K-ras mutations and benefit from cetuximab in advanced colorectal cancer

KRAS mutation in stage III colon cancer and clinical outcome following intergroup trial CALGB 89803

PURPOSE

Alterations in the RAS and RAF pathway relate to epigenetic and epigenomic aberrations, and are important in colorectal carcinogenesis. KRAS mutation in metastatic colorectal cancer predicts resistance to anti-epidermal growth factor receptor (EGFR)-targeted therapy (cetuximab or panitumumab). It remains uncertain, however, whether KRAS mutation predicts prognosis or clinical outcome of colon cancer patients independent of anti-EGFR therapy.

METHODS

We conducted a study of 508 cases identified among 1,264 patients with stage III colon cancer who enrolled in a randomized adjuvant chemotherapy trial (5-fluorouracil, leucovorin with or without irinotecan) in 1999-2001 (CALGB 89803). KRAS mutations were detected in 178 tumors (35%) by pyrosequencing. Kaplan-Meier and Cox proportional hazard models assessed the prognostic significance of KRAS mutation and adjusted for potential confounders including age, sex, tumor location, tumor/node stage, performance status, adjuvant chemotherapy arm, and microsatellite instability status.

RESULTS

Compared with patients with KRAS-wild-type tumors, patients with KRAS-mutated tumors did not experience any difference in disease-free, recurrence-free, or overall survival. The 5-year disease-free, recurrence-free, and overall survival rates (KRAS-mutated versus KRAS-wild-type patients) were 62% versus 63% (log-rank P = 0.89), 64% versus 66% (P = 0.84), and 75% versus 73% (P = 0.56), respectively. The effect of KRAS mutation on patient survival did not significantly differ according to clinical features, chemotherapy arm, or microsatellite instability status, and the effect of adjuvant chemotherapy assignment on outcome did not differ according to KRAS status.

CONCLUSIONS

In this large trial of chemotherapy in stage III colon cancer patients, KRAS mutational status was not associated with any significant influence on disease-free or overall survival.

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.

Antiangiogenic drugs in ovarian cancer

BACKGROUND

There is a critical need to develop effective new strategies for the management of patients with advanced epithelial ovarian cancer.

OBJECTIVE

The purpose of this manuscript is to discuss the rationale for, and initial clinical results of, attempts to interfere with the process of tumor angiogenesis as a novel treatment paradigm in ovarian cancer.

RESULTS/CONCLUSION

Phase II clinical trial data provide strong support for the suggestion that antiangiogenic agents have the potential to play a major therapeutic role in this difficult malignancy. It is reasonable to acknowledge that the pending results of several ongoing evidence-based randomized Phase III trials that directly explore the clinical utility of this strategy may substantially alter the current standard management approaches in advanced ovarian cancer.

KRAS mutation in colon cancer: a marker of resistance to EGFR-I therapy

Introduction and Design

The introduction of the epidermal growth factor receptor inhibitors (EGFR-I) has increased the treatment options available for patients with metastatic colorectal cancer (mCRC). Two EGFR-I agents currently approved for the treatment of mCRC are the fully human monoclonal antibody panitumumab and the mouse-human chimeric monoclonal antibody cetuximab. While these agents have demonstrated activity across multiple lines of therapy, early studies suggested that clinical benefit was confined to a subset of patients treated. Mutation of the KRAS oncogene has emerged as a powerful negative predictive biomarker to identify patients with mCRC who do not benefit from EGFR-I therapy. Multiple retrospective analyses have demonstrated that clinical benefit from treatment with EGFR-I is limited to patients with tumors harboring the wild-type KRAS gene. In this review, the KRAS pathway and studies evaluating KRAS as a prognostic marker in CRC are discussed along with advances in KRAS gene mutation testing. Clinical trials evaluating the role of KRAS status in response to EGFR-I monotherapy or in combination with chemotherapy are also highlighted along with ongoing studies evaluating the role of EGFR-I treatment on curative resections rates.

Results and Conclusion

Future studies investigating EGFR-I therapy in mCRC should incorporate KRAS mutation testing into the study protocol in order to more accurately determine the patient population that will obtain clinical benefit from these novel agents.

Epidermal growth factor receptor in relation to tumor development: EGFR-targeted anticancer therapy

The discovery that signaling by the epidermal growth factor receptor (EGFR) plays a key role in tumorigenesis prompted efforts to target this receptor in anticancer therapy. Two different types of EGFR-targeted therapeutic agents were subsequently developed: mAbs, such as cetuximab and panitumumab, which target the extracellular domain of the receptor, thereby inhibiting ligand-dependent EGFR signal transduction; and small-molecule tyrosine kinase inhibitors, such as gefitinib and erlotinib, which target the intracellular tyrosine kinase domain of the EGFR. Furthermore, recent clinical and laboratory studies have identified molecular markers that have the potential to improve the clinical effectiveness of EGFR-targeted therapies. This minireview summarizes the emerging role of molecular profiling in guiding the clinical use of anti-EGFR therapeutic agents.

Profiling critical cancer gene mutations in clinical tumor samples

BACKGROUND

Detection of critical cancer gene mutations in clinical tumor specimens may predict patient outcomes and inform treatment options; however, high-throughput mutation profiling remains underdeveloped as a diagnostic approach. We report the implementation of a genotyping and validation algorithm that enables robust tumor mutation profiling in the clinical setting.

METHODOLOGY

We developed and implemented an optimized mutation profiling platform ("OncoMap") to interrogate approximately 400 mutations in 33 known oncogenes and tumor suppressors, many of which are known to predict response or resistance to targeted therapies. The performance of OncoMap was analyzed using DNA derived from both frozen and FFPE clinical material in a diverse set of cancer types. A subsequent in-depth analysis was conducted on histologically and clinically annotated pediatric gliomas. The sensitivity and specificity of OncoMap were 93.8% and 100% in fresh frozen tissue; and 89.3% and 99.4% in FFPE-derived DNA. We detected known mutations at the expected frequencies in common cancers, as well as novel mutations in adult and pediatric cancers that are likely to predict heightened response or resistance to existing or developmental cancer therapies. OncoMap profiles also support a new molecular stratification of pediatric low-grade gliomas based on BRAF mutations that may have immediate clinical impact.

CONCLUSIONS

Our results demonstrate the clinical feasibility of high-throughput mutation profiling to query a large panel of "actionable" cancer gene mutations. In the future, this type of approach may be incorporated into both cancer epidemiologic studies and clinical decision making to specify the use of many targeted anticancer agents.

