Review article: panitumumab--a fully human anti-EGFR monoclonal antibody for treatment of metastatic colorectal cancer

Immunogenicity of Monoclonal Antibodies and the Potential Use of HLA Haplotypes to Predict Vulnerable Patients

The use of monoclonal antibodies (mAbs) in the clinic has successfully expanded to treatment of cancer, viral infections, inflammations, and other indications. However, some of the classes of mAbs that are used in the clinic show the formation of anti-drug antibodies (ADAs) leading to loss of efficacy. This review describes ADA formation for the various mAbs, and its clinical effect. Lastly, this review considers the use of HLA-haplotypes as biomarkers to predict vulnerability of patients sensitive to formation of ADAs.

Oxidative Stress in Cancer Cell Metabolism

Reactive oxygen species (ROS) are important in regulating normal cellular processes whereas deregulated ROS leads to the development of a diseased state in humans including cancers. Several studies have been found to be marked with increased ROS production which activates pro-tumorigenic signaling, enhances cell survival and proliferation and drives DNA damage and genetic instability. However, higher ROS levels have been found to promote anti-tumorigenic signaling by initiating oxidative stress-induced tumor cell death. Tumor cells develop a mechanism where they adjust to the high ROS by expressing elevated levels of antioxidant proteins to detoxify them while maintaining pro-tumorigenic signaling and resistance to apoptosis. Therefore, ROS manipulation can be a potential target for cancer therapies as cancer cells present an altered redox balance in comparison to their normal counterparts. In this review, we aim to provide an overview of the generation and sources of ROS within tumor cells, ROS-associated signaling pathways, their regulation by antioxidant defense systems, as well as the effect of elevated ROS production in tumor progression. It will provide an insight into how pro- and anti-tumorigenic ROS signaling pathways could be manipulated during the treatment of cancer.

Correlation Between Bevacizumab Exposure and Survival in Patients with Metastatic Colorectal Cancer

BACKGROUND

Bevacizumab treatment is subject to large interpatient variability in efficacy, which may partly be explained by differences in complex bevacizumab pharmacokinetic characteristics that influence bevacizumab exposure. Exposure-response relationships have been identified for other monoclonal antibodies. We aimed to identify possible exposure-survival relationships in bevacizumab-treated patients with metastatic colorectal cancer (mCRC).

MATERIALS AND METHODS

Patients with mCRC who started first-line bevacizumab-based chemotherapy between July 2012 and July 2014, and from whom serial blood samples and survival were prospectively collected, were included. Follow-up was carried out until July 2018. Total bevacizumab trough concentrations were measured from cycle 2 to cycle 30 of treatment. The receiver operating characteristic (ROC) curve analysis and Cox analysis were used to identify the relationship between concentrations and overall survival (OS). In addition, OS was compared between different trough concentration groups.

RESULTS

One hundred fifty-seven blood samples from 46 patients were evaluable for analyses. ROC analysis showed a clear separation in survival based on trough levels (area under the curve = 0.739, p = .009). Cox regression also showed a strong positive correlation between trough levels and survival (p = .0004). Three distinct groups of exposure were identified: low (median trough concentration [C_tm ] ≤41.9 mg/L); medium (C_tm 43-87.2 mg/L) with median OS of 12.8 and 36 months, respectively (p = .0003); and high (C_tm ≥7.9 mg/L), where the majority of patients were still alive 60 months after the initiation of treatment.

CONCLUSION

This study shows that survival was proportional to the magnitude of exposure in patients with mCRC. Further clinical research should focus on clarifying these exposure-outcome relationships in order to optimize dosing.

IMPLICATIONS FOR PRACTICE

Bevacizumab-based chemotherapy is standard first-line treatment in metastatic colorectal cancer. Moreover, bevacizumab presents complicated pharmacokinetics, and in many cases, clinical outcomes can be highly variable, with some patients responding remarkably well and others not. This study's results show that patients who experienced longer overall survival also had significantly higher exposure to bevacizumab. Therefore, bevacizumab trough concentrations could be used both as a predictive biomarker and as a tool for treatment monitoring and optimization. Finally, the development of validated, rapid, and sensitive assays for bevacizumab concentration measurements in combination with these results may lead to a therapeutic drug monitoring-guided approach in bevacizumab treatment with better clinical outcomes.

