The KRAS mutation detection within the initial management of patients with metastatic colorectal cancer: a status report in France in 2011

[BRAF V600E-mutant colorectal cancers: Where are we?]

The BRAF^V600E mutation, observed in 8 % of colorectal cancers (CRC), introduces a particular phenotype and a poor prognosis at the localized or metastatic stage. BRAF mutant CRCs are more often localized in the right colon, poorly differentiated and mucinous. They affect an older population (more often female) and are associated with a more frequent metastatic lymph node and peritoneal evolution. The BRAF^V600E mutation is associated with a sporadic microsatellite instability (MSI) status in 20 to 40% of cases. In localized colon cancer, it does not imply any modification of the adjuvant treatment. In metastatic CRC, the first action must be the systematic search for an MSI phenotype, given its frequent association with the presence of a BRAF mutation, in order to propose immunotherapy that has been demonstrated to be very effective in MSI metastatic CRC. In non-MSI CRC, a first-line trichimiotherapy associated with bevacizumab is an option to be favored in patients in good general condition but the association with an anti-EGFR can be discussed, especially when the objective is tumor response. At the same time, surgical resection must be systematically discussed in the case of resectable hepatic metastases since the presence of a BRAF^V600E mutation is not a risk factor for recurrence and that prolonged survival may be observed after surgery. In the second or third line, the triplet encorafenib, binimetinib and cetuximab, as well as the doublet encorafenib and cetuximab are superior to the association of irinotecan plus cetuximab in terms of response and survival (phase III study BEACON) and represent a new therapeutic standard. Their use on the front line is under study.

Guideline-recommended incorporation of biomarker testing results in metastatic colorectal cancer therapy

Aim: To describe pharmacogenomic tumor testing among patients with metastatic colorectal cancer. Methods: This was a retrospective study of patients with metastatic colorectal cancer diagnosed between 1 January 2014 and 30 June 2018. Patients were assessed for pharmacogenomic testing and appropriateness of chemotherapy use. Results: Overall, 112/167 (67.1%) patients had at least one of the three recommended pharmacogenomic tests and 41/167 (24.6%) had all tests. Twenty-four patients were treated with cetuximab with 8/167 (4.7%) identified as being treated with a RAS variant (n = 3) or incomplete testing (n = 5); thus, not in accordance with guidelines. Conclusion: Uptake of testing was variable but increased over time; however, a small proportion of patients received cetuximab with a variant or not all recommended tests being performed.

Withholding the Introduction of Anti-Epidermal Growth Factor Receptor: Impact on Outcomes in RAS Wild-Type Metastatic Colorectal Tumors: A Multicenter AGEO Study (the WAIT or ACT Study)

BACKGROUND

Patients with RAS wild-type (WT) nonresectable metastatic colorectal cancer (mCRC) may receive either bevacizumab or an anti-epidermal growth factor receptor (EGFR) combined with first-line, 5-fluorouracil-based chemotherapy. Without the RAS status information, the oncologist can either start chemotherapy with bevacizumab or wait for the introduction of the anti-EGFR. Our objective was to compare both strategies in a routine practice setting.

MATERIALS AND METHODS

This multicenter, retrospective, propensity score-weighted study included patients with a RAS WT nonresectable mCRC, treated between 2013 and 2016 by a 5-FU-based chemotherapy, with either delayed anti-EGFR or immediate anti-vascular endothelial growth factor (VEGF). Primary criterion was overall survival (OS). Secondary criteria were progression-free survival (PFS) and objective response rate (ORR).

RESULTS

A total of 262 patients (129 in the anti-VEGF group and 133 in the anti-EGFR group) were included. Patients receiving an anti-VEGF were more often men (68% vs. 56%), with more metastatic sites (>2 sites: 15% vs. 9%). The median delay to obtain the RAS status was 19 days (interquartile range: 13-26). Median OS was not significantly different in the two groups (29 vs. 30.5 months, p = .299), even after weighting on the propensity score (hazard ratio [HR] = 0.86, 95% confidence interval [CI], 0.69-1.08, p = .2024). The delayed introduction of anti-EGFR was associated with better median PFS (13.8 vs. 11.0 months, p = .0244), even after weighting on the propensity score (HR = 0.74, 95% CI, 0.61-0.90, p = .0024). ORR was significantly higher in the anti-EGFR group (66.7% vs. 45.6%, p = .0007).

