Panitumumab monotherapy compared with cetuximab and irinotecan combination therapy in patients with previously treated KRAS wild-type metastatic colorectal cancer

BACKGROUND

The survival benefit for single-agent anti-epidermal growth factor receptor (egfr) therapy compared with combination therapy with irinotecan in KRAS wildtype (wt) metastatic colorectal cancer (mcrc) patients in the third-line treatment setting is not known. The objective of the present study was to describe the characteristics of, and to compare survival outcomes in, two cohorts of patients treated with either singleagent panitumumab or combination therapy with cetuximab and irinotecan.

METHODS

The study enrolled patients with KRAS wt mcrc previously treated with both irinotecan and oxaliplatin who had received either panitumumab or combination cetuximab-irinotecan before April 1, 2011, at the BC Cancer Agency (bcca). Patients were excluded if they had received anti-egfr agents in earlier lines of therapy. Data were prospectively collected, except for performance status (ps), which was determined by chart review. Information about systemic therapy was extracted from the bcca Pharmacy Database.

RESULTS

Of 178 eligible patients, 141 received panitumumab, and 37 received cetuximab-irinotecan. Compared with patients treated with cetuximab-irinotecan, panitumumab-treated patients were significantly older and more likely to have an Eastern Cooperative Oncology Group (ecog) ps of 2 or 3 (27.7% vs. 2.7%, p = 0.001). Other baseline prognostic variables and prior and subsequent therapies were similar. Median overall survival was 7.7 months for the panitumumab group and 8.3 months for the cetuximab-irinotecan group. Multivariate analysis demonstrated that survival outcomes were similar regardless of the therapy selected (hazard ratio: 1.28; p = 0.34). An ecog ps of 2 or 3 compared with 0 or 1 was the only significant prognostic factor in this treatment setting (hazard ratio: 3.37; p < 0.01).

CONCLUSIONS

Single-agent panitumumab and cetuximab-irinotecan are both reasonable third-line treatment options, with similar outcomes, for patients with chemoresistant mcrc.

Management of advanced colorectal cancer, Part 2

PURPOSE

Important developments in chemotherapy for advanced colorectal cancer over the past 15 years are reviewed, with an emphasis on the most recently published data from clinical trials of newer multidrug regimens, administration techniques, and dosing schedules.

SUMMARY

Eight agents are approved by the Food and Drug Administration (FDA) for use in treating patients with advanced colorectal cancer. Fluorouracil and leucovorin still constitute the foundation of most chemotherapy regimens for this population; combination fluorouracil-leucovorin therapy plus either irinotecan (the FOLFIRI regimen) or oxaliplatin (the FOLFOX regimen) are two firmly established first-line treatments shown to produce similar outcomes. In Phase III trials conducted over the past six to seven years, regimens of capecitabine plus oxaliplatin (CapeOx) were demonstrated to have clinical effectiveness comparable to that of FOLFOX therapy. Response rates of 35-55% and median overall survival of ≥20 months have been documented with some of the newer regimens. Research to define the optimal role of the three monoclonal antibody agents approved by FDA for use in managing advanced colorectal cancer is ongoing; bevacizumab has been shown to confer significant survival benefits when added to certain chemotherapy regimens, and other monoclonal antibodies (cetuximab and panitumumab) also appear to offer significant benefits in select patients as first- or second-line therapies.

CONCLUSION

Over the past 15 years, a shift toward multiagent treatment strategies including a variety of chemotherapy agents and monoclonal antibodies has yielded improved rates of response and prolonged survival among patients with advanced colorectal cancer. The CapeOx, FOLFOX, and FOLFIRI regimens are currently among the most widely used first-line treatments.

Economic analysis of bevacizumab, cetuximab, and panitumumab with fluoropyrimidine-based chemotherapy in the first-line treatment of KRAS wild-type metastatic colorectal cancer (mCRC)

OBJECTIVE

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in Canada (excluding non-melanoma skin cancers). Bevacizumab is a recombinant humanized monoclonal antibody that selectively binds to human vascular endothelial growth factor. A sub-study confirmed its effectiveness in KRAS wild-type patients. Recent evidence has shown clinical benefit from anti-epidermal growth factor treatments cetuximab and panitumumab in these patients. The cost-effectiveness, to the Canadian healthcare system, of fluoropyrimidine-based chemotherapy (FBC) in combination with bevacizumab, cetuximab, or panitumumab was assessed for first-line treatment of KRAS wild-type mCRC patients.

METHODS

A Markov model was developed and calibrated to progression-free/overall survival, using separately reported trial survival and adverse event results for each comparator. Health-state resource utilization was derived from published data and oncologist input. Utilities and unit prices were obtained from published literature and standard Canadian sources.

RESULTS

Results per patient are over a lifetime horizon, to a maximum of 10 years, with 5% annual discounting. Comparators are ordered by total cost and the incremental cost-effectiveness ratio (ICER) of each is determined against the previous non-dominated therapy. Compared to FBC alone, bevacizumab + FBC has an ICER of $131,600 per QALY gained. Compared to bevacizumab + FBC, panitumumab + FBC is dominated and cetuximab + FBC has an ICER of $3.8 million per QALY. In probabilistic sensitivity analysis, bevacizumab + FBC had ∼100%, ∼100%, and 98.9% probabilities of being more cost-effective than both of the other combination treatments at thresholds of $50,000/QALY, $100,000/QALY, and $200,000/QALY, respectively.

CONCLUSION

For first-line treatment of KRAS-WT mCRC, bevacizumab + FBC is associated with substantially lower costs as compared to panitumumab + FBC or cetuximab + FBC. Key limitations were that survival curves and adverse event rates were taken from separate clinical trials and that an indirect comparison was not included. Given these findings, bevacizumab is likely to offer the best value for money for this patient population.

Conversion chemotherapy followed by hepatic resection in colorectal cancer with initially unresectable liver-limited metastases

The best management choice in colorectal cancer patients with unresectable liver-only metastases should be represented by conversion chemotherapy aiming to reduce liver cancer deposits, thereby permitting curative surgery. Forty-eight consecutive stage IV colorectal cancer patients were treated with different chemotherapeutic regimens including biological drugs. Objective responses to chemotherapy were seen in 27 patients (56.2%; 95% CI 42.1-70.2%). Four patients (8.3%) showed complete response, 23 patients (47.9%) partial and 13 patients (27.1%) stable response. Eight patients (16.7%) progressed. The conversion rate was 35.4% (95% CI 21.8-48.9%) with 17 patients suitable for liver resection. Four complete responder patients refused surgery. The remaining 13 patients underwent curative hepatic resection (resection rate 27.1%; 95% CI 14.5-39.6%). The likelihood of a successful conversion chemotherapy appeared significantly related to the best response and to the K-Ras status. Wild-type K-Ras patients undergoing cetuximab therapy showed the best conversion rate. The four-year survival rate was significantly enhanced in converted compared to non-converted patients (57.1 and 0%, respectively), and in resected compared to non-resected patients (53.3 and 10.1%, respectively). Synchronous metastases and no conversion were shown to be the only covariates independently associated with a poorer long-term outcome. The possibility of curative liver surgery significantly prolongs outcome for colorectal cancer patients with unresectable liver-limited metastases. Prospective randomized trials are required to define the conversion rates with biological drugs.

