Clinical relevance of KRAS mutation detection in metastatic colorectal cancer treated by Cetuximab plus chemotherapy

The predictive value of KRAS mutation in metastatic colorectal cancer (MCRC) patients treated with cetuximab plus chemotherapy has recently been suggested. In our study, 59 patients with a chemotherapy-refractory MCRC treated with cetuximab plus chemotherapy were included and clinical response was evaluated according to response evaluation criteria in solid tumours (RECIST). Tumours were screened for KRAS mutations using first direct sequencing, then two sensitive methods based on SNaPshot and PCR-ligase chain reaction (LCR) assays. Clinical response was evaluated according to gene mutations using the Fisher exact test. Times to progression (TTP) were calculated using the Kaplan-Meier method and compared with log-rank test. A KRAS mutation was detected in 22 out of 59 tumours and, in six cases, was missed by sequencing analysis but detected using the SNaPshot and PCR-LCR assays. Remarkably, no KRAS mutation was found in the 12 patients with clinical response. KRAS mutation was associated with disease progression (P=0.0005) and TTP was significantly decreased in mutated KRAS patients (3 vs 5.5 months, P=0.015). Our study confirms that KRAS mutation is highly predictive of a non-response to cetuximab plus chemotherapy in MCRC and highlights the need to use sensitive molecular methods, such as SNaPshot or PCR-LCR assays, to ensure an efficient mutation detection.     

HER2 gene copy number status may influence clinical efficacy to anti-EGFR monoclonal antibodies in metastatic colorectal cancer patients

Background:

In metastatic colorectal cancer (mCRC), KRAS is the only validated biomarker used to select patients for administration of epidermal growth factor receptor (EGFR)-targeted therapies. To identify additional predictive markers, we investigated the importance of HER2, the primary EGFR dimerisation partner, in this particular disease.

Methods:

We evaluated the HER2 gene status by fluorescence in situ hybridisation (FISH) in 170 KRAS wild-type mCRC patients treated with cetuximab or panitumumab.

Results:

Depending on HER2 gene copy number status, patients showed three distinct cytogenetic profiles: 4% of patients had HER2 gene amplification (R:HER2/CEP17⩾2) in all neoplastic cells (HER2-all-A), 61% of patients had HER2 gain due to polysomy or to gene amplification in minor clones (HER2-FISH+*), and 35% of patients had no or slight HER2 gain (HER2-FISH−). These subgroups were significantly correlated with different clinical behaviours, in terms of response rate (RR; P=0.0006), progression-free survival (PFS; P<0.0001) and overall survival (OS; P<0.0001). Patients with HER2-all-A profile experienced the worst outcome, patients with HER2-FISH− profile showed an intermediate behaviour and patients with HER2-FISH+* profile were related to the highest survival probability (median PFS in months: 2.5 vs 3.9 vs 7.6, respectively; median OS in months: 4.2 vs 9.7 vs 13, respectively).

Conclusion:

HER2 gene copy number status may influence the clinical response to anti-EGFR-targeted therapy in mCRC patients.     

KRAS as a predictor of poor prognosis and benefit from postoperative FOLFOX chemotherapy in patients with stage II and III colorectal cancer

Purpose

The KRAS gene frequently mutates in colorectal cancer (CRC). Here we investigated the prognostic and predictive role of KRAS mutation in patients with stage II or III CRC.

Experimental design

A consecutive cohort of patients with stage II or III CRC from a single center database was studied. The association between KRAS status, adjuvant FOLFOX therapy, and 3‐year disease‐free survival (3‐y DFS) was analyzed.

Results

Of our 433 patients, 166 (38.3%) exhibited the KRAS mutation. Among the 190 patients who did not receive adjuvant therapy, those with KRAS mutation tumors had a worse 3‐y DFS (hazard ratio [HR], 1.924; 95% confidence interval [CI], 1.078–3.435; P = 0.027). Among patients who received adjuvant chemotherapy, KRAS mutation was not correlated with worse 3‐y DFS (HR, 1.083; 95% CI, 0.618–1.899; P = 0.781). Adjuvant chemotherapy improved 3‐y DFS only among patients with KRAS mutant tumors (78.0% vs 69.2%) on multivariate analysis adjusted for age, stage, grade, site, vessel invasion, and carcinoembryonic antigen level (HR, 0.454; 95% CI, 0.229–0.901; P = 0.024). In contrast, there was no benefit of adjuvant chemotherapy in the KRAS wild‐type group (84.3% vs 82.0%).

