Biomarkers, bundled payments, and colorectal cancer care

Changes in the management of cancers such as colorectal cancer (CRC) are urgently needed, as such cancers continue to be one of the most commonly diagnosed cancers; CRC accounts for 21% of all cancers and is responsible for mortalities second only to lung cancer in the United States. A comprehensive science-driven approach towards markedly improved early detection/screening to efficacious targeted therapeutics with clear diagnostic and prognostic markers is essential. In addition, further changes addressing rising costs, stemming from recent health care reform measures, will be brought about in part by changes in how care is reimbursed. For oncology, the advances in genomics and biomarkers have the potential to define subsets of patients who have a prognosis or response to a particular type of therapy that differs from the mean. Better definition of a cancer's behavior will facilitate developing care plans tailored to the patient. One method under study is episode-based payment or bundling, where one payment is made to a provider organization to cover all expenses associated with a discrete illness episode. Payments will be based on the average cost of care, with providers taking on a risk for overutilization and outliers. For providers to thrive in this environment, they will need to know what care a patient will require and the costs of that care. A science-driven "personalized approach" to cancer care has the potential to produce better outcomes with reductions in the use of ineffectual therapies and costs. This promising scenario is still in the future, but progress is being made, and the shape of things to come for cancer care in the age of genomics is becoming clearer.

Correlation of progression-free and post-progression survival with overall survival in advanced colorectal cancer

BACKGROUND

Polychemotherapy and biological drugs have increased therapeutic options and outcomes of advanced colorectal cancer (CRC). We examined the relation between progression-free survival (PFS), post-progression survival (PPS) and overall survival (OS) in trials of modern (oxaliplatin- and irinotecan-based) chemotherapy alone or with targeted therapies for advanced CRC. We also evaluated surrogacy of PFS and OS.

PATIENTS AND METHODS

A PubMed search identified 34 randomized trials. We split the OS, PFS and PPS and evaluated the correlation between OS and either PFS or PPS.

RESULTS

The median PPS and PFS were 10.75 and 8.4 months, respectively. For all trials, PPS was strongly associated with OS [regression coefficient (R2)=0.8; Spearman's rank correlation coefficient (r)=0.88], whereas PFS was moderately associated with OS (R2)=0.43; r=0.64). In trials with targeted therapies, the correlation of PPS with OS was 0.88. However, across all trials, correlation between differences in median PFS (ΔPFS) and median OS (ΔOS) is 0.59 (P=0.0007), confirming PFS/OS surrogacy.

CONCLUSION

Our findings indicate that in recent first-line, phase III, trials, OS becomes more associated with PPS than PFS. However, improvements in PFS are strongly associated with improvements in OS. In this setting so, PFS may be an appropriate surrogate for OS.

Treatment with bevacizumab and FOLFOXIRI in patients with advanced colorectal cancer: presentation of two novel trials (CHARTA and PERIMAX) and review of the literature

BACKGROUND

More than half of patients with colorectal cancer will develop metastatic disease either evident at the time of initial diagnosis or during their course of disease. Besides multidisciplinary management further treatment intensification is warranted to improve the still limited prognosis.

METHODS/DESIGN

In these two multi-centre, randomized phase II trials, conducted in Germany, 380 patients with R0-resectable colorectal liver metastases (PERIMAX) and with unresectable, metastatic colorectal cancer (CHARTA) will be recruited. Patients previously untreated for metastatic disease with either synchronous or metachronous metastases are randomly assigned in a 1:1 ratio to resection of colorectal liver metastases followed by postoperative FOLFOX for 6 months or perioperative FOLFOXIRI and bevacizumab for 3 months pre- and postoperative and resection (PERIMAX), or to induction chemotherapy with FOLFOX and bevacizumab +/- irinotecan for a maximum of 6 months followed by maintenance treatment with fluoropyrimidine and bevacizumab. The primary objective of these trials is to evaluate the feasibility and efficacy of FOLFOXIRI and bevacizumab in metastatic colorectal cancer. Primary endpoint is failure free survival rate at 18 months in the PERIMAX trial and progression free survival rate at 9 months in CHARTA. Secondary objectives include efficacy, safety and tolerability.

DISCUSSION

The CHARTA and PERIMAX trials are designed to evaluate the benefits and limitations of a highly active four-drug regimen in distinct treatment situations of metastatic CRC. Eligible patients are classified into resectable liver metastases to be randomized to perioperative treatment with FOLFOXIRI and bevacizumab or postoperative FOLFOX in the PERIMAX, or unresectable metastatic CRC to be randomized between FOLFOX and bevacizumab with or without irinotecan, stratified for clinical groups according to disease and patients' characteristics in the CHARTA trial.

TRIAL REGISTRATION

Clinical trial identifier CHARTA: NCT01321957, PERIMAX: NCT01540435.

Panitumumab: a summary of clinical development in colorectal cancer and future directions

Panitumumab is a fully human, monoclonal antibody targeting the EGF receptor with proven clinical activity in KRAS wild-type metastatic colorectal carcinoma. Treatment with panitumumab has been shown to significantly improve response rate and progression-free survival in this subgroup of patients, with a manageable toxicity profile. Panitumumab's first worldwide indication was as a single agent in chemorefractory patients. Recently, the EMA approved its use as part of a chemotherapy regimen in first- and second-line settings, following the encouraging results of large randomized Phase III trials. In order to identify patients with higher chances of benefiting from the treatment, additional molecular aberrations in the EGF receptor signaling pathway are being investigated as predictive biomarkers. In this article we review 10 years of drug development, focusing on the clinical evidence for panitumumab's indication in metastatic colorectal cancer and future strategies of investigation.

Sanger sequencing in routine KRAS testing: a review of 1720 cases from a pathologist's perspective

Background

Sanger sequencing (SS) of PCR products is still the most frequent method to test colorectal cancer for KRAS mutations in routine practice.