EGFR monoclonal antibody panitumumab inhibits chronic proliferative cholangitis by downregulating EGFR

In hepatolithiasis, chronic proliferative cholangitis (CPC), an active and longstanding inflammation of stone-containing bile ducts with enhanced mucin-producing activity, not only affects the progression of the disease, it can also induce biliary carcinogenesis. The present study aimed to examine the effect of the epidermal growth factor receptor (EGFR) monoclonal antibody panitumumab (Pani) on CPC. Following the establishment of CPC rat models, periodic acid Schiff staining was used to observe the positive rate of EGFR expression. The expression levels of EGFR, mucin 5AC (MUC5AC), Ki-67, type I collagen and mammalian target of rapamycin (mTOR), and the activity of β-glucuronidase (β-G), were measured. The rats treated with Pani demonstrated a significantly lower degree of hyperproliferation of the epithelium and submucosal glands of the bile duct and collagen fibers of the bile duct wall, a significantly decreased positive rate of EGFR, reduced phosphorylation of mTOR, decreased expression of EGFR, MUC5AC, Ki-67 and type I collagen, and reduced β-G activity. The therapeutic effects in rats treated with 4 and 6 mg/kg of Pani were more marked than those in rats treated with 2 mg/kg of Pani. Collectively, the data obtained in the present study suggest that the EGFR monoclonal antibody Pani can effectively inhibit the excessive proliferation and stone-forming potential of bile duct mucosa in CPC with a receptor saturation effect. Therefore, Pani offers promise as a treatment for the prevention and control of intra-hepatic choledocholithiasis caused by CPC.

Monoclonal antibodies for the treatment of non-hematological tumors: a safety review

Introduction: The introduction of monoclonal antibodies (moAbs) into clinical practice revolutionized the treatment strategies in several solid tumors. These agents differ from cytotoxic chemotherapy for their mechanism of action and toxicity. By targeting specific antigens present on healthy cells and modulating immune system activity, these biological drugs are able to generate a wide spectrum of peculiar adverse events that can negatively impact on patients' quality of life. Areas covered: In this review, the main side effects associated with the use of moAbs have been described to show their incidence and current management strategies, which may drive clinicians in their daily practice. Expert opinion: The majority of these drugs represents an example of successful innovation, since they are able to induce a significant improvement of patients' survival and quality of life without any increase in related side effects as compared to standard cancer treatments. For this reason, they have become new milestones in personalized therapy for different non-hematological malignancies. With the increasing use of moAbs in treatment regimens, it is strongly recommended that clinicians are knowledgeable about the side effects associated with these agents, their management and monitoring, to optimize the clinical treatment of cancer patients.

Panitumumab-Conjugated Pt-Drug Nanomedicine for Enhanced Efficacy of Combination Targeted Chemotherapy against Colorectal Cancer

Targeted combination chemotherapy (TCT) has recently been used to increase the induction of tumor cell death. In particular, the combination of Panitumumab and the platinum (Pt)-derived chemotherapeutic drug Oxaliplatin is clinically effective against KRAS and BRAF wild-type colorectal cancer (CRC) cells that overexpress epidermal growth factor receptors, and significantly greater efficacy is observed than with either drug alone. However, low accumulation of Pt drug in tumor sites prevents achievement of ideal efficacy. To develop an alternative drug therapy that achieves the ideal efficacy of TCT, the novel nanomedicine NANO_Pt-Pan using self-assembled dichloro(1,2-diaminocyclohexane)Pt(II)-modified Panitumumab is generated. Treatments with NANO_Pt-Pan lead to significant accumulation of Pt drug and Panitumumab in tumors, reflecting enhanced permeability and retention effect, active targeting, and sustained circulation of the Pt drug in the blood. In addition, NANO_Pt-Pan has excellent in vivo anti-CRC efficacy. These data indicate that NANO_Pt-Pan has high potential as a candidate nanomedicine for CRC.