RAS mutations: impact on treatment outcome

SUMMARY RAS proteins belong to the MAPK network, an essential pathway for maintenance of normal vital processes such as proliferation and differentiation. RAS mutations are observed in 30–50% of colorectal carcinomas. The MAPK pathway and RAS proteins are part of a complex system that mediate signaling from the EGF receptors (EGFRs). Our review discusses the most recent evidence highlighting the role of KRAS mutations in patients who are offered anti-EGFR therapy. Furthermore, we discuss emerging evidence of the role of other predictive markers such as PI3K, PTEN, BRAF, NRAS, MET, IGFR-1 and p53 in patients who are receiving anti-EGFR therapy.

Anti-angiogenic therapies for metastatic colorectal cancer: current and future perspectives

Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer and the second leading cause of cancer death in both men and women in the United States, with about 142820 new cases and 50830 deaths expected in 2013. Metastatic disease (mCRC) remains a challenge for oncologists worldwide due to its potential comorbidities. Recently, chemotherapy regimens containing 5-fluorouracil, leucovorin, oxaliplatin and irinotecan combinations are a standard of care in the metastatic disease. Currently, biological therapies involving vascular endothelial growth factor and epidermal growth factor receptor pathways, such as bevacizumab and cetuximab, have emerged as good option for improving mCRC patient survival. Now, aflibercept plus standard chemotherapy has also been approved in second line regimen for mCRC patients. Our review will discuss novel biological drugs and their indications for mCRC patients and will bring future perspectives in this regard.

Biomarker enrichment strategies: matching trial design to biomarker credentials

The use of biomarkers to identify patients who can benefit from treatment with a specific anticancer agent has the potential to both improve patient care and accelerate drug development. The development of targeted agents and their accompanying biomarkers frequently occurs contemporaneously, and confidence in a putative biomarker's performance might, therefore, be insufficient to restrict the definitive testing of a new agent to the subgroup of biomarker-positive patients. This Review considers which clinical trial designs and analysis strategies are appropriate for use in phase III, biomarker-driven, randomized clinical trials, on the basis of pre-existing evidence that the biomarker can successfully identify patients who will respond to the treatment in question. The types of interim monitoring that are appropriate for these trials are also discussed. In addition, enrichment strategies based on the use of prognostic biomarkers to separate a population into subgroups with better and worse outcomes, regardless of treatment, are described. Finally, the possibility of formally using a biomarker during phase II drug development, to select what type of biomarker-driven strategy should be used in the phase III trial, is discussed.

Personalized treatment for advanced colorectal cancer: KRAS and beyond

Targeted therapies have improved the survival of patients with advanced colorectal cancer (CRC). However, further improvements in patient outcomes may be gained by the development of predictive biomarkers in order to select individuals who are most likely to benefit from treatment, thus personalizing treatment. Using the epidermal growth-factor receptor (EGFR) pathway, we discuss the existing and potential predictive biomarkers in clinical development for use with EGFR-targeted agents in metastatic CRC. The data and technological issues surrounding such biomarkers as expression of EGFR or its family members or ligands, KRAS-, NRAS-, and BRAF-mutation status, PI3K/PTEN expression, and imaging and clinical biomarkers, such as rash and hypomagnesemia, are summarized. Although the discovery of KRAS mutations has improved patient selection for EGFR-targeted treatments, further biomarkers are required, especially for those patients who exhibit KRAS mutations rather than the wild-type gene.

Extravascular use of drug-eluting beads: a promising approach in compartment-based tumor therapy

Intraperitoneal carcinomatosis (PC) may occur with several tumor entities. The prognosis of patients suffering from PC is usually poor. Present treatment depends on the cancer entity and includes systemic chemotherapy, radiation therapy, hormonal therapy and surgical resection. Only few patients may also benefit from hyperthermic intraperitoneal chemotherapy with a complete tumor remission. These therapies are often accompanied by severe systemic side-effects. One approach to reduce side effects is to target chemotherapeutic agents to the tumor with carrier devices. Promising experimental results have been achieved using drug-eluting beads (DEBs). A series of in vitro and in vitro experiments has been conducted to determine the suitability of their extravascular use. These encapsulation devices were able to harbor CYP2B1 producing cells and to shield them from the hosts immune system when injected intratumorally. In this way ifosfamide--which is transformed into its active metabolites by CYP2B1--could be successfully targeted into pancreatic tumor growths. Furthermore DEBs can be used to target chemotherapeutics into the abdominal cavity for treatment of PC. If CYP2B1 producing cells are proven to be save for usage in man and if local toxic effects of chemotherapeutics can be controlled, DEBs will become promising tools in compartment-based anticancer treatment.

Towards defining biomarkers indicating resistances to targeted therapies

An impressive, but often short objective response was obtained in many tumor patients treated with different targeted therapies, but most of the patients develop resistances against these drugs. So far, a number of distinct mechanisms leading to intrinsic as well as acquired resistances have been identified in tumors of distinct origin. These can arise from genetic alterations, like mutations, truncations, and amplifications or due to deregulated expression of various proteins and signal transduction pathways, but also from cellular heterogeneity within tumors after an initial response. Therefore, biomarkers are urgently needed for cancer prognosis and personalized cancer medicine. The application of "ome"-based technologies including cancer (epi)genomics, next generation sequencing, cDNA microarrays and proteomics might led to the predictive or prognostic stratification of patients to categorize resistance mechanisms and to postulate combinations of treatment strategies. This review discusses the implementation of proteome-based analysis to identify markers of pathway (in)activation in tumors and the resistance mechanisms, which represent major clinical problems as a tool to optimize individually tailored therapies based on targeted drugs. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.

Factors influencing choice of chemotherapy in metastatic colorectal cancer (mCRC)

Management of metastatic colorectal cancer requires a multimodal approach and must be performed by an experienced, multidisciplinary expert team. The optimal choice of the individual treatment modality, according to disease localization and extent, tumor biology, and patient clinical characteristics, will be one that can maintain quality of life and long-term survival, and even cure selected patients. This review is an overview of the different therapeutic approaches available in metastatic colorectal cancer, for the purpose of defining personalized therapeutic algorithms according to tumor biology and patient clinical features.

Optical molecular imaging for diagnosing intestinal diseases

Real-time visualization of the molecular signature of cells can be achieved with advanced targeted imaging techniques using molecular probes and fluorescence endoscopy. This molecular optical imaging in gastrointestinal endoscopy is promising for improving the detection of neoplastic lesions, their characterization for patient stratification, and the assessment of their response to molecular targeted therapy and radiotherapy. In inflammatory bowel disease, this method can be used to detect dysplasia in the presence of background inflammation and to visualize inflammatory molecular targets for assessing disease severity and prognosis. Several preclinical and clinical trials have applied this method in endoscopy; however, this field has just started to evolve. Hence, many problems have yet to be solved to enable the clinical application of this novel method.