Conclusions

KRAS mutation indicates poor prognosis. FOLFOX adjuvant chemotherapy benefits patients with stage II or III colorectal cancer with KRAS mutant tumors and is worth further investigation.     

Prognostic and predictive value of TOPK stratified by KRAS and BRAF gene alterations in sporadic, hereditary and metastatic colorectal cancer patients

Background:

Our aim was to investigate the prognostic and predictive value of the oncogenic MAPKK-like protein T-cell-originated protein kinase (TOPK) stratified by KRAS and BRAF mutations in patients with sporadic, hereditary and metastatic colorectal cancer (CRC) treated with anti-EGFR therapy.

Methods:

Immunohistochemistry (IHC) for TOPK was performed on four study groups. Group 1 included two subgroups of 543 and 501 sporadic CRC patients used to test the reliability of TOPK expression by IHC. In Group 2, representing an additional 222 sporadic CRCs, the prognostic effect of TOPK stratified by KRAS and BRAF was assessed. The prognostic effect of TOPK was further analysed in Group 3, representing 71 hereditary Lynch syndrome-associated CRC patients. In Group 4, the predictive and prognostic value of TOPK was analysed on 45 metastatic patients treated with cetuximab or panitumumab stratified by KRAS and BRAF gene status.

Results:

In both sporadic CRC subgroups (Group 1), associations of diffuse TOPK expression with clinicopathological features were reproducible. Molecular analysis of sporadic CRCs in Group 2 showed that diffuse TOPK expression was associated with KRAS and BRAF mutations (p<0.001) and with poor outcome in patients with either mutation in univariate and multivariate analysis (P=0.017). In hereditary patients (Group 3), diffuse TOPK was linked to advanced pT stage. In metastatic patients treated with anti-EGFR therapy (Group 4), diffuse TOPK expression was linked to dismal outcome despite objective response to treatment (P=0.01).

Conclusions:

TOPK expression is an unfavourable prognostic indicator in sporadic patients with KRAS or BRAF mutations and also in patients with metastatic disease experiencing a response to anti-EGFR therapies. The inhibition of TOPK, which could benefit 30–40% of CRC patients, may represent a new avenue of investigation for targeted therapy.     

Sorafenib and irinotecan (NEXIRI) as second- or later-line treatment for patients with metastatic colorectal cancer and KRAS-mutated tumours: a multicentre Phase I/II trial

Background:

This trial evaluated the feasibility and efficacy of combined sorafenib and irinotecan (NEXIRI) as second- or later-line treatment of patients with KRAS-mutated metastatic colorectal cancer (mCRC), who had progressed after irinotecan-based chemotherapy.

Methods:

In Phase I, in a 3+3 dose escalation schedule, patients received irinotecan (125, 150 or 180 mg m⁻² every 2 weeks), in combination with 400 mg sorafenib b.d. The primary end point was the maximum-tolerated dose of irinotecan. In Phase II, the primary end point was disease control rate (DCR). Secondary end points were progression-free survival (PFS), overall survival (OS) and toxicity.

Results:

Phase I included 10 patients (median age 63 (49–73)); no dose-limiting toxicity was seen. In Phase II, 54 patients (median age 60 (43–80) years) received irinotecan 180 mg m⁻² every 2 weeks with sorafenib 400 mg b.d. Nine patients (17%) remained on full-dose sorafenib. The DCR was 64.9% (95% CI, 51–77). Median PFS and OS were 3.7 (95% CI, 3.2–4.7) and 8.0 (95% CI, 4.8–9.7) months, respectively. Toxicities included Grade 3 diarrhoea (37%), neutropenia (18%), hand-foot syndrome (13%) and Grade 4 neutropenia (17%).