Biological agents in gastrointestinal cancers: adverse effects and their management

Biological therapy comprises agents that by virtue of their unique mechanisms of action, are able to specifically incite a response against or target malignant cells. They differ from conventional chemotherapy with regard to mechanisms of action, indications and side effect profile. Biologic agents have revolutionized therapy for a number of malignancies. In the setting of gastrointestinal (GI) malignancies, agents targeting vascular endothelial growth factor (VEGF), human epidermal growth factor receptor 2 (Her2/Neu) and epidermal growth factor receptor (EGFR) have proven to be invaluable additions to chemotherapy. However, these agents bring with them a set of side effects attributable to their unique mechanisms of action. The anti VEGF agents-bevacizumab, aflibercept and ramucirumab, can result in renal and vascular complications such as hypertension, arterial thrombotic events (ATE), proteinuria and GI perforations. The anti EGFR agents classically cause dermatological toxicities, in addition to hypomagnesemia, which can be dose limiting for patients. Trastuzumab, a monoclonal antibody that targets Her2/Neu, is known to cause cardiotoxicity, especially when used with anthracyclines. Use of immunotherapy agents such as nivolumab is associated with the development immune related adverse events (irAEs). The use of these agents is expected to increase over the next few years and it is crucial that patients and practitioners are aware of their adverse effects and current management strategies. This review highlights the adverse events associated with the use of biologic and immunologic therapies in GI cancers, their incidence and current management strategies.

Randomized controlled trial on the skin toxicity of panitumumab in Japanese patients with metastatic colorectal cancer: HGCSG1001 study; J-STEPP

AIM

We planned a randomized, open-label trial to evaluate differences between pre-emptive and reactive skin treatment for panitumumab (Pmab)-associated skin toxicities in Japanese patients with metastatic colorectal cancer.

PATIENTS & METHODS

Patients receiving third-line Pmab-containing regimens were randomized to pre-emptive or reactive treatment. The primary end point was the cumulative incidence of ≥grade 2 skin toxicities during 6 weeks. Retrospectively, a dermatologist reviewed skin toxicities, in a blinded manner.

RESULTS

A total of 95 patients were enrolled (pre-emptive: 47, reactive: 48). The primary end point was achieved (21.3 and 62.5% [risk ratio: 0.34; p < 0.001], for pre-emptive and reactive treatment, respectively). A similar trend was observed in central review.

CONCLUSION

Pre-emptive skin treatment could reduce the severity of Pmab-associated skin toxicities in Japanese metastatic colorectal cancer patients.

Cancer immunotherapy by a recombinant phage vaccine displaying EGFR mimotope: an in vivo study

To date, several small molecule inhibitors and monoclonal-antibodies (like ICR-62) have been used to treat tumors over-expressing epidermal growth factor receptor (EGFR). However, the limitations associated with these conventional applications accentuate the necessity of alternative approaches. Mimotopes as compelling molecular tools could rationally be employed to circumvent these drawbacks. In the present study, an M13 phage displaying ICR-62 binding peptide mimotope is exploited as a vaccine candidate. It exhibited high affinity towards ICR62 and polyclonal anti-P-BSA antibodies. Following the mice immunization, phage-based mimotope vaccine induced humoral immunity. Elicited anti-EGFR mimotope antibodies were detected using ELISA method. Moreover, the phage vaccine was tested on the Lewis lung carcinoma mice model to investigate the prophylactic and therapeutic effects. The tumor volume was measured and recorded in different animal groups to evaluate the anti-tumor effects of the vaccine. Our data indicate that the reported phage-based mimotope could potentially elicit specific antibodies resulting in low titers of EGFR-specific antibodies and reduced tumor growth. However, in vivo experiments of prophylactic or therapeutic vaccination showed no specific advantage. Furthermore, phage-mimotope vaccine might be a promising approach in the field of cancer immunotherapy.

TIMP-1 and CEA as biomarkers in third-line treatment with irinotecan and cetuximab for metastatic colorectal cancer