Locally advanced rectal cancer: from molecular profiling to clinical practice. A literature review: Part 2

Colorectal cancer is the third most common cause of cancer deaths worldwide. The management of rectal cancer has undergone, and continues to undergo, significant evolutions. In the last two decades, new multimodality strategies have been developed. The ability to predict tumor response before treatment could significantly impact the selection of patients for preoperative combined-modality therapy, as well as potentially modify postoperative treatment plans. The present review analyzes the new molecular targets that could be involved in predicting response and prognosis.

Implications of KRAS mutation status for the treatment of metastatic colorectal cancer

Targeted agents have become an integral part of the treatment of a number of malignant diseases and regimens containing agents that disrupt the epidermal growth factor receptor (EGFR) signaling pathway are now considered a standard therapeutic approach for a range of tumor types. Recently, the mutational status of the KRAS gene in tumors was shown to be predictive of outcome to treatment with EGFR-targeted therapies in metastatic colorectal cancer (mCRC). The immoglobulin (Ig) G1 EGFR-targeting monoclonal antibody (mAb), cetuximab, has been shown to provide significant clinical benefits when added to standard irinotecan- and oxaliplatin-containing chemotherapy regimens, first-line, in patients with KRAS wild-type mCRC. Its effects on tumor response and resectability of metastases make cetuximab a particularly useful treatment option for patients with bulky or initially unresectable disease. With an ever-increasing array of management options available, it is important that patients with mCRC receive the treatment that offers them the best chance of prolonged survival. In view of this, testing for tumor KRAS mutation status should be mandatory at diagnosis of mCRC, prior to treatment decision-making.

KRAS and BRAF mutations in patients with rectal cancer treated with preoperative chemoradiotherapy

BACKGROUND AND PURPOSE

KRAS and BRAF are mutated in 35% and 10% of colorectal cancers, respectively. However, data specifically for locally advanced rectal cancers are scarce, and the frequency of KRAS mutations in codons 61 and 146 remains to be established.

MATERIALS AND METHODS

DNA was isolated from pre-therapeutic biopsies of 94 patients who were treated within two phase-III clinical trials receiving preoperative chemoradiotherapy. Mutation status of KRAS exons 1-3 and BRAF exon 15 was established using the ABI PRISM Big Dye Sequencing Kit and subsequently correlated with clinical parameters.

RESULTS

Overall, KRAS was mutated in 45 patients (48%). Twenty-nine mutations (64%) were located in codon 12, 10 mutations (22%) in codon 13, and 3 mutations (7%) in codons 61 and 146. No V600E BRAF mutation was detected. The presence of KRAS mutations was correlated neither with tumor response or lymph node status after preoperative chemoradiotherapy nor with overall survival or disease-free survival. When KRAS exon 1 mutations were separated based on the amino-acid exchange, we again failed to detect significant correlations (p=0.052). However, G12V mutations appeared to be associated with higher rates of tumor regression than G13D mutations (p=0.012).

CONCLUSION

We are the first to report the mutation status of KRAS and BRAF in pre-therapeutic biopsies from locally advanced rectal cancers. The high number of KRAS mutations in codons 61 and 146 emphasizes the importance to expand current mutation analyses, whereas BRAF mutations are not relevant for rectal carcinogenesis. Although the KRAS mutation status was not correlated with response, the subtle difference between G12V and G13D mutations warrants analysis of a larger patient population.

Targeted KRAS mutation assessment on patient tumor histologic material in real time diagnostics

BACKGROUND

Testing for tumor specific mutations on routine formalin-fixed paraffin-embedded (FFPE) tissues may predict response to treatment in Medical Oncology and has already entered diagnostics, with KRAS mutation assessment as a paradigm. The highly sensitive real time PCR (Q-PCR) methods developed for this purpose are usually standardized under optimal template conditions. In routine diagnostics, however, suboptimal templates pose the challenge. Herein, we addressed the applicability of sequencing and two Q-PCR methods on prospectively assessed diagnostic cases for KRAS mutations.

METHODOLOGY/PRINCIPAL FINDINGS

Tumor FFPE-DNA from 135 diagnostic and 75 low-quality control samples was obtained upon macrodissection, tested for fragmentation and assessed for KRAS mutations with dideoxy-sequencing and with two Q-PCR methods (Taqman-minor-groove-binder [TMGB] probes and DxS-KRAS-IVD). Samples with relatively well preserved DNA could be accurately analyzed with sequencing, while Q-PCR methods yielded informative results even in cases with very fragmented DNA (p<0.0001) with 100% sensitivity and specificity vs each other. However, Q-PCR efficiency (Ct values) also depended on DNA-fragmentation (p<0.0001). Q-PCR methods were sensitive to detect<or=1% mutant cells, provided that samples yielded cycle thresholds (Ct)<29, but this condition was met in only 38.5% of diagnostic samples. In comparison, FFPE samples (>99%) could accurately be analyzed at a sensitivity level of 10% (external validation of TMGB results). DNA quality and tumor cell content were the main reasons for discrepant sequencing/Q-PCR results (1.5%).

CONCLUSIONS/SIGNIFICANCE

Diagnostic targeted mutation assessment on FFPE-DNA is very efficient with Q-PCR methods in comparison to dideoxy-sequencing. However, DNA fragmentation/amplification capacity and tumor DNA content must be considered for the interpretation of Q-PCR results in order to provide accurate information for clinical decision making.

KRAS and BRAF mutations in advanced colorectal cancer are associated with poor prognosis but do not preclude benefit from oxaliplatin or irinotecan: results from the MRC FOCUS trial

PURPOSE

Activating mutation of the KRAS oncogene is an established predictive biomarker for resistance to anti-epidermal growth factor receptor (anti-EGFR) therapies in advanced colorectal cancer (aCRC). We wanted to determine whether KRAS and/or BRAF mutation is also a predictive biomarker for other aCRC therapies.

PATIENTS AND METHODS

The Medical Research Council Fluorouracil, Oxaliplatin and Irinotecan: Use and Sequencing (MRC FOCUS) trial compared treatment sequences including first-line fluorouracil (FU), FU/irinotecan or FU/oxaliplatin in aCRC. Tumor blocks were obtained from 711 consenting patients. DNA was extracted and KRAS codons 12, 13, and 61 and BRAF codon 600 were assessed by pyrosequencing. Mutation (mut) status was assessed first as a prognostic factor and then as a predictive biomarker for the benefit of adding irinotecan or oxaliplatin to FU. The association of BRAF-mut with loss of MLH1 was assessed by immunohistochemistry.

