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Author(s): Bediz Kurt İnci (corresponding author) [1]; Fatih Gürler [1]; Osman Sütcüoğlu [1]; Gözde Tahtacı [1]; Aytuğ Üner [1]; Ahmet Özet [1]; Nazan Günel [1]; Ozan Yazıcı [1] Introduction Metastatic [...], Background: In metastatic colorectal cancer (mCRC), the genetic structure and cell metabolism of the primary tumor lesion might be different from metastatic lesions. It is thought that cell-level glucose metabolism may differ due to the difference in RAS wild and mutant mCRC patients' prognosis. In this study, we aimed to compare 2-deoxy-2-[fluorine-18]-fluoro-D-glucose Positron Emission Tomography (18F-FDG PET/CT) uptake levels for KRAS mutation status and primary-metastatic tumor localization. Methods: Our study is a retrospective cohort analysis that included RAS mutation status study and staging-oriented 18F-FDG PET/CT conducted on mCRC patients. Results: There was no significant relationship between metastasis and primary tumor maximum Standardized uptake value (SUVmax) values according to the KRAS mutational status (P > 0.05). Patients with liver metastasis along with mutant BRAF mutation status had significantly higher SUVmax values in PET-CT scans (P = 0.04). There was a negative correlation between SUVmax values of lung metastases and overall survival (r = -0.35, P = 0.04). Patients with high carcinoembryonic antigen (CEA) levels had significantly higher SUVmax values of lung metastasis than patients with normal CEA levels (P = 0.009). Patients with high CA19-9 levels had significantly higher SUVmax values of liver, peritoneal, and bone metastasis than patients with normal CA19-9 levels (P = 0.002, P = 0.001, P = 0.004, respectively). There was no significant correlation between SUVmax values of metastasis and Lactate dehydrogenase (LDH) values. Liver metastasis of right-sided mCRCs had significantly higher SUVmax values (P = 0.03). Conclusion: We could not demonstrate a significant association between KRAS mutation and SUVmax values of PET scan in primary or metastatic tumor sites in advanced CRC. Keywords: Colorectal neoplasms, genes, positron-emission tomography, RAS

Author(s): Sandra Assoun [sup.1], Virginie Lemiale [sup.1], Elie Azoulay [sup.1] Author Affiliations: (1) 0000 0001 2300 6614, grid.413328.f, Médecine Intensive et Réanimation AP-HP, Hôpital Saint-Louis, , University Paris-7 Paris-Diderot, 1 [...], Background Molecular targeted therapy increased overall and disease-free survival in a wide range of malignancies. Although generally well tolerated compared to chemotherapy, molecular targeted therapy may be associated with adverse events requiring ICU admission. Informing clinicians about clinical features of these toxic events might maintain awareness and favor early recognition, prompt diagnosis and treatment. Methods We performed a systematic review of published case reports of molecular targeted therapy-related life-threatening toxicity that led to ICU admission. The search used the Pubmed database using medical subject heading (Mesh) terms, including all FDA-approved molecular targeted therapy (TT), up to March 2019. No language restriction was applied. All cases reports of patients admitted to the ICU for molecular targeted therapy-related toxicity were included. Non-FDA-approved combinations of treatments or hormonal therapy were not included. Results Two hundred and fifty-three cases were identified. Nearly half of them (n = 102; 40.3%) were related to anti-angiogenic agents, mostly for gastrointestinal and cardiovascular complications. Other molecules responsible for adverse events were chiefly immune checkpoint inhibitors (n = 85, 33.6%), EGFR inhibitors (n = 33; 13.0%), and anti-HER2 (n = 10; 4.0%). They were associated with adverse events such as respiratory or hypersensitivity events. Management and outcomes associated with these life-threatening complications are reported. Conclusions Based on the vast number of treated patients, only 253 cases of molecular therapy-related severe toxicity are reported in cancer patients. Symptoms and biomarkers that depict these events need to be better identified as to allow appropriate reporting and improving dose and schedule of the treatment adapted to each patient.

