Effect of KRAS codon13 mutations in patients with advanced colorectal cancer (advanced CRC) under oxaliplatin containing chemotherapy. Results from a translational study of the AIO colorectal study group

  • Anke Reinacher-Schick1, 9, 10Email author,

    Affiliated with

    • Karsten Schulmann1,

      Affiliated with

      • Dominik P Modest2,

        Affiliated with

        • Nina Bruns1,

          Affiliated with

          • Ulrich Graeven3,

            Affiliated with

            • Malgorzata Jaworska4,

              Affiliated with

              • Richard Greil5,

                Affiliated with

                • Rainer Porschen6,

                  Affiliated with

                  • Dirk Arnold7,

                    Affiliated with

                    • Wolff Schmiegel1, 8, 9 and

                      Affiliated with

                      • Andrea Tannapfel4

                        Affiliated with

                        BMC Cancer201212:349

                        DOI: 10.1186/1471-2407-12-349

                        Received: 18 September 2011

                        Accepted: 26 June 2012

                        Published: 9 August 2012

                        Abstract

                        Background

                        To evaluate the value of KRAS codon 13 mutations in patients with advanced colorectal cancer (advanced CRC) treated with oxaliplatin and fluoropyrimidines.

                        Methods

                        Tumor specimens from 201 patients with advanced CRC from a randomized, phase III trial comparing oxaliplatin/5-FU vs. oxaliplatin/capecitabine were retrospectively analyzed for KRAS mutations. Mutation data were correlated to response data (Overall response rate, ORR), progression-free survival (PFS) and overall survival (OS).

                        Results

                        201 patients were analysed for KRAS mutation (61.2% males; mean age 64.2 ± 8.6 years). KRAS mutations were identified in 36.3% of tumors (28.8% in codon 12, 7.4% in codon 13). The ORR in codon 13 patients compared to codon 12 and wild type patients was significantly lower (p = 0.008). There was a tendency for a better overall survival in KRAS wild type patients compared to mutants (p = 0.085). PFS in all patients was not different in the three KRAS genetic groups (p = 0.72). However, we found a marked difference in PFS between patients with codon 12 and 13 mutant tumors treated with infusional 5-FU versus capecitabine based regimens.

                        Conclusions

                        Our data suggest that the type of KRAS mutation may be of clinical relevance under oxaliplatin combination chemotherapies without the addition of monoclonal antibodies in particular when overall response rates are important.

                        Trial registration number

                        2002-04-017

                        Keywords

                        Codon 13 mutation Colorectal cancer KRAS Oxaliplatin Prognosis

                        Background

                        The oncogene KRAS belongs to the protein family of small G-proteins and is mutated in 35-40% of colorectal cancers (CRC) [1]. RAS mutations are considered early events in colon carcinogenesis and are well conserved between primary tumor and corresponding metastases [2]. KRAS mutations tested routinely include six mutations in codon 12 and one mutation in codon 13.

                        KRAS has been studied extensively as a prognostic marker in CRC, but results are still conflicting. Overall, there seems a tendency towards inferior outcome for patients with KRAS mutant tumors even in large randomized trials [37]. Importantly, KRAS has recently been identified as a strong predictive marker for patients with advanced CRC under anti-EGFR-treatment. Various studies demonstrated that while patients with tumors expressing wild type KRAS may benefit from anti-EGFR (epidermal growth factor receptor)-antibody treatment, patients carrying a mutated KRAS gene do not [5, 810]. In contrast, two large trials using oxaliplatin-based chemotherapy-backbones did not confirm KRAS wild type to be a powerful predictor of treatment efficacy in metastatic CRC [4, 11]. However, the studies published until recently did not differentiate between the different KRAS mutations and other histopathological or molecular features of their patients. The clinical observation, that some patients with KRAS mutation may respond to anti-EGFR-antibody therapy, as well as experimental data, that the biological effects of KRAS mutations may differ, was addressed recently by de Roock and Tejpar [12, 13]. They reported that patients with codon 13 mutations in KRAS exhibit a worse overall prognosis with short overall survival times under standard chemotherapy, but may benefit from anti-EGFR-antibody therapy similar to wild type patients. These observations prompted us to look for the effect of the KRAS mutational status in correlation with response and survival data in patients with advanced colorectal cancer receiving oxaliplatin containing chemotherapy from a prospective randomized multicenter phase III trial of the German AIO study group.