RESULTS

Three hundred eight (43.3%) of 711 patients had KRAS-mut and 56 (7.9%) of 711 had BRAF-mut. Mutation of KRAS, BRAF, or both was present in 360 (50.6%) of 711 patients. Mutation in either KRAS or BRAF was a poor prognostic factor for overall survival (OS; hazard ratio [HR], 1.40; 95% CI, 1.20 to 1.65; P < .0001) but had minimal impact on progression-free survival (PFS; HR, 1.16; 95% CI, 1.00 to 1.36; P = .05). Mutation status did not affect the impact of irinotecan or oxaliplatin on PFS or OS. BRAF-mut was weakly associated with loss of MLH1 staining (P = .012).

CONCLUSION

KRAS/BRAF mutation is associated with poor prognosis but is not a predictive biomarker for irinotecan or oxaliplatin. There is no evidence that patients with KRAS/BRAF mutated tumors are less likely to benefit from these standard chemotherapy agents.

Sensitivity and resistance to EGF-R inhibitors: approaches to enhance the efficacy of EGF-R antibodies

The epidermal growth factor receptor (EGF-R) constitutes one of the most broadly targeted antigens in tumor therapy since it is commonly expressed on many epithelial cancers, as well as on glioblastomas. Both EGF-R-directed tyrosine kinase inhibitors and monoclonal antibodies have been approved, but clinical response rates are often limited. A more detailed understanding of the mechanisms underlying sensitivity or resistance against EGF-R inhibitors may assist in identifying patient populations who optimally benefit from currently available reagents. In addition, these insights may guide the development of more effective molecules. In this short review, we will summarize some of the current knowledge in this rapidly evolving field with particular emphasis on EGF-R-directed antibodies.

Gene expression profiling of primary and metastatic colon cancers identifies a reduced proliferative rate in metastatic tumors

The objective of this study was to gain insights into the biological basis of the metastatic process by characterizing the gene expression differences between primary and metastatic colon cancers. Recent studies have demonstrated that few new mutational changes are acquired during the metastatic progression of colon tumors [Jones et al., Proc Natl Acad Sci USA 105 (11): 4283-4288, 2008]. However, the extent to which epigenetic and transcriptional changes occur between primary and metastatic colon cancer remains unknown. We approached these issues using Affymetrix microarrays to assess the similarities and differences in gene expression profiles between macro-dissected primary and metastatic colon tumors. Unexpectedly, we found that expression of a number of cell proliferation markers were reduced in the liver metastases of colon tumors when compared to primary tumors. This finding was validated by immunohistochemical staining of Ki67 and Cyclin D1 in Formalin-Fixed Paraffin-Embedded (FFPE) section of the same samples, and in an independent cohort of FFPE matched tumor and metastatic tissue samples. These results indicate that significant transcriptional differences exist between primary and metastatic colon tumors, and demonstrate that metastatic lesions have a lower proliferative rate compared to primary tumors. These findings may have implications for interpreting differences in response rates between primary and metastatic lesions and suggest that measurement of expression-based biomarkers in metastatic tissue will be most informative for understanding the basis of response of metastatic tumors to therapeutic intervention.

Overview of systemic therapy for colorectal cancer

Colorectal cancer (CRC) is the third most common cancer and second leading cause of death from cancer in North America. The authors provide an overview of the indications for both chemotherapy and targeted therapy, as well as discuss the efficacy and toxicity of systemic therapy. They highlight the key studies that lead to the initial historical use of fluorouracil (5FU) based chemotherapy in the adjuvant and metastatic setting, the recent adoption of 5FU plus leucovorin (LV) and oxaliplatin (FOLFOX) chemotherapy over 5FU when treating adjuvant patients, and the use of FOLFOX or 5FU plus LV and irinotecan (FOLFIRI) in metastatic patients. They also review the role of chemotherapy in treating rectal cancer and resectable liver metastatic disease. Future areas of research focus for systemic therapy of colorectal cancer are highlighted.

Detection of N-, H-, and KRAS codons 12, 13, and 61 mutations with universal RAS primer multiplex PCR and N-, H-, and KRAS-specific primer extension

OBJECTIVES

Mutations of all three RAS genes, N-, H-, and KRAS, are identified mainly in codons 12, 13, and 61 of exons 2 and 3 in human cancers.

DESIGN AND METHODS

DNA samples were isolated from 58 oral cancer and 106 colorectal cancer patients. Multiplex amplification of codons 12 and 13 of exon 2 and codon 61 of exon 3 of three RAS genes using two pairs of universal primers for exons 2 and 3 was performed in a single tube. The products were cleaned and split in three tubes. Each was subjected for primer extension using seven different-sized RAS primers for different RAS gene separately to detect base changes in codons 12, 13, and 61 of each RAS gene.

RESULTS

We compared the results with that from direct sequencing for detecting N-, H-, and KRAS mutations in 58 oral cancers and 106 colorectal cancers. The two methods yield identical results, but our method is superior to direct sequencing in terms the amount of work and time required.

CONCLUSIONS

We presented a rapid method to detect codons 12, 13, and 61 mutations of N-, H-, and KRAS genes in human cancers.

MDR1 polymorphism role in patients treated with cetuximab and irinotecan in irinotecan refractory colorectal cancer

The aim of the study was to evaluate the influence of the MDR1 C3435T polymorphism on the therapeutic response in 23 patients treated with cetuximab plus irinotecan for irinotecan refractory liver metastatic colorectal cancer considering their KRAS status. Indeed, irinotecan and its active metabolite (SN-38) are both substrates of P-glycoprotein (P-gp) encoded by MDR1. Patients received cetuximab and irinotecan up to progression. The overall survival was 55% at 10 months. Overall, four patients had an undetermined KRAS status and two patients with mutated KRAS were in progression disease. The response to treatment was observed after 3 months among the 17 wild-type KRAS patients. Two patients presented a progressive disease (1 TT and 1 CT), eight patients had a stable disease (5 CC and 3CT) and five patients had a partial response (3 CC and 2 CT). Importantly, 2 patients (2 TT) were in complete response and still alive 5 years after starting the treatment, which suggests that the combination of wild-type KRAS and MDR1 3435 TT may be a factor of good prognosis. These results suggest that EGFR inhibition by cetuximab may overcome this irinotecan resistance by abrogating drug efflux depending on MDR1 3435 polymorphism. Among patients resistant to irinotecan, it is still possible to use the association of cetuximab plus irinotecan to obtain a complete resection of hepatic metastases that is necessary to improve their survival.