The understanding of the molecular pathogenesis of cancer has led to the development of chemotherapeutic agents that target specific genetic alterations such as mutations in the epidermal growth factor receptor [...], Context.--In some instances the standard method of doing molecular testing from formalin-fixed, paraffin-embedded block is not possible because of limited tissue. Tumor cell-enriched cell-transfer technique has been proven useful for performing immunocytochemistry and molecular testing on cytologic smears. Objective.--To establish the cell-transfer technique as a viable option for isolating tumor cells from hematoxylin-eosin (H&E)-stained slides. Design.--Molecular testing was performed by using the cell-transfer technique on 97 archived H&E-stained slides from a variety of different tumors. Results were compared to the conventional method of molecular testing. Results.--Polymerase chain reaction-based molecular testing via the cell-transfer technique was successfully performed on 82 of 97 samples (85%). This included 39 of 47 cases for EGFR, 10 of 11 cases for BRAF, and 33 of 39 cases for KRAS mutations. Eighty-one of 82 cell-transfer technique samples (99%) showed agreement with previous standard method results, including 4 mutations and 35 wild-type alleles for EGFR, 4 mutations and 6 wild-type alleles for BRAF, and 11 mutations and 21 wild-type alleles for KRAS. There was only 1 discrepancy: a cell-transfer technique with a false-negative KRAS result (wild type versus G12C). Conclusions.--Molecular testing performed on H&E-stained sections via cell-transfer technique is useful when tissue from cell blocks and small surgical biopsy samples is exhausted and the only available material for testing is on H&E-stained slides. (doi: 10.5858/arpa.2015-0454-OA)

Molecular testing to select targeted and conventional therapies for patients with colorectal cancer (CRC) has been the focus of a number of recent studies and is becoming standard practice for [...], Objectives.--To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens. Methods.--The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted. Results.--Twenty-one guideline statements were established. Conclusions.--Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented. (Arch Pathol Lab Med. 2017; 141:625-657; doi: 10.5858/arpa.2016-0554-CP)

The understanding of the molecular pathogenesis of cancer has led to the development of chemotherapeutic agents that target specific genetic alterations such as mutations in the epidermal growth factor receptor [...], Context.--In some instances the standard method of doing molecular testing from formalin-fixed, paraffin-embedded block is not possible because of limited tissue. Tumor cell-enriched cell-transfer technique has been proven useful for performing immunocytochemistry and molecular testing on cytologic smears. Objective.--To establish the cell-transfer technique as a viable option for isolating tumor cells from hematoxylineosin (H&E)-stained slides. Design.--Molecular testing was performed by using the cell-transfer technique on 97 archived H&E-stained slides from a variety of different tumors. Results were compared to the conventional method of molecular testing. Results.--Polymerase chain reaction-based molecular testing via the cell-transfer technique was successfully performed on 82 of 97 samples (85%). This included 39 of 47 cases for EGFR, 10 of 11 cases for BRAF, and 33 of 39 cases for KRAS mutations. Eighty-one of 82 cell-transfer technique samples (99%) showed agreement with previous standard method results, including 4 mutations and 35 wild-type alleles for EGFR, 4 mutations and 6 wild-type alleles for BRAF, and 11 mutations and 21 wild-type alleles for KRAS. There was only 1 discrepancy: a cell-transfer technique with a false-negative KRAS result (wild type versus G12C). Conclusions.--Molecular testing performed on H&E-stained sections via cell-transfer technique is useful when tissue from cell blocks and small surgical biopsy samples is exhausted and the only available material for testing is on H&E-stained slides. (Arch Pathol Lab Med. 2016;140:1383-1389; doi:10.5858/arpa.2015-0454-OA)

BIOMARKERS IN COLORECTAL TUMORS Colorectal carcinoma (CRC) is the third most common cancer diagnosed in men and women in the United States, with 96 830 new cases of colon cancer [...], Context.--Advances in molecular biomarkers of the gastrointestinal tract have contributed to a decline in the incidence of and mortality from diseases of the gastrointestinal tract. The discovery and clinical validation of new biomarkers are important to personalized cancer therapy, and numerous clinical trials are currently ongoing to help identify individualized therapy affecting these biomarkers and molecular mechanisms they represent. Distinct molecular pathways leading to cancers of the colorectum, esophagus, stomach, small bowel, and pancreas have been identified. Using biomarkers in these pathways to direct patient care, including selection of proper molecular testing for identification of actionable mutations and reporting the results of these biomarkers to guide clinicians and genetic counselors, is paramount. Objective.--To examine and review select clinically actionable biomarkers of the colon, esophagus, stomach, small bowel, and pancreas, including present and future biomarkers with relevant clinical trials. Data Sources.--Extensive literature review and practical and consultation experience of the authors. Conclusions.--Although numerous biomarkers have been identified and are currently guiding patient therapy, few have shown evidence of clinical utility in the management of patients with gastrointestinal cancers. Inconsistent results and discordant proposed algorithms for testing were identified throughout the literature; however, the potential for biomarkers to improve outcomes for patients with gastrointestinal cancer remains high. Continued advances through high-quality studies are needed. (Arch Pathol Lab Med. 2015;139:457-468; doi: 10.5858/arpa.2014-0189-RA)