CONCLUSION

Delayed introduction of anti-EGFR had no deleterious effect on OS, PFS, and ORR, compared with doublet chemotherapy with anti-VEGF.

IMPLICATIONS FOR PRACTICE

For RAS/RAF wild-type metastatic colorectal cancer, patients may receive 5-fluorouracil-based chemotherapy plus either bevacizumab or an anti-epidermal growth factor receptor (EGFR). In daily practice, the time to obtain the RAS status might be long enough to consider two options: to start the chemotherapy with bevacizumab, or to start without a targeted therapy and to add the anti-EGFR at reception of the RAS status. This study found no deleterious effect of the delayed introduction of an anti-EGFR on survival, compared with the introduction of an anti-vascular endothelial growth factor from cycle 1. It is possible to wait one or two cycles to introduce the anti-EGFR while waiting for RAS status.

Are there variations in adherence to colorectal cancer clinical guidelines depending on treatment place and recommendation novelty? The French EvaCCoR observational study

BACKGROUND

Studies have shown clinical practices variation between centers in colorectal cancer (CRC) management. After the implementation of national cancer plans, we tested for differences in center and patients' socioeconomic position (SEP)-related variation in CRC guidelines.

METHODS

All patients aged 18 years and over, cared for a first CRC in 2010 in Southwest of France. We used mixed effect model to test for center-related heterogeneity (CRH) in recommendation, from the oldest to the more recent: (1) at least 12 lymph nodes analysed for stage II, (2) the prescription of adjuvant chemotherapy stage III and (3) the assessment of CRC molecular phenotype regarding KRAS status for stage IV. Patients' SEP was approached by an ecological social deprivation index.

RESULTS

We found: higher adherence for the oldest than for the most recent recommendations; no CRH in recommendation No. 2 but lower adherence in academic centers; a CRH for recommendations No. 1 and 3; no SEP-related differences in clinical practices.

CONCLUSION

Results showed that older recommendations have higher adherence but did not support increasing influence of centers characteristics and CRH as recommendations are more recent.

Tumor mutational burden in non-small cell lung cancer-the pathologist's point of view

In non-small cell lung cancer (NSCLC), the pathologist has contributed to the development of personalized medicine from the determination of the right histological type to EGFR and ALK/ROS1 molecular screening for targeted therapies. With the development of immunotherapies, pathologists intervene forefront with programmed death-ligand 1 (PD-L1) immunohistochemical testing, companion test for pembrolizumab monotherapy, first line and complementary test to the other programmed cell death-1 (PD-1) PD-L1 inhibitors. Recently, tumor mutational burden has emerged as a promising tool to evaluate sensitivity to immunotherapy (IO). The pathologist has a crucial role in the setting of tumor mutational burden (TMB) testing for the selection and the preparation of the sample for high throughput molecular analysis, and in the first steps of the next-generation sequencing (NGS) workflow.

Role of circulating tumor DNA in the management of patients with colorectal cancer

Colorectal cancer is a major health burden with a prognosis that has been improved with the progresses in diagnosis and the advance of chemotherapy and personalized medicine. However, because of intra-tumor heterogeneity, clonal evolution and selection, tumors often develop resistance to treatments. "Liquid biopsy" is a minimally invasive method, based on analysis of tumor-specific material in peripheral blood samples of patients. Analysis of tumor specific genetic or epigenetic alterations in cell-free circulating nucleic acids may reflect the molecular heterogeneity of the underlying disease process and serial testing could allow to monitor its temporal genomic changing without using re-biopsy. In this review, we focused on the role of circulating tumor DNA (ctDNA) as a biomarker in the management of patients with colorectal cancer at early and advanced stages. Through recent studies, we described its promising clinical applications for diagnosis, detection of recurrence after surgery and monitoring for tumor response or therapeutic resistance in metastatic setting. Such recent developments offer new perspectives for personalized medicine in colorectal cancer but still needs some standardized detection methods and further studies to validate its use in clinical routine.