                        Methods

                        Patients

                        All patients participated in a prospective randomized phase III first-line palliative chemotherapy trial of advanced CRC of the AIO colorectal study group (Arbeitsgemeinschaft Internistische Onkologie of the German Cancer Society). The study was performed according to the Helsinki declaration and it was approved by the ethics review board of the Central Hospital Bremen and of the Medical Faculty of the Ruhr-University Bochum. The study design, patient characteristics, treatment plans and results of the clinical trial have been reported previously [14]. Briefly, a total of 474 patients were randomized to be treated with either 5-FU/folinic acid (FA) and oxaliplatin (FUFOX: oxaliplatin, 50 mg/m2; FA, 500 mg/m2; continuous 5-FU, 2,000 mg/m2/22 h; on day 1, 8, 15, 22; q day 36) or capecitabine and oxaliplatin (CAPOX: oxaliplatin, 70 mg/m2 on day 1 and 8; capecitabine, 2 × 1,000 mg/m2/day consecutively for 2 weeks, q day 22). No clinical factor was found to be predictive for definition of a subgroup of patients benefiting more or less from each fluoropyrimidine backbone. We here present data on a subcohort of 201 patients (42.4%) with available formalin-fixed paraffin-embedded tissue. Samples were retrieved from pathologists responsible for first diagnosis, pseudononymized and forwarded to the Institute of Pathology of the Ruhr-University Bochum, which was blinded to treatment allocation and prognostic outcomes.

                        DNA extraction and mutation analysis

                        DNA was extracted from anonymized formalin-fixed paraffin embedded tissue samples. For each patient, five 10-μm sections were prepared. An additional representative 1-μm section was deparaffinized, stained with H&E, and analyzed for detailed morphology. Regions displaying tumor cellularity of >70% were marked and macrodissected. Tissue was extracted using QIAmp DNA Mini kit (Qiagen, Hilden, Germany). Real-Time PCR amplification for the most frequent seven KRAS mutations was performed using commercially available kits from DxS Ltd. (Manchester, UK) according to the manufacturer’s instructions. This kit detects >95% of known KRAS mutations. Laboratory staff was blinded to the patient data and clinical outcome. BRAF mutation analysis to detect the V600E substitution was performed by RT-PCR (see supplemental file for further details).

                        Statistical analysis

                        Chi-square test was used to evaluate the associations between KRAS status and other dichotomous variables. The analysis of progression-free survival (PFS) and overall survival (OS) was done using the Kaplan-Meier method and differences between subgroups were calculated by log-rank test. Data have been analyzed using SPSS 18.0 (Munich, Germany). All tests were two sided. For all tests, p values <0.05 were considered significant.

                        Results

                        Patient characteristics

                        The subcohort of patients successfully analyzed for KRAS mutations consisted of 201 patients (61.2% males with a mean age of 64.2 ± 8.6 years, range 35 – 82). Colon cancer was diagnosed in 131 (65.2%) patients while rectal cancer was diagnosed as primary tumor in 61 (30.3%) patients. Localization was not known for 9 cases (4.5%). 105 (52.2%) patients were treated with FUFOX, whereas 96 (47.7%) patients received CAPOX. 115 (57.2%) patients had synchronous metastases, whereas 59 (29.4%) had metachronous metastases. Whether metastases were synchronous or metachronous was not known for 27 ( 13.4%) patients (Table1). The subcohort reported here was representative of the complete study cohort with respect to age, gender, treatment plans (i.e. percentage of patients with FUFOX and CAPOX respectively). Median PFS and OS of the total ITT (intention-to-treat) population [14] and the biomarker subpopulation were fully comparable (PFS under FUFOX was 8.0 in the ITT cohort vs. 7.8 in the KRAS cohort; PFS under CAPOX was 7.1 vs. 7.0; OS under FUFOX was 18.8 in the ITT cohort vs. 17.5 in the KRAS subcohort and OS under CAPOX was 16.8 vs. 18.4).
                        Table 1