Cetuximab and panitumumab are monoclonal antibodies approved for treatment of metastatic colorectal cancers (CRCs) by inhibiting the epidermal growth factor receptor (EGFR) signaling pathway. (1,2) Activated EGFR signals through both [...], Context.--Detection of KRAS mutation is mandatory to predict response to anti-epidermal growth factor receptor monoclonal antibodies in patients with metastatic colorectal cancers. Objective.--To demonstrate challenges posed to pathologists in the clinical detection of KRAS mutations in colorectal cancers. Design.--In this retrospective analysis for quality assessment of the pyrosequencing assay, we survey the characteristics of 463 formalin-fixed, paraffin-embedded neoplastic tissues submitted for KRAS mutation detection during a 26-month period. Results.--The KRAS mutation was detected in 39.2% of tumors. This included 2 tumors with complex pyrograms (GGT.GAG at codon 12 and GGC.GTT at codon 13, as resolved by a Pyromaker software program) and 3 tumors with an indeterminate percentage of mutant alleles (defined as 4% to 5% and confirmed by a next-generation sequencing platform). Among the 25 specimens (5.5%) with fewer than 20% tumor cells, 22 were resected after chemotherapy/radiation. Significant depletion of tumor cells was observed in rectal cancers resected after neoadjuvant therapy (31.0%) versus those without previous treatment (0%) (P = .01). We also explore other specimens with low tumor cellularity and potential causes of discrepancy between the estimated tumor cell percentage and detected mutant allele frequency, such as intratumor heterogeneity of KRAS mutation. Conclusions.--Neoadjuvant therapy may deplete tumor cells and confound the molecular diagnosis of KRAS mutations. Accurate detection of specimens with poor tumor cellularity requires the appropriate selection of neoplastic tissues, evaluation of tumor cellularity, use of assays with high sensitivity, and prospective quality assessment. (Arch Pathol Lab Med. 2015; 139:211-218; doi: 10.5858/arpa.2013-0649-OA)

Cetuximab is an immunoglobulin [G.sub.1] monoclonal antibody that binds specifically to the epidermal growth factor receptor (EGFR). Cetuximab inhibits the proliferation and survival of tumor cells that express EGFR and [...], * Context.--The therascreen KRAS RGQ polymerase chain reaction kit is being developed as a companion diagnostic to aid clinicians, through detection of KRAS mutations, in the identification of patients with metastatic colorectal cancer (mCRC) who are more likely to benefit from cetuximab. Objective.--To assess whether KRAS mutation status, determined by using the therascreen KRAS kit, is a predictive marker of cetuximab efficacy. Design.--Tissue samples were obtained from patients with mCRC treated on the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) CO.17 phase 3 study of cetuximab plus best supportive care (BSC) versus BSC alone. Tumor DNA samples were assessed for the presence of KRAS mutations by using the therascreen KRAS kit. Efficacy and safety were assessed to determine whether mutation status was predictive of outcomes. Results.--Evaluable samples were available from 453 patients (79.2%) enrolled in the NCIC CTG CO.17 trial. The KRAS wild-type subset represented 54.1% (245 of 453) of the evaluated population. Median overall survival of patients with KRAS wild-type tumors was 8.6 months among those who received cetuximab plus BSC and 5.0 months among patients who received BSC alone (hazard ratio [HR], 0.63; P = .002). Among patients with KRAS mutant mCRC, no meaningful difference in overall survival was observed between arms (HR, 0.91; P = .55). These results are consistent with a previous report that analyzed patient tumor samples by using bidirectional sequencing. Conclusions.--These data support the utility of the therascreen KRAS kit as a means of selecting patients who may benefit from cetuximab therapy. (Arch Pathol Lab Med. 201337:820-827; doi: 10.5858/arpa.2012-0367-OA)