Methods

An audit of SS on 1720 routine cases was carried out, taking into account age, gender, specimen type (resection vs biopsies), tumour site (primary vs metastasis), tumour stage, neoplastic cells abundance (>30% vs <30%) and fixation type (buffered formalin vs simple formalin). In a subset of 50 wild-type (WT) patients correlations between SS findings and response rate (RR), progression-free survival (PFS) and overall survival (OS) were also evaluated.

Results

The tests were informative in 1691 cases (98.3%). Mutations were detected in 671 cases (39.6%). No significant differences in mutation rates were observed with respect to age (p=0.2), gender (p=0.2), specimen type (p=0.3) and formalin fixation (p=0.08). Conversely, KRAS mutant rate was higher in metastatic tissue (50% vs 39%, p=0.02), in samples with over 30% of neoplastic cells (43.4% vs 26.6%, p=0.02) and in tumours tested in stage IV (p=0.05). The RR of SS KRAS WT patients was 26% (one complete and 12 partial responses). The disease control rate (objective responses plus stable disease) was 56%. Median PFS was 4.4 months and median OS was 10.4 months.

Conclusions

Pathological criteria that make SS a more robust method for KRAS testing and treatment response prediction are neoplastic cell abundance, metastatic tissue sample and stage IV primary tumour.

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.

Resectability and outcome with anti-EGFR agents in patients with KRAS wild-type colorectal liver-limited metastases: a meta-analysis

BACKGROUND

Cetuximab (C) and panitumumab (P) increase response rate and survival in KRAS wild-type metastatic colorectal cancer (mCRC). We performed a meta-analysis of randomised controlled trials (RCTs) to assess their effect on overall response rate (ORR), the rate of radical resection (R0) and survival in patients with liver-limited initially unresectable mCRC.

MATERIALS AND METHODS

We searched MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials for RCTs comparing first-line chemotherapy plus or minus C or P and reporting data in patients with KRAS wild-type, unresectable liver-limited mCRC. Relative risks (RRs) with 95% confidence interval were calculated. Meta-analysis of hazard ratios (HRs) for progression-free and overall survival (PFS and OS) was also performed.

RESULTS

Four RCTs involving 484 KRAS wild-type patients were included. Compared to chemotherapy alone, the addition of C or P significantly increased the ORR (RR 1.67, p = 0.0001), the R0 resection rate from 11% to 18% (RR 1.59, p = 0.04) and PFS (HR 0.68, p = 0.002), but not OS (p = 0.42).

CONCLUSIONS

The addition of C and P increased the R0 resection rate by 60% and reduced the risk of progression by 32% in patients with mCRC and unresectable liver-limited disease. This combination represents one of the preferred choices as conversion therapy in KRAS wild-type patients with unresectable liver metastases.

Guidelines for biomarker testing in colorectal carcinoma (CRC): a national consensus of the Spanish Society of Pathology (SEAP) and the Spanish Society of Medical Oncology (SEOM)

This consensus statement, conceived as a joint initiative of the Spanish Society of Pathology and the Spanish Society of Medical Oncology, makes diagnostic and treatment recommendations for the management of patients with hereditary, localised and advanced CRC based on the current scientific evidence on biomarker use. This consensus statement thus provides an opportunity to improve healthcare efficiency and resource use, which will benefit these patients. Based on the currently available data on this subject, this expert group recommends testing for microsatellite instability (MSI) in patients with localised CRC, as this is a strong predictive factor for deciding on adjuvant treatment. However, although the ColoPrint(®) and Oncotype Dx(®) gene expression signatures have been shown to have prognostic value, no consensus yet exists concerning their use in clinical practice. For advanced CRC, it is essential to test for KRAS mutation status before administering an anti-EGFR treatment, such as cetuximab or panitumumab. However, testing for other biomarkers, such as BRAF, EGFR, PI3K and PTEN mutations, should not be done routinely, because this does not influence treatment planning at the present time. Other important issues addressed include organisational requirements and the quality controls needed for proper testing of these biomarkers as well as the legal implications to be borne in mind when testing some biomarkers.

Individualized chemotherapy for colorectal cancer based on the collagen gel droplet-embedded drug sensitivity test

The leucovorin (FOL) and fluorouracil (5-FU) plus oxaliplatin (l-OHP; FOLFOX) or FOL and 5-FU plus irinotecan (SN-38; FOLFIRI) regimens with or without molecularly-targeted drugs are widely used as first-line chemotherapy in the treatment of advanced colorectal cancer (CRC). Whether FOLFOX or FOLFIRI is administered first is not significant, however, it is essential that full administration of the targeted dosages of all 3 drugs, 5-FU, l-OHP and SN-38, is achieved. However, this is not always possible and second-line chemotherapy must be abandoned in certain cases. Where possible, the most effective regimen should be selected as the first line of treatment. The aim of this study was to determine whether first-line chemotherapy may be individualized using the collagen gel droplet-embedded drug sensitivity test (CD-DST). Specimens of primary tumors were obtained from 43 CRC patients who had received no preoperative chemotherapy. Informed consent to measure drug sensitivity was obtained from all patients. The CD-DST allows evaluation of drug sensitivity using isolated, 3-dimensionally cultured tumor cells in a small collagen gel droplet. The CD-DST was performed and the growth inhibition rate (IR) was obtained under incubation conditions (5-FU with l-OHP at 6.0 and 3.0 μg/ml, or 5-FU with SN-38 at 6.0 and 0.2 μg/ml, respectively, for 24 h). The cumulative distributions of the growth IRs under each condition were evaluated based on the evidence that the clinical response rates to FOLFOX and FOLFIRI were almost the same. Individualization of first-line treatment was possible in all patients, with FOLFOX and FOLFIRI showing higher efficacy in 26 and 15 patients, respectively, and equal efficacy in 2 cases. This method has the potential to facilitate the establishment of individualized first-line chemotherapy for CRC and improve the prognosis in such patients.