In silico-guided sequence modifications of K-ras epitopes improve immunological outcome against G12V and G13D mutant KRAS antigens

Background

Somatic point substitution mutations in the KRAS proto-oncogene primarily affect codons 12/13 where glycine is converted into other amino acids, and are highly prevalent in pancreatic, colorectal, and non-small cell lung cancers. These cohorts are non-responsive to anti-EGFR treatments, and are left with non-specific chemotherapy regimens as their sole treatment options. In the past, the development of peptide vaccines for cancer treatment was reported to have poor AT properties when inducing immune responses. Utilization of bioinformatics tools have since become an interesting approach in improving the design of peptide vaccines based on T- and B-cell epitope predictions.

Methods

In this study, the region spanning exon 2 from the 4th to 18th codon within the peptide sequence of wtKRAS was chosen for sequence manipulation. Mutated G12V and G13D K-ras controls were generated in silico, along with additional single amino acid substitutions flanking the original codon 12/13 mutations. IEDB was used for assessing human and mouse MHC class I/II epitope predictions, as well as linear B-cell epitopes predictions, while RNA secondary structure prediction was performed via CENTROIDFOLD. A scoring and ranking system was established in order to shortlist top mimotopes whereby normalized and reducing weighted scores were assigned to peptide sequences based on seven immunological parameters. Among the top 20 ranked peptide sequences, peptides of three mimotopes were synthesized and subjected to in vitro and in vivo immunoassays. Mice PBMCs were treated in vitro and subjected to cytokine assessment using CBA assay. Thereafter, mice were immunized and sera were subjected to IgG-based ELISA.

Results

In silico immunogenicity prediction using IEDB tools shortlisted one G12V mimotope (68-V) and two G13D mimotopes (164-D, 224-D) from a total of 1,680 candidates. Shortlisted mimotopes were predicted to promote high MHC-II and -I affinities with optimized B-cell epitopes. CBA assay indicated that: 224-D induced secretions of IL-4, IL-5, IL-10, IL-12p70, and IL-21; 164-D triggered IL-10 and TNF-α; while 68-V showed no immunological responses. Specific-IgG sera titers against mutated K-ras antigens from 164-D immunized Balb/c mice were also elevated post first and second boosters compared to wild-type and G12/G13 controls.

Discussion

In silico-guided predictions of mutated K-ras T- and B-cell epitopes were successful in identifying two immunogens with high predictive scores, Th-bias cytokine induction and IgG-specific stimulation. Developments of such immunogens are potentially useful for future immunotherapeutic and diagnostic applications against KRAS(+) malignancies, monoclonal antibody production, and various other research and development initiatives.

RAS mutation testing in patients with metastatic colorectal cancer in French clinical practice: A status report in 2014

BACKGROUND

RAS (NRAS + KRAS) mutation testing is required in addition to simple KRAS testing prior to initiating anti-epidermal-growth-factor-receptor (EGFR) antibodies (MAb) as in metastatic colorectal cancer (mCRC).

AIMS

To assess prescription and implementation rates of RAS/KRAS mutation testing. To describe the RAS/KRAS mutation test procedure and its impact on therapeutic strategy.

PATIENTS AND METHODS

Observational retrospective study conducted from June to September 2014 in all consecutive patients with newly diagnosed mCRC.

RESULTS

Data from 375 patients (male: 57.8%; mean age, 65.7 ± 11.7 years) were analysed. RAS/KRAS mutation testing was prescribed in 90.1% of patients (338/375). The test was prescribed within 1 month around mCRC diagnosis and prior to first-line therapy in 73.1% (242/331) and 85.4% (280/328) of patients, respectively. Time from test request to receipt of results was 24.6 ± 17.2 days. 59.7% of patients (190/318) had a mutation, mainly KRAS (47.9%; 152/317). Anti-EGFR MAb was prescribed in 90.9% of RAS-wild-type cases (60/66), consistent with the goal of genotyping-testing in this population.