Conclusion:

The NEXIRI regimen showed promising activity as second- or later-line treatment in this heavily pretreated mCRC population (ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00989469","term_id":"NCT00989469"}}NCT00989469).     

Down-regulation of KRAS-interacting miRNA-143 predicts poor prognosis but not response to EGFR-targeted agents in colorectal cancer

Background:

MicroRNA-143 (miRNA-143) is frequently down-regulated in colorectal cancer (CRC) and may influence CRC cell proliferation, apoptosis and sensitivity to 5-fluorouracil. mRNA encoded by the KRAS oncogene has been identified as a target of miRNA-143. However, the prognostic significance of miRNA-143 expression and the ability to predict patient response to epidermal growth factor receptor (EGFR)-targeted agents have not yet been explored.

Methods:

We examined 77 CRC patients who were identified by pyrosequencing to have wild-type KRAS and were subsequently treated with EGFR-targeted therapy with the monoclonal antibodies cetuximab or panitumumab. MicroRNA-143 expression was measured in CRC tissue and corresponding non-neoplastic colon tissue by RT–PCR and its expression level was correlated with clinico-pathological characteristics. Univariate and multivariate analyses were used to calculate cancer-specific survival (CSS). The progression-free survival (PFS) and objective response rates on EGFR-targeted therapy were also evaluated.

Results:

Down-regulation of miRNA-143 was observed in 47 out of 77 (61%) tumours. Multivariate Cox regression analysis identified low levels of miRNA-143 expression as an independent prognostic factor with respect to CSS (hazard ratio=1.92, confidence interval=1.1–3.4, P=0.024). A significant difference was also observed with regard to PFS on EGFR-targeted therapy (P=0.031), but there were no significant differences with regard to the objective response rates.

Conclusion:

Our data indicate that miRNA-143 expression levels serve as an independent prognostic biomarker for CRC in KRAS wild-type patients. No role for miRNA-143 expression as a predictive biomarker for EGFR-targeted agents could be identified. Given its negative impact on CSS and PFS, miRNA-143 represents a novel prognosticator and a promising drug target for patients with CRC.     

EGFR gene copy number assessment from areas with highest EGFR expression predicts response to anti-EGFR therapy in colorectal cancer

Background:

Only 40–70% of metastatic colorectal cancers (mCRCs) with wild-type (WT) KRAS oncogene respond to anti-epidermal growth factor receptor (anti-EGFR) antibody treatment. EGFR amplification has been suggested as an additional marker to predict the response. However, improved methods for bringing the EGFR analysis into routine laboratory are needed.

Methods:

The material consisted of 80 patients with mCRC, 54 of them receiving anti-EGFR therapy. EGFR gene copy number (GCN) was analysed by automated silver in situ hybridisation (SISH). Immunohistochemical EGFR protein analysis was used to guide SISH assessment.

Results:

Clinical benefit was seen in 73% of high (⩾4.0) EGFR GCN patients, in comparison with 59% of KRAS WT patients. Only 20% of low EGFR GCN patients responded to therapy. A high EGFR GCN number associated with longer progression-free survival (P<0.0001) and overall survival (P=0.004). Together with KRAS analysis, EGFR GCN identified the responsive patients to anti-EGFR therapy more accurately than either test alone. The clinical benefit rate of KRAS WT/high EGFR GCN tumours was 82%.

Conclusion:

Our results show that automated EGFR SISH, in combination with KRAS mutation analysis, can be a useful and easily applicable technique in routine diagnostic practise for selecting patients for anti-EGFR therapy.     