Targeted therapy at the end of life in advanced cancer patients

OBJECTIVE

We describe the use of systemic therapy in advanced cancer patients admitted to an acute care hospital, with a focus on targeted therapy. We aim to spotlight the utilization of targeted agents in the last months of life.

METHODS

Adult patients (N=252) with advanced solid tumors who died as inpatients in the National University Hospital, Singapore, were included in this retrospective study. Patients' demographic and clinical data were extracted from hospital records. Information on systemic therapy was extracted from the time of diagnosis and all other data limited to the last three months before death.

RESULTS

187 adult patients received palliative systemic therapy from the time of diagnosis, of which 125 (66.8%) received it within three months of death. Of patients receiving only nontargeted systemic treatment (n=106), 60 (56.6%) and 26 (24.5%) received it within three months and one month of death respectively. Comparatively, 81 patients received palliative targeted systemic therapy, of which 65 (80.3%) and 40 (49.4%) had treatment within three months and one month of death respectively (p=0.001 and p<0.001). Targeted therapy was first initiated in the last three months of life in 38 patients. Oral agents targeting epidermal growth factor receptor (lung cancer patients) and vascular endothelial growth factor receptor (non-lung cancer patients) pathways were commonly employed. Lung cancer patients were more likely to have targeted therapy as their last line of systemic therapy: 26/54 lung cancer patients compared with 29/133 non-lung cancer patients (48.1% versus 21.8%, p<0.001).

CONCLUSIONS

Targeted therapy is used in more than half of patients who received systemic therapy within three months of death. The degree to which these agents are being utilized near the end of life suggests the need to reexamine the risk/benefit profile of targeted therapy for this population, and the decision-making process around their use.

Involvement of K-RAS mutations and amino acid substitutions in the survival of metastatic colorectal cancer patients

The efficacy of epidermal growth factor-targeting therapies has been found to be limited in tumors with the wild-type K-RAS gene, suggesting a predictive value of K-RAS gene analysis in tumoral response. However, the prognostic value of K-RAS is controversial. This study included patients diagnosed with metastatic colorectal cancer. The presence of K-RAS mutations was analyzed, and the tumors positive for a K-RAS mutation were further analyzed to identify the mutation type. Similarly, the following clinical and pathological variables were also collected. The study was composed of 53.3 % of patients with wild-type K-RAS and 46.7 % of patients with mutated K-RAS (mutated codon 12 was the most frequent). With a mean follow-up of 15 months (range, 1-45), the median survival of patients with wild-type K-RAS was 31.6 months. The median survival was 24.8 months for patients with K-RAS mutated in codon 12 and 17.8 months for patients with mutated codon 13 (p = 0.37). In a univariate analysis, K-RAS was associated with stage IV at diagnosis (p < 0.005). When K-RAS was mutated, a lower overall survival was observed in cases of G → A transition compared with G → T transversion (19.5 vs. 24.2 months, respectively; p = 0.47). When the amino acid change resulted in an acidic substitution, survival was lower, but it increased when the substitution resulted in a polar or nonpolar amino acid (19.5 vs. 23.2 vs. 24.4 months, p = 0.79). The type of K-RAS mutation or amino acid changes may have prognostic implications in metastatic colon cancer patients. Further research is needed in patients treated in prospective controlled trials.

Multicenter phase II study of second-line bevacizumab plus doublet combination chemotherapy in patients with metastatic colorectal cancer progressed after upfront bevacizumab plus doublet combination chemotherapy

BACKGROUND

To investigate the efficacy and safety of bevacizumab beyond first progression combined with doublet chemotherapy in patients with metastatic colorectal cancer.

METHODS

This multicenter phase II study included 76 patients with metastatic colorectal cancer progressed after first-line bevacizumab plus doublet chemotherapy. Study treatment consisted of second-line continuation of bevacizumab plus crossover standard doublet chemotherapy, consisting of FOLFOX, CapeOX, or FOLFIRI. Bevacizumab was administered in doses of 5 mg/kg/2-week or 7.5 mg/kg/3-week according to the schedules of the combined regimen.

RESULTS

Median progression-free survival (PFS) and overall survival (OS) was 6.5 months (95 % CI, 5.2-7.8) and 12.8 months (95 % CI, 8.8-16.9), respectively, with no significant differences according to combined doublet chemotherapy. The response rate (RR) was 17.1 % (95 % CI, 8.6-5.6) with no statistical significance between regimens (p = 0.053). The first-line RR and PFS did not affect the second-line efficacy outcomes; RR (14.0 % vs 21.2 %, p = 0.405), median PFS (5.6 vs 6.7 months, p = 0.335), and OS (15.4 vs 11.0 months, p = 0.383) were not different between previous responders and non-responders, and the median PFS (p = 0.186) and OS (p = 0.495) were not different either according to the length of first-line PFS; however, OS from the first-line chemotherapy was longer in patients with longer first-line PFS (26.4 vs 14.8 months, p = 0.010). Bevacizumab-related significant adverse events included proteinuria (1.3 %) and thromboembolism (1.3 %).

CONCLUSIONS

Bevacizumab beyond first progression could be considered a treatment strategy even in patients progressed after first-line bevacizumab plus doublet chemotherapy. Second-line efficacy outcomes did not differ according to the first-line responses.