CONCLUSION

In 2014, RAS genotyping-testing in addition to KRAS testing was routinely prescribed and performed in mCRC patients in France. Time to receive results remains long and must be reduced so as to match clinical practice.

Analysis of factors influencing molecular testing at diagnostic of colorectal cancer

BACKGROUND

The aim of the study was to evaluate the current rate of molecular testing prescription (KRAS codons 12/13, BRAF and microsatellite instability (MSI)) in newly diagnosed colorectal cancer (CRC) patients and to determine which factors influence testing.

METHODS

All incident CRC cases in 2010 were identified in the Poitou-Charentes General Cancer Registry. The exhaustive molecular testing performed was accessed in the French molecular genetics platform. Factors influencing prescription were analyzed using logistic regression.

RESULTS

Among the 1269 CRCs included in the study, KRAS, BRAF and MSI testing accounted for 35.1%, 10.5% and 10.9%, respectively. KRAS testing was carried out in 65.5% of metastatic CRCs, and 26.1% of non-metastatic CRCs. Among metastatic CRCs, age (<60 years), site of primary tumour (left colon) and geographical area of treatment were factors related to KRAS testing. BRAF testing was contemporary to KRAS testing for 92.5% of patients. Factors related to MSI testing were age (<60 years), TNM stage (stage IV) and geographical area of treatment. Among CRC patients under 60 years old, only 37.5% had MSI testing.

CONCLUSION

These results underscore the need to reduce disparities in CRC molecular testing and highlight the limited application of the French guidelines, especially concerning MSI testing.

Survival Outcomes in Patients With RAS Wild Type Metastatic Colorectal Cancer Classified According to Köhne Prognostic Category and BRAF Mutation Status

BACKGROUND

Köhne prognostic score is used to classify patients with metastatic colorectal cancer (mCRC) as high, intermediate, or low risk. Using data from 2 phase III trials, we analyzed survival in patients categorized according to Köhne prognostic category and virus-induced rapidly accelerated fibrosarcoma murine sarcoma viral oncogene homolog B (BRAF) mutation.

PATIENTS AND METHODS

PRIME (Panitumumab Randomized Trial In Combination With Chemotherapy for Metastatic Colorectal Cancer to Determine Efficacy) (first-line) and 20050181 (second-line) were studies of chemotherapy with or without panitumumab. Progression-free survival (PFS) and overall survival (OS) were analyzed retrospectively in rat sarcoma viral oncogene homolog (RAS) wild type (WT) and RAS WT+BRAF WT mCRC in each Köhne category, and in BRAF mutant (MT) mCRC.

RESULTS

In PRIME (n = 495) and 20050181 (n = 420), 53 (11%) and 44 (10%) patients, respectively, had BRAF MT mCRC. Of the RAS WT+BRAF WT/unknown populations, 85/267/90 and 82/211/83 were categorized as high/medium/low risk, respectively. PFS and OS hazard ratios (HRs), adjusted for Köhne group, for patients with RAS WT + BRAF WT/unknown mCRC favored panitumumab with chemotherapy versus chemotherapy alone in both studies. In PRIME, the PFS HR was 0.74 (95% confidence interval [CI], 0.61-0.90) and OS HR was 0.78 (95% CI, 0.64-0.95). In 20050181, PFS and OS HRs were 0.80 (95% CI, 0.65-0.99) and 0.78 (95% CI, 0.62-0.99), respectively. Median PFS and OS were lower in patients with BRAF MT mCRC than in any of the 3 risk categories for patients with RAS WT+BRAF WT/unknown mCRC.

CONCLUSION

During first- and second-line treatment, Köhne prognostic score allows accurate risk classification in RAS WT mCRC. BRAF MT mCRC should be classified as high risk regardless of other parameters. Panitumumab with chemotherapy might provide survival benefits versus chemotherapy alone in RAS WT and RAS WT+BRAF WT/unknown mCRC, overall and across risk categories.