                        Baseline characteristics of the investigated subcohort

                        Biomarker population

                        N

                        %

                        Age

                          

                        Mean 64.15 years

                          

                        Range 35–82 years

                          

                        ≤60 y

                        58

                        28.9

                        >60 y

                        143

                        71.1

                        Sex

                          

                        Female

                        78

                        38.8

                        Male

                        123

                        61.2

                        Treatment arm

                          

                        FUFOX

                        105

                        52.2

                        CAPOX

                        96

                        47.8

                        Localization of primary tumor

                          

                        Colon

                        131

                        65.2

                        Rectum

                        61

                        30.3

                        n.k.

                        9

                        4,5

                        T stage at initial diagnosis

                          

                        T1

                        1

                        0.4

                        T2

                        15

                        7.5

                        T3

                        132

                        65.7

                        T4

                        49

                        24.4

                        n.k.

                        4

                        2.0

                        N stage at initial diagnosis

                          

                        N0

                        46

                        22.9

                        N1

                        57

                        28.3

                        N2

                        89

                        44.3

                        n.k.

                        9

                        4.5

                        M stage at initial diagnosis

                          

                        M0*

                        59

                        29.4

                        M1

                        115

                        57.2

                        n.k.

                        27

                        13.4

                        *M0 indicates metachronous metastatic disease at initial diagnosis of CRC, M1 indicates synchronous metastatic disease at initial diagnosis of CRC. n.k. = not known – there were no data available.

                        Mutation frequency

                        KRAS mutations could be successfully analyzed in 201 samples. We identified KRAS mutations in 73/201 (36.3%) tumors. 58 (28.9%) of KRAS mutations were located in codon 12, whereas 15 (7.46%) were found in codon 13(see Table2). The three most frequent KRAS alterations in our samples were c.35 G > A (G12D, n = 25; 12.4%), c.38 G > A (G13D, n = 15; 7.46%), and c.35 G > T (G12V, n = 13, 6.46%). In 128 patients no KRAS mutation was found (63.6%). In these patients we detected 13 mutations in the BRAF gene (V600E) (10% of wild type patients).
                        Table 2

                         KRAS  mutation frequency in the investigated subcohort (  KRAS  Wild type: 128 (63.7%),  KRAS  Mutation 73 (36.3%))

                           

                        relative frequency of occurrence (%)

                        absolute frequency of occurrence

                        CODON 12 mutation:

                           

                        Aspartate (G12D)

                        c.35G>A

                        12,4

                        25

                        Valine (G12V)

                        c.35G>T

                        6,5

                        13

                        Alanine (G12A)

                        c.35G>C

                        3,4

                        7

                        Cysteine (G12C)

                        c.34G>T

                        3

                        6

                        Serine (G12S)

                        c.34G>A

                        3

                        6

                        Arginine (G12R)

                        c.34G>C

                        0,5

                        1

                        CODON 13 mutation:

                           

                        Aspartate (G13D)

                        c.38G>A

                        7,5

                        15

                        Correlation between mutations and response rate

                        Tumor response evaluation was available for 201 patients. Grouping all KRAS mutations together, mutated tumors were associated with a significantly lower response rate (RR; defined as partial or complete remission by RECIST) as compared to tumors without KRAS mutations (44.4% vs. 63.0%, p = 0.012). When patients with codon 13 mutated tumors were analysed separately the overall response rate in this cohort was 23% as compared to 49% in codon 12 mutated tumors and 63% in wild type tumors (Table3, p = 0.008). Disease control rates (DCR) were 77%, 81% and 88%, respectively, which was not statistically significant (Table3, p = 0.29).
                        Table 3

                        Tumor response assessment and correlation to  KRAS  mutational status

                        All patients

                        All

                        WT

                        Codon 12 mutation

                        Codon 13 mutation

                        p-value

                        No. of patients%

                        201

                        128

                        58

                        15

                         

                        100

                        63.6

                        28.9

                        7.5

                        ORR%

                        55

                        63

                        49

                        23

                        0.008

                        95% CI

                        (49–61)

                        (54–71)

                        (37–62)

                        (8–51)

                        (Chi-Square)

                        DCR%

                        85

                        88

                        81

                        77

                        0.29

                        95% CI

                        (80–90)

                        (80–92)

                        (68–89)

                        (49–93)

                        (Chi-Square)

                        All patients. Percentages based on non-missing data, p-values for WT vs Codon 12 mutations vs codon 13 mutations; WT wild type; ORR overall response rate, DCR disease control rate.