Overview of biomarkers in metastatic colorectal cancer: tumour, blood and patient-related factors

During the last 20 years there have been major therapeutic developments in colorectal cancer (CRC) with the introduction of multiple novel therapeutic agents into routine clinical practice. This has improved survival in both the adjuvant and advanced disease settings. However, improvements have come with substantial increases in expense to the community and potential toxicity to the patient. There has been substantial research to identify tumour factors in CRC that predict treatment response and survival outcomes. This research has identified clinically useful predictive biomarkers to aid clinical decision making, such as the presence or absence of KRAS gene mutations which can determine the benefit of using epidermal growth factor receptor (EGFR) inhibiting antibodies. However, less attention has been paid to the identification and impact of predictive patient-derived factors such as age, gender and the presence of comorbid conditions or evidence of a systemic inflammatory response. In this article, the current concepts of tumour and patient-related predictive factors in CRC management are reviewed.

Intrapatient cetuximab dose escalation in metastatic colorectal cancer according to the grade of early skin reactions: the randomized EVEREST study

PURPOSE

Skin toxicity in patients receiving cetuximab has been associated positively with clinical outcome in several tumor types. This study investigated the effect of cetuximab dose escalation in patients with irinotecan-refractory metastatic colorectal cancer who had developed no or mild skin reactions after 21 days of treatment at the standard dose. This article reports clinical and pharmacokinetic (PK) data.

PATIENTS AND METHODS

After 21 days of standard-dose cetuximab (400 mg/m(2) initial dose, then 250 mg/m(2) per week) plus irinotecan, patients with ≤ grade 1 skin reactions were randomly assigned to standard-dose (group A) or dose-escalated (to 500 mg/m(2) per week; group B) cetuximab. Patients with ≥ grade 2 skin reactions continued on standard-dose cetuximab plus irinotecan (group C).

RESULTS

The intent-to-treat population comprised 157 patients. PK profiles reflected the dose increase and were predictable across the dose range investigated. Weekly cetuximab doses of up to 500 mg/m(2) were well tolerated, and grade 3 and 4 adverse events were generally comparable between treatment groups. Dose escalation (n = 44) was associated with an increase in skin reactions ≥ grade 2 compared with standard (n = 45) dosing (59% v 38%, respectively). Dose escalation, compared with standard dosing, showed some evidence for improved response rate (30% v 16%, respectively) and disease control rate (70% v 58%, respectively) but no indication of benefit in relation to overall survival. In an exploratory analysis, dose escalation seemed to increase response rate compared with standard dosing in patients with KRAS wild-type but not KRAS mutant tumors.

CONCLUSION

Cetuximab serum concentrations increased predictably with dose. Higher dose levels were well tolerated. The possible indication for improved efficacy in the dose-escalation group warrants further investigation.

In vitro and in vivo antitumor activity of cetuximab in human gastric cancer cell lines in relation to epidermal growth factor receptor (EGFR) expression and mutational phenotype

BACKGROUND

Targeting the epidermal growth factor receptor (EGFR) pathway is an important approach for a variety of tumors. This study assessed the effect of cetuximab, an anti-EGFR monoclonal antibody, on three gastric cancer cell lines with different phenotypes in vitro and in a therapeutic orthotopic murine gastric cancer model.

METHODS

Three human gastric cancer cell lines (AGS, MKN-45, NCI-N87) were evaluated for cell surface EGFR expression, and K-ras and BRAF mutations. In vitro, the effects of cetuximab, carboplatin, irinotecan, and docetaxel were investigated. Orthotopic tumors derived from MKN-45 and NCI-N87 were established in nude mice. After 4 weeks, the animals received cetuximab (1 mg/kg, weekly i.p.) or carboplatin (20 mg/kg, weekly i.p.), or both agents. The volume of the primary tumor and local and systemic tumor spread were determined at autopsy at 14 weeks. Tumor sections were immunostained for EGFR, as well as stained for CD31 to analyze microvessel density.

RESULTS

Cell surface expression of EGFR was found only in AGS and NCI-N87 cells. AGS cells displayed a codon 12 K-ras mutation, and all three cell lines were BRAF wild-type. In vitro, cetuximab significantly reduced cell viability and proliferation only in EGFR-positive/K-ras wild-type NCI-N87 cells (-48%). In vivo, cetuximab in combination with carboplatin synergistically reduced tumor volume (-75%), dissemination (-63%), and vascularization (-47%) in NCI-N87 xenografts. Tumors derived from EGFR-negative MKN-45 cells were unaffected by cetuximab.

CONCLUSIONS

Cetuximab is effective in K-ras wild-type, EGFR-expressing gastric cancer cell lines and xenografts. In vivo, the combination of cetuximab with carboplatin displayed synergistic antitumor activity.

Selecting the best targeted agent in first-line treatment of unresectable liver metastases from colorectal cancer: does the bench have the answers?

For physicians facing patients with organ-limited metastases from colorectal cancer, tumor shrinkage and sterilization of micrometastatic disease is the main goal, giving the opportunity for secondary surgical resection. At the same time, for the majority of patients who will not achieve a sufficient tumor response, disease control remains the predominant objective. Since FOLFOX or FOLFIRI have similar efficacies, the challenge is to define which could be the most effective targeted agent (anti-EGFR or anti-VEGF) to reach these goals. Therefore, a priori molecular identification of patients that could benefit from anti-EGFR or anti-VEGF monoclonal antibodies (i.e. the currently approved targeted therapies for metastatic colorectal cancer) is of critical importance. In this setting, the KRAS mutation status was the first identified predictive marker of response to anti-EGFR therapy. Since it has been demonstrated that tumors with KRAS mutation do not respond to anti-EGFR therapy, KRAS status must be determined prior to treatment. Thus, for KRAS wild-type patients, the choices that remain are either anti-VEGF or anti-EGFR. In this review, we present the most updated data from translational research programs dealing with the identification of biomarkers for response to targeted therapies.

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.