K-Ras gene mutation status as a prognostic and predictive factor in patients with colorectal cancer undergoing irinotecan- or oxaliplatin-based chemotherapy

Background: CRC caused more than 600,000 estimated deaths in 2008. Dysregulated signaling through the RAS/RAF/mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway due to mutations in K-Ras and B-Raf are common events in CRC. Methods: Incidence of mutations in codons 12 and 13 of K-Ras and exons 11 and 15 of B-Raf were analyzed in amplified PCR products from primary tumors of 273 patients with CRC, and their prognostic and predictive significance was assessed. The prognostic role of clinical and pathological factors was also examined. Results: K-Ras mutations were present in 89 patients (32.6%), of whom 76 (85.4%) had mutations in codon 12 and 10 (11.2%) had mutations in codon 13. B-Raf gene mutations were present in 17 patients (6.9%), of whom 6 (35.3%) had mutations in exon 15. Multivariate analysis revealed a predictive significance for K-Ras mutations with respect to time to progression in patients treated with irinotecan and oxaliplatin as first-line chemotherapy. There was no predictive significance for B-Raf gene mutation status in these patients. The following risk factors were found to affect overall survival (OS) rates: primary tumor location, lymph node involvement grade, carcinoembryonic antigen (CEA) level before treatment, and performance status according to WHO criteria. Conclusions: Based on the results of this study, K-Ras mutation status may be a suitable indicator of patient eligibility and a prognostic indicator for responsiveness to anti-EGFR therapy alone, or in combination with chemotherapy. Also, K-Ras mutation status may predict time to progression in patients treated with irinotecan and oxaliplatin.     

TP53 mutations predict disease control in metastatic colorectal cancer treated with cetuximab-based chemotherapy

Recent studies have suggested that activation of the EGFR pathway leads to malignant transformation only if the p53 protein is inactivated. Therefore, we evaluated the impact of TP53 mutations on cetuximab-based chemotherapy (CT) sensitivity in combination with KRAS mutations that have been associated with cetuximab resistance. KRAS and TP53 status were assessed in tumours from 64 metastatic colorectal cancer patients treated with cetuximab-based CT and correlated to clinical response using the Fisher''s exact test. Times to progression (TTPs) according to gene status were calculated using the Kaplan–Meier method and compared with log-rank test. TP53 mutations were found in 41 patients and were significantly associated with controlled disease (CD), as defined as complete response, partial response or stable disease (P=0.037) and higher TTP (20 vs 12 weeks, P=0.004). Remarkably, in the subgroup of 46 patients without KRAS mutation, but not in patients with KRAS mutation, TP53 mutations were also associated with CD (P=0.008) and higher TTP (24 vs 12 weeks, P=0.0007). This study suggests that TP53 mutations are predictive of cetuximab sensitivity, particularly in patients without KRAS mutation, and that TP53 genotyping could have a clinical interest to select patients who should benefit from cetuximab-based CT.     

Cost-effectiveness of first-line treatments for patients with KRAS wild-type metastatic colorectal cancer

Background

Combinations of chemotherapy regimens and monoclonal antibodies have been demonstrated to improve clinical outcomes in patients with metastatic colorectal cancer (mcrc). Although these combination treatment strategies are safe and effective in first-line treatment for mcrc, little is known about their economic consequences and resource allocation implications. In the present study, we evaluated the cost-effectiveness of bevacizumab plus folfiri, cetuximab plus folfiri, and panitumumab plus folfiri for patients with KRAS wild-type mcrc.

Methods

A Markov model simulated the lifetime patient outcomes and costs of each first-line treatment strategy and subsequent lines of treatment from the perspective of the health care payer in Ontario. The model was parameterized using data from the Ontario Cancer Registry, Ontario health administrative databases, and published randomized control trials. Patient outcomes were measured in quality-adjusted life years (qalys), and costs were measured in monetary terms. Costs and outcomes were both discounted at 5% and expressed in 2012 Canadian dollars.

Results

For mcrc patients with KRAS wild-type disease, the treatment strategy of bevacizumab plus folfiri was found to dominate the other two first-line treatment strategies. Sensitivity analyses revealed that the incremental cost-effectiveness ratio values were sensitive to the effectiveness of treatment, the costs of bevacizumab and cetuximab, and health utility values.