KRAS wild-type (wt) status determines indication for treatment with combination therapy, including epidermal growth factor receptor (EGFR) inhibitors, but still, the overall response rate in KRAS wt patients is less than 40 %. Consequently, the majority of patients will suffer from substantial side effects and no apparent benefit. Tissue inhibitor of metalloproteinases-1 is a glycoprotein, which regulates metalloproteinases and may consequently imply a central role in tumour progression. Furthermore, it is closely related to the EGFR regulation and has shown promising potential as a biomarker in colorectal cancer (CRC). The aim of the present study was to investigate the clinical value of TIMP-1 in patients with metastatic colorectal cancer (mCRC) treated with cetuximab and irinotecan. Patients with chemotherapy-resistant mCRC referred to third-line treatment with cetuximab (initial 400 mg/m(2) followed by weekly 250 mg/m(2))/irinotecan (350 mg/m(2) q3w) were prospectively included in the biomarker study, as previously published. Pre-treatment blood samples were collected, and plasma TIMP-1 was measured by a validated in-house ELISA assay. In addition, carcinoembryonic antigen (CEA) measurement was performed with a standardised method. A total of 107 patients were included in the biomarker study. The median baseline plasma TIMP-1 level was 271.1 ng/ml (range 65.9-1432 ng/ml) with no significant associations with baseline clinical characteristics. Median baseline plasma TIMP-1 levels were significantly higher in patients with early progression compared to patients who achieved disease control, 349 ng/ml (233-398 95 % confidence interval (CI)) and 215 ng/ml (155-289 95 % CI), respectively, p = 0.03, suggesting some association with treatment efficacy. When dividing patients according to TIMP-1 tertiles, the median progression-free survival (PFS) in patients with a high level of TIMP-1 was 2.4 months (95 % CI 2.1-4.1) compared to 3.3 months (95 % CI 2.1-6.2) and 4.7 months (95 % 3.2-7.6) in patients with intermediate or low levels, respectively. Analysis of TIMP-1 as a continuous variable revealed a shorter PFS associated with increasing levels of TIMP-1 (hazard ratio (HR) 1.36). These results translated into a significantly lower overall survival (OS) in patients with a high baseline TIMP-1 level (4.5 months (95 % CI 3.4-5.4)), compared to those with intermediate or low TIMP-1 levels (7.8 months (95 % CI 4.4-13.7) and 12.0 months (95 % CI 10.1-14.3), respectively, p < 0.0001). An 83 % higher hazard for death was revealed (HR = 1.83) with each twofold increase in the TIMP-1 level. Pre-treatment levels of CEA were not associated with any of the baseline characteristics (except primary tumour localisation) or to differences in PFS or OS. The rank correlation between CEA and TIMP-1 was r = 0.50, and a test for interaction between TIMP-1 and CEA (dichotomised at 5 ng/ml) in survival analysis was not significant (p = 0.18). A multivariate analysis for PFS and OS resulted in a model with significant contributions from TIMP-1, KRAS, and the number of metastatic sites. We have confirmed the potential prognostic value of TIMP-1 measurement prior to palliative chemotherapy for mCRC. However, validation in randomised trials will be essential with the perspective of establishing a potential predictive role of plasma TIMP-1 in this setting.

Panitumumab following disease progression on cetuximab in patients with metastatic colorectal cancer: A retrospective review

Despite advances in treatment options for metastatic colorectal cancer over the past decade, the number of chemotherapy agents available remains limited. We report here a retrospective review of 11 patients who were treated with panitumumab following documented disease progression on cetuximab. Two patients demonstrated minor radiographic responses, albeit only for a short period of time. We conclude that the use of one epidermal growth factor receptor inhibitor following failure on the other may be of benefit to patients who would otherwise have no other treatment options. However, studies to help identify the subset of patients who might benefit from this strategy are needed.

Eyelash trichomegaly secondary to panitumumab therapy

We report a recently encountered toxicity of therapy targeting the epidermal growth factor receptor (EGFR) that may be of interest to the wider community of oncologists. [...]

Concordance of preclinical and clinical pharmacology and toxicology of therapeutic monoclonal antibodies and fusion proteins: cell surface targets

Monoclonal antibodies (mAbs) and fusion proteins directed towards cell surface targets make an important contribution to the treatment of disease. The purpose of this review was to correlate the clinical and preclinical data on the 15 currently approved mAbs and fusion proteins targeted to the cell surface. The principal sources used to gather data were: the peer reviewed Literature; European Medicines Agency 'Scientific Discussions'; and the US Food and Drug Administration 'Pharmacology/Toxicology Reviews' and package inserts (United States Prescribing Information). Data on the 15 approved biopharmaceuticals were included: abatacept; abciximab; alefacept; alemtuzumab; basiliximab; cetuximab; daclizumab; efalizumab; ipilimumab; muromonab; natalizumab; panitumumab; rituximab; tocilizumab; and trastuzumab. For statistical analysis of concordance, data from these 15 were combined with data on the approved mAbs and fusion proteins directed towards soluble targets. Good concordance with human pharmacodynamics was found for mice receiving surrogates or non-human primates (NHPs) receiving the human pharmaceutical. In contrast, there was poor concordance for human pharmacodynamics in genetically deficient mice and for human adverse effects in all three test systems. No evidence that NHPs have superior predictive value was found.