                        Correlation between mutations and progression-free survival

                        During follow-up, 170 of 201 evaluable patients had progressed. The median PFS in all patients of the KRAS subcohort was not statistically different in relation to the KRAS mutational status (wild type: 7.5 months, mutation codon 12: 8.2 months, mutation codon 13: 10.0 months; p = 0.71) (Figure1). However, when analysing the two treatment arms separately, we found a substantial, non-significant, difference in PFS in codon 13 mutated tumors versus codon 12 mutated tumors. While median PFS was as low as 6.1 months for codon 13 patients receiving infusional 5-FU, median PFS was 13.3 months in patients treated with capecitabine (HR: 2.52, p = 0.22). Patients with codon 12 mutations showed a trend towards the opposite effect: median PFS was 7.0 months under CAPOX therapy while median PFS was 9.9 months under FUFOX (HR: 0.62, p = 0.12) (Table4).
                        http://static-content.springer.com/image/art%3A10.1186%2F1471-2407-12-349/MediaObjects/12885_2011_3261_Fig1_HTML.jpg
                        Figure 1

                        Progression-free survival according to  KRAS  status.

                        Table 4

                        PFS (progression free survival) according to  KRAS  mutation for the two different treatment arms

                        PFS

                        FUFOX

                        CAPOX

                        p-value (log rank)

                         

                        n = 105

                        n = 96

                        HR (95% CI)

                        All patients

                        8.2 months

                        6.4 months

                        0.18

                        0.81 (0.61-1.09)

                        WT

                        8.1months

                        6.4months

                        0.29

                           

                        0.82 (0.56-1.19)

                        Codon 12 mutation

                        9.9months

                        7.0months

                        0.12

                           

                        0.62 (0.33-1.14)

                        Codon 13 mutation

                        6.1months

                        13.3months

                        0.22

                           

                        2.52 (0.54-11.70)

                        PFS, HR hazard ratio by cox regression, CI confidence interval, WT wild type.

                        Correlation between mutations and overall survival

                        During follow-up 135 of 201 evaluated patients had died. We observed a trend towards a better survival time in patients with wild type tumors compared to those with a mutation of KRAS. The overall survival of wild type KRAS patients was 19.2 months, for patients with codon 12 mutations 15.6 months and for patients with codon 13 mutations 16.5 months. These differences were of marginal significance (p = 0.085) (Figure2).
                        http://static-content.springer.com/image/art%3A10.1186%2F1471-2407-12-349/MediaObjects/12885_2011_3261_Fig2_HTML.jpg
                        Figure 2

                        Overall survival according to KRAS status.

                        Evaluating the different treatment arms separately, we found comparable survival times without significant differences (Table5). Since the survival curves seemed to separate for wild type KRAS and mutant KRAS patients at 14 months we hypothesised that this difference was most likely caused by the influence of post-study treatment. 71 out of 128 (55.4%) wild type patients received further lines of therapy while 32 out of 128 wild type patients (25%) received cetuximab. Out of 73 patients with KRAS mutations 42 were treated in further lines (57.5%) with 10 patients receiving cetuximab (13.7%). When analysing post progression survival (PPS) in these patients receiving second and further line therapies, patients receiving cetuximab had a significant better overall survival when compared to those patients under irinotecan therapy only, irrespective of the KRAS status. PPS in KRAS wild type patients: 32.2 months when cetuximab was given and 18.8 months when cetuximab was not included (p < 0.001). PPS for KRAS mutant patients: 27.9 months under cetuximab and 16.9 months without cetuximab (p = 0.032).
                        Table 5

                        OS (overall survival) according to  KRAS  mutation for the two different treatment arms

                        OS

                        FUFOX

                        CAPOX

                        p-value (log rank)

                         

                        n = 105

                        n = 96

                        HR (95% CI)

                        WT

                        24.2months

                        18.9months

                        0.31

                           

                        0.79 (0.51-1.24)

                        Codon 12

                        15.6months

                        15.5months

                        0.54

                        mutation

                          

                        0.83 (0.45-1.53)

                        Codon 13

                        16.1months

                        16.5months

                        0.62

                        mutation

                          

                        1.39 (0.37-5.37)

                        OS, HR hazard ratio by cox regression, CI confidence interval.