Conclusions

Evidence from Ontario showed that bevacizumab plus folfiri is the cost-effective first-line treatment strategy for patients with KRAS wild-type mcrc. The panitumumab plus folfiri and cetuximab plus folfiri options were both dominated, but the cetuximab plus folfiri strategy must be further investigated given that, in the sensitivity analyses, the cost-effectiveness of that strategy was found to be superior to that of bevacizumab plus folfiri under certain ranges of parameter values.     

Molecular determinants of anti-EGFR sensitivity and resistance in metastatic colorectal cancer

Since 2004, the clinical impact of monoclonal antibodies (mAbs) targeting the epidermal growth factor receptor (EGFR) on patients with metastatic colorectal cancer (MCRC) has been clearly established. The combination of these biological agents with conventional chemotherapy has led to a significant improvement in response rate, progression-free survival and overall survival in first-line as well as in second- or third-line treatment of MCRC. However, the high variability of response and outcome in MCRC patients treated with these anti-EGFR mAbs has highlighted the need of identifying clinical and/or molecular predictive markers to ensure appropriate use of targeted therapies. The presence of somatic KRAS mutations has been clearly identified as a predictive marker of resistance to anti-EGFR in MCRC, and the use of anti-EGFR mAbs is now restricted to patients with no detectable KRAS mutation. Several studies have indicated that amplification of EGFR, overexpression of the EGFR ligands and inactivation of the anti-oncogene TP53 are associated with sensitivity to anti-EGFR mAbs, whereas mutations of BRAF and PIK3CA and loss of PTEN expression are associated with resistance. Besides these somatic variations, germline polymorphisms such as those affecting genes involved in the EGFR pathway or within the immunoglobulin receptors may also modulate response to anti-EGFR mAbs. Until now, all these markers are not completely validated and only KRAS genotyping is mandatory in routine practice for use of the anti-EGFR mAbs in MCRC.     

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.     

KRAS mutation analysis: a comparison between primary tumours and matched liver metastases in 305 colorectal cancer patients

Background:

KRAS mutation is a negative predictive factor for treatment with anti-epidermal growth factor receptor antibody in metastatic colorectal cancer (CRC). KRAS mutation analysis is usually performed on primary tumour tissue because metastatic tissue is often not available. However, controversial data are available on the concordance of test results between primary tumours and corresponding metastases. We assessed the concordance of KRAS mutation status in a study of 305 primary colorectal tumours and their corresponding liver metastases.

Methods:

Patients with histologically confirmed CRC who underwent surgical resection of the primary tumour and biopsy or surgical resection of the corresponding liver metastasis were included. KRAS mutation analysis was performed for codons 12 and 13.

Results:

KRAS mutation was detected in 108 out of 305 primary tumours (35.4%). In 11 cases (3.6%), we found a discordance between primary tumour and metastasis: 5 primary tumours had a KRAS mutation with a wild-type metastasis, 1 primary tumour was wild type with a KRAS mutation in the metastasis, and in 5 cases the primary tumour and the metastasis had a different KRAS mutation.

Conclusion:

We observed a high concordance of KRAS mutation status of 96.4% (95% CI 93.6–98.2%) between primary colorectal tumours and their corresponding liver metastases. In only six patients (2.0% 95% CI 0.7–4.2%), the discordance was clinically relevant. In this largest and most homogenous study to date, we conclude that both primary tumours and liver metastases can be used for KRAS mutation analysis.     

KRAS codon 61, 146 and BRAF mutations predict resistance to cetuximab plus irinotecan in KRAS codon 12 and 13 wild-type metastatic colorectal cancer

Background:

KRAS codons 12 and 13 mutations predict resistance to anti-EGFR monoclonal antibodies (moAbs) in metastatic colorectal cancer. Also, BRAF V600E mutation has been associated with resistance. Additional KRAS mutations are described in CRC.

Methods:

We investigated the role of KRAS codons 61 and 146 and BRAF V600E mutations in predicting resistance to cetuximab plus irinotecan in a cohort of KRAS codons 12 and 13 wild-type patients.