Off-Target Platelet Activation in Macaques Unique to a Therapeutic Monoclonal Antibody

AMG X, a human neutralizing monoclonal antibody (mAb) against a soluble human protein, caused thrombocytopenia, platelet activation, reduced mean arterial pressure, and transient loss of consciousness in cynomolgus monkeys after first intravenous administration. In vitro, AMG X induced activation in platelets from macaque species but not from humans or baboons. Other similar mAbs against the same pharmacological target failed to induce these in vivo and in vitro effects. In addition, the target protein was known to not be expressed on platelets, suggesting that platelet activation occurred through an off-target mechanism. AMG X bound directly to cynomolgus platelets and required both the Fab and Fc portion of the mAb for platelet activation. Binding to platelets was inhibited by preincubation of AMG X with its pharmacological target or with anti-human Fc antibodies or by preincubation of platelets with AMG X F(ab′)2 or human immunoglobulin (IVIG). AMG X F(ab′)2 did not activate platelets. Thus, platelet activation required both recognition/binding of a platelet ligand with the Fab domain and interaction of platelet Fc receptors (i.e., FcγRIIa) with the Fc domain. These findings reflect the complexity of the mechanism of action of mAbs and the increasing awareness of potential for unintended effects in preclinical species.

Analysis of KRAS Mutations of Exon 2 Codons 12 and 13 by SNaPshot Analysis in Comparison to Common DNA Sequencing

Due to the call for fast KRAS mutation status analysis for treatment of patients with monoclonal antibodies for metastatic colorectal cancer, sensitive, economic, and easily feasible methods are required. Under this aspect, the sensitivity and specificity of the SNaPshot analysis in comparison to the commonly used DNA sequencing was checked. We examined KRAS mutations in exon 2 codons 12 and 13 with DNA sequencing and SNaPshot analysis in 100 formalin-fixed paraffin-embedded tumor tissue samples of pancreatic carcinoma, colorectal carcinoma, and nonsmall cell lung cancer specimens of the primary tumor or metastases. 40% of these samples demonstrated mutated KRAS genes using sequencing and SNaPshot-analysis; additional five samples (45/100) were identified only with the SNaPshot. KRAS mutation detection is feasible with the reliable SNaPshot analysis method. The more frequent mutation detection by the SNaPshot analysis shows that this method has a high probability of accuracy in the detection of KRAS mutations compared to sequencing.

Chromogenic in situ hybridization to detect EGFR gene copy number in cell blocks from fine-needle aspirates of non small cell lung carcinomas and lung metastases from colo-rectal cancer

Background

Several studies demonstrated that epidermal growth factor receptor (EGFR) gene copy number (GCN) correlates to the response to tyrosine kinase inhibitors in non small cell lung cancer (NSCLC) and to anti-EGFR monoclonal antibodies (MoAbs) in metastatic colorectal cancer (CRC). In the presence of lung nodules, cytology is often the only possible diagnostic approach. Chromogenic in situ hybridization (CISH) is an alternative technique to fluorescence in situ hybridization (FISH), but its feasibility in detecting EGFR GCN in cell blocks from fine-needle aspiration cytology (FNAC) of lung nodules has not yet been established.

Methods

We evaluated the feasibility of CISH on 33 FNAC from 20 primary NSCLC (5 squamous carcinomas, 8 large cell carcinomas and 7 adenocarcinomas) and 13 lung metastases from CRC.

Results

Of the 33 FNAC analyzed by CISH, 27 (82%) presented a balanced increase in EGFR gene and chromosome 7 number: 10 cases (30%) showed a low polysomy, 15 (45%) a high polysomy and 2 (6%) NSCLC were amplified. No significant differences between NSCLC and CRC lung metastases were found in relation to disomic or polysomic status. In addition, no correlation between EGFR GCN and EGFR immunohistochemical overexpression was found. Furthermore, we compared CISH results with those obtained by FISH on the same samples and we found 97% overall agreement between the two assays (k = 0.78, p < 0.0001). Two cases were amplified with both assays, whereas 1 case of NSCLC was amplified by FISH only. CISH sensitivity was 67%, the specificity and positive predictive value (PPV) was 100%, and the negative predictive value (NPV) was 97%.

Conclusions

Our study shows that CISH is a valid method to detect EGFR GCN in cell blocks from FNAC of primary NSCLC or metastatic CRC to the lung.