Anti-angiogenic drug discovery: lessons from the past and thoughts for the future

INTRODUCTION

Since the pioneering work of Judah Folkman, the discovery of bevacizumab has introduced the use of anti-angiogenic agents as a new modality for the treatment of cancer. Currently, hundreds of clinical trials involving anti-angiogenic agents, targeting different elements of the tumour angiogenesis pathway, are underway. However, thus far, the benefits of anti-angiogenic therapy in unselected patient populations are often marginal with harmful side effects.

AREAS COVERED

This article presents a detailed discussion of the lessons learnt from the use of bevacizumab and other VEGF pathway inhibitors in the clinical setting. Specifically, this article provides a review of the literature on anti-VEGF agents and other angiogenesis inhibitors used in pre-clinical and clinical trials for cancer treatment.

EXPERT OPINION

Future anti-angiogenic drug design centres on multiple protein targets and combinations including: growth factors, hypoxia-inducible factor and tumour endothelial cell markers unique to the tumour vasculature. Furthermore, treatment dosing, scheduling and combination with radiation and chemotherapy require further investigation, as does the potential of treating early disease, and the development of biomarkers which accurately predict response to therapy. These are essential for the future development of these drugs with individualised therapy likely to be the ultimate goal.

Targeting the epidermal growth factor receptor in solid tumor malignancies

The epidermal growth factor receptor (EGFR) is over-expressed, as well as mutated, in many types of cancers. In particular, the EGFR variant type III mutant (EGFRvIII) has attracted much attention as it is frequently and exclusively found on many tumor cells, and hence both EGFR and EGFRvIII have been proposed as valid targets in many cancer therapy settings. Different strategies have been developed in order to either inhibit EGFR/EGFRvIII activity or to ablate EGFR/EGFRvIII-positive tumor cells. Drugs that inhibit these receptors include monoclonal antibodies (mAbs) that bind to the extracellular part of EGFR, blocking the binding sites for the EGFR ligands, and intracellular tyrosine kinase inhibitors (TKIs) that block the ATP binding site of the tyrosine kinase domain. Besides an EGFRvIII-targeted vaccine, conjugated anti-EGFR mAbs have been used in different settings to deliver lethal agents to the EGFR/EGFRvIII-positive cells; among these are radio-labelled mAbs and immunotoxins. This article reviews the current status and efficacy of EGFR/EGFRvIII-targeted therapies.

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.

Cetuximab in the first-line treatment of K-ras wild-type metastatic colorectal cancer: the choice and schedule of fluoropyrimidine matters

BACKGROUND

Cetuximab, a monoclonal antibody against the epidermal growth factor receptor, inconsistently improves response rates (RR), progression-free survival (PFS) and overall survival (OS) in the first-line treatment of advanced colorectal cancer patients with K-ras wild-type (WT) tumors.

METHODS

We performed a meta-analysis of four trials where K-ras WT Pts received a fluoropyrimidine (infusional vs. bolus 5-fluorouracil (5-FU) vs. capecitabine) and oxaliplatin or irinotecan with and without cetuximab (CRYSTAL, OPUS, COIN and NORDIC VII trials) and two trials, where K-ras WT and mutant patients received cetuximab and a fluoropyrimidine (capecitabine in a German AIO study and infusional 5-FU in the CECOG study) with oxaliplatin versus irinotecan. We sought to determine whether the choice of fluoropyrimidine or of oxaliplatin versus irinotecan affects the response to cetuximab. Meta-analysis was performed in the context of a mixed effects model with a random effect for each study.

RESULTS

Only patients treated with infusional 5-FU-based chemotherapy derived benefit from cetuximab. Relative to infusional 5-FU, patients treated with capecitabine/bolus 5-FU-based doublet chemotherapy had a 42 % (95 % CI 21-58 %; p < 0.001) decrease in response probability and a 52 % (95 % CI 20-93 %; p < 0.001) and 33 % (95 % CI 7-65 %; p = 0.012) increase, respectively, in risk of progression and death. The choice of oxaliplatin or irinotecan did not affect benefit from cetuximab.

CONCLUSION

The lack of benefit for cetuximab with capecitabine/bolus 5-FU regimens is unexpected. Cetuximab should only be used with infusional 5-FU regimens in the first-line treatment of K-ras WT colorectal cancer patients. Further study is urgently needed to elucidate the basis of this observation.

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.

Optimizing first-line chemotherapy for metastatic colorectal cancer

SUMMARY Up to half of all patients who develop colorectal cancer will be treated for metastatic disease; some can be cured but most are simply palliated. The optimum use of the available drugs tailored to the patient should be informed by evidence, where it is available, and are of much current debate. Treatment objectives must be clear in making these decisions. Improved response rate may be appropriate where disease may become resectable, with an aim for cure. Tolerability and quality of life balanced with long-term survival may be most relevant where this is not feasible. A good start appropriate to the individual in the first-line metastatic setting is of both physical and psychological importance and may affect subsequent therapeutic decisions. Where Phase III randomized controlled trial evidence is missing, clinical decisions must still be made. Here we explore the data available for optimized first-line therapy, the options created from this data and balance this against the benefits to the patient as a whole.

KRASness and PIK3CAness in patients with advanced colorectal cancer: outcome after treatment with early-phase trials with targeted pathway inhibitors

Purpose

To evaluate clinicopathologic and molecular features of patients with metastatic colorectal cancer (mCRC) and their outcomes in early-phase trials using pathway-targeting agents.

Patients and Methods

We analyzed characteristics of 238 patients with mCRC referred to the phase 1 trials unit at MD Anderson Cancer Center. KRAS, PIK3CA and BRAF status were tested using PCR-based DNA sequencing.