Targeted therapies in the treatment of advanced/metastatic NSCLC

The treatment of advanced non-small cell lung cancer (NSCLC) has evolved substantially during the last years. Chemotherapy remains the cornerstone of treatment and prolongs survival with a positive impact on quality of life. However, we seem to have reached a plateau of activity in the treatment of NSCLC. Recently, the addition of bevacizumab or cetuximab to chemotherapy doublets has improved the outcome in selected patients with advanced NSCLC. Furthermore, the use of erlotinib and gefitinib is an alternative for second line treatment. Advances in our understanding of molecular biology of cancer and mechanisms of tumourigenesis have further enabled the discovery of several potential molecular targets and development of novel 'targeted therapies'. The purpose of this study is to review current data on the role of targeted therapies in the treatment of advanced NSCLC.

Comprehensive genomic analysis reveals clinically relevant molecular distinctions between thymic carcinomas and thymomas

PURPOSE

Thymomas and thymic carcinomas are rare intrathoracic malignancies that can be invasive and refractory to conventional treatment. Because these tumors both originate from the thymus, they are often grouped together clinically. However, whether the underlying biology of these tumors warrants such clustering is unclear, and the optimum treatment of either entity is unknown.

EXPERIMENTAL DESIGN

All thymic tumors were profiled for mutations in genes encoding components of the EGFR and KIT signaling pathways, assessed for EGFR and KIT expression by immunohistochemistry, and analyzed by array-based comparative genomic hybridization. Previously untreated tumors were subjected to global gene expression arrays.

RESULTS

We analyzed 45 thymic tumors [thymoma, n = 38 (type A, n = 8; type B2, n = 22; type B3, n = 8); thymic carcinoma, n = 7]. One thymoma and one thymic carcinoma harbored KRAS mutations (G12A and G12V, respectively), and one thymoma had a G13V HRAS mutation. Three tumors displayed strong KIT staining. Two thymic carcinomas harbored somatic KIT mutations (V560del and H697Y). In cell viability assays, the V560del mutant was associated with similar sensitivities to imatinib and sunitinib, whereas the H697Y mutant displayed greater sensitivity to sunitinib. Genomic profiling revealed distinct differences between type A to B2 thymomas versus type B3 and thymic carcinomas. Moreover, array-based comparative genomic hybridization could readily distinguish squamous cell carcinomas of the thymus versus the lung, which can often present a diagnostic challenge.

CONCLUSIONS

Comprehensive genomic analysis suggests that thymic carcinomas are molecularly distinct from thymomas. These data have clinical, pathologic, and therapeutic implications for the treatment of thymic malignancies.

Phase I and pharmacokinetic study of cetuximab and irinotecan in children with refractory solid tumors: a study of the pediatric oncology experimental therapeutic investigators' consortium

PURPOSE

To determine the dose of cetuximab that can be safely combined with irinotecan for treatment of pediatric and adolescent patients with refractory solid tumors.

PATIENTS AND METHODS

This open-label, phase I study enrolled patients ages 1 to 18 years with advanced refractory solid tumors, including tumors of the CNS. Patient cohorts by age group (children, ages 1 to 12 years; adolescents, ages 13 to 18 years) received escalating weekly doses of cetuximab (75, 150, 250 mg/m(2)) in a 3 + 3 design, plus irinotecan (16 or 20 mg/m(2)/d) for 5 days for 2 consecutive weeks every 21 days. The primary end points were establishing the maximum-tolerated dose (MTD), recommended phase II dose (RPIID), and pharmacokinetics of the combination. Preliminary safety and efficacy data were also collected.

RESULTS

Twenty-seven children and 19 adolescents received a median of 7.1 and 6.0 weeks of cetuximab therapy, respectively. Cetuximab 250 mg/m(2) weekly plus irinotecan 16 mg/m(2)/d (pediatric) or 20 mg/m(2)/d (adolescent) have been established as the MTD/RPIID. Dose-limiting toxicities included diarrhea and neutropenia. Mild to moderate (grade 1 to 2) acneiform rash occurred in a majority of patients; no grade 3 to 4 rashes were observed. Cetuximab demonstrated dose-dependent clearance in both children and adolescents, similar to that in adults. There were two confirmed partial responses, both in patients with CNS tumors. Stable disease was achieved in 18 patients overall, including 10 patients with CNS tumors (38.5%).

CONCLUSION

The cetuximab/irinotecan combination can be given safely to children and adolescents with cancer. Promising activity, particularly in CNS tumors, warrants phase II evaluation of this regimen.

A phase II, multicenter study of cetuximab monotherapy in patients with refractory, metastatic colorectal carcinoma with absent epidermal growth factor receptor immunostaining

PURPOSE

To determine antitumor activity of cetuximab monotherapy in patients with refractory metastatic colorectal carcinoma (mCRC) with lack of specific membrane immunostaining for the epidermal growth factor receptor (EGFR).

PATIENTS AND METHODS

Patients had immunohistochemical (IHC)-determined mCRC with absent EGFR immunostaining that progressed after receiving at least one standard, fluoropyrimidine-containing chemotherapeutic regimen. Absent EGFR immunostaining was defined as the IHC absence of specific membrane staining in ≥500 cancer cells examined in well-preserved tissue. The study was performed prior to results of studies linking cetuximab sensitivity to K-ras mutation status. Patients received 400 mg/m(2) of intravenous (i.v.) cetuximab followed by once-weekly i.v. cetuximab 250 mg/m(2) until disease progression or unacceptable toxicity. Patients were evaluated for objective response at least every 6 weeks. Kaplan-Meier estimates were calculated for duration of response, time to progression (TTP), and overall survival (OS).

RESULTS

Seven (8.2%) of 85 mCRC patients whose tumors lacked EGFR immunostaining had major responses following cetuximab treatment. The median duration of response was 5.1 months. Median TTP and OS were 2.5 months and 10.0 months, respectively; the 1-year survival rate was 39.6%. The most frequently reported cetuximab-related adverse events were acneiform dermatitis, fatigue, headache, and dry skin.

CONCLUSION

Cetuximab monotherapy produces objective antitumor activity in patients with mCRC that does not express EGFR as determined by IHC. The activity and safety profiles of cetuximab monotherapy in mCRC lacking EGFR immunostaining are similar to previous observations in EGFR IHC-positive disease that was not selected based on K-ras mutation status.

The role of KRAS mutation testing in the management of patients with metastatic colorectal cancer

CONTEXT

KRAS mutations can be detected in approximately 30% to 40% of all patients with colorectal cancer. Several recent studies have shown that patients with KRAS mutations in codons 12 or 13 in metastatic tumors do not benefit from anti-epidermal growth factor receptor therapy with cetuximab or panitumumab.