Rechallenge therapy and treatment holiday: different strategies in management of metastatic colorectal cancer

Fluoropyrimidines, oxaliplatin, irinotecan and biologic therapies (Bevacizumab, Panitumumab, and Cetuximab) represent the backbone of metastatic colorectal cancer (CRC) treatment. The improvement in survival for mCRC patient led to two main outstanding issues: 1) there is a significant number of patients progressing beyond the third or fourth line of treatment still suitable for further therapy when enrollment into clinical trial is not possible. In this situation, the role of any therapy rechallenge (either chemotherapy alone, chemotherapy and biologic therapy or biologic therapy alone) is still not clear, particularly in patients who had previously responded, and if treatment choice is based on traditional dogma of primary and secondary resistance, rechallenge does not seem to be justified. 2) Prolonged intensive treatment is burdened from the high risk of cumulative toxicity, worsening in quality of life and a not well defined possibility of early acquired resistance.Different hypothesis could justify the research of different strategy in treatment of mCRC:1) Epigenetic changes might drive resistance and treatment could induce these changes. Re-expression of silenced tumor suppressive genes might resensitize tumors to therapy. It is therefore possible that a drug holiday (intermittent treatment) could allow reversion to a previous epigenetic profile. Moreover an intermittent treatment could delay acquired resistance. 2) It is plausible that tumor grows as a polyclonal mass. If it responds but then becomes resistant to one or more treatments, retreatment might be successful if changing therapies allows to that clone of cells to re-emerge. On these basis, we focused this review on the actual evidences in management of mCRC patients in terms of chemotherapy or biological therapies rechallenge and intermittent treatment. Moreover, we will discuss the potential biological mechanisms of the observed results of early clinical trials.

FOLFOX4 with cetuximab vs. UFOX with cetuximab as first-line therapy in metastatic colorectal cancer: The randomized phase II FUTURE study

INTRODUCTION

The purpose of this study was to assess the efficacy and safety of FOLFOX4, comprising infusional 5-fluorouracil (5-FU)/leucovorin (LV) and oxaliplatin, with cetuximab compared with UFOX, comprising UFT, an oral prodrug of 5-FU, LV, and oxaliplatin, with cetuximab as first-line treatment for mCRC.

PATIENTS AND METHODS

Patients, unselected by tumor KRAS status, were randomized 1:1 to FOLFOX4 with cetuximab or UFOX with cetuximab. Treatment was continued until disease progression or unacceptable toxicity. The primary end point, assessed in the intention-to-treat population, was progression-free survival (PFS). Secondary end points included tumor response, overall survival, and safety. Outcome according to KRAS mutation status was investigated.

RESULTS

Recruitment was curtailed at 302 patients after reporting of the importance of tumor KRAS mutation status for cetuximab activity. Baseline characteristics were balanced between treatment groups. PFS was significantly longer in the FOLFOX4 with cetuximab group compared with UFOX with cetuximab group (median 8.2 vs. 6.6 months; hazard ratio, 0.68; 95% confidence interval [CI], 0.52-0.89; P = .0048). The response rate was also significantly greater in the FOLFOX4 with cetuximab group (51.3% vs. 37.5%, respectively; odds ratio, 1.76; 95% CI, 1.11-2.78; P = .0160), although overall survival was comparable. In the KRAS wild type subgroup, efficacy outcomes were similar to those in the intention-to-treat population. Side effect profiles were manageable and consistent with expectations.

CONCLUSION

In the first-line treatment of mCRC, UFOX with cetuximab had an acceptable safety profile but inferior activity compared with FOLFOX4 with cetuximab in relation to PFS and response. The regimens were comparable with regard to overall survival.

Toward a Molecular Classification of Colorectal Cancer: The Role of BRAF

Different genetic aberrations of BRAF have been reported in various malignancies. BRAF is member of the RAS/RAF/MEK/ERK pathway and constitutive activity of this pathway can lead to increased cellular growth, invasion, and metastasis. The most common activating BRAF mutation in colorectal cancer is the V600E mutation, which is present in 5–15% of all tumors, and up to 80% of tumors with high microsatellite instability (MSI) harbor this mutation. BRAF mutation is associated with proximal location, higher age, female gender, MSI-H, high grade, and mucinous histology, and is a marker of poor prognosis in colorectal cancer. The role of BRAF mutation as a predictive marker in respect of EGFR targeted treatments is controversial. BRAF V600 selective inhibitors have been approved for the treatment of V600 mutation positive metastatic melanoma, but the response rates in colorectal cancer are poor. This might be due to innate resistance mechanisms of colorectal cancers against the treatment solely targeting BRAF. To overcome resistance the combination of treatments, simultaneous inhibition of BRAF and MEK or PI3K/mTOR, might emerge as a successful therapeutic concept.

Genetic and immune factors underlying the efficacy of cetuximab and panitumumab in the treatment of patients with metastatic colorectal cancer

Efficacy of monoclonal anti-EGFR antibodies (cetuximab, panitumumab) used in combination with chemotherapy or alone has been demonstrated in clinical trials of patients with mCRC. Both drugs block signaling EGFR pathway in malignant cells (blocking ligand binding and EGFR dimerization). Obtaining treatment responses with anti-EGFR agents is possible only in a selected subgroup of patients with mCRC. Successful treatment with cetuximab and panitumab is possible almost exclusively in patients without RAS mutations. Research on predictive value of EGFR gene copy number, PI3KCA gene mutations, P53 and PTEN, and EGFR their ligands concentrations is ongoing. Cetuximab, as IgG1 class antibody, can cause antibody dependent cellular cytotoxicity against neoplasm cells, while panitumumab, as IgG2 class antibody, does not induce such effect. Therefore a potential predictor cetuximab therapy may be the presence of different polymorphic forms of the genes for receptor immunoglobulin Fc fragments: FcγRIIa and FcγRIII subclasses.

PIK3CA, BRAF, and PTEN status and benefit from cetuximab in the treatment of advanced colorectal cancer--results from NCIC CTG/AGITG CO.17

PURPOSE

Cetuximab improves survival in patients with K-ras wild-type advanced colorectal cancer. We examined the predictive and prognostic significance of additional biomarkers in this setting, in particular BRAF, PIK3CA, and PTEN.

EXPERIMENTAL DESIGN

Available colorectal tumor samples were analyzed from the CO.17 study. BRAF mutations were identified in tumor-derived DNA by direct sequencing and PIK3CA mutations were identified using a high-resolution melting screen with confirmation by sequencing. PTEN expression by immunohistochemistry (IHC) was performed on tissue microarrays. For each biomarker, prognostic and predictive effects were examined using a Cox model with tests for treatment-biomarker interaction.

RESULTS

A total of 572 patients with pretreated colorectal cancer were randomly assigned to receive cetuximab or best supportive care (BSC). Of 401 patients assessed for BRAF status, 13 (3.2%) had mutations. Of 407 patients assessed for PIK3CA status, 61 (15%) had mutations. Of 205 patients assessed for PTEN, 148 (72%) were negative for IHC expression. None of BRAF, PIK3CA, or PTEN was prognostic for overall or progression-free survival in the BSC arm. None was predictive of benefit from cetuximab, either in the whole study population or the K-ras wild-type subset. In the K-ras wild-type subgroup, the overall survival adjusted HR according to BRAF mutation status was 1.39 (interaction P = 0.69), PIK3CA mutation status HR = 0.79 (interaction P = 0.63), and PTEN expression HR = 0.75 (interaction P = 0.61).