                        Discussion and conclusions

                        We assessed the prognostic value of KRAS codon 12 and codon 13 mutations in tumor tissue from patients with advanced CRC recruited into a phase III clinical trial using CAPOX or FUFOX treatment regimens. This is the first randomized phase III trial retrospectively investigating the role of codon 13 mutations in advanced CRC patients treated with oxaliplatin combination chemotherapy only, without the addition of a monoclonal antibody. While the overall response rate in codon 13 patients was significantly lower, PFS was not different in the three KRAS mutational groups. Interestingly, we found a substantial difference in PFS between patients with codon 12 and 13 mutant tumors when looking at infusional 5-FU versus capecitabine based regimens. Patients with codon 13 mutations seem to benefit more in terms of PFS from the oral capecitabine based protocols. Moreover, there was a strong trend towards better overall survival in patients with wild type KRAS compared to all mutant KRAS patients. Lastly, when analysing OS in patients who received second and further line therapy we found that KRAS wild type and KRAS mutant patients alike showed a significantly higher OS post progression when treated with cetuximab.

                        A number of studies have looked at the potential prognostic or predictive value of KRAS mutations on response rates and survival in patients with CRC and several studies found a negative impact of KRAS mutations on prognosis [3, 7, 1517].

                        Recently, a number of randomized trials have included translational research programs to evaluate certain target genes and their role as prognostic or predictive markers in patients with metastatic disease. Thereby, the mutational status of KRAS has now been established as a strong predictive marker of resistance to anti-EGFR-antibody treatment [5, 8, 10], although some trials could not fully confirm these results [4, 11]. We still do not exactly know whether KRAS mutations influence the response to other treatment regimens such as standard chemotherapy or bevacizumab combinations. While bevacizumab efficacy seems independent from the KRAS status [18], the activity of certain chemotherapeutic agents may be influenced by KRAS mutations. There, patients seem to do worse under oxaliplatin combinations when carrying a mutant KRAS gene within their primary cancer [4, 5, 7, 16, 19, 20]. For example, in the recently reported COIN study patients under oxaliplatin/5-FU combinations showed a median PFS of 8.6 months in the wild type KRAS cohort while median PFS was only 6.9 months in the KRAS mutant cohort [4]. Similarily, ORR was lower in KRAS mutant patients receiving chemotherapy with oxaliplatin only (41% vs. 50%). Furthermore, another recent small study evaluated the KRAS status in 66 patients receiving a second line chemotherapy with oxaliplatin and infusional 5-FU refractory to 5-FU/irinotecan based chemotherapy [16]. This study found a significantly lower response rate (7% vs. 27%, p = 0.026) and significantly shorter median PFS (3.1 vs. 5.2 months, p = 0.007) for patients with mutant KRAS tumors compared to patients with wild type KRAS tumors under oxaliplatin containing therapy.

                        Very recently, experimental and some clinical reports suggested that not all KRAS mutations behave alike [12, 13, 21]. In fact, there is evidence that patients carrying mutations in codon 13 of the KRAS oncogene which is found in about 8% of patients with advanced CRC have a substantially worse overall prognosis but may, on the other hand, benefit from anti-EGFR-treatment.

                        In our study we found a similar rate of codon 13 mutations as described before. The overall response rate in patients with codon 13 mutations in our analysis was as low as 23%, significantly lower than in patients with wild type or codon 12 mutations. The CRYSTAL- and the OPUS-studies alike found low response rates in patients with codon 13 mutations treated with combination chemotherapy only (17% for irinotecan combinations and 33% for oxaliplatin combinations) [13]. In contrast to previous reports, ORR was substantially higher in this codon 13 mutant patient cohort when cetuximab was added.

