermal growth factor receptor (EGFR) therapies. However, CRC is a complex disease, with at least 3 molecular pathways of carcinogenesis. The importance of the EGFR signaling pathway in colorectal carcinogenesis is underscored by the availability of anti-EGFR monoclonal antibodies for the treatment of some metastatic CRCs. Potentially, mutations in any of the genes in the EGFR signaling pathway may be associated with prognosis and may predict response to anti-EGFR or other targeted therapies. Although not currently the standard of care, molecular testing of CRCs is expanding to include mutational analysis of the genes in the EGFR pathway, in addition to more widely performed tests for identifying cancers with high microsatellite instability. Multiplex molecular prognostic panels for therapeutic decision making in stage II CRCs also represent expanding use of molecular testing for this common cancer.

Genetic polymorphisms in MicroRNA-related genes as predictors of clinical outcomes in colorectal adenocarcinoma patients

PURPOSE

To evaluate the effects of single-nucleotide polymorphisms (SNP) in microRNA-related genes on clinical outcomes in patients with colorectal cancer (CRC) receiving first-line fluoropyrimidine-based chemotherapy.

EXPERIMENTAL DESIGN

Forty-one SNPs in 26 microRNA-related genes were genotyped in 1,097 patients with CRC recruited at the University of Texas MD Anderson Cancer Center (Houston, TX). Patients were enrolled between 1990 and 2008 and last follow-up was in 2010. The associations between genotypes and recurrence-free survival (RFS), progression-free survival (PFS), and overall survival (OS) stratified by clinical stage were analyzed in 741 newly diagnosed patients (diagnosed within 1 year) and replicated the findings in an additional 356 patients.

RESULTS

In patients with stage III disease, mir608: rs4919510 was associated with increased risk for both recurrence [HR, 2.72; 95% confidence interval (CI), 1.38-5.33] and death (HR, 3.53; 95%CI, 1.42-8.73). The associations were confirmed in the replication set, and the combined HRs for training and replication sets were 1.65 (95% CI, 1.13-2.41) for recurrence and 1.96 (95% CI, 1.19-3.21) for death, respectively. The mir219-1:rs213210 showed consistent association with death in the training set (HR, 3.86; 95% CI, 1.33-11.22), the replication set (HR, 3.33; 95% CI, 1.39-7.98), and combined data set (HR, 3.22; 95% CI, 1.70-6.10). In combined analysis of these two SNPs, patients carrying the variant genotypes at both sites exhibited a 5.6-fold increased risk of death.

CONCLUSION

Genetic polymorphisms in the microRNA pathway may predict prognosis in patients with stage III CRC treated with fluoropyrimidine-based chemotherapy.

Application of molecular techniques in the diagnosis, prognosis and management of patients with colorectal cancer: a practical approach

There has been an increasing role for molecular diagnostics in the diagnosis and management of cancer, and colorectal carcinoma is no exception. Recent molecular advances have elucidated 3 broad molecular subtypes of colorectal cancer, including chromosomal instability, microsatellite instability, and cytosine-phosphoguanine island methylator phenotype, which will be discussed. Also, the common syndromes associated with colorectal carcinoma will be reviewed with a focus on the differentiation between Lynch syndrome and microsatellite unstable tumors. Molecular biomarkers for predictive and prognostic markers are also becoming widely used, and due to the clinical use of monoclonal antibodies to the epidermal growth factor receptor, an emphasis is placed on that pathway.

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.