Results:

Among 87 KRAS codons 12 and 13 wild-type patients, KRAS codons 61 and 146 were mutated in 7 and 1 case, respectively. None of mutated patients responded vs 22 of 68 wild type (P=0.096). Eleven patients were not evaluable. KRAS mutations were associated with shorter progression-free survival (PFS, HR: 0.46, P=0.028). None of 13 BRAF-mutated patients responded vs 24 of 74 BRAF wild type (P=0.016). BRAF mutation was associated with a trend towards shorter PFS (HR: 0.59, P=0.073). In the subgroup of BRAF wild-type patients, KRAS codons 61/146 mutations determined a lower response rate (0 vs 37%, P=0.047) and worse PFS (HR: 0.45, P=0.023). Patients bearing KRAS or BRAF mutations had poorer response rate (0 vs 37%, P=0.0005) and PFS (HR: 0.51, P=0.006) compared with KRAS and BRAF wild-type patients.

Conclusion:

Assessing KRAS codons 61/146 and BRAF V600E mutations might help optimising the selection of the candidate patients to receive anti-EGFR moAbs.     

Identification of candidate predisposing copy number variants in familial and early-onset colorectal cancer patients

In the majority of colorectal cancers (CRCs) under clinical suspicion for a hereditary cause, the disease-causing genetic factors are still to be discovered. To identify such genetic factors we stringently selected a discovery cohort of 41 CRC index patients with microsatellite-stable tumors. All patients were below 40 years of age at diagnosis and/or exhibited an overt family history. We employed genome-wide copy number profiling using high-resolution SNP arrays on germline DNA, which resulted in the identification of novel copy number variants (CNVs) in six patients (15%) encompassing, among others, the cadherin gene CDH18, the bone morphogenetic protein antagonist family gene GREM1, and the breakpoint cluster region gene BCR. In addition, two genomic deletions were encountered encompassing two microRNA genes, hsa-mir-491/KIAA1797 and hsa-mir-646/AK309218. None of these CNVs has previously been reported in relation to CRC predisposition in humans, nor were they encountered in large control cohorts (>1,600 unaffected individuals). Since several of these newly identified candidate genes may be functionally linked to CRC development, our results illustrate the potential of this approach for the identification of novel candidate genes involved in CRC predisposition.     

Circulating cell-free AR and CYP17A1 copy number variations may associate with outcome of metastatic castration-resistant prostate cancer patients treated with abiraterone

Background:

This study aimed to investigate copy number variations (CNVs) of CYP17A1 and androgen receptor (AR) genes in serum cell-free DNA collected before starting abiraterone in 53 consecutive patients with castration-resistant prostate cancer (CRPC).

Methods:

Serum DNA was isolated and CNVs were analysed for AR and CYP17A1 genes using Taqman copy number assays. The association between CNVs and progression-free/overall survival (PFS/OS) was evaluated by the Kaplan–Meier method and log-rank test.

Results:

Median PFS of patients with AR gene gain was 2.8 vs 9.5 months of non-gained cases (P<0.0001). Patients with CYP17A1 gene gain had a median PFS of 2.8 months vs 9.2 months in the non-gained patients (P=0.0014). A lower OS was reported in both cases (AR: P<0.0001; CYP17A1: P=0.0085). Multivariate analysis revealed that PSA decline ⩾50%, AR and CYP17A1 CNVs were associated with shorter PFS (P<0.0001, P=0.0004 and P=0.0450, respectively), while performance status, PSA decline ⩾50%, AR CNV and DNA concentration were associated with OS (P=0.0021, P=0.0014, P=0.0026 and P=0.0129, respectively).

Conclusions:

CNVs of AR and CYP17A1 genes would appear to be associated with outcome of CRPC patients treated with abiraterone.     

Evaluation of efficacy and safety markers in a phase II study of metastatic colorectal cancer treated with aflibercept in the first-line setting

Background:

Aflibercept (ziv-aflibercept) is an anti-angiogenic agent recently approved in combination with FOLFIRI for the treatment of metastatic colorectal cancer (mCRC) patients previously treated with oxaliplatin. Despite heterogeneity in response to aflibercept, no biomarkers for efficacy or adverse effects have been identified. Here we present biomarker data from the randomised phase II AFFIRM trial assessing aflibercept in combination with mFOLFOX6 first line in mCRC.