In this exciting new era of targeted cancer therapy guided by molecular biomarkers, the work of the pathologist goes beyond initial tumor diagnosis and staging. The role of the pathologist [...], Context.--Mutation status of the KRAS gene identifies a distinct disease subtype of metastatic colorectal carcinoma that does not respond to antibody therapeutics targeting the epidermal growth factor receptor. This is currently the only validated marker in metastatic colorectal carcinoma with a clear implication in treatment selection. KRAS testing is widely accepted in clinical practice to guide metastatic colorectal carcinoma therapeutic decisions, and there are many commercially available platforms to perform the test. Objective.--To evaluate the critical role of pathologists in the full implementation of KRAS testing by optimizing tumor tissue collection and fixation procedures and by choosing testing technologies and reliable Clinical Laboratory Improvement Amendments of 1988-certified laboratories to perform the tests. Data Sources.--Prospective clinical trials, retrospective studies, and quality assessment and survey reports were identified in the following databases: PubMed, American Society of Clinical Oncology Proceedings (American Society of Clinical Oncology Annual Meeting and Gastrointestinal Cancer Symposium) and European Society for Medical Oncology Proceedings (Annals of Oncology European Society for Medical Oncology Congress and Annals of Oncology World Congress on Gastrointestinal Cancers). Conclusions.--More bona fide standards are needed to address the variety of available test methods, which have different performance characteristics including speed, sensitivity to detect rare mutations, and technical requirements. Refined standards addressing timing of KRAS testing, laboratory performance and accuracy, quality assurance and control, proper tissue collection, and appropriate result reporting would also be greatly beneficial. Pathologists should be aware that the amount of information they need to manage will increase, because future trends and technological advances will enhance the predictive power of diagnostic tests or the scope of the biomarker panels tested routinely across tumor types. (Arch Pathol Lab Med. 2012;136:1298-1307; doi: 10.5858/arpa.2011-0478-RA)

Therapeutic agents targeting molecular changes are involved in the treatment of several human cancers. The epidermal growth factor receptor (EGFR) is one of the targets in colorectal cancer therapy because [...], Context.--As the availability of targeted therapies for several tumor types increases, the need for rapid and sensitive mutation screening is growing. KRAS mutations constitutively activate the RAS/RAF/mitogen-activated protein kinase (MAPK) pathway and therefore play an important role in anti-epidermal growth factor receptor therapy for patients with colorectal cancers. Mutationally activated PIK3CA and AKT1 genes are promising therapeutic targets in breast cancer. In 60% to 70% of malignant melanomas, a mutation in BRAF can be found. Thus, the blocking of the oncogenic signaling induced by this mutation is now used as treatment approach. Objective.--To establish high-resolution melting assays for routinely used predictive analyses of KRAS, AKT1, PIK3CA, and BRAF mutations. Design.--High-resolution melting assays were developed by using specifically designed primers and genomic DNA isolated either from cell lines or formalin-fixed paraffin-embedded tissues, oligonucleotides, or plasmids. Melting curve analyses were performed on the LightCyler platform and mutation analyses were additionally confirmed by Sanger sequencing. Results.--We developed high-resolution melting assays by using genomic DNA containing the desired mutation, which enabled us to detect percentages of mutated DNA (3.1% to 12.5%) mixed in a wild-type background. Assays were evaluated by hybridization probes and/or Sanger sequencing to exclude pseudogene amplification. The high-resolution melting assays were validated with genomic DNA from different tumor entities. The concordance between Sanger sequencing and high-resolution melting was 99% for KRAS exon 2 and PIK3CA exon 20 and 100% for the remaining assays. Conclusions.--High-resolution melting provides a valid and powerful tool for detecting genomic mutations efficiently. (Arch Pathol Lab Med. 2012;136:983-992; doi: 10.5858/arpa.2011-0176-OA)