CONCLUSIONS

In chemotherapy-refractory colorectal cancer, neither PIK3CA mutation status nor PTEN expression were prognostic, nor were they predictive of benefit from cetuximab. Evaluation of predictive significance of BRAF mutations requires a larger sample size.

The quest to overcome resistance to EGFR-targeted therapies in cancer

All patients with metastatic lung, colorectal, pancreatic or head and neck cancers who initially benefit from epidermal growth factor receptor (EGFR)-targeted therapies eventually develop resistance. An increasing understanding of the number and complexity of resistance mechanisms highlights the Herculean challenge of killing tumors that are resistant to EGFR inhibitors. Our growing knowledge of resistance pathways provides an opportunity to develop new mechanism-based inhibitors and combination therapies to prevent or overcome therapeutic resistance in tumors. We present a comprehensive review of resistance pathways to EGFR-targeted therapies in lung, colorectal and head and neck cancers and discuss therapeutic strategies that are designed to circumvent resistance.

Aurora kinases in head and neck cancer

In healthy cells, controlled activation of aurora kinases regulates mitosis. Overexpression and hyperactivation of aurora kinases A and B have major roles in tumorigenesis, and can induce aneuploidy and genomic instability. In squamous-cell carcinomas of the head and neck, overexpression of aurora kinase A is associated with decreased survival, and a reduction in aurora kinase A and aurora kinase B expression inhibits cell growth and increases apoptosis. In this Review, we provide an overview of the biological functions of aurora kinases in healthy cells and in cancer cells, and we review small studies and high-throughput datasets that particularly implicate aurora kinase A in the pathogenesis of squamous-cell carcinomas of the head and neck. Early phase trials are beginning to assess the activity of small-molecule inhibitors of aurora kinases. We summarise trials of aurora kinase inhibitors in squamous-cell carcinomas of the head and neck, and discuss directions for future drug combination trials and biomarkers to use with drugs that inhibit aurora kinases.

Colorectal cancer diagnostics: biomarkers, cell-free DNA, circulating tumor cells and defining heterogeneous populations by single-cell analysis

Reliable biomarkers are needed to guide treatment of colorectal cancer, as well as for surveillance to detect recurrence and monitor therapeutic response. In this review, the authors discuss the use of various biomarkers in addition to serum carcinoembryonic antigen, the current surveillance method for metastatic recurrence after resection. The clinical relevance of mutations including microsatellite instability, KRAS, BRAF and SMAD4 is addressed. The role of circulating tumor cells and cell-free DNA with regards to their implementation into clinical use is discussed, as well as how single-cell analysis may fit into a monitoring program. The detection and characterization of circulating tumor cells and cell-free DNA in colorectal cancer patients will not only improve the understanding of the development of metastasis, but may also supplant the use of other biomarkers.

Research and clinical applications of molecular biomarkers in gastrointestinal carcinoma (Review)

Gastrointestinal (GI) carcinoma is a common malignant disease worldwide. Its development and progression is a multistage process involving a multifactorial etiology. Although the detailed mechanisms of the development of GI carcinoma remain controversial, the elucidation of its molecular biology over the last few years has resulted in a better perspective on its epidemiology, carcinogenesis and pathogenesis. More significantly, it is currently possible to use biological indicators or biomarkers in differential diagnosis, prognostic evaluation and specific clinical interventions. In this review, we aimed to describe the biomarkers of pathogenesis, invasion, metastasis and prognosis of GI carcinoma and discuss their potential clinical applications. The majority of these biomarkers, such as tumor-associated antigens, oncogenes and tumor suppressor genes, metastasis-associated genes, cell adhesion molecules, cytokines, growth factors and microRNAs, are currently broadly applicable.

Prognostic significance of extramural vascular invasion in T4 rectal cancer

AIM

Extramural vascular invasion (EMVI) has been proposed as an adverse prognostic indicator in colorectal cancer, although its use remains both variable and controversial. This study aimed to determine the survival effect of EMVI in T4 rectal cancer.

METHOD

Patients undergoing surgery with curative intent for primary T4 rectal cancer between 1971 and 2011 were included from two prospectively collected rectal cancer databases. The main end-point was 3-year survival.

RESULTS

From 1142 patients undergoing resection of rectal cancer during the study period, 126 (11.0%) had T4 rectal cancer and were included in the study group. Sphincter preservation was performed in 61 (48%) and a pathologically negative resection margin (R0) was achieved in 104 patients (82.5%). EMVI was present in 51 patients (40.5%) and was an independent predictor of positive lymph node status (adjusted odds ratio 2.66, P = 0.013). Considering all patients, EMVI was associated with reduced overall survival (P = 0.007) and disease-free survival (P = 0.002), but not local recurrence-free survival (P = 0.198). In only those undergoing R0 resection, EMVI predicted reduced disease-free survival with positive nodal status (P = 0.021); it did not predict survival with negative nodal status.

CONCLUSION

Overall, EMVI was a strong prognostic marker of survival. However, after complete surgical resection in patients with node-negative disease, EMVI did not predict local recurrence.

Survival in stage II/III colorectal cancer is independently predicted by chromosomal and microsatellite instability, but not by specific driver mutations

OBJECTIVES

Microsatellite instability (MSI) is an established marker of good prognosis in colorectal cancer (CRC). Chromosomal instability (CIN) is strongly negatively associated with MSI and has been shown to be a marker of poor prognosis in a small number of studies. However, a substantial group of "double-negative" (MSI-/CIN-) CRCs exists. The prognosis of these patients is unclear. Furthermore, MSI and CIN are each associated with specific molecular changes, such as mutations in KRAS and BRAF, that have been associated with prognosis. It is not known which of MSI, CIN, and the specific gene mutations are primary predictors of survival.

METHODS

We evaluated the prognostic value (disease-free survival, DFS) of CIN, MSI, mutations in KRAS, NRAS, BRAF, PIK3CA, FBXW7, and TP53, and chromosome 18q loss-of-heterozygosity (LOH) in 822 patients from the VICTOR trial of stage II/III CRC. We followed up promising associations in an Australian community-based cohort (N=375).

RESULTS

In the VICTOR patients, no specific mutation was associated with DFS, but individually MSI and CIN showed significant associations after adjusting for stage, age, gender, tumor location, and therapy. A combined analysis of the VICTOR and community-based cohorts showed that MSI and CIN were independent predictors of DFS (for MSI, hazard ratio (HR)=0.58, 95% confidence interval (CI) 0.36-0.93, and P=0.021; for CIN, HR=1.54, 95% CI 1.14-2.08, and P=0.005), and joint CIN/MSI testing significantly improved the prognostic prediction of MSI alone (P=0.028). Higher levels of CIN were monotonically associated with progressively poorer DFS, and a semi-quantitative measure of CIN was a better predictor of outcome than a simple CIN+/- variable. All measures of CIN predicted DFS better than the recently described Watanabe LOH ratio.

CONCLUSIONS

MSI and CIN are independent predictors of DFS for stage II/III CRC. Prognostic molecular tests for CRC relapse should currently use MSI and a quantitative measure of CIN rather than specific gene mutations.

How do we optimally use cetuximab in first-line treatment for metastatic colorectal cancer?

