Ανίχνευση μεταλλάξεων του EGFR και KRAS σε ασθενείς με μη-μικροκυτταρικό καρκίνο του πνεύμονα και διερεύνηση της αξίας τους ως προβλεπτικών παραγόντων ανταπόκρισης στη θεραπεία

Abstract

The purpose of this study was to investigate whether the EGFR and KRASmutation status are predictive factors for Greeks patients with NSCLC. Initially, wecalculated the rate and the pattern of EGFR and KRAS mutations in 639 patients withNSCLC and then we correlated the mutations status with clinicopathologicalcharacteristics, the response to 1st line chemotherapy and patients’ overall survival.We also investigated the association of EGFR mutations with the EGFR geneamplification. Finally, in a group of 25 patients the mutation status of these genes inthe primary tumors and the corresponding metastasis was evaluated.The genetic analysis performed in FFPE tissue samples of primary tumor ormetastasis. DNA was extracted using universal techniques. For mutation analysis exons18, 19, 20 and 21 of the EGFR and exon 2 of KRAS genes were sequentially amplified bypolymerase chain reaction (PCR) and subjected to direct sequencing. Finally, EGFRamplification was determined by quantitative real time PCR.Analysis of EGFR mutations was successful performed in 634 patients andmutations were detected in 100 (15.8%) of them. Activating mutations were detected in 8.4%. The most common mutations were deletions of 4-5 codons in exon 19 (del 19,71.7%, 38/53) and the missense mutation at position 858 (L858R) in exon 21 (22.6%,12/53). Also in 47 (7.4%) patients other mutations were detected in four exons ofEGFR, which have been reported previously or are new. We found that the incidenceof EGFR mutations was statistically significant in women with no smoking history andwith adenocarcinoma histology.The mutation analysis of the KRAS gene was successfully performed on 399patients and mutations detected in 20.8% of them (83/399). Especially, 92.8% of themutations were found at codon 12 and 7.2% at codon 13. KRAS mutations weresignificantly associated with smoking history with higher incidence in smokers thannonsmokers. There was also a significant association between KRAS mutations andadenocarcinoma histology.The predictive value of EGFR and KRAS mutations was examined in a subgroupof patients (n=162) with NSCLC who received chemotherapy as 1st line therapy.Patients with classical EGFR mutations had a higher probability of response (55.6%) to front-line chemotherapy as compared to those with wild type EGFR (21.8%) (p =0.023). Multivariate analysis revealed the 'classical' activating EGFR mutations as anindependent predictive factor for response to 1st line chemotherapy. There was nosignificant correlation between the EGFR or KRAS mutation status and the time totumor progression. The presence of activating EGFR but not of KRAS mutations wasassociated with a significantly higher overall survival compared to patients withoutmutations treated with platinum-based front-line chemotherapy.Epidermal growth factor receptor and KRAS mutation status was differentbetween primary tumors and corresponding metastases in 7 (28%) and 6 (24%) of the25 patients, respectively. This discrepancy was not statistically significant with theMcNemar’s test.EGFR amplification was found in 7.2% (6/83) of primary tumors. Among thepatients with EGFR gene amplification none carried KRAS mutations while 2 had EGFR exon 19 deletion.