T cell-engaging BiTE antibodies specific for EGFR potently eliminate KRAS- and BRAF-mutated colorectal cancer cells

Epidermal growth factor receptor (EGFR)-specific monoclonal antibodies predominantly inhibit colorectal cancer (CRC) growth by interfering with receptor signaling. Recent analyses have shown that patients with CRC with mutated KRAS and BRAF oncogenes do not profit from treatment with such antibodies. Here we have used the binding domains of cetuximab and pantitumumab for constructing T cell-engaging BiTE antibodies. Both EGFR-specific BiTE antibodies mediated potent redirected lysis of KRAS- and BRAF-mutated CRC lines by human T cells at subpicomolar concentrations. The cetuximab-based BiTE antibody also prevented at very low doses growth of tumors from KRAS- and BRAF-mutated human CRC xenografts, whereas cetuximab was not effective. In nonhuman primates, no significant adverse events were observed during treatment for 3 wk at BiTE serum concentrations inducing, within 1 d, complete lysis of EGFR-overexpressing cancer cells. EGFR-specific BiTE antibodies may have potential to treat CRC that does not respond to conventional antibodies.

A review of the most promising biomarkers in colorectal cancer: one step closer to targeted therapy

Rapidly growing insights into the molecular biology of colorectal cancer (CRC) and recent developments in gene sequencing and molecular diagnostics have led to high expectations for the identification of molecular markers to be used in optimized and tailored treatment regimens. However, many of the published data on molecular biomarkers are contradictory in their findings and the current reality is that no molecular marker, other than the KRAS gene in the case of epidermal growth factor receptor (EGFR)- targeted therapy for metastatic disease, has made it into clinical practice. Many markers investigated suffer from technical shortcomings, resulting from lack of quantitative techniques to capture the impact of the molecular alteration. This understanding has recently led to the more comprehensive approaches of global gene expression profiling or genome-wide analysis to determine prognostic and predictive signatures in tumors. In this review, an update of the most recent data on promising biological prognostic and/or predictive markers, including microsatellite instability, epidermal growth factor receptor, KRAS, BRAF, CpG island methylator phenotype, cytotoxic T lymphocytes, forkhead box P3-positive T cells, receptor for hyaluronic acid-mediated motility, phosphatase and tensin homolog, and T-cell originated protein kinase, in patients with CRC is provided.

IgG2m4, an engineered antibody isotype with reduced Fc function

The Fc region of an antibody mediates effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC), and plays a key role in the in vivo half-life of an antibody. In designing antibody therapeutics, it is sometimes desirable that the antibody has altered Fc-mediated properties. In the case of a "benign blocker" antibody, it is often desirable to diminish or abolish the ADCC and CDC functions while retaining its PK profile. Here, we report a novel engineered IgG isotype, IgG2m4, with reduced Fc functionality. IgG2m4 is based on the IgG2 isotype with four key amino acid residue changes derived from IgG4 (H268Q, V309L, A330S and P331S). An IgG2m4 antibody has an overall reduction in complement and Fc gamma receptor binding in in vitro binding analyses while maintaining the normal in vivo serum half-life in rhesus.

Oncogenic mutant forms of EGFR: lessons in signal transduction and targets for cancer therapy

The EGF-receptor is frequently mutated in a large variety of tumors. Here we review the most frequent mutations and conclude that they commonly enhance the intrinsic tyrosine kinase activity, or they represent loss-of-function of suppressive regulatory domains. Interestingly, the constitutive activity of mutant receptors translates to downstream pathways, which are subtly different from those stimulated by the wild-type receptor. Cancer drugs intercepting EGFR signaling have already entered clinical application. Both kinase inhibitors specific to EGFR, and monoclonal antibodies to the receptor are described, along with experimental approaches targeting the HSP90 chaperone. Deeper understanding of signaling pathways downstream to mutant receptors will likely improve the outcome of current EGFR-targeted therapies, as well as help develop new drugs and combinations.