A number of Phase II/III clinical trials have now been reported assessing the role of cetuximab use in combination with chemotherapy for the first-line treatment of metastatic colorectal cancer. Here we review the current position of cetuximab in this context from two important perspectives. First, we address whether clinicians should prioritize its use with oxaliplatin- or irinotecan-based chemotherapy doublets. Second, we review the trial evidence for the use of cetuximab in patients suffering from colorectal cancer with wild-type and mutant Ras.

A personalized preclinical model to evaluate the metastatic potential of patient-derived colon cancer initiating cells

PURPOSE

Within the aim of advancing precision oncology, we have generated a collection of patient-derived xenografts (PDX) characterized at the molecular level, and a preclinical model of colon cancer metastasis to evaluate drug-response and tumor progression.

EXPERIMENTAL DESIGN

We derived cells from 32 primary colorectal carcinomas and eight liver metastases and generated PDX annotated for their clinical data, gene expression, mutational, and histopathological traits. Six models were injected orthotopically into the cecum wall of NOD-SCID mice in order to evaluate metastasis. Three of them were treated with chemotherapy (oxaliplatin) and three with API2 to target AKT activity. Tumor growth and metastasis progression were analyzed by positron emission tomography (PET).

RESULTS

Patient-derived cells generated tumor xenografts that recapitulated the same histopathological and genetic features as the original patients' carcinomas. We show an 87.5% tumor take rate that is one of the highest described for implanted cells derived from colorectal cancer patients. Cecal injection generated primary carcinomas and distant metastases. Oxaliplatin treatment prevented metastasis and API2 reduced tumor growth as evaluated by PET.

CONCLUSIONS

Our improved protocol for cancer cell engraftment has allowed us to build a rapidly expanding collection of colorectal PDX, annotated for their clinical data, gene expression, mutational, and histopathological statuses. We have also established a mouse model for metastatic colon cancer with patient-derived cells in order to monitor tumor growth, metastasis evolution, and response to treatment by PET. Our PDX models could become the best preclinical approach through which to validate new biomarkers or investigate the metastatic potential and drug-response of individual patients.

Current opinion on optimal treatment for colorectal cancer

The medical treatment of colorectal cancer (CRC) has evolved greatly in the last 10 years, involving complex combined chemotherapy protocols and, in more recent times, new biologic agents. Advances in adjuvant therapy have been limited to the addition of oxaliplatin and the substitution of oral fluoropyrimidine (e.g., capecitabine) for intravenous 5-fluorouracil with no evidence for improved outcome with biological agents. Clinical benefit from the use of the targeted monoclonal antibodies, bevacizumab, cetuximab and panitumumab, in the treatment of metastatic CRC is now well established, but the optimal timing of their use requires careful consideration to derive the maximal benefit. Evidence to date suggests potentially distinct roles for bevacizumab and EGF receptor-targeted biological agents (cetuximab and panitumumab) in the treatment of metastatic CRC. This article reviews the evidence in support of modern treatments for CRC and the decision-making behind the treatment choices, their benefits and toxicities.

Concomitant tumor expression of EGFR and TATI/SPINK1 associates with better prognosis in colorectal cancer

Background

Epidermal growth factor receptor (EGFR) activation plays a role in colorectal cancer (CRC) carcinogenesis, and anti-EGFR drugs are used in treatment of advanced CRC. One of the EGFR ligands is tumor-associated trypsinogen inhibitor TATI, also called serine protease inhibitor Kazal type1 (SPINK 1), which we recently showed to be an independent prognostic marker in CRC.

Methods

We studied the prognostic value of immunohistochemical expression of EGFR and concomitant expression of EGFR and TATI/SPINK1 in a series of 619 colorectal cancer patients.

Results

Of the samples, 92% were positive for EGFR. EGFR+/TATI+ was seen in 62.8%, EGFR+/TATI− in 29.5%, EGFR−/TATI+ in 4.9%, and EGFR−/TATI− in 2.7% of patients. EGFR expression correlated with WHO grade (p = 0.040). In univariate analysis, EGFR expression correlated with favourable survival (p = 0.006). EGFR+/TATI+ patients showed better survival than did those with other combinations (p<0.001). In multivariate analysis, EGFR+/TATI+ was an independent prognostic factor of favourable prognosis (p<0.001).

Conclusion

Concomitant positivity of EGFR and TATI/SPINK1 predicts favourable prognosis in CRC.

Impact of molecular alterations and targeted therapy in appendiceal adenocarcinomas

Appendiceal adenocarcinomas (AAs) are rare and this has limited their molecular understanding. The purpose of our study was to characterize the molecular profile of AA and explore the role of targeted therapy against cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR).

PATIENTS AND METHODS

We performed a retrospective review of 607 patients with AA at a single institution. A total of 149 patients underwent molecular testing for at least one of the following: activating mutations in KRAS, BRAF, cKIT, EGFR, or PI3K; protein expression of c-KIT or COX-2; or microsatellite instability (MSI) status by immunohistochemistry. Kaplan-Meier product limit method and log-rank test were used to estimate overall survival (OS) and to determine associations among OS, COX-2 expression, KRAS mutations, and other characteristics.

RESULTS

Age, grade, stage, signet ring cells, mucinous histology, and completeness of cytoreduction score correlated with survival outcomes. COX-2 expression, KRAS, PI3K, and BRAF mutations were seen in 61%, 55%, 17%, and 4% of patients, respectively. High MSI was seen in 6% of patients. KRAS mutation was strongly associated with well differentiated or moderately differentiated AA (p < .01). COX-2 expression (p = .33) and the presence of KRAS mutation (p = .91) had no impact on OS. The use of celecoxib in patients whose tumors expressed COX-2 (p = .84) and the use of cetuximab or panitumumab in patients with KRAS wild-type tumors (p = .83) also had no impact on OS.

CONCLUSION

In this cohort, we demonstrated that COX-2 expression and KRAS mutations were frequently seen in AA, although neither exhibited any prognostic significance. MSI was infrequent in AA. Targeted therapy against COX-2 and EGFR appeared to provide no clinical benefit. Well and moderately differentiated AA were molecularly distinct from poorly differentiated AA.

