Correspondence
K-ras Mutations and Cetuximab in Colorectal Cancer
N Engl J Med 2009; 360:833-836February 19, 2009
- Article
To the Editor:
Karapetis et al. (Oct. 23 issue)1 investigated K-ras mutations by means of direct sequencing of polymerase-chain-reaction (PCR) products. The detection of low-prevalence mutations by means of direct sequencing is problematic.2 Very sensitive techniques, including the Amplification Refractory Mutation System (ARMS) with the Scorpions real-time PCR technique (DxS) and mutation-enriched sequencing,3 are now available. We have compared direct sequencing with mutation-enriched sequencing in 90 colorectal carcinomas. The prevalence of tumors harboring K-ras mutations was 40% by means of direct sequencing and 55% by means of mutation-enriched sequencing. Thus, we found mutations in minor clones in about 15% of colorectal cancers.
3 ReferencesAntonio Marchetti, M.D.
University Foundation, 66013 Chieti, Italy
amarchetti@unich.it Giampietro Gasparini, M.D.
San Filippo Neri Hospital, 00135 Rome, Italy1
Karapetis CS ,Khambata-Ford S ,Jonker DJ , et al. K-ras mutations and benefit from cetuximab in advanced colorectal cancer. N Engl J Med 2008;359:1757-1765
Full Text | Web of Science | Medline2
Vogelstein B ,Kinzler KW . Digital PCR. Proc Natl Acad Sci U S A 1999;96:9236-9241
CrossRef | Web of Science | Medline3
Gormally E ,Vineis P ,Matullo G , et al. TP53 and KRAS2 mutations in plasma DNA of healthy subjects and subsequent cancer occurrence: a prospective study. Cancer Res 2006;66:6871-6876
CrossRef | Web of Science | Medline
To the Editor:
Karapetis et al. analyzed K-ras mutations in codons 12 and 13 only and did not consider mutations in codon 61 or in the other dominant members of the ras gene family (H-ras and N-ras). The high degree of sequence homology among the three genes, along with the similar ability of mutated forms to transform cells, provides support for the concept that all ras proteins have a similar role in oncogenesis.1,2
We analyzed 572 paraffin-embedded colon-cancer samples for mutations in codons 12, 13, and 61 of the K-ras, N-ras, and H-ras genes, and we found that 11% of ras mutations would have been missed if only codons 12 and 13 of the K-ras gene had been analyzed. No mutations in the H-ras gene were detected. We recommend that testing for ras mutations in colorectal cancer include N-ras and K-ras genes encompassing codon 61 in addition to codons 12 and 13.
Maher Albitar, M.D.
Chenhsiung Yeh, Ph.D.
Wanlong Ma, M.S.
Quest Diagnostics Nichols Institute, San Juan Capistrano, CA 92690
maher.x. albitar@questdiagnostics. com Dr. Albitar, Dr. Yeh, and Ms. Ma report being employees of Quest Diagnostics Nichols Institute, a diagnostic company that offers testing for ras mutations. No other potential conflict of interest relevant to this letter was reported.
2 References1
Rodriguez-Viciana P ,Tetsu O ,Oda K ,Okada J ,Rauen K ,McCormick F . Cancer targets in the Ras pathway. Cold Spring Harb Symp Quant Biol 2005;70:461-467
CrossRef | Medline2
Umanoff H ,Edelmann W ,Pellicer A ,Kucherlapati R . The murine N-ras gene is not essential for growth and development. Proc Natl Acad Sci U S A 1995;92:1709-1713
CrossRef | Web of Science | Medline
To the Editor:
Karapetis et al. report that the benefit of cetuximab monotherapy in chemotherapy-refractory advanced colorectal cancer is limited to patients with wild-type K-ras tumors. However, only 13% of patients with wild-type K-ras status in their cetuximab-monotherapy group and 40% of patients with wild-type K-ras status in our series of patients who received cetuximab with irinotecan1 had a response to cetuximab. Therefore, it is possible that other, less frequent mutations constitutively activating the ras–erk pathway are present.