Most cancers are traditionally treated with either chemotherapeutic agents, radiotherapy, or both. Identification of specific molecular characteristics of tumors and the advent of translational or applied research have generated numerous [...], * Context.--In recent years, there has been a tremendous amount of interest in the development of targeted therapies for the treatment of human cancers. Increased understanding of the specific molecular pathways and driver mutations critical to cancer cell growth have allowed the development of these advanced therapeutics. Among these, inhibitors of the epidermal growth factor receptor and HER2/neu pathways now play a major role in the management of gastrointestinal cancers in addition to other solid malignancies. In colorectal and gastric cancers, the use of epidermal growth factor receptor inhibitors and HER2/neu inhibitors has increased the available treatment options for patients with advanced disease. Objective.--To focus on the current targeted therapies and predictors of response in malignancies of the gastrointestinal tract. Data Sources.--Medical literature searchable on PubMed (US National Library of Medicine) as well as older studies revealed by the literature review were used as the source of data. Conclusion.--Gene testing of critical elements of the pathways targeted by these agents (such as KRAS mutational analysis in colorectal tumors and HER2/neu testing in gastric cancers) allows the ability to predict which patients will respond to these treatments. As the molecular profiling of tumors and our understanding of cancer genomics and epigenetic alterations continues to grow, it is expected that these personalized targeted therapies will form one of the mainstays of gastrointestinal cancer treatment. (Arch Pathol Lab Med. 2012; 136:496-503; doi: 10.5858/arpa.2011-0167-RA)

Colorectal cancer is a common disease and a major cause of cancer death in Western nations. (1) Recently, the median overall survival of the subset of patients with metastatic colorectal [...], Context.--KRAS mutation status is a molecular marker for predicting patient response to treatment with anti-EGFR antibodies (cetuximab and panitumumab) in metastatic colorectal carcinoma. Different approaches may be taken to detect KRAS mutations. There currently are no US Food and Drug Administration-approved assays for the detection of KRAS mutations. For assays that are not approved by the US Food and Drug Administration, the performance characteristics of the assay must be determined and validated by the clinical laboratory before implementation. Objective.--To provide an example of how a KRAS mutation-analysis assay may be validated in a clinical laboratory. Design.--Describing the approach used by an individual laboratory to compare different assays for validation of KRAS mutation analysis in metastatic colon carcinoma. Results.--Specific validation data are provided, illustrating how a laboratory established assay performance characteristics for KRAS mutation analysis. Conclusions.--All clinical laboratories must establish several performance specifications mandated by the Clinical Laboratory Improvement Amendments of 1988 before implementation of any laboratory-developed test. Approaches to the validation of such assays may vary among laboratories. We describe an approach used for validation of a KRAS mutation-analysis assay by one laboratory. (Arch Pathol Lab Med. 2012; 136:26-32; doi: 10.5858/arpa.2011-0220-OA)

With the advent of targeted therapies for metastatic colorectal cancer (CRC), molecular analysis of tumors before initiation of treatment has become a vital component of patient care. Molecular assays guide [...], * Context.--Rational anticancer therapy is beginning to expand the practice of surgical pathology beyond a primarily morphologic and immunophenotypic analysis into the molecular arena. Molecular testing of tumors can have both diagnostic and therapeutic value, which guides treatment decisions. This is true for colorectal cancer in which mutations in signaling mediators predict resistance to anti-epidermal growth factor receptor (anti-EGFR) therapy. Objective.--To review the clinically relevant mutations that currently guide treatment decisions in metastatic colorectal cancer, summarize additional mutations that are expected to improve the prognostic sensitivity of molecular testing, and provide practical suggestions for submitting specimens for molecular analysis. Data Sources.--Peer-reviewed literature reporting pertinent clinical trial data, mutation analysis, and molecular mechanisms of drug resistance, as well as comprehensive review articles germane to the topic and published testing recommendations from the College of American Pathologists. Conclusions.--Molecular analysis of colorectal cancer is now mandated before initiation of anti-EGFR therapy and directly impacts treatment options and outcomes. Familiarity with the mutations that determine utility and efficacy of therapy, as well as the importance of careful sample selection, will facilitate appropriate testing and optimize patient care. doi:10.5858/arpa.2011-0047-RA