Promising biomarkers for predicting the outcomes of patients with KRAS wild-type metastatic colorectal cancer treated with anti-epidermal growth factor receptor monoclonal antibodies: a systematic review with meta-analysis

KRAS mutations have been established as a major predictive biomarker for resistance to the treatment of metastatic colorectal cancer (mCRC) with anti-epidermal growth factor receptor monoclonal antibodies (anti-EGFR MoAbs). However, many patients with KRAS wild-type tumors still do not respond to the treatment. We conducted a systematic review with meta-analysis to assess whether BRAF mutations, PIK3CA mutations and PTEN loss can predict the outcomes of patients with KRAS wild-type mCRC treated with anti-EGFR MoAbs. Studies that explored the association of one or more of the three biomarkers with progression-free survival (PFS), overall survival (OS) and/or objective response rate (ORR) were identified through August 2012. Summary hazard ratios (HRs) and rate differences (RDs) and corresponding 95% confidence intervals (CIs) were calculated by using the random-effects model. BRAF mutations, PIK3CA exon 20 mutations and PTEN loss were all associated with shorter PFS (HR = 2.59, 95% CI 1.67-4.03; HR = 2.52, 95% CI 1.33-4.78 and HR = 1.75, 95% CI 1.19-2.56, respectively), shorter OS (HR = 2.74, 95% CI 1.79-4.19; HR = 3.29, 95% CI 1.60-6.75 and HR = 1.85, 95% CI 1.30-2.64, respectively) and lower ORR (RD = -36%, 95% CI -44 to -28%; RD = -38%, 95% CI -51 to -24% and RD = -41%, 95% CI -68 to -14%, respectively). PIK3CA exon 9 mutations were associated with none of the outcomes. Studies with relevant data consistently demonstrated a stronger predictive power of combined multiple biomarkers as compared to one alteration alone. These results suggest that BRAF mutations, PIK3CA exon 20 mutations and PTEN loss are predictive of worseoutcomes in KRAS wild-type mCRC treated with anti-EGFR MoAbs [corrected]. However, the quality of included studies varied, and some of the meta-analyses were limited by significant between-study heterogeneity. In the future, well-designed large randomized controlled trials conducted in KRAS wild-type mCRC patients with subgroup analysis according to BRAF, PIK3CA exon 20 and PTEN status are essential to fully assess the clinical relevance of these biomarkers.

FOLFOXIRI plus bevacizumab as first-line treatment in BRAF mutant metastatic colorectal cancer

BACKGROUND

BRAF V600E mutation plays a negative prognostic role in metastatic colorectal cancer (mCRC), leading to a median Progression Free Survival (PFS) of 4-6months with first-line conventional treatments. Our group recently reported in a retrospective exploratory analysis of a phase II trial that FOLFOXIRI (5-FU/LV+Oxaliplatin+Irinotecan) plus bevacizumab might allow to achieve remarkable results in terms of PFS and Overall Survival (OS) also in this poor-prognosis subgroup. The aim of this work was to prospectively validate our retrospective finding.

PATIENTS AND METHODS

This phase II trial was designed to detect an increase in 6month-Progression Free Rate (6m-PFR) from 45% to 80% in a population of BRAF mutant mCRC patients treated with first-line FOLFOXIRI plus bevacizumab. Secondary end-points were PFS, OS, response rate (RR) and the analysis of outcome parameters in the pooled population consisting of both retrospectively and prospectively included patients. This trial is registered with ClinicalTrials.gov, number NCT01437618.

RESULTS

Two-hundred-fourteen potentially eligible mCRC patients were screened for BRAF mutational status. Fifteen BRAF mutant patients (7%) were included in the validation cohort. At a median follow up of 25.7months, 6m-PFR was 73%. Median PFS and OS were 9.2 and 24.1months, respectively. In the pooled population, at a median follow up of 40.4months, 6m-PFR was 84%. Median PFS and OS were 11.8 and 24.1months, respectively. Overall RR and disease control rate were 72% and 88%, respectively.

CONCLUSION

Lacking randomised trials in this specific molecular subgroup, FOLFOXIRI plus bevacizumab might be a reasonable option for the first-line treatment of BRAF mutant mCRC patients.

Epidermal growth factor receptor and metastatic colorectal cancer: insights into target therapies

Colorectal cancer (CRC) has high incidence and mortality worldwide. In 2012, CRC was the second most prevalent cancer among males (9%) and the third among females (8%). In recent decades, standard chemotherapies protocols combining 5-fluorouracil, leucovorin, irinotecan and oxaliplatin were important for improve survival in this set of patients. Further, biological drugs throughout epidermal growth factor receptor (EGFR) pathways showed interesting results in metastatic disease (mCRC) control when in association to standard chemotherapy regimens. Cetuximab and panitumumab are two cornerstones for mCRC treatment and are both approved in Europe and United States based on previous results phase III trials. This paper will briefly summarize those anti-EGFR therapies framework in mCRC and discusses some issues in this regard.

Improvement of the quality of BRAF testing in melanomas with nationwide external quality assessment, for the BRAF EQA group

Background

Knowledge about tumour gene mutation status is essential for the treatment of increasing numbers of cancer patients, and testing quality has a major impact on treatment response and cost. In 2012, 4,629 tests for BRAF p.V600 were performed in France, in patients with melanomas.

Methods

Two batches of unstained melanoma sections were sent, in May and November 2012, to the 46 laboratories supported by the French National Institute of Cancer (INCa). An external quality assessment (EQA) evaluated mutation status, response times and compliance with INCa recommendations.

Results

All the French laboratories involved in testing participated in the EQA. Fourteen different methods were used to detect BRAF mutations, most consisting of combinations of in-house techniques. False responses were noted in 25/520 cases (4.8%), 11 of which concerned confusion between p.V600E and p.V600K. Thus, 2.7% of responses would have led to inappropriate treatment. Within six months, mean response times decreased from 22 to 12 days (P<0.001), and the percentage of samples evaluated by a pathologist for tumour cell content increased, from 75.2% to 96.9% (P<0.001).

Conclusion

Despite the use of non-certified methods, the false response rate was low. Nationwide EQA can improve the quality of molecular pathology tests on tumours.

Increased TGF-α as a mechanism of acquired resistance to the anti-EGFR inhibitor cetuximab through EGFR-MET interaction and activation of MET signaling in colon cancer cells

PURPOSE

Although cetuximab, an anti-EGF receptor (EGFR) monoclonal antibody, is an effective treatment for patients with KRAS wild-type metastatic colorectal cancer (mCRC), its clinical use is limited by onset of resistance.

EXPERIMENTAL DESIGN

We characterized two colorectal cancer models to study the mechanisms of acquired resistance to cetuximab.

RESULTS

Following chronic treatment of nude mice bearing cetuximab-sensitive human GEO colon xenografts, cetuximab-resistant GEO (GEO-CR) cells were obtained. In GEO-CR cells, proliferation and survival signals were constitutively active despite EGFR inhibition by cetuximab treatment. Whole gene expression profiling identified a series of genes involved in the hepatocyte growth factor (HGF)-MET-dependent pathways, which were upregulated in GEO-CR cells. Furthermore, activated, phosphorylated MET was detected in GEO-CR cells. A second colorectal cancer cell line with acquired resistance to cetuximab was obtained (SW48-CR). Inhibition of MET expression by siRNA restored cetuximab sensitivity in GEO-CR and SW48-CR cells, whereas exogenous activation of MET by HGF stimulation in cetuximab-sensitive GEO and SW48 cells induced resistance to cetuximab. Treatment of GEO-CR and SW48-CR cells with PHA665752, a selective MET inhibitor, inhibited cell growth, proliferation, and survival signals and impaired cancer cell migration. Overexpression of TGF-α, a specific EGFR ligand, was involved in the acquisition of cetuximab resistance in GEO-CR and SW48-CR cells. In fact, TGF-α overexpression induced the EGFR-MET interaction, with subsequent MET phosphorylation and activation of MET downstream effectors in GEO-CR and SW48-CR cells.

CONCLUSIONS

These results suggest that overexpression of TGF-α through induction of EGFR-MET interaction contributes to cetuximab resistance in colorectal cancer cells. The combined inhibition of EGFR and MET receptor could represent a strategy for preventing and/or overcoming cetuximab resistance in patients with colorectal cancer.