                        Our study was conducted using combination chemotherapy with oxaliplatin in first line treatment without the addition of monoclonal antibodies. Interestingly, the PFS and OS in our codon 13 cohort compared to the other mutated groups and other previously published works was rather long with a PFS of 10 months and an OS of 16.5 months [13]. We do not know why PFS and OS of the codon 13 cohort in our study was prolonged when response rates were as low as 23%. Either low patient numbers or a yet unknown functional mechanism of codon 13 mutated KRAS proteins within colon cancers may be responsible for the observation.

                        The present analysis also suggests that there may be an interaction between the type of KRAS mutation and the mode of application of 5-FU, i.e. whether administered intravenously or orally as capecitabine. In particular, patients with codon 13 mutations showed longer median PFS intervals when receiving capecitabine compared to infusional 5-FU. Although the overall efficacy of infusional 5-FU and capecitabine in advanced CRC has been found to be comparable [22] there may be some patient subpopulations or treatment regimen where the mode of application of the fluoropyrimidine is more crucial. For example, anti-EGFR antibodies in wild type KRAS patients may only be active when infusional 5-FU regimens are used, but not when capecitabine based protocols are applied [4].

                        The potential resistance of KRAS mutated tumors to oxaliplatin containing regimens seems interesting and may reveal more general mechanisms of drug resistance in cancers. Oxaliplatin belongs to the platinum containing compounds like cisplatinum and carboplatinum. Metabolites of platinum compounds interact with DNA and form crosslinks. In addition, platinum-DNA-adducts strongly inhibit DNA polymerases and therefore act antineoplastic. Some authors have studied in cell culture systems and preclinical models the influence of oncogenic RAS mutations on the activity of platinum compounds and found that the nucleotide excision repair protein ERCC-1 may be upregulated through activated RAS. ERCC-1 may subsequently activate DNA repair capacity and thus mediate platinum resistance. A recent study evaluated the role of ERCC-1 mRNA levels in 191 patients treated with FOLFOX within the CONFIRM1 and CONFIRM2 studies. Low ERCC-1 gene expression was correlated with higher response rates to FOLFOX chemotherapy and better overall survival. In contrast patients with high ERCC-1 did not have benefit from FOLFOX chemotherapy [23]. Of note, we have examined the expression of ERCC-1 by immunohistochemistry in our cohort and found no obvious correlation with KRAS status, response rates or survival and ERCC-1 expression (data not shown). The analysis of the ERCC-1 expression levels by RT-PCR as reported by other studies has not been performed so far [24].

                        Median overall survival after first progression correlated with cetuximab-treatment in patients bearing KRAS wild type and mutant tumors alike. The role of codon 13 mutation in this setting appears minor since there were only two patients with a codon 13 mutated tumor in the cohort with KRAS mutations of whom we know about cetuximab application. However, there are at least two limitations to our analysis. First, numbers are low in particular in the cetuximab group and secondly addition of cetuximab was not randomized for. There seems to be a selection of patients with good performance status and good prognosis who received third line therapy compared to those who did not. Therefore, we can not draw definite conclusions from our analysis whether anti-EGFR antibodies are effective in patients with KRAS G13D mutations or not.

                        We presently can not draw final conclusions regarding patient management from this study. It remains unclear whether chemotherapy backbones with irinotecan are less prone to interactions with mutated KRAS because data regarding this issue are conflicting. Independent validation of the findings is essential. Therefore, the standardized, thorough and comprehensive collection of tissue and blood samples of all trial patients within independent cancer tissue banks should be a major goal of modern clinical cancer trials.

                        Misc

                        Anke Reinacher-Schick and Karsten Schulmann are contributed equally

                        Declarations

                        Acknowledgments

                        The authors wish to thank the AIO colorectal cancer study group for approval of the biomarker study, participating AIO study centers and their pathologists for providing tissue blocks, patients for providing written consent for biomarker studies, Petra Freitag for administrative regarding tissue acquisition and Sabine Geiger for DNA isolation. This work was funded by the Protein Research Unit Ruhr within Europe, PURE, from the Ministry of Science and Technology, Northrhine-Westfalia, Germany.