Among 79 colorectal cancers with wild-type K-ras status, Di Nicolantonio et al.2 found 11 B-type Raf kinase (BRAF) mutations (14%); none of the 11 tumors with these mutations had a response to cetuximab. In our series, BRAF mutations were found in 16 of 136 colorectal cancers with wild-type K-ras genes (12%); 15 of these tumors did not have a response to cetuximab, and the patients had relatively short median progression-free and overall survival (P<0.001). In addition, we found N-ras mutations in 5 of 108 tumors with wild-type K-ras status (5%); none of these tumors had a response to cetuximab. Since K-ras, BRAF, and N-ras mutations are mutually exclusive, these BRAF and N-ras mutations could explain the lack of a response in an additional 17% of patients with wild-type K-ras colorectal tumors who were treated with cetuximab.
Wendy De Roock, M.D.
University Hospital Gasthuisberg, 3000 Leuven, BelgiumDiether Lambrechts, Ph.D.
Flanders Interuniversity Institute for Biotechnology, 3000 Leuven, BelgiumSabine Tejpar, M.D., Ph.D.
University Hospital Gasthuisberg, 3000 Leuven, Belgium
sabine.tejpar@uzleuven. be Dr. Tejpar reports receiving research funding from Merck Serono; and Dr. De Roock, receiving grant support from the Institute for the Promotion of Innovation through Science and Technology in Flanders. No other potential conflict of interest relevant to this letter was reported.
2 References1
De Roock W ,Piessevaux H ,De Schutter J , et al. KRAS wild-type state predicts survival and is associated to early radiological response in metastatic colorectal cancer treated with cetuximab. Ann Oncol 2008;19:508-515
CrossRef | Web of Science | Medline2
Di Nicolantonio F ,Martini M ,Molinari F , et al. Wild-type BRAF is required for response to panitumumab or cetuximab in metastatic colorectal cancer. J Clin Oncol 2008;26:5705-5712
CrossRef | Web of Science | Medline
To the Editor:
The results of the study by Karapetis et al. raise the question of whether different K-ras mutations at codons 12 and 13 correlated with overall and progression-free survival among patients treated with best supportive care alone. Different K-ras mutations at codons 12 and 13 have been reported to be associated with decreased overall survival and tumor relapse1,2; these associations might be explained by the fact that guanosine triphosphatase (GTPase) activity of a mutation in K-ras codon 12 with substitution of valine for glycine (G12V) is one quarter that of aspartic acid for glycine (G12D) and one tenth that of wild-type ras. In addition, the affinity of the guanosine triphosphate analogue S′-guanylylimidodiphosphate for binding to G12D appears to be reduced by a factor of eight as compared with its affinity for binding to G12V or wild-type ras.3,4 Karapetis et al. could help to address this issue by providing survival curves according to the different mutations at codons 12 and 13.
4 ReferencesThomas Winder, M.D.
Academic Teaching Hospital Feldkirch, A-6800 Feldkirch, Austria
thomas.winder@lkhf. at Werner Scheithauer, M.D.
Medical University Vienna, 1090 Vienna, AustriaAlois Lang, M.D.