Capecitabine and bevacizumab for non-resectable metastatic colorectal cancer patients: final results from phase II AIO KRK 0105 trial

BACKGROUND

Current guidelines recommend treatment with capecitabine and bevacizumab for patients (pts) with non-resectable metastatic colorectal cancer (mCRC), although clinical data in this particular patient group are lacking.

METHODS

Previously untreated patients with non-resectable mCRC were to receive capecitabine (1,250 mg/sqm bid d1-14 oral) and bevacizumab (7.5 mg/kg i.v.) every 3 weeks. Progression-free survival (PFS) was the primary endpoint. Secondary endpoints include overall survival (OS), objective response rate (ORR) and toxicity.

RESULTS

82 pts were included: 40 female, median age 70 (range 50-86). ECOG PS 0/1/2 was 38/52/10%, respectively. Synchronous metastases were present in 58 pts. 16 pts had primary tumor in situ. Median treatment duration was 4.1 months (6 cycles). Toxicity was generally mild. ORR was 38%, with 5 complete and 23 partial responses. Median PFS was 7.0 months [95% CI (5.0-9.1)] and OS 17.9 months [95% CI (14.6-21.6)]. Second- and third-line systemic therapy was given to 57% and 33% of pts, respectively.

CONCLUSIONS

Besides the favourable tolerability, PFS and OS were shorter than reported by other trials. Careful patient selection for upfront capecitabine and bevacizumab is essential.

Pharmacokinetics, clinical indications, and resistance mechanisms in molecular targeted therapies in cancer

The strategy for discovery and development of new cancer drugs has shifted the field from cytotoxic agents to therapies that selectively target oncogenic drivers. In the last decade, a number of targeted cancer therapies have been discovered and proven effective in a variety of hematological and solid malignancies. In this article, we review clinical pharmacokinetic characteristics of the U.S. Food and Drug Administration-approved targeted therapies and provide an overview of key clinical trials that led to approval of these drugs. The major limiting factor of targeted treatment is the development of resistance. We describe general principles of resistance and specific, clinically confirmed mechanisms of resistance to several therapies in different malignancies.

Ultra-deep sequencing confirms immunohistochemistry as a highly sensitive and specific method for detecting BRAF V600E mutations in colorectal carcinoma

The activating BRAF (V600) mutation is a well-established negative prognostic biomarker in metastatic colorectal carcinoma (CRC). A recently developed monoclonal mouse antibody (clone VE1) has been shown to detect reliably BRAF (V600E) mutated protein by immunohistochemistry (IHC). In this study, we aimed to compare the detection of BRAF (V600E) mutations by IHC, Sanger sequencing (SaS), and ultra-deep sequencing (UDS) in CRC. VE1-IHC was established in a cohort of 68 KRAS wild-type CRCs. The VE1-IHC was only positive in the three patients with a known BRAF (V600E) mutation as assessed by SaS and UDS. The test cohort consisted of 265 non-selected, consecutive CRC samples. Thirty-nine out of 265 cases (14.7%) were positive by VE1-IHC. SaS of 20 randomly selected IHC negative tumors showed BRAF wild-type (20/20). Twenty-four IHC-positive cases were confirmed by SaS (24/39; 61.5%) and 15 IHC-positive cases (15/39; 38.5%) showed a BRAF wild-type by SaS. UDS detected a BRAF (V600E) mutation in 13 of these 15 discordant cases. In one tumor, the mutation frequency was below our threshold for UDS positivity, while in another case, UDS could not be performed due to low DNA amount. Statistical analysis showed sensitivities of 100% and 63% and specificities of 95 and 100% for VE1-IHC and SaS, respectively, compared to combined results of SaS and UDS. Our data suggests that there is high concordance between UDS and IHC using the anti-BRAF(V600E) (VE1) antibody. Thus, VE1 immunohistochemistry is a highly sensitive and specific method in detecting BRAF (V600E) mutations in colorectal carcinoma.

Treatment of BRAF-mutant melanoma: the role of vemurafenib and other therapies

The discovery of activating BRAF mutations in melanomas has led to the investigation of small molecular inhibitors targeting BRAF mutation and MEK, a downstream protein within the mitogen-activated protein kinase (MAPK) pathway. This article reviews the role of mutant BRAF in melanoma and summarizes the results of clinical trials evaluating inhibitors of BRAF and MEK in BRAF-mutant melanoma. We further describe recent findings on the mechanisms of resistance to BRAF inhibitors and discuss ongoing efforts to combine BRAF inhibitors with other targeted agents. Finally, we review the results of immunotherapy in BRAF-mutant melanoma and address the current status of efforts to either combine or determine the optimal sequence of these two distinct treatment approaches. Although the recent advances in melanoma therapy have been dramatic, greater understanding of melanoma biology coupled with the successful development of several new treatments and combination regimens will further improve patient outcomes in the future.

The S492R EGFR ectodomain mutation is never detected in KRAS wild-type colorectal carcinoma before exposure to EGFR monoclonal antibodies

The activity of the epidermal growth factor receptor (EGFR) antibodies cetuximab and panitumumab in metastatic colorectal carcinoma (mCRC) is significantly limited by molecular mechanisms leading to intrinsic or acquired resistance. The S492R mutation of the EGFR, which is caused by either the 1476C>A or the 1474A>C substitution, interferes with binding to cetuximab but not to panitumumab, and has been detected in mCRC with acquired resistance to cetuximab. Since mechanisms of acquired and intrinsic resistance to EGFR monoclonal antibodies in CRC significantly overlap, we evaluated the frequency of the S492R mutation in a series of KRAS-exon 2 wild-type CRC patients. Genomic DNA was extracted from formalin fixed paraffin embedded (FFPE) tissues that were obtained from 505 systemic therapy-naïve CRC patients. A PCR/sequencing method for the detection of the S492R mutation was developed, by using as positive control a plasmid in which the 1474A>C mutation was generated by site directed mutagenesis. The lowest level of detection of this assay was approximately 10% mutant DNA in a background of wild-type DNA. PCR sequencing analysis revealed no S492R mutations in any of the analyzed 505 CRC specimens. Our findings suggest that the S492R mutation is not involved in primary resistance to cetuximab in CRC. Therefore, patients with mCRC should not be routinely screened for this mutation prior therapy with cetuximab.

Surgery for colorectal liver metastases

Half of all patients with colorectal cancer develop metastatic disease. The liver is the principal site for metastases, and surgical resection is the only modality that offers the potential for long-term cure. Appropriate patient selection for surgery and improvements in perioperative care have resulted in low morbidity and mortality rates, resulting in this being the therapy of choice for suitable patients. Modern management of colorectal liver metastases is multimodal incorporating open and laparoscopic surgery, ablative therapies such as radiofrequency ablation or microwave ablation and (neo)adjuvant chemotherapy. The majority of patients with hepatic metastases should be considered for resectional surgery, if all disease can be resected, as this offers the only opportunity for prolonged survival.