OBJECTIVE

To review the literature on the role of KRAS mutation testing for management of patients with metastatic colorectal cancer and to discuss testing strategies.

DATA SOURCES

This review is based on published, peer-reviewed literature; available information from medical organizations (eg, National Comprehensive Cancer Network, American Society of Clinical Oncology, College of American Pathologists); and information from clinical laboratories conducting KRAS mutation analysis.

CONCLUSIONS

Multiple methods for detecting KRAS mutations in colorectal tumors are available, and all methods in current clinical use appear to have adequate clinical sensitivity for predicting a lack of response to cetuximab and panitumumab. Pathologist expertise is essential to quality KRAS testing and to determining effective treatment for patients with metastatic colorectal cancer.

Mammary-derived growth inhibitor alters traffic of EGFR and induces a novel form of cetuximab resistance

PURPOSE

Only few predictive factors for the clinical activity of anti-epidermal growth factor receptor (EGFR) therapy are available. Mammary-derived growth inhibitor (MDGI) is a small cytosolic protein suggested to play a role in the differentiation of epithelial cells. Here, we have investigated the effect of MDGI expression on the EGFR signaling and cetuximab responsiveness of cancer cells.

EXPERIMENTAL DESIGN

MDGI mRNA expression was investigated in clinical breast and lung cancer samples and in nontransformed and malignant cell lines. The effect of ectopic expression of MDGI on EGFR, ErbB2, and integrin function and traffic was investigated in breast and lung cancer cell lines using multiple methods. The effect of anti-EGFR agents on these cells were tested by cell proliferation measurements and by assessing tumor growth of breast cancer cells in cetuximab treated and control athymic nude mice.

RESULTS

Here, we show that although MDGI is absent in cultured cell lines because of epigenetic silencing, MDGI mRNA is expressed in 40% of clinical breast carcinomas and 85% of lung cancers. Ectopic expression of MDGI rendered breast and lung cancer cells resistant to the anti-EGFR antibody cetuximab in vitro and in an orthotopic breast cancer xenograft model in vivo. When expressed in cancer cells, MDGI induces intracellular accumulation of EGFR, but not ErbB2, and the internalized receptor is phosphorylated and not degraded.

CONCLUSIONS

MDGI-driven inherent desensitization of cancer cells is a novel molecular mechanism for resistance to the anti-EGFR antibody therapy, and MDGI may be a biomarker for responsiveness to anti-EGFR antibody therapy.

Use of archived specimens in evaluation of prognostic and predictive biomarkers

The development of tumor biomarkers ready for clinical use is complex. We propose a refined system for biomarker study design, conduct, analysis, and evaluation that incorporates a hierarchal level of evidence scale for tumor marker studies, including those using archived specimens. Although fully prospective randomized clinical trials to evaluate the medical utility of a prognostic or predictive biomarker are the gold standard, such trials are costly, so we discuss more efficient indirect "prospective-retrospective" designs using archived specimens. In particular, we propose new guidelines that stipulate that 1) adequate amounts of archived tissue must be available from enough patients from a prospective trial (which for predictive factors should generally be a randomized design) for analyses to have adequate statistical power and for the patients included in the evaluation to be clearly representative of the patients in the trial; 2) the test should be analytically and preanalytically validated for use with archived tissue; 3) the plan for biomarker evaluation should be completely specified in writing before the performance of biomarker assays on archived tissue and should be focused on evaluation of a single completely defined classifier; and 4) the results from archived specimens should be validated using specimens from one or more similar, but separate, studies.

Biomarkers predicting clinical outcome of epidermal growth factor receptor-targeted therapy in metastatic colorectal cancer

The monoclonal antibodies panitumumab and cetuximab that target the epidermal growth factor receptor (EGFR) have expanded the range of treatment options for metastatic colorectal cancer. Initial evaluation of these agents as monotherapy in patients with EGFR-expressing chemotherapy-refractory tumors yielded response rates of approximately 10%. The realization that detection of positive EGFR expression by immunostaining does not reliably predict clinical outcome of EGFR-targeted treatment has led to an intense search for alternative predictive biomarkers. Oncogenic activation of signaling pathways downstream of the EGFR, such as mutation of KRAS, BRAF, or PIK3CA oncogenes, or inactivation of the PTEN tumor suppressor gene is central to the progression of colorectal cancer. Tumor KRAS mutations, which may be present in 35%-45% of patients with colorectal cancer, have emerged as an important predictive marker of resistance to panitumumab or cetuximab treatment. In addition, among colorectal tumors carrying wild-type KRAS, mutation of BRAF or PIK3CA or loss of PTEN expression may be associated with resistance to EGFR-targeted monoclonal antibody treatment, although these additional biomarkers require further validation before incorporation into clinical practice. Additional knowledge of the molecular basis for sensitivity or resistance to EGFR-targeted monoclonal antibodies will allow the development of new treatment algorithms to identify patients who are most likely to respond to treatment and could also provide rationale for combining therapies to overcome primary resistance. The use of KRAS mutations as a selection biomarker for anti-EGFR monoclonal antibody (eg, panitumumab or cetuximab) treatment is the first major step toward individualized treatment for patients with metastatic colorectal cancer.

Multi-determinants analysis of molecular alterations for predicting clinical benefit to EGFR-targeted monoclonal antibodies in colorectal cancer

Background

KRAS mutations occur in 35–45% of metastatic colorectal cancers (mCRC) and preclude responsiveness to EGFR-targeted therapy with cetuximab or panitumumab. However, less than 20% patients displaying wild-type KRAS tumors achieve objective response. Alterations in other effectors downstream of the EGFR, such as BRAF, and deregulation of the PIK3CA/PTEN pathway have independently been found to give rise to resistance. We present a comprehensive analysis of KRAS, BRAF, PIK3CA mutations, and PTEN expression in mCRC patients treated with cetuximab or panitumumab, with the aim of clarifying the relative contribution of these molecular alterations to resistance.

Methodology/Principal Findings

We retrospectively analyzed objective tumor response, progression-free (PFS) and overall survival (OS) together with the mutational status of KRAS, BRAF, PIK3CA and expression of PTEN in 132 tumors from cetuximab or panitumumab treated mCRC patients. Among the 106 non-responsive patients, 74 (70%) had tumors with at least one molecular alteration in the four markers. The probability of response was 51% (22/43) among patients with no alterations, 4% (2/47) among patients with 1 alteration, and 0% (0/24) for patients with ≥2 alterations (p<0.0001). Accordingly, PFS and OS were increasingly worse for patients with tumors harboring none, 1, or ≥2 molecular alteration(s) (p<0.001).