Academic Teaching Hospital Feldkirch, A-6800 Feldkirch, Austria1
Andreyev HJ ,Norman AR ,Cunningham D , et al. Kirsten ras mutations in patients with colorectal cancer: the `RASCAL II' study. Br J Cancer 2001;85:692-696
CrossRef | Web of Science | Medline2
Bazan V ,Migliavacca M ,Zanna I , et al. Specific codon 13 K-ras mutations are predictive of clinical outcome in colorectal cancer patients, whereas codon 12 K-ras mutations are associated with mucinous histotype. Ann Oncol 2002;13:1438-1446
CrossRef | Web of Science | Medline3
Al Mulla F ,Milner-White EJ ,Going JJ ,Birnie GD . Structural differences between valine-12 and aspartate-12 Ras proteins may modify carcinoma aggression. J Pathol 1999;187:433-438
CrossRef | Web of Science | Medline4
Al Mulla F ,MacKenzie EM . Differences in in vitro invasive capacity induced by differences in Ki-Ras protein mutations. J Pathol 2001;195:549-556
CrossRef | Web of Science | Medline
To the Editor:
Data concerning the concordance of the K-ras mutation status between primary and metastatic colorectal cancer are inconsistent.1,2 We investigated the K-ras mutation status in specimens from 106 patients who had metastatic colorectal cancer with at least two multifocal synchronous or metachronous metastases (a total of 268 specimens). We found an overall concordance of K-ras status between the primary and metastatic tumors. We also found K-ras–mutation mosaicism in one patient with heterogeneously differentiated colorectal cancer, which might explain the discordant results between primary colorectal cancers and metastases reported previously.2,3
3 ReferencesStefan Gattenlohner, M.D.
Christoph Germer, M.D.
Hans-Konrad Muller-Hermelink, M.D.
University of Würzburg, 97080 Würzburg, Germany
stefan.gattenloehner@mail. uni-wuerzburg. de 1
van Krieken JH ,Jung A ,Kirchner T , et al. KRAS mutation testing for predicting response to anti-EGFR therapy for colorectal carcinoma: proposal for a European quality assurance program. Virchows Arch 2008;453:417-431
CrossRef | Web of Science | Medline2
Artale S ,Sartore-Bianchi A ,Veronese SM , et al. Mutations of KRAS and BRAF in primary and matched metastatic sites of colorectal cancer. J Clin Oncol 2008;26:4217-4219
CrossRef | Web of Science | Medline3
Tortola S ,Steinert R ,Hantschick M , et al. Discordance between K-ras mutations in bone marrow micrometastases and the primary tumor in colorectal cancer. J Clin Oncol 2001;19:2837-2843
Web of Science | Medline
To the Editor:
The article by Karapetis et al. is an important step forward in the identification of patients who may benefit from targeted therapy. Can the authors comment on whether the 6-month difference between the median progression-free survival (which presumably corresponds to the median duration of treatment with cetuximab) and overall survival among patients with wild-type K-ras tumors can be attributed to a carryover effect?
Also, is there any relation between the cetuximab-induced rash associated with overall survival and the K-ras mutation status?
Giovanni Codacci-Pisanelli, M.D.
Gianpaolo Spinelli, M.D.
Silverio Tomao, M.D.
University La Sapienza, 00161 Rome, Italy
giovanni.codacci-pisanelli@uniroma1. it Author/Editor Response
The method that we used for detecting K-ras mutations by means of direct sequencing appears to be comparable to one of the techniques suggested by Marchetti and Gasparini. The frequency of K-ras mutations and the distribution of types of K-ras mutations that we observed were almost identical to those observed by Amado et al.,1 who used ARMS real-time PCR. Additional mutations within the ras family could be explored, as suggested by Albitar et al., and the role of mutations in BRAF and other downstream-pathway genes is being investigated, as recommended by De Roock et al. The effect of specific K-ras mutations on prognosis may differ, given their differential GTPase activity, as highlighted by Winder et al. All these suggestions merit further evaluation.
If, as Marchetti and Gasparini and Albitar et al. state, our method missed 11 to 15% of activating K-ras mutations, the differential benefit of wild-type K-ras might be underestimated, since these missed mutations would be included in our wild-type group. Given that the bias introduced by this possible misclassification is toward the null hypothesis, our statistically significant results remain robust.
Gattenlohner et al. report virtually complete concordance of K-ras status between the primary and metastatic tumor. This finding provides further support for the use of either primary or metastatic tissue for K-ras mutation analyses.