Use of early tumor shrinkage to predict long-term outcome in metastatic colorectal cancer treated with cetuximab

PURPOSE

Early tumor shrinkage (ETS) is associated with long-term outcome in patients with chemorefractory metastatic colorectal cancer (mCRC) receiving cetuximab. This association was investigated in the first-line setting in the randomized CRYSTAL and OPUS mCRC trials, after controlling for KRAS tumor mutation status.

METHODS

Radiologic assessments at week 8 were used to calculate the relative change in the sum of the longest diameters of the target lesions. Time-dependent receiver operating characteristics provided Cτ-indices (time-dependent c-index). Cox regression models and subpopulation treatment effect pattern plot analysis investigated associations between ETS (radiologic tumor size decrease at week 8) and survival and progression-free survival (PFS).

RESULTS

In both trials, in patients with KRAS wild-type mCRC, Cτ values for PFS and survival were higher (P < .001) in those receiving chemotherapy plus cetuximab versus chemotherapy alone, indicating a stronger predictive value of ETS for long-term outcome in these patients. In the CRYSTAL and OPUS trials, respectively, the cutoff value of ETS ≥ 20% (v < 20%) identified patients with KRAS wild-type mCRC receiving chemotherapy plus cetuximab with longer PFS (medians 14.1 v 7.3 months, hazard ratio [HR] = 0.32; P < .001, and medians 11.9 v 5.7 months, HR = 0.22; P < .001) and survival (medians 30.0 v 18.6 months, HR = 0.53; P < .001 and medians 26.0 v 15.7 months, HR = 0.43; P = .006).

CONCLUSION

ETS was significantly associated with long-term outcome in patients with KRAS wild-type mCRC treated first-line with chemotherapy plus cetuximab. Validation in prospective trials is required to assess the value of this on-treatment marker in the clinical decision-making process.

Panitumumab-FOLFOX4 treatment and RAS mutations in colorectal cancer

BACKGROUND

Patients with metastatic colorectal cancer that harbors KRAS mutations in exon 2 do not benefit from anti-epidermal growth factor receptor (EGFR) therapy. Other activating RAS mutations may also be negative predictive biomarkers for anti-EGFR therapy.

METHODS

In this prospective-retrospective analysis, we assessed the efficacy and safety of panitumumab plus oxaliplatin, fluorouracil, and leucovorin (FOLFOX4) as compared with FOLFOX4 alone, according to RAS (KRAS or NRAS) or BRAF mutation status. A total of 639 patients who had metastatic colorectal cancer without KRAS mutations in exon 2 had results for at least one of the following: KRAS exon 3 or 4; NRAS exon 2, 3, or 4; or BRAF exon 15. The overall rate of ascertainment of RAS status was 90%.

RESULTS

Among 512 patients without RAS mutations, progression-free survival was 10.1 months with panitumumab-FOLFOX4 versus 7.9 months with FOLFOX4 alone (hazard ratio for progression or death with combination therapy, 0.72; 95% confidence interval [CI], 0.58 to 0.90; P=0.004). Overall survival was 26.0 months in the panitumumab-FOLFOX4 group versus 20.2 months in the FOLFOX4-alone group (hazard ratio for death, 0.78; 95% CI, 0.62 to 0.99; P=0.04). A total of 108 patients (17%) with nonmutated KRAS exon 2 had other RAS mutations. These mutations were associated with inferior progression-free survival and overall survival with panitumumab-FOLFOX4 treatment, which was consistent with the findings in patients with KRAS mutations in exon 2. BRAF mutations were a negative prognostic factor. No new safety signals were identified.

CONCLUSIONS

Additional RAS mutations predicted a lack of response in patients who received panitumumab-FOLFOX4. In patients who had metastatic colorectal cancer without RAS mutations, improvements in overall survival were observed with panitumumab-FOLFOX4 therapy. (Funded by Amgen and others; PRIME ClinicalTrials.gov number, NCT00364013.).

Novel targets in HPV-negative head and neck cancer: overcoming resistance to EGFR inhibition

Cancers of the head and neck that arise from habitual exposure to carcinogens have lower cure rates than those that arise from infection with human papillomavirus (HPV), and intensification of cytotoxic chemotherapy and radiation has not improved outcomes. HPV-negative head and neck cancers abundantly express EGFR, and the monoclonal antibody cetuximab, directed against EGFR, is the only targeted therapy that has improved disease survival so far. However, response rates to single-agent cetuximab are lower than 15%, and cetuximab given with chemotherapy or radiation leads to only a modest effect on survival. Thus, investigating the mechanisms of resistance to EGFR inhibition in HPV-negative head and neck cancer might help identify novel and active therapies. In this Review, we focus on therapies in development that target redundant receptor tyrosine kinases (eg, HER2 and MET), reduce or abrogate nuclear functions of EGFR, affect cellular trafficking by inhibition of histone deacetylase, or treatments that might address resistance that arises in the EGFR signalling stream (eg, aurora-kinase inhibitors and STAT decoys).

Methods of overcoming treatment resistance in colorectal cancer

Metastatic colorectal cancer remains a lethal disease with a poor prognosis in the majority of patients. Multiple drug combinations have been developed in recent years that have significantly improved response rates and overall survival however resistance to these drugs is inevitable. Novel agents are currently being developed and participation in clinical trials should be encouraged. In the absence of other treatment options in a patient with good performance status, there is compelling evidence for re-challenging with previously administered agents in different combinations. The aim of this review is to discuss mechanisms of resistance and methods to overcome treatment resistance in patients with metastatic colorectal cancer who are refractory to 5-FU, irinotecan, oxaliplatin, cetuximab and bevacizumab therapy.

Markers of resistance to anti-EGFR therapy in colorectal cancer

Epidermal growth factor receptor (EGFR) is a therapeutic target in colorectal cancer (CRC). The benefit from EGFR inhibitors appears to be limited to a subset of patients with CRC. Mechanisms of resistance to EGFR inhibitors are being identified. KRAS codon 12 activating mutation is a predominate mechanism of resistance to EGFR inhibitors in around 40% of patients with advanced CRC. Other potential mechanisms of resistance include ligand expression, increased EGFR number, mutations of BRAF and activation of alternate signaling pathways.

Integrating anti-EGFR therapies in metastatic colorectal cancer

Colorectal cancer remains one of the most common causes of cancer diagnoses and mortality in the United States. The treatment of metastatic colorectal cancer has evolved significantly over the last decade with near-tripling of patient survival rate. A significant contribution to this outcome was the advent of novel targeted agents, such as the epidermal growth factor (EGFR) inhibitors. In an era of emphasis on refining therapy, the presence of KRAS mutation will predict for resistance and limit exposure to patients who are more likely to benefit. In contrast, the presence of BRAF mutations does not seem to have a predictive value. Agents that are thought to reverse resistance to EGFR inhibitors such as those targeting PI3K, c-MET or IGF-1R are currently under study. EGFR inhibitors have exhibited single agent activity, and seem to synergize very well with standard chemotherapy except for cetuximab and 5-fluorouracil, leucovorin, oxaliplatin (FOLFOX). Preliminary data suggests that EGFR inhibitors have similar effectiveness to vascular endothelial growth factor (VEGF) inhibitors in the first line setting. Skin toxicity remains the main limiting factor for the utilization of EGFR inhibitors, but strategies including the use of agents such as minocycline or doxycycline added to topical care seem to limit the severity of the rash.