Conclusions/Significance

When expression of PTEN and mutations of KRAS, BRAF and PIK3CA are concomitantly ascertained, up to 70% of mCRC patients unlikely to respond to anti-EGFR therapies can be identified. We propose to define as ‘quadruple negative’, the CRCs lacking alterations in KRAS, BRAF, PTEN and PIK3CA. Comprehensive molecular dissection of the EGFR signaling pathways should be considered to select mCRC patients for cetuximab- or panitumumab-based therapies.

[The development of the first line treatment of metastatic colorectal cancer (mCRC)]

Chemotherapy options of metastatic colorectal cancer (mCRC) have been progressed rapidly in the last years. Besides of the standard fluorouracil/folinic acid treatment some new active agents (oxaliplatin and irinotecan) have been introduced, and more recently the "targeted" biologicals (bevacizumab, cetuximab, panitumumab) have demonstrated their high effectiveness. This review summarizes the development of the first line treatment of mCRC.

Clinical biomarkers in oncology: focus on colorectal cancer

Rapidly growing insight into the molecular biology of colorectal cancer has led to high hopes for the identification of molecular markers to be used in optimized and tailored treatment regimens. However, many of the published data on gene-specific biomarkers are contradictory in their findings, and no tests are currently used in clinical practice, with the exception of microsatellite instability (MSI) and guanylyl cyclase C (GCC) testing in the adjuvant setting, and in Europe KRAS mutation testing is used in the setting of epidermal growth factor receptor (EGFR)-targeted therapy for metastatic disease. There are many reasons for the failure of the initial marker hypothesis-driven approach. Although supported by a good biologic rationale, single markers such as tumor protein p53 (TP53) gene mutations, when applied to a complex tumor type containing many synchronous alterations, do not perform well in predicting outcome. Many markers also suffer from technical shortcomings, resulting from the lack of quantitative techniques to capture the impact of the molecular alteration. The impact of markers obtained from microarray expression profiling needs to be further investigated in studies based on much larger cohorts, and cross-validation studies will be essential. Recently, mutations in the KRAS gene were shown to be strong negative predictors of response to EGFR inhibitors in metastatic disease. It has also been suggested that BRAF gene mutations may be predictive of EGFR inhibitor resistance, and there are some conflicting data regarding the role of the PIK3CA gene. Further studies are needed to help integrate the latest findings into clinically useful tools for personalized medicine.

Anti-epidermal growth factor receptor monoclonal antibodies in cancer therapy

The epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor involved in the proliferation and survival of cancer cells. EGFR is the first molecular target against which monoclonal antibodies (mAb) have been developed for cancer therapy. Here we review the mechanisms underlying the effects of EGFR-specific mAb in cancer therapy. The efficacy of EGFR-specific mAb in cancer occurs thanks to inhibition of EGFR-generated signalling; furthermore, the effects of antibodies on the immune system seem to play an important role in determining the overall anti-tumour response. In this review, attention is focused on cetuximab and panitumumab, two mAb introduced recently into clinical practice for treatment of metastatic colorectal and head and neck cancer which target the external part of EGFR.

Drug development in advanced colorectal cancer: challenges and opportunities

Despite recent advances in treatment options, advanced colorectal cancer (ACC) remains a leading cause of cancer death worldwide, and new therapies are needed to improve the grim prognosis of this disease. Drug development in ACC faces the challenges of a constrained pipeline, a paucity of patients enrolled in clinical trials, and an outdated "one drug fits all" model of clinical research. This article discusses potential innovations in clinical trial design--including enrichment strategies, novel patient populations, and the use of randomization in the phase 2 setting--to optimize the testing of new therapies. It concludes with a selection of promising agents and pathways under investigation in ACC.

Assessment of K-ras mutation: a step toward personalized medicine for patients with colorectal cancer

Some of the most significant therapeutic advances in the treatment of cancer have occurred in the management of colorectal metastases. The introduction of new cytotoxic chemotherapeutic and biologic agents has changed the approach to these patients from both an oncologic and a surgical perspective. In addition, an understanding of the molecular mechanisms by which these agents affect tumors is developing. This molecular information will be critical in the future in designing therapeutic regimens based on an individual tumor's genetic profile rather than treatment for a specific tumor type. The rapidly evolving treatment of colon cancer has provided several interesting genetic biomarkers/pathways/genes-/kinases that have been targeted or seem to play an important role. Of particular interest is the blockade of epidermal growth factor receptor (EGFR) with monoclonal antibodies. This treatment is efficacious when used alone or combined with chemotherapy. However, recent data revealed that patients with tumors positive for the K-ras mutation do not benefit from EGFR blockade. Compelling evidence has indicated that mutated K-ras is an important oncogene involved at the early stage of the development of colorectal cancer. Furthermore, mutations in the K-ras gene have been associated with aggressive tumor biology. K-ras mutational analysis is an important step in the overarching goal of developing personalized medicine. New treatment strategies are needed to more effectively treat patients with the K-ras mutation.

Prolonged survival in a patient with BRCA2 associated metastatic pancreatic cancer after exposure to camptothecin: a case report and review of literature

Germline mutations in the tumor suppressor genes BRCA1 and BRCA2 have been proven to predict a drastically increased lifetime risk of breast and ovarian cancers in the individuals who carry them. A number of studies have shown that the third most common cancer associated with these mutations is pancreatic cancer. There is evidence of in vivo therapeutic response to the cross-linking agents; such as mitomycin C (MMC) in BRCA2 mutated pancreatic cell lines. We present the 'first patient' who achieved a prolonged survival on irinotecan, a topoisomerase I poison, administered alone and then in combination with cetuximab. Our patient presented at the age of 71 years with a dual diagnosis of prostate carcinoma and pancreatic carcinoma on the background of a significant family history of cancer. On genetic testing, he was found to have the common Ashkenazi Jewish BRCA2 mutation, 6174delT. To date, he has received 22 cycles of docetaxel, capecitabine, and gemcitibine followed by single agent irinotecan every 3 weeks for 27 cycles, and then weekly cetuximab was added to the regimen at cycle 28. His disease then remained stable for an additional 13 months. He did not have mutated KRAS. MMC and oxaliplatin was then introduced upon progression. His current treatment is MMC plus irinotecan as oxaliplatin was removed because of a hypersensitivity reaction. This patient is stable with an Eastern Cooperative Oncology Group performance status of 0, four and a half years (56 months) after his initial diagnosis. DNA topoisomerases are nuclear enzymes responsible for the regulation of DNA topology. They are involved in basic DNA transactions during replication, transcription, and recombination. BRCA2-deficient human cells are deficient in the repair of double-strand breaks and DNA cross-links through homologous recombination. Active poisons of topoisomerase I include derivatives of camptothecin. Our case is the first clinical piece of evidence that demonstrates an increased sensitivity to camptothecin-11 and a reduced topoisomerase I relaxation activity in BRCA2 associated pancreatic cancer. This case shows that patients with metastatic pancreatic carcinoma and BRCA2 mutations may have disease that is biologically more chemosensitive and consequently prolong survival despite prognostically unfavorable disease.