Results

Fifty-one percent of patients harbored KRAS mutations; 15% had PIK3CA mutations. In the multivariate regression model for clinical characteristics KRAS mutations were associated with an increased incidence of lung and bone metastases and decreased incidence of adrenal metastases; PIK3CA mutations were marginally correlated with mucinous tumors (p = 0.05). In the univariate analysis, KRAS and PIK3CA mutations were strongly associated. Advanced Duke's stage (p<0.0001) and KRAS mutations (p = 0.01) were the only significant independent predictors of poor survival (Cox proportional hazards model). Patients with PIK3CA mutations had a trend toward shorter progression-free survival when treated with anti-EGFR therapies (p = 0.07). Eighteen of 78 assessable patients (23%) treated with PI3K/Akt/mTOR axis inhibitors achieved stable disease [SD] ≥6 months or complete response/partial response (CR/PR), only one of whom were in the subgroup (N = 15) with PIK3CA mutations, perhaps because 10 of these 15 patients (67%) had coexisting KRAS mutations. No SD ≥6 months/CR/PR was observed in the 10 patients treated with mitogen-activating protein kinase (MAPK) pathway targeting drugs.

Conclusions

KRAS and PIK3CA mutations frequently coexist in patients with colorectal cancer, and are associated with clinical characteristics and outcome. Overcoming resistance may require targeting both pathways.

Antiepidermal growth factor receptor monoclonal antibody improves survival outcomes in the treatment of patients with metastatic colorectal cancer

The aim of this study was to determine whether or not the addition of anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibody (mAb) to standard chemotherapy or best supportive care (BSC), compared with chemotherapy or BSC alone, can improve overall survival (OS) and progression-free survival (PFS) in patients with metastatic colorectal cancer (mCRC), and evaluate the influence of KRAS mutant status on the efficacy of anti-EGFR mAb. Medline, Embase, the Cochrane controlled trials register, and the Science Citation Index were searched. Nine trials were identified, covering a total of 7941 patients. The treatment of mCRC with a combination of anti-EGFR mAb and chemotherapy or BSC, as compared with chemotherapy or BSC alone, improved the OS [hazard ratio (HR), 0.90 (0.84-0.96); P=0.002]. The benefit of anti-EGFR mAb in patients with KRAS wild-type tumors was apparent in relation to a marginal trend toward improved OS [HR, 0.84 (0.70-1.01); P=0.06], and significantly improved PFS [HR, 0.64 (0.51-0.81); P<0.001]. No benefit for the addition of anti-EGFR mAb was detected for any efficacy end-point in patients with KRAS mutant tumors. The summary HRs (anti-EGFR mAb vs control) were 0.98 (0.88-1.08) (P=0.71) for OS and 1.08 (0.94-1.25) (P=0.27) for PFS, respectively. In conclusion, this analysis provides confirmation that, compared with chemotherapy or BSC alone, anti-EGFR mAb with chemotherapy or BSC reduces the risk of progression and death of mCRC and that this benefit is seen only in patients with wild-type KRAS tumors.

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.

Cetuximab in preoperative treatment of rectal cancer - term outcome of the XERT trial

BACKGROUND

Preoperative capecitabine-based chemoradiotherapy (CRT) is feasible for the treatment of resectable locally advanced rectal cancer (LARC). To try to improve efficacy, we conducted a phase II study in which the epidermal growth factor receptor-targeting monoclonal antibody cetuximab was added to capecitabine-based CRT. The results for long-term survival and for an analysis investigating the relationship between survival and patient and disease characteristics, including tumour KRAS mutation status, and surgery type, are presented. PATIENTS AND METHODS.: Patients with resectable LARC received capecitabine (1250 mg/m(2) twice daily, orally) for 2 weeks followed by cetuximab alone (400 mg/m(2) for 1 week) and then with CRT (250 mg/m(2)/week) comprising capecitabine (825 mg/m(2) twice daily) and radiotherapy to the small pelvis (45 Gy in 25 1.8-Gy fractions), five days a week for five weeks. Surgery was conducted six weeks following CRT, with post-operative chemotherapy with capecitabine (1250 mg/m(2) twice daily for 14 days every 21 days) three weeks later.

RESULTS

Forty-seven patients were enrolled and 37 underwent treatment. Twenty-eight of the patients (75.7%) had T3N+ disease. Thirty-six patients were evaluable for efficacy. The median follow-up time was 39.0 months (range 5.0--87.0). The three-year local control, disease-free survival, relapse-free survival and overall survival rates were 96.9% (95% CI 90.0--100), 72.2% (57.5--86.9), 74.3% (95% CI 59.8--88.8) and 68.1% (95% CI 36.7--99.4), respectively. There was no significant association between survival and gender, age, tumour location in the rectum, type of surgery, pathological T or N status, tumour regression grade or tumour KRAS mutation status, although sample sizes were small.

CONCLUSIONS

Preoperative cetuximab plus capecitabine-based CRT was feasible in patients with resectable LARC and was associated with an impressive three-year local control rate. The use of tumour KRAS mutation status as a biomarker for the efficacy of cetuximab-based regimens in this setting requires further investigation.

Phase III trial of cetuximab with continuous or intermittent fluorouracil, leucovorin, and oxaliplatin (Nordic FLOX) versus FLOX alone in first-line treatment of metastatic colorectal cancer: the NORDIC-VII study

PURPOSE

The NORDIC-VII multicenter phase III trial investigated the efficacy of cetuximab when added to bolus fluorouracil/folinic acid and oxaliplatin (Nordic FLOX), administered continuously or intermittently, in previously untreated metastatic colorectal cancer (mCRC). The influence of KRAS mutation status on treatment outcome was also investigated.

PATIENTS AND METHODS

Patients were randomly assigned to receive either standard Nordic FLOX (arm A), cetuximab and FLOX (arm B), or cetuximab combined with intermittent FLOX (arm C). Primary end point was progression-free survival (PFS). Overall survival (OS), response rate, R0 resection rate, and safety were secondary end points.