In response to Codacci-Pisanelli et al.: there was no possibility of a carryover effect of earlier therapy, since patients were randomly assigned according to previous treatment. There was an expected correlation between progression-free and overall survival, since delaying tumor growth was expected to lead to prolongation of survival. Although most patients had tumor progression by 6 months, the delay in this event did “carry over” to eventual postponement of death. In response to this observation and the comments by De Roock et al., tumor “response” may not be the optimal method of measuring the benefit associated with therapy directed against the epidermal growth factor receptor in colorectal cancer, since delays in tumor progression without tumor shrinkage can provide a benefit with respect to survival. In our study, there was an observed correlation between wild-type K-ras and rash, but further analysis is required.
1 ReferencesChristos Karapetis, M.D.
Flinders Medical Centre, Adelaide, SA 5042, Australia
c.karapetis@flinders. edu. au Chris O'Callaghan, Ph.D.
National Cancer Institute of Canada, Kingston, ON K7L 3N6, CanadaShirin Khambata-Ford, Ph.D.
Bristol-Myers Squibb Research and Development, Princeton, NJ 085431
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
CrossRef | Web of Science | Medline
- Citing Articles (7)
Citing Articles
1
Lihui Chow, Peng-Chan Lin, Jeffrey S. Chang, Pei-Yi Chu, Pao-Kung Lee, Shan-Na Chen, Ying-Min Cheng, Jenq-Chang Lee, Jang-Yang Chang, Tsang-Wu Liu. (2012) Differences in the frequencies of K-ras c12-13 genotypes by gender and pathologic phenotypes in colorectal tumors measured using the allele discrimination method. Environmental and Molecular Mutagenesis 53:1, 22-31
CrossRef2
Umberto Malapelle, Claudio Bellevicine, Pio Zeppa, Lucio Palombini, Giancarlo Troncone, Zubair Baloch. (2011) Cytology-based gene mutation tests to predict response to anti-epidermal growth factor receptor therapy: A review. Diagnostic Cytopathology 39:9, 703-710
CrossRef3
Huidan Zhang, Xiaonan Wang, Qian Ma, Zhe Zhou, Jin Fang. (2011) Rapid detection of low-abundance K-ras mutation in stools of colorectal cancer patients using chip-based temperature gradient capillary electrophoresis. Laboratory Investigation 91:5, 788-798
CrossRef4
Pietro Carotenuto, Cristin Roma, Anna Maria Rachiglio, Fabiana Tatangelo, Carmine Pinto, Fortunato Ciardiello, Oscar Nappi, Vincenzo Iaffaioli, Gerardo Botti, Nicola Normanno. (2010) Detection of KRAS mutations in colorectal carcinoma patients with an integrated PCR/sequencing and real-time PCR approach. Pharmacogenomics 11:8, 1169-1179
CrossRef5
C Cremolini, A Ruzzo, F Graziano, A Falcone, F Loupakis. (2010) Reply: KRAS status analysis and anti-EGFR therapies: is comprehensiveness a biologist's fancy or a clinical necessity?. British Journal of Cancer 102:6, 1076-1077
CrossRef6
Marwan M. Fakih. (2010) <i>KRAS</i> Mutation Screening in Colorectal Cancer: From Paper to Practice. Clinical Colorectal Cancer 9:1, 22-30
CrossRef7
Vicki Whitehall, Kayla Tran, Aarti Umapathy, Fabienne Grieu, Chelsee Hewitt, Tiffany-Jane Evans, Tuty Ismail, Wei Qi Li, Peter Collins, Paul Ravetto, Barbara Leggett, Manuel Salto-Tellez, Richie Soong, Stephen Fox, Rodney J. Scott, Alexander Dobrovic, Barry Iacopetta. (2009) A Multicenter Blinded Study to Evaluate KRAS Mutation Testing Methodologies in the Clinical Setting. The Journal of Molecular Diagnostics 11:6, 543-552
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