Advances in molecular medicine have brought the field of oncologic pathology to a new level. Pathologists have abundant ancillary tools at their disposal not only to aid in the diagnosis [...], Context.--Of all gastrointestinal tract epithelial malignancies, molecular diagnostics has impacted colorectal cancer the most. Molecular testing can detect sporadic and inherited colorectal cancers that arise through the microsatellite instability pathway and can determine the efficacy of targeted drug therapy. Objectives.--To review the microsatellite instability pathway of colorectal carcinoma carcinogenesis and to demonstrate the diagnostic utility of molecular testing in the detection of patients with Lynch syndrome, an inherited disorder of this pathway. Also, to review the significance of detection of KRAS and BRAF gene mutations in predicting the response to anti-epidermal growth factor receptor therapies. Data Sources.--This article is based on original publications and review articles that are accessible through the PubMed biomedical database (US National Library of Medicine). Conclusions.--In modern pathology practice, molecular testing is a standard tool that is used to diagnose an inherited colorectal cancer predisposition syndrome (Lynch syndrome) and to help predict outcome and response to therapy for patients with advanced colorectal cancer. (Arch Pathol Lab Med. 2011;135:578-587)

Colorectal cancer (CRC) is an important global health problem. In 2002, it was the third most commonly occurring cancer with about 1 million new cases (9.4% of the world total). [...], Context.--Colorectal cancer is the third most common cancer and the fourth most common cause of cancer death worldwide. Patient cases are discussed in multidisciplinary meetings to decide on the best management on an individual basis. Until recently, the main task of the pathologist in such teams was to provide clinically useful reports comprising staging of colorectal cancer in surgical specimens. The advent of total mesorectal excision and the application of anti-epidermal growth factor receptor (EGFR)--targeted therapies for selected patients with metastasized colorectal cancer have changed the role of the pathologist. Objectives.--To present the traditional role of the pathologist in the multidisciplinary team treating patients with colorectal cancer, to address the technique of total mesorectal excision and its implications for the evaluation of surgical specimens, to offer background information on the various EGFR-targeted therapies, and to review the currently investigated tissue biomarkers assumed to be predictive for efficacy of such therapies, with a focus on the role of the pathologist in determining the status of such biomarkers in individual tumors. Data Sources.--This article is based on selected articles pertaining to biopsy evaluation of colorectal carcinoma and reviews of EGFR-targeted therapies for this cancer. All references are accessible via the PubMed database (US National Library of Medicine and the National Institutes of Health). Conclusions.--Pathologists play an increasingly important role in the diagnosis and management of colorectal cancer because of the advent of new surgical techniques and of targeted therapies. It is expected that this role will increase further in the near future. (Arch Pathol Lab Med. 2010;134:853-863)

Colorectal cancer (CRC) is a common malignancy worldwide, and despite significant developments in the treatment of this disease, it still causes considerable morbidity and mortality. A multistep model for the [...], * Context.--Monoclonal anti-epidermal growth factor receptor antibodies bind to the epidermal growth factor receptor and inhibit receptor kinase activity. Clinical trials have indicated that evaluation of the mutational status of KRas and BRaf is necessary to exclude patients who are resistant to the clinical benefit of anti-epidermal growth factor receptor therapy. Objective.--To develop a multiplex polymerase chain reaction-based assay for the evaluation of KRas and BRaf mutational status. Design.--A sample-saving and cost-effective, multiplex polymerase chain reaction-based assay to detect somatic mutations in KRAS exon 2 and exon 3 as well as in BRAF exon 15 was developed. The same primer pairs could be successfully used in amplification of a single DNA fragment under the same conditions. Results.--DNA isolated from 20 retrospective formalin-fixed, paraffin-embedded samples of colorectal cancer was screened for mutations using the multiplex polymerase chain reaction assay followed by dideoxy-termination sequencing. Five samples bearing mutations--p.G12D (identified twice), p.G12V, p.G12S, and p.G13D, all encoded in KRAS exon 2--were identified. Three samples were found bearing amino acid substitution p.V600E of BRaf. The detected KRas and BRaf mutations were found to be mutually exclusive. Conclusions.--A multiplex polymerase chain reaction-based amplification followed by dideoxy-termination sequencing may be used advantageously for the evaluation of KRas and BRaf mutational status from formalin-fixed, paraffin-embedded samples. (Arch Pathol Lab Med. 2010;134:620-624)

In the United States, an estimated 108070 cases of colon cancer and 40 740 cases of rectal cancer were expected to occur in 2008. (1) Colorectal cancer (CRC) is the [...], * 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. (Arch Pathol Lab Med. 2009;133:1600-1606)