                        Authors’ Affiliations

                        (1)
                        Department of Internal Medicine, Knappschaftskrankenhaus, Ruhr-University Bochum
                        (2)
                        Department of Internal Medicine III, Klinikum der Universität
                        (3)
                        Department of Hematology, Oncology and Gastroenterology, Kliniken Maria Hilf
                        (4)
                        Institute of Pathology, Ruhr-University Bochum
                        (5)
                        3rd Medical Department with Hematology and Medical Oncology, Oncologic Centre Paracelsus Medical University
                        (6)
                        Klinikum Bremen-Ost
                        (7)
                        Hubertus Wald Cancer Center, University Hospital Hamburg
                        (8)
                        Department of Gastroenterology & Hepatology, Berufsgenossenschaftliches Klinikum Bergmannsheil, Ruhr-University Bochum
                        (9)
                        Center for Clinical Studies in Oncology within PURE, Ruhr-University Bochum
                        (10)
                        Medical Department, Knappschaftskrankenhaus, Ruhr-University Bochum

                        References

                        1. Bamford S, Dawson E, Forbes S, et al.: The COSMIC (Catalogue of Somatic Mutations in Cancer) database and website. Br J Cancer 2004,91(2):355–358.PubMed
                        2. Etienne-Grimaldi MC, Formento JL, Francoual M, et al.: KRAS mutations and treatment outcome in colorectal cancer patients receiving exclusive fluoropyrimidine therapy. Clin Cancer Res 2008,14(15):4830–4835.PubMedView Article
                        3. Andreyev HJ, Norman AR, Cunningham D, et al.: RAS mutations in patients with colorectal cancer: the multicenter "RASCAL" study. J Natl Cancer Inst 1998,90(9):675–684.PubMedView Article
                        4. Maughan TS, Adams RA, Smith CG, et al.: Addition of cetuximab to oxaliplatin-based first-line combination chemotherapy for treatment of advanced colorectal cancer: results of the randomised phase 3 MRC COIN trial. Lancet 2011,377(9783):2103–2114.PubMedView Article
                        5. Bokemeyer C, Bondarenko I, Makhson A, et al.: Fluorouracil, leucovorin, and oxaliplatin with and without cetuximab in the first-line treatment of metastatic colorectal cancer. J Clin Oncol 2009,27(5):663–671.PubMedView Article
                        6. Punt CJ, Tol J, Rodenburg CJ: Randomized phase III study of capecitabine, oxaliplatin, and bevacizumab with or without cetuximab in advanced colorectal cancer (ACC), the CAIRO2 study of the Dutch Colorectal Cancer Group (DCCG). J Clin Oncol 2008., 26: May 20 suppl; abstr BA401
                        7. Richman SD, Seymour MT, Chambers P, et al.: KRAS and BRAF Mutations in Advanced Colorectal Cancer Are Associated With Poor Prognosis but Do Not Preclude Benefit From Oxaliplatin or Irinotecan: Results From the MRC FOCUS Trial. JCO Dec 2009, 10:5931–5937.View Article
                        8. Amado RG, Wolf M, Peeters M, et al.: Wild type KRAS is required for panitumumab efficacy in patients with metastatic colorectal cancer. J Clin Oncol 2008, 26:1626–1634.PubMedView Article
                        9. Lièvre A, Bachet JB, Boige V, et al.: KRAS mutations as an independent prognostic factor in patients with advanced colorectal cancer treated with cetuximab. J Clin Oncol 2008,26(3):374–379.PubMedView Article
                        10. Van Cutsem E, Köhne CH, Hitre E, et al.: Cetuximab and chemotherapy as initial treatment for metastatic colorectal cancer. N Engl J Med 2009,360(14):1408–1417.PubMedView Article
                        11. Tveit K, Guren T, Glimelius B, et al.: Randomized phase III study of 5-fluorouracil/folinate/oxaliplatin given continuously or intermittently with or without cetuximab. as first-line treatment of metastatic colorectal cancer: The NORDIC VII Study (NCT00145314). 2010, ESMO:# LBA20.