Amphiregulin and epiregulin mRNA expression in primary tumors predicts outcome in metastatic colorectal cancer treated with cetuximab

PURPOSE

To study the power of the epidermal growth factor receptor (EGFR) epiregulin (EREG) and amphiregulin (AREG) ligands' expression in primary tumors to predict the outcome in patients with chemorefractory metastatic colorectal cancer (cmCRC) treated with the combination of cetuximab and irinotecan.

PATIENTS AND METHODS

Gene expression measurements and KRAS mutation analysis were performed on archival formalin-fixed paraffin-embedded primary tumors of 220 cmCRC patients. Response was measured using RECIST (Response Evaluation Criteria in Solid Tumors) criteria. The relation between ligand expression levels and outcome was evaluated using logistic regression for response and Cox regression for survival data. Receiver operating characteristics analysis was performed for response and survival data. CIs for the performance indices were obtained with a nonparametric bootstrap procedure. Findings were externally validated on a series of 67 samples treated in a similar setting.

RESULTS

In KRAS wild type (WT) patients, there was a significant association between log-transformed ligand expression and response for EREG (odds ratio for objective response, 1.90; 95% CI, 1.27 to 2.83; P = .0005; concordance index [c-index], 0.681) and for AREG (odds ratio for objective response, 1.862; 95% CI, 1.22 to 2.72; P = .0017; c-index, 0.673). In a Cox regression model, dichotomized ligand expression was significantly associated with progression-free survival (PFS) and overall survival (OS). EREG PFS hazard ratio (HR) was 0.41 (95% CI, 0.274 to 0.609; P < .001; time-dependent c-index [Ctau index], 0.640), and AREG PFS HR was 0.43 (95% CI, 0.29 to 0.64; P < .001; Ctau index, 0.627). EREG OS HR was 0.42 (95% CI, 0.28 to 0.63; P < .0001; Ctau index, 0.639), and AREG OS HR was 0.40 (95% CI, 0.27 to 0.64; P < .0001; Ctau index, 0.625). There was no predictive power of ligand expression in patients with KRAS mutation.

CONCLUSION

Expression of EGFR ligands in primary tumors significantly predicts outcome in KRAS WT cmCRC treated with cetuximab and irinotecan.

Medical treatment of advanced colorectal cancer in 2009

The treatment options currently available in the medical therapy of advanced colorectal cancer (CRC) appear to be an abundance of riches. The integration of oxaliplatin and irinotecan as conventional cytotoxic agents as well as bevacizumab and the epidermal growth factor receptor (EGFR) antibodies, cetuximab and panitumumab, as novel targeted agents into standard medical therapy have improved median overall survival in metastatic CRC beyond 2 years. It cannot be overemphasized that these significant improvements in outcome of patients with CRC are closely linked to the number of active drugs available to treat this disease. The abundance of treatment options, however, comes with specific challenges for the practical management of palliative medical therapy in advanced CRC, in particular with regard to the utilization of targeted agents. In this context, bevacizumab has established itself as the standard component of first-line chemotherapy. It is of interest for clinical practice that so far no predictive marker for the activity of bevacizumab in metastatic CRC has been identified. The key questions surrounding the use of bevacizumab in the palliative setting are whether its continuation beyond tumor progression provides clinical benefit, and which patient group is at higher risk for bevacizumab-related toxicities. Cetuximab and panitumumab have demonstrated efficacy both in combination with chemotherapy or - in contrast to bevacizumab - as single agent. In unselected patients, the effect of both EGFR antibodies on time-related parameters, progression free survival and overall survival, is moderate at best with emphasis more on the induction of tumor responses in a select group of patients. Therefore, until recently, EGFR antibodies were mainly regarded as salvage therapy options, in particular, since there did not appear to be a loss of activity when used in later lines of therapy. The finding that CRC harboring KRAS (and BRAF) mutations are resistant to EGFR antibodies, has allowed us to enrich the patient population with CRC that have a chance to benefit from cetuximab or panitumumab therapy. Biomarker-based treatment decisions are therefore now an integral part of clinical practice and trial design in CRC. In conclusion, targeted agents have become an integral part of medical therapy for advanced CRC. The challenge for current oncologic practice is to develop a rationale and biomarker-based treatment algorithm utilizing all potentially active agents as individualized therapy.

Population pharmacokinetic analysis of panitumumab in patients with advanced solid tumors

Panitumumab is a fully human monoclonal antibody targeted to the extracellular domain of human epidermal growth factor receptor (EGFR). A comprehensive population pharmacokinetic model of panitumumab was developed using nonlinear mixed-effects modeling of 1200 patients with advanced solid tumors in 14 clinical studies. The disposition of panitumumab was best described with a 2-compartment model with parallel linear and nonlinear (Michaelis-Menten) elimination pathways. For a typical male patient with colorectal cancer (80 kg, 60 years old), the estimates for the linear clearance (CL), the maximum nonlinear clearance (V(max)/K(m)), the central volume of distribution (V(1)), the peripheral volume of distribution (V(2)), and the Michaelis-Menten constant (K(m)) are 0.273 L/d, 28.4 L/d, 3.95 L, 2.59 L, and 0.426 mcg/mL, respectively. Baseline covariates such as body weight, cancer type, age, sex, and race were studied for their influence on panitumumab pharmacokinetics. Body weight was found to be the most influential covariate on panitumumab exposure, affecting CL, V(max), and V(1). The administration of concomitant chemotherapy (IFL, FOLFIRI, or paclitaxel/carboplatin) or intensity of baseline tumor EGFR expression did not alter the pharmacokinetics of panitumumab. The presence of antipanitumumab antibodies in patients (immunogenicity rate 3.4%) did not appear to affect panitumumab exposure substantially (AUC difference 8%). In support of a new drug application in Japan, the model was used to assess panitumumab pharmacokinetics in Japanese patients compared to other racial groups; there were no significant differences in model-predicted steady-state panitumumab AUC, C(max), or C(min) after accounting for the effect of body weight.