Methods:

Ninety-six somatic mutations in key oncogenic drivers of mCRC and 133 common single-nucleotide polymorphisms (SNPs) in vascular endothelial growth factor (VEGF) pathway genes were analysed, and 27 plasma markers measured at baseline, during and after treatment. We assessed correlations of these three classes of biomarkers with progression-free survival (PFS) and adverse events (AEs).

Results:

Somatic mutations identified in KRAS, BRAF, NRAS, PIK3CA and PIK3R1 did not significantly correlate with PFS (multiple testing-adjusted false discovery rate (FDR) or multiple testing-adjusted FDR>0.3). None of the individual SNPs correlated with PFS (multiple testing-adjusted FDR>0.22), but at the gene level variability in VEGFB significantly correlated with PFS (multiple testing-adjusted FDR=0.0423). Although none of the plasma markers measured at baseline significantly correlated with PFS, high levels of circulating IL8 at baseline together with increased levels of IL8 during treatment were significantly associated with reduced PFS (multiple testing-adjusted FDR=0.0478). No association was found between biomarkers and AEs.

Conclusions:

This represents the first biomarker study in mCRC treated with aflibercept. High IL8 plasma levels at baseline and subsequent increases in IL8 were associated with worse PFS, suggesting that IL8 may act as a potentially predictive biomarker of aflibercept treatment outcome.     

c-Ki-ras mutations in colorectal adenocarcinomas from a country with a rapidly changing colorectal cancer incidence.

We have examined the incidence of mutation of the c-Ki-ras proto-oncogene in colorectal adenocarcinomas from two different time periods, namely 1962-1966 and 1994-1996. The first cohort of samples consisted of formalin-fixed, archival paraffin block and represent the oldest colorectal cancer samples for which ras mutation has been examined, while the second cohort of tumours were fresh, flash-frozen samples representative of genetic events occurring in contemporary times. Analysis of mutation status was undertaken by a mismatch-specific oligonucleotide hybridization analysis of exon 1 of the c-Ki-ras proto-oncogene after amplification by the polymerase chain reaction. Mutations in codon 12 or 13 of c-Ki-ras were detected in 28% (14/50) of contemporary samples, a figure consistent with locally established mutation rates. In contrast no mutation was detected in any of the 18 samples from the earlier period, a result that is statistically significant (P = 0.007). Age-standardized rates of colorectal cancer in Singapore have seen a marked increase over the last 30 years, and for the first time we have shown that such an increase in colorectal cancer is associated, at least in part with an increase in incidence of a specific mutagenic change.     

KRAS mutations in primary tumours and post-FOLFOX metastatic lesions in cases of colorectal cancer

Background:

KRAS mutations are predictive markers for the efficacy of anti-EGFR antibody therapies in patients with metastatic colorectal cancer. Although the mutational status of KRAS is reportedly highly concordant between primary and metastatic lesions, it is not yet clear whether genotoxic chemotherapies might induce additional mutations.

Methods:

A total of 63 lesions (23 baseline primary, 18 metastatic and 24 post-treatment metastatic) from 21 patients who were treated with FOLFOX as adjuvant therapy for stage III/IV colorectal cancer following curative resection were examined. The DNA samples were obtained from formalin-fixed paraffin-embedded specimens, and KRAS, NRAS, BRAF and PIK3CA mutations were evaluated.

Results:

The numbers of primary lesions with wild-type and mutant KRAS codons 12 and 13 were 8 and 13, respectively. The mutational status of KRAS remained concordant between the primary tumours and the post-FOLFOX metastatic lesions, irrespective of patient background, treatment duration and disease-free survival. Furthermore, the mutational statuses of the other genes evaluated were also concordant between the primary and metastatic lesions.

Conclusion:

Because the mutational statuses of predictive biomarker genes were not altered by FOLFOX therapy, specimens from both primary tumours and post-FOLFOX tumour metastases might serve as valid sources of DNA for known genomic biomarker testing.