RAS testing in metastatic colorectal cancer: advances in Europe

Personalized medicine shows promise for maximizing efficacy and minimizing toxicity of anti-cancer treatment. KRAS exon 2 mutations are predictive of resistance to epidermal growth factor receptor-directed monoclonal antibodies in patients with metastatic colorectal cancer. Recent studies have shown that broader RAS testing (KRAS and NRAS) is needed to select patients for treatment. While Sanger sequencing is still used, approaches based on various methodologies are available. Few CE-approved kits, however, detect the full spectrum of RAS mutations. More recently, "next-generation" sequencing has been developed for research use, including parallel semiconductor sequencing and reversible termination. These techniques have high technical sensitivities for detecting mutations, although the ideal threshold is currently unknown. Finally, liquid biopsy has the potential to become an additional tool to assess tumor-derived DNA. For accurate and timely RAS testing, appropriate sampling and prompt delivery of material is critical. Processes to ensure efficient turnaround from sample request to RAS evaluation must be implemented so that patients receive the most appropriate treatment. Given the variety of methodologies, external quality assurance programs are important to ensure a high standard of RAS testing. Here, we review technical and practical aspects of RAS testing for pathologists working with metastatic colorectal cancer tumor samples. The extension of markers from KRAS to RAS testing is the new paradigm for biomarker testing in colorectal cancer.

[What future for circulating tumor DNA? Current data and prospects in colorectal, non-small cell lung and pancreatic cancers]

Ten years after the discovery of the predictive value of KRAS status for anti-EGFR antibodies, other genes involved in oncogenesis and therapeutic responses were identified and are now systematically sought. Molecular diagnosis often requires invasive procedures, sometimes iatrogenic, and is limited by feasibility problems, quantity and quality of samples. Identifying these mutations from blood biomarkers would reduce costs and diagnostic delay. The circulating tumor DNA (ctDNA) is one of the most promising blood biomarkers. In this review, we report and discuss the latest results obtained with ctDNA in colorectal cancer, non-small cell lung cancer, and adenocarcinoma of the pancreas. If the methods highlighting appear very heterogeneous, the correlation between mutations found in tumor and those identified in the blood exceeds 95 % specificity in numerous studies. The detection sensitivity is in turn strongly related to tumor stage patients. The presence of ctDNA appears as a prognostic factor for progression-free survival and overall survival. Finally, recent studies have shown that the changing rate ctDNA during systemic treatments had a predictive value for therapeutic efficacy. These results allow to consider the use of ctDNA in monitoring patients to identify early recurrence or progression.

KRAS testing of patients with metastatic colorectal cancer in a community-based oncology setting: a retrospective database analysis

BACKGROUND

In 2009, treatment guidelines were updated to recommend KRAS testing at diagnosis for patients with metastatic colorectal cancer (mCRC). We investigated KRAS testing rates over time and compared characteristics of KRAS-tested and not-tested patients in a community-based oncology setting.

METHODS

Adult patients with a diagnosis of mCRC from 2008-2011 were selected from the ACORN Data Warehouse (ACORN Research LLC, Memphis, TN). Text mining of physician progress notes and full chart reviews identified KRAS-tested patients, test dates, and test results (KRAS status). The overall proportion of eligible patients KRAS-tested in each calendar year was calculated. Among KRAS-tested patients, the proportion tested at diagnosis (within 60 days) was calculated by year. Univariate and multivariate analyses were used to compare patient characteristics at diagnosis between tested and not-tested cohorts, and to identify factors associated with KRAS testing.

RESULTS

Among 1,363 mCRC patients seen from 2008-2011, 648 (47.5%) were KRAS-tested. Among newly diagnosed mCRC patients, the rate of KRAS testing increased from 5.9% prior to 2008, to 13.9% in 2008, and then jumped dramatically to 32.3% in 2009, after which a modest yearly increase continued. The proportions of KRAS-tested patients who had been diagnosed in previous years but not tested previously increased from 17.7% in 2008 to 27.0% in 2009, then decreased to 19.0% in 2010 and 17.6% in 2011. Among patients who were KRAS-tested, the proportions tested at the time of diagnosis increased annually (to 78.4% in 2011). Patients more likely to have been tested included those with lung metastases, poor performance status, more comorbidities, and mCRC diagnosis in 2009 or later.