Divide and conquer: progress in the molecular stratification of cancer

Cancer remains an outstanding cause of global morbidity and mortality, despite intensive research and unprecedented insights into the basic mechanisms of cancer development. A plethora of clinical and experimental evidence suggests that cancers from individual patients are likely to be molecularly heterogeneous in their use of distinct oncogenic pathways and biological programs. Efforts to significantly impact cancer patient outcomes will almost certainly require the development of robust strategies to subdivide such heterogeneous panels of cancers into biologically and clinically homogenous subgroups, for the purposes of personalizing treatment protocols and identifying optimal drug targets. In this review, I describe recent progress in the development of both targeted and genome-wide approaches for the molecular stratification of cancers, drawing examples from both the haematopoietic and solid tumor malignancies.

Improving disease control in advanced colorectal cancer: Panitumumab and cetuximab

Colorectal cancer remains a major public health concern in Europe and North America. It is responsible for one million new cases and half a million deaths per year worldwide. During the past few years new effective treatments have evolved improving the outcome of patients with this disease. Several alternatives are currently available for advanced colorectal cancer patients including different chemotherapeutic regimens (fluoropyrimidines, irinotecan and oxaliplatin) and targeted therapies such as bevacizumab and cetuximab. Different combinations achieve a median survival of over 2 years. Intense efforts focus on identifying agents targeting growth factor receptors, signal transduction pathways or angiogenesis mediators. One of the last available drugs for the management of advanced colorectal cancer is panitumumab, a well-tolerated and effective anti-EGFR monoclonal antibody approved as a single agent in chemotherapy refractory patients. We discuss the current evidence supporting panitumumab for metastatic colorectal cancer treatment, potential predictive biomarkers and ongoing clinical trials with different combinations including panitumumab.

Clinical trial designs for predictive biomarker validation: theoretical considerations and practical challenges

PURPOSE

Biomarkers can add substantial value to current medical practice by providing an integrated approach to prediction using the genetic makeup of the tumor and the genotype of the patient to guide patient-specific treatment selection. We discuss and evaluate various clinical trial designs for the validation of biomarker-guided therapy.

METHODS

Designs for predictive marker validation are broadly classified as retrospective (ie, using data from previously well-conducted randomized controlled trials [RCTs]) versus prospective (enrichment, unselected, hybrid, or adaptive analysis). We discuss the salient features of each design in the context of real trials.

RESULTS

Well-designed retrospective analysis from well-conducted prospective RCTs can bring forward effective treatments to marker-defined subgroups of patients in a timely manner (eg, KRAS and colorectal cancer). Enrichment designs are appropriate when preliminary evidence suggest that patients with or without that marker profile do not benefit from the treatments in question; however, this may sometimes leave questions unanswered (eg, trastuzumab and breast cancer). An unselected design is optimal where preliminary evidence regarding treatment benefit and assay reproducibility is uncertain (eg, epidermal growth factor receptor and lung cancer). Hybrid designs are appropriate when preliminary evidence demonstrate the efficacy of certain treatments for a marker-defined subgroup, making it unethical to randomly assign patients with that marker status to other treatments (eg, multigene assay and breast cancer). Adaptive analysis designs allow for prespecified marker-defined subgroup analyses of data from an RCT.

CONCLUSION

The implementation of these design strategies will lead to a more rapid clinical validation of biomarker-guided therapy.

Tumor biology and cancer therapy - an evolving relationship

The aim of palliative chemotherapy is to increase survival whilst maintaining maximum quality of life for the individual concerned. Although we are still continuing to explore the optimum use of traditional chemotherapy agents, the introduction of targeted therapies has significantly broadened the therapeutic options. Interestingly, the results from current trials put the underlying biological concept often into a new, less favorable perspective. Recent data suggested that altered pathways underlie cancer, and not just altered genes. Thus, an effective therapeutic agent will sometimes have to target downstream parts of a signaling pathway or physiological effects rather than individual genes. In addition, over the past few years increasing evidence has suggested that solid tumors represent a very heterogeneous group of cells with different susceptibility to cancer therapy. Thus, since therapeutic concepts and pathophysiological understanding are continuously evolving a combination of current concepts in tumor therapy and tumor biology is needed. This review aims to present current problems of cancer therapy by highlighting exemplary results from recent clinical trials with colorectal and pancreatic cancer patients and to discuss the current understanding of the underlying reasons.

Evaluation and validation of diagnostic tests for guiding therapeutic decisions

The term "theranostics" characterizes a particular combination of the coupled use of a drug therapy with a diagnostic test (called "companion diagnostics"). The diagnostic test marks out the technical means used to identify a biomarker which allows for adjusting the use of the new drug.Theranostics promise a significant step forward for the use of personalized medicine, better tailored for patients in terms of efficacy and tolerance. The development process of theranostics is complex since it requires a proper phasing from development to reimbursement, through a collaborative and controlled approach.The task force's recommendations should form the basis for reflection and action amongst the different players in the field of the development of theranostics.All stages of the system meeting heterogeneous and asynchronous rules should be harmonized to allow for simultaneous availability of, and access to the drug and test. Nevertheless, it is necessary to simplify the regulations to enable a better adaptation of theranostics to the speed of innovation.

Genetics: Predictive value of KRAS mutations in chemoresistant CRC

On the basis of the results of KRAS analysis from the CO.17 randomized, controlled, phase III study by Karapetis et al., KRAS mutations have emerged as a valid predictive marker associated with resistance to cetuximab and lack of survival benefit from this anti-EGFR antibody in patients with chemoresistant colorectal cancer.

Biomarkers of response and resistance to antiangiogenic therapy

No validated biological markers (or biomarkers) currently exist for appropriately selecting patients with cancer for antiangiogenic therapy. Nor are there biomarkers identifying escape pathways that should be targeted after tumors develop resistance to a given antiangiogenic agent. A number of potential systemic, circulating, tissue and imaging biomarkers have emerged from recently completed phase I-III studies. Some of these are measured at baseline (for example VEGF polymorphisms), others are measured during treatment (such as hypertension, MRI-measured K(trans), circulating angiogenic molecules or collagen IV), and all are mechanistically based. Some of these biomarkers might be pharmacodynamic (for example, increase in circulating VEGF, placental growth factor) while others have potential for predicting clinical benefit or identifying the escape pathways (for example, stromal-cell-derived factor 1alpha, interleukin-6). Most biomarkers are disease and/or agent specific and all of them need to be validated prospectively. We discuss the current challenges in establishing biomarkers of antiangiogenic therapy, define systemic, circulating, tissue and imaging biomarkers and their advantages and disadvantages, and comment on the future opportunities for validating biomarkers of antiangiogenic therapy.