RESULTS

Of the 571 patients randomly assigned, 566 were evaluable in intention-to-treat (ITT) analyses. KRAS and BRAF mutation analyses were obtained in 498 (88%) and 457 patients (81%), respectively. KRAS mutations were present in 39% of the tumors; 12% of tumors had BRAF mutations. The presence of BRAF mutations was a strong negative prognostic factor. In the ITT population, median PFS was 7.9, 8.3, and 7.3 months for the three arms, respectively (not significantly different). OS was almost identical for the three groups (20.4, 19.7, 20.3 months, respectively), and confirmed response rates were 41%, 49%, and 47%, respectively. In patients with KRAS wild-type tumors, cetuximab did not provide any additional benefit compared with FLOX alone. In patients with KRAS mutations, no significant difference was detected, although a trend toward improved PFS was observed in arm B. The regimens were well tolerated.

CONCLUSION

Cetuximab did not add significant benefit to the Nordic FLOX regimen in first-line treatment of mCRC.

Chemotherapy and molecular-targeted treatment for unresectable hepatic metastases: a Japanese perspective

Liver metastasis from colorectal cancer has become a common disease associated with the increase of primary colorectal cancer in Japan. The standard treatment for resectable liver metastases is still complete liver resection. Recent advances in systemic chemotherapy have introduced another strategy, i.e., conversion chemotherapy, for patients with initially diagnosed unresectable liver metastases. The conversion rate after neo-adjuvant chemotherapy is increasing with multidisciplinary approaches. Long-term clinical data have not been established yet. Indications for liver resection after neo-adjuvant chemotherapy; optimal chemotherapy regimens; and histological changes in the normal liver are important research issues for the future.

Influence of KRAS p.G13D mutation in patients with metastatic colorectal cancer treated with cetuximab

BACKGROUND

Patients with metastatic colorectal cancer (mCRC) with activating mutations at codon 12 or 13 of the KRAS gene are currently excluded from treatment with monoclonal antibodies against the epidermal growth factor receptor (EGFR), for example, cetuximab. Occasionally, some of these patients benefit from treatment with cetuximab, especially patients with a mutation at codon 13. We conducted an analysis to study the influence of the KRAS p.G13D mutation in patients with mCRC who were treated with cetuximab.

MATERIALS AND METHODS

We analyzed the KRAS mutation status of 110 patients who were treated with cetuximab between September 2003 and October 2008 at Hospital Clínico, San Carlos. We compared progression-free survival, overall survival, and response rate according to KRAS mutation status.

RESULTS

Patients with mutations at codon 13 compared with those with other KRAS mutations showed no statistically significant differences in progression-free survival (4.96 months [95% CI, 3.04-6.89 months] vs. 3.10 months [95% CI, 1.58-4.61 months]; hazard ratio [HR] 0.88 [95% CI, 44-1.75]; P = .72) and overall survival (8.2 months [95% CI, 4.2-12.1 months] vs. 14.6 months [95% CI, 8.0-21.2 months]; HR 0.50 [95% CI, 0.23-1.09]; P = .084). Patients with KRAS wild-type tumors have a longer progression-free survival (7.30 months [95% CI, 4.48-10.12 months]; HR 0.46 [95% CI, 0.23-0.91]; P = .025) and overall survival (19.0 months [95% CI, 10.2-27.8 months]; HR 0.32 [95% CI, 0.15-0.69]; P = .004) than patients with p.G13D-mutated tumors. Differences in the response rate were not observed between groups.

CONCLUSION

Patients with mCRC and mutation at codon 13 of the KRAS gene do not appear to benefit from treatment with cetuximab. These results support the current clinical practice.

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

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

Combined metallothioneins and p53 proteins expression as a prognostic marker in patients with Dukes stage B and C colorectal cancer

Our study aimed to evaluate metallothionein and p53 expression in colorectal cancer and to correlate their combined expression with selected clinical and pathologic variables of the disease, to define their prognostic significance. Colorectal cancer specimens from 99 patients were retrospectively analyzed by immunohistochemistry for metallothionein and p53 expression. Survival curves were generated according to the Kaplan-Meier method, and univariate survival distributions were compared with the use of the log-rank test. Multivariate models were computed using Cox proportional hazards regression. This research was approved by the institutional review boards of all centers. Tumors showing concomitant high metallothionein expression and negative p53 (metallothionein(H)/p53(-)) were significantly inversely related to depth of invasion, frequency of nodal metastasis, and Dukes stage (P < .01). In univariate analysis, patients with metallothionein(H)/p53(-) phenotype showed a better overall survival (hazard ratio [HR], 2.83; P < .05) and disease-free survival (HR, 2.03; P < .05). In multivariate analysis, considering staging, metallothionein, and metallothionein + p53 variables, in 83 patients with Dukes stages B and C, metallothionein(H)/p53(-) combination was the sole factor showing an independent prognostic value for overall survival (HR, 3.88; P < .1) and disease-free survival (HR, 2.56; P < .1). In conclusion, the combined analysis of metallothionein and p53 may enhance the prognostic power of each individual marker by predicting the progression of the disease and contributing to a better identification of patients at low risk for mortality, especially for those with Dukes stage B and C colorectal cancer.

[Neoadjuvant therapy concepts for liver metastases]

The resection of liver metastases offers the option of long-term survival for patients with colorectal carcinoma. With regard to resectability three clinical situations can be identified: patients with resectable liver metastases, those with potentially resectable liver metastases and patients with disseminated metastatic disease. Patients with potentially resectable liver metastases should be treated with regimens with high response rates. According to a metaanalysis patients with resectable liver metastases have a better disease-free survival with the combination of resection and chemotherapy. If neoadjuvant therapy is planned in resectable patients the FOLFOX regimen is the schedule with the highest level of evidence. In potentially resectable liver metastases the regimens FOLFIRI/cetuximab and FOLFOXIRI have demonstrated higher response and resection rates in phase III trials. During neoadjuvant therapy resectability should be regularly reevaluated. Operations should be planned as soon as resectability is achieved because a longer therapy will increase morbidity and because of uncertainty over the approach to patients with complete remission.