CONCLUSIONS

The frequency of KRAS testing increased over time, corresponding to changes in treatment guidelines and epidermal growth factor receptor inhibitor product labels; however, approximately 50% of eligible patients were untested during the study period.

Metastatic colorectal cancer treatment patterns according to kirsten rat sarcoma viral oncogene homolog genotype in U.S. Community-based oncology practices

INTRODUCTION

In 2008, the National Comprehensive Cancer Network guidelines were revised in light of the identification of the Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) gene as a biomarker of nonresponse to epidermal growth factor receptor inhibitors. This study sought to describe and compare real-world treatment patterns of metastatic colorectal cancer (mCRC) according to KRAS genotype in community-based oncology practices in the United States.

MATERIALS AND METHODS

Data from the ACORN (ACORN LLC, Memphis, TN) electronic medical record data warehouse, containing data of approximately 180,000 patients from 12 oncology practices across the United States were used. Records of adult patients with mCRC who had undergone KRAS testing between January 2008 and December 2011 were evaluated. Patient demographic characteristics, KRAS genotype, and treatment patterns were identified and compared.

RESULTS

Six hundred forty-eight mCRC patients who were tested for KRAS were identified. Of these, 48.1% had wild type (WT), 42.3% mutant, and 9.6% unknown genotypes. Most patients (72.1%) were tested in 2009 or later, after the guideline revision. Bevacizumab-containing combinations were the most common first-line regimens in KRAS mutant and WT patients. Approximately 90% of patients received at least 1 line of therapy, however, WT patients received significantly more lines of therapy than KRAS mutant patients (2.6 ± 1.5 vs. 2.1 ± 1.2; P < .001).

CONCLUSIONS

KRAS WT and mutant genotypes had similar first-line regimens; however, WT patients received more lines of therapy. Although there does not appear to be a lag between changes in guidelines and treatment practice, professional and government organizations must keep up with the changing science and disseminate this information to oncologists in a timely manner.

KRAS early testing: consensus initiative and cost-effectiveness evaluation for metastatic colorectal patients in an Italian setting

KRAS testing is relevant for the choice of the most appropriate first-line therapy of metastatic colorectal cancer (CRC). Strategies for preventing unequal access to the test should be implemented, but their relevance in the practice is related to economic sustainability. The study adopted the Delphi technique to reach a consensus on several topics. Issues related to execution of KRAS testing were identified by an expert’s board and proposed to 108 Italian oncologists and pathologists through two subsequent questionnaires. The emerging proposal was evaluated by decision analyses models employed by technology assessment agencies in order to assess cost-effectiveness. Alternative therapeutic strategies included most commonly used chemotherapy regimens alone or in combination with cetuximab or bevacizumab. The survey indicated that time interval for obtaining KRAS test should not exceed 15 days, 10 days being an optimal interval. To assure the access to proper treatment, a useful strategy should be to anticipate the test after radical resection in patients at high risk of relapse. Early KRAS testing in high risk CRC patients generates incremental cost-effectiveness ratios between 6,000 and 13,000 Euro per quality adjusted life year (QALY) gained. In extensive sensitivity analyses ICER’s were always below 15,000 Euro per QALY gained, far within the threshold of 60,000 Euro/QALY gained accepted by regulatory institutions in Italy. In metastatic CRC a time interval higher than 15 days for result of KRAS testing limits access to therapeutic choices. Anticipating KRAS testing before the onset of metastatic disease in patients at high risk does not affect the sustainability and cost-effectiveness profile of cetuximab in first-line mCRC. Early KRAS testing may prevent this inequality in high-risk patients, whether they develop metastases, and is a cost-effective strategy. Based on these results, present joined recommendations of Italian societies of Oncology and Pathology should be updated including early KRAS testing.