                        12. De Roock W, Claes B, Bernascon D, et al.: Effects of KRAS, BRAF, NRAS, and PIK3CA mutations on the efficacy of cetuximab plus chemotherapy in chemotherapy-refractory metastatic colorectal cancer: a retrospective consortium analysis. Lancet Oncol 2011,12(6):594–603.PubMedView Article
                        13. Tejpar S, Bokemeyer C, Celik I, et al.: Influence of KRAS G13D mutations on outcome in patients with metastatic colorectal cancer (mCRC) treated with first-line chemotherapy with or without cetuximab. J Clin Oncol 2011., 29: suppl; abstr 3511
                        14. Porschen R, Arkenau HT, Kubicka S, et al.: AIO Colorectal Study Group. Phase III study of capecitabine plus oxaliplatin compared with fluorouracil and leucovorin plus oxaliplatin in metastatic colorectal cancer: a final report of the AIO Colorectal Study Group. J Clin Oncol 2007,25(27):4217–4223.PubMedView Article
                        15. Bazan V, Migliavacca M, Zanna I, et al.: Specific codon 13 KRAS mutations are predictive of clinical outcome in colorectal cancer patients, whereas codon 12 KRAS mutations are associated with mucinous histotype. Ann Oncol 2002,13(9):1438–1446.PubMedView Article
                        16. Zhang W, El-Khoueiry A, Yang D, et al.: KRAS mutation status associated with clinical outcome in metastatic colorectal cancer patients treated with 5-fluorouracil/oxaliplatin. 2009.
                        17. Moosmann N, Fischer von Weikersthal L, Vehling-Kaiser U, et al.: Cetuximab Plus Capecitabine and Irinotecan Compared With Cetuximab Plus Capecitabine and Oxaliplatin As First-Line Treatment for Patients With MetastaticColorectal Cancer: AIO KRK-0104—A Randomized Trial of the German AIO CRC Study Group. J Clin Oncol 2011, 29:1050–1058.PubMedView Article
                        18. Ince WL, Jubb AM, Holden SN, et al.: Association of KRAS, b-raf, and p53 status with the treatment effect of bevacizumab. J Natl Cancer Inst 2005,97(13):981–989.PubMedView Article
                        19. Ocvirk J, Brodowicz T, Wrba F, et al.: Cetuximab plus FOLFOX6 or FOLFIRI in metastatic colorectal cancer: CECOG trial. World J Gastroenterol 2010,16(25):3133–43.PubMedView Article
                        20. Reinacher-Schick A, Arnold D, Kubicka S, et al.: Impact of KRAS status on survival in patients (pts.) with metastatic colorectal cancer (MCRC) undergoing Bevacizumab (BEV) containing chemotherapy regimen – Analysis of the AIO Colorectal Cancer Study Group. Ann Oncol 2010.,21(8): abstr 584PD
                        21. Stinchcombe TE, Der CJ: Are all KRAS mutations created equal? Lancet Oncol 2011,12(8):717–718.PubMedView Article
                        22. Arkenau HT, Arnold D, Cassidy J, et al.: Efficacy of oxaliplatin plus capecitabine or infusional fluorouracil/leucovorin in patients with metastatic colorectal cancer: a pooled analysis of randomized trials. J Clin Oncol 2008,26(36):5910–5917.PubMedView Article
                        23. Lenz HJ, Zhang W, Shi MM, et al.: ERCC-1 gene expression levels and outcome to FOLFOX chemotherapy in patients enrolled in CONFIRM1 and CONFIRM2. J Clin Oncol 2008., 26: May 20 suppl; abstr 4131
                        24. Friboulet L, Barrios-Gonzales D, Commo F, et al.: Molecular Characteristics of ERCC1-Negative versus ERCC1-Positive Tumors in Resected NSCLC. Clin Cancer Res 2011,17(17):5562–5572.PubMedView Article
                        25. Pre-publication history

                          1. The pre-publication history for this paper can be accessed here:http://​www.​biomedcentral.​com/​1471-2407/​12/​349/​prepub

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                        © Reinacher-Schick et al.; licensee BioMed Central Ltd. 2012

                        This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://​creativecommons.​org/​licenses/​by/​2.​0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.