Electrolyte and protein imbalance following anti-EGFR therapy in cancer patients: A comparative study

Electrolytic changes in blood have been associated with the use of anti-epidermal growth factor receptor (EGFR) antibodies. The objective of this retrospective study was to compare the rate of incidence and the severity of blood electrolyte and protein imbalances occurring in patients receiving cetuximab or panitumumab with or without concurrent chemotherapy. Treatment data of 58 patients who received cetuximab and 21 patients who received panitumumab were analyzed. Cetuximab caused hypomagnesemia in more than half of the patients, among whom 4 had severity up to grade 2/3 level, whereas panitumumab induced hypomagnesemia in 90% of the patients with severity up to grade 2 level occurring in 38% of the patients. Intravenous magnesium supplementation on the day of anti-EGFR treatment did not always adequately control the magnesium wasting in these patients. Often treatments with these agents had to be interrupted or terminated as a result of severe electrolyte depletion despite supplementation. Taking into consideration the mechanism of magnesium wasting from the kidney and the magnesium transport process in the gut, intravenous magnesium infusion coupled with oral supplementation with more tolerant oral magnesium products may help improve the treatment outcome in these patients. Surprisingly, more than half of these patients showed significant decreases in their albumin levels, which were correlated with the initiation or discontinuation of anti-EGFR therapy. The underlying mechanism of this decrease in albumin level is not known. The increased likelihood of poor outcomes such as mortality, morbidity and prolonged hospital stay in acutely ill patients with hypoalbuminemia is well recognized. Moreover, the maintenance of adequate serum albumin levels in these patients receiving anti-EGFR therapy may play an important role in containing some of the adverse effects of concurrently administered chemotherapeutic agents.

KRAS genotyping of paraffin-embedded colorectal cancer tissue in routine diagnostics: comparison of methods and impact of histology

KRAS mutation testing before anti-epidermal growth factor receptor therapy of metastatic colorectal cancer has become mandatory in Europe. However, considerable uncertainty exists as to which methods for detection can be applied in a reproducible and economically sound manner in the routine diagnostic setting. To answer this question, we examined 263 consecutive routine paraffin slide specimens. Genomic DNA was extracted from microdissected tumor tissue. The DNA was analyzed prospectively by Sanger sequencing and array analysis as well as retrospectively by melting curve analysis and pyrosequencing; the results were correlated to tissue characteristics. The methods were then compared regarding the reported results, costs, and working times. Approximately 40% of specimens contained KRAS mutations, and the different methods reported concordant results (kappa values >0.9). Specimens harboring fewer than 10% tumor cells showed lower mutation rates regardless of the method used, and histoanatomical variables had no influence on the frequency of the mutations. Costs per assay were higher for array analysis and melting curve analysis when compared with the direct sequencing methods. However, for sequencing methods equipment costs were much higher. In conclusion, Sanger sequencing, array analysis, melting curve analysis, and pyrosequencing were equally effective for routine diagnostic KRAS mutation analysis; however, interpretation of mutation results in conjunction with histomorphologic tissue review and on slide tumor tissue dissection is required for accurate diagnosis.

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.

Frequency and type of KRAS mutations in routine diagnostic analysis of metastatic colorectal cancer

Mutation analysis of the KRAS oncogene is now established as a predictive biomarker in colorectal cancer (CRC). Large prospective clinical trials have shown that only CRCs with wild-type KRAS respond to anti-epidermal growth factor receptor (EGFR) treatment. Therefore, mutation analysis is mandatory before treatment, and reliable benchmarks for the frequency and types of KRAS mutations have to be established for routinely testing large numbers of metastatic CRCs. A thousand and eighteen cases (879 primary tumors and 139 metastases) of metastatic colorectal cancer were analyzed for the KRAS mutational status of codons 12 and 13 of the KRAS gene by genomic sequencing in a routine setting. Results were analyzed separately for specimens derived from primary tumors and metastases. KRAS mutations in codons 12 and 13 were present in 39.3% of all analyzed CRCs. The most frequent types of mutations were glycine to aspartate on codon 12 (p.G12D, 36.0%), glycine to valine on codon 12 (pG12V, 21.8%), and glycine to aspartate on codon 13 (p.G13D, 18.8%). They account for 76.6% of all mutations and prevail in primary tumors and distant metastases, indicating a robustness of the KRAS mutational status during neoplastic dissemination. The frequency of KRAS mutations and the preponderance of three types of mutations in codons 12 and 13 in a large, unselected cohort of metastatic CRC confirm the previous data of small and selected CRC samples. Thus, a mutation frequency of 40% and a cluster of three mutation types (p.G12D, pG12V, and p.G13D) in primaries and metastases can be defined as benchmarks for routine KRAS analyses.