Resistance to EGF receptor-targeted monoclonal antibodies in the management of advanced colorectal cancer

SUMMARY Molecular markers that predict benefit associated with treatments for advanced colon cancer are now part of routine clinical practice. Monoclonal antibodies that target the EGF receptor have been shown to lack efficacy in cancers that have KRAS gene mutations. The antibodies are now used exclusively for patients with KRAS wild-type colon cancer. Such cancers may not respond to EGF receptor-targeted therapy at all. Those that initially respond will eventually develop resistance and inevitably progress. We will review mechanisms of primary and secondary resistance to EGF receptor monoclonal antibody therapy and suggest strategies to overcome resistance.

Drug repositioning for personalized medicine

Human diseases can be caused by complex mechanisms involving aberrations in numerous proteins and pathways. With recent advances in genomics, elucidating the molecular basis of disease on a personalized level has become an attainable goal. In many cases, relevant molecular targets will be identified for which approved drugs already exist, and the potential repositioning of these drugs to a new indication can be investigated. Repositioning is an accelerated route for drug discovery because existing drugs have established clinical and pharmacokinetic data. Personalized medicine and repositioning both aim to improve the productivity of current drug discovery pipelines, which expend enormous time and cost to develop new drugs, only to have them fail in clinical trials because of lack of efficacy or toxicity. Here, we discuss the current state of research in these two fields, focusing on recent large-scale efforts to systematically find repositioning candidates and elucidate individual disease mechanisms in cancer. We also discuss scenarios in which personalized drug repositioning could be particularly rewarding, such as for diseases that are rare or have specific mutations, as well as current challenges in this field. With an increasing number of drugs being approved for rare cancer subtypes, personalized medicine and repositioning approaches are poised to significantly alter the way we diagnose diseases, infer treatments and develop new drugs.

Concordance in KRAS and BRAF mutations in endoscopic biopsy samples and resection specimens of colorectal adenocarcinoma

BACKGROUND

KRAS testing is mandatory if anti-EGFR therapy is considered in patients with metastatic colorectal cancer (CRC). In addition, BRAF mutations seem to be an important negative prognostic factor. The aim of this study is to establish the concordance of KRAS and BRAF mutational status in paired biopsy and resection specimens of primary CRC using several analytic methods.

METHODS

DNA was extracted from paraffin blocks of 126 CRC patients. KRAS codon 12/13 and BRAF V600E mutational status was assessed using high resolution melting (HRM), direct sequencing (DS) of the HRM polymerase chain reaction (PCR) product. In addition, the Therascreen Amplification Refractory Mutation System (ARMS)-Scorpion KRAS assay and BRAF pyrosequencing were employed; both assays claim to require less tumour cells in comparison with DS.

RESULTS

KRAS and BRAF were found to be mutually exclusive. Mutation frequencies were 33.9% for KRAS, and for BRAF 19.0%, respectively. Concordance of KRAS mutational status between biopsy and resection specimens was 97.4% (ARMS), 98.4% (DS) and 99.2% (HRM), respectively. For BRAF concordance was 98.4% (Pyro, DS) and 99.2% (HRM).

CONCLUSIONS

KRAS and BRAF mutational status of endoscopic biopsies and resection specimens of CRC showed a >95% concordance. Endoscopic biopsies can be confidently used for molecular analysis.

Inhibition of MEK and PI3K/mTOR suppresses tumor growth but does not cause tumor regression in patient-derived xenografts of RAS-mutant colorectal carcinomas

PURPOSE

Gene mutations along the Ras pathway (KRAS, NRAS, BRAF, PIK3CA) occur in approximately 50% of colorectal cancers (CRC) and correlate with poor response to anti-EGF receptor (EGFR) therapies. We assessed the effects of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK) and phosphoinositide 3-kinase (PI3K)/mTOR inhibitors, which neutralize the major Ras effectors, in patient-derived xenografts from RAS/RAF/PIK3CA-mutant metastatic CRCs (mCRC).

EXPERIMENTAL DESIGN

Forty mCRC specimens harboring KRAS, NRAS, BRAF, and/or PIK3CA mutations were implanted in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. Each xenograft was expanded into four treatment arms: placebo, the MEK inhibitor AZD6244, the PI3K/mTOR inhibitor, BEZ235, or AZD6244 + BEZ235. Cases initially treated with placebo crossed over to AZD6244, BEZ235, and the anti-EGFR monoclonal antibody cetuximab.

RESULTS

At the 3-week evaluation time point, cotreatment of established tumors with AZD6244 + BEZ235 induced disease stabilization in the majority of cases (70%) but did not lead to overt tumor regression. Monotherapy was less effective, with BEZ235 displaying higher activity than AZD6244 (disease control rates, DCRs: AZD6244, 27.5%; BEZ235, 42.5%). Triple therapy with cetuximab provided further advantage (DCR, 88%). The extent of disease control declined at the 6-week evaluation time point (DCRs: AZD6244, 13.9%; BEZ235, 16.2%; AZD6244 + BEZ235, 34%). Cross-analysis of mice harboring xenografts from the same original tumor and treated with each of the different modalities revealed subgroups with preferential sensitivity to AZD6244 (12.5%), BEZ235 (35%), or AZD6244 + BEZ235 (42.5%); another subgroup (10%) showed equivalent response to any treatment.

CONCLUSIONS

The prevalent growth-suppressive effects produced by MEK and PI3K/mTOR inhibition suggest that this strategy may retard disease progression in patients. However, data offer cautionary evidence against the occurrence of durable responses.