metastasized cancers (Cetuximab, Panitumumab). In order to predict response to EGFR-targeted treatment, EGFR expression within tumors was detected using ...
EGFR and K-RAS testing: Central Lab? Local lab? Availability in Europe Daniela E. Aust and Gustavo B. Baretton Institute for Pathology, University Hospital Carl Gustav Carus at the TU Dresden The epidermal growth factor receptor (EGFR) is a membrane bound protein which transducts growth signals coming from outside the cell into the cytoplasm and finally the nucleus. Several signaling cascades receive signals from EGFR, one of them is the RAS-RAF-MAPKinase pathway, through which cell survival (antiapoptosis), angiogenesis, invasiveness and metastasis formation can be modulated. Several antibodies abrogating EGFR-signaling are being used in the treatment of metastasized cancers (Cetuximab, Panitumumab). In order to predict response to EGFR-targeted treatment, EGFR expression within tumors was detected using immunohistochemistry. However, EGFR expression – at least when detected with currently available antibodies – could not predict response to anti-EGFR treatment. Instead, KRAS mutational status turned out to predict non-response for almost all patients with KRAS mutations. Since KRAS mutations constitutively activate the downstream signaling, upstream anti-EGFR proved to be ineffective. There is a hot spot for KRAS mutations in codon 12 and 13 of the second exon. Therefore, mutational analyses are fairly easy to conduct because only a short segment of the gene needs to be analysed. This can be done in formalin-fixed, paraffin-embedded tumor samples. The samples should be enriched for tumor cells by macro- or microdissection, DNA can then be extracted and analysed using either Sanger sequencing, allele specific PCR or pyrosequencing. All three methods will be explained and illustrated with examples. An estimate of cost and working hours for all three methods will be given. As of now, there is no “gold standard” of KRAS mutational analysis. All methods can be used, but quality controls including interlaboratory tests should be conducted to ensure high quality of the methology and correct results of the mutational analyses. The experience of the German Panitumumab Advisory Board will be discussed to illustrate the use of interlaboratory tests. The KRAS mutational analyses can be conducted using the primary tumor, there is no need for a pretreatment biopsy of the metastasis since there is almost complete agreement regarding the KRAS status of primary tumor and metastasis. Data will be shown to prove that. The experience of the German Panitumumab Advisory Board will be discussed. References Editorials and Reviews about targeted therapy Wong R, Cunningham D. Using predictive biomarkers to select patients with advanced colorectal cancer for treatment with epidermal growth factor receptor antibodies. J Clin Oncol 2008; 26:5668-70 This is a JCO editorial giving a good overview of the predictive value of KRAS and possible other markers influencing the response to anti-EGFR-treatment. Hamilton, S. R. Targeted therapy of cancer: new roles for pathologists in colorectal cancer. Mod Pathol; 21 Suppl2: S23-30 This is a lecture held at the USCAP meeting giving a very good overview of different predictive markers and the future role of the pathologist in “guiding” the therapy. Predictive value of KRAS in anti-EGFR treated patients
The following manuscripts present the results of important clinical trials or review the predictive value of KRAS. 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; 26:1626-34 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; 19:508-15 Di Fiore F, Blanchard F, Charbonnier F, et al. Clinical relevance of KRAS mutation detection in metastatic colorectal cancer treated by Cetuximab plus chemotherapy. Br J Cancer 2007; 96:1166-9 Lievre 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; 26:374-9 Lievre A, Bachet JB, Le Corre D, et al. KRAS mutation status is predictive of response to cetuximab therapy in colorectal cancer. Cancer Res 2006; 66:3992-5 Milano G, Etienne-Grimaldi MC, Dahan L, et al. Epidermal growth factor receptor (EGFR) status and K-Ras mutations in colorectal cancer. Ann Oncol 2008 Intratumoral heterogeneity of KRAS mutational status All the following articles deal with intratumoral heterogeneity and agreement of KRAS status between primary tumor and metastases. Please note, that the newer studies show a complete homogeneity between primary tumor and metastases while older studies report some heterogeneity both within the primary tumor and tumor vs metastasis. Albanese I, Scibetta AG, Migliavacca M, et al. Heterogeneity within and between primary colorectal carcinomas and matched metastases as revealed by analysis of Ki-ras and p53 mutations. Biochem Biophys Res Commun 2004; 325:784-91 Al-Mulla F, Going JJ, Sowden ET, Winter A, Pickford IR, Birnie GD. Heterogeneity of mutant versus wild-type Ki-ras in primary and metastatic colorectal carcinomas, and association of codon-12 valine with early mortality. J Pathol 1998; 185:130-8 Etienne-Grimaldi MC, Formento JL, Francoual M, et al. K-Ras mutations and treatment outcome in colorectal cancer patients receiving exclusive fluoropyrimidine therapy. Clin Cancer Res 2008; 14:4830-5 Giaretti W, Monaco R, Pujic N, Rapallo A, Nigro S, Geido E. Intratumor heterogeneity of K-ras2 mutations in colorectal adenocarcinomas: association with degree of DNA aneuploidy. Am J Pathol 1996; 149:237-45 Losi L, Baisse B, Bouzourene H, Benhattar J. Evolution of intratumoral genetic heterogeneity during colorectal cancer progression. Carcinogenesis 2005; 26:916-22 EGFR analyses The following papers deal with the assessment of EGFR expression / alterations. Milano G, Etienne-Grimaldi MC, Dahan L, et al. Epidermal growth factor receptor (EGFR) status and K-Ras mutations in colorectal cancer. Ann Oncol 2008; Personeni N, Fieuws S, Piessevaux H, et al. Clinical usefulness of EGFR gene copy number as a predictive marker in colorectal cancer patients treated with cetuximab: a fluorescent in situ hybridization study. Clin Cancer Res 2008; 14:5869-76
