Abstract 3867: EGFR genotype impacts expression of chemotherapeutic target biomarkers in NSCLC

BACKGROUND: Non small cell lung cancer EGFR mutations are prevalent in the East Asian population, especially in female non-smokers, the L858R and del 747-753 in exons 18-21 of the EGFR tyrosine kinase domains are activating mutations with increased sensitivity to the EGFR tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib. EGFR gene amplification also increases susceptibility to EGFR TKIs as has been reported in the IDEAL / INTACT non small cell lung cancer (NSCLC) trials. Our study evaluated chemotherapeutic target biomarkers in Chinese NSCLC patients with varying EGFR genotypes. METHODS: Seventy NSCLC patients with known EGFR genotype received chemotherapy and EGFR TKI therapy with known response and survival, their pathology specimen were retrospectively retrieved for evaluation. EGFR and KRAS were sequenced for mutations and deletions. Fluorescent in situ hybridization (FISH) was performed for EGFR genes. Immunohistochemical analyses were performed for topoisomerase 1, c-myc, RRM-1, class III beta tubulin, topoisomerase IIα, p53, thymidylate synthase, and ERCC-1. The percentage of nuclear-stained malignant cells were recorded for T IIα, T1, p53, ERCC-1, c-myc, whereas for TS, tau, RRM-1, class III beta tubulin were cytoplasmic stains, only positive or negative was reported, eventually only 63 patients had complete data for evaluation. RESULTS: Significant increase in overall survival was found in females (p=0.002), non-smokers (p=0.005), younger age (p=0.001), less advanced staging (p=0.048), EGFR mutation (p=0.038); but not with KRAS genotype, or expression of any chemotherapeutic markers. Patients in this study were consecutive patients, 60-70% received treatment. When EGFR mutant tumors were compared to EGFR wildtype tumors, the mutant tumors had lower KRAS mutation (4% vs 19%, p=0.1238), more were ERCC1- (76% vs 63%, p=0.2925), more topoisomerase 1 + (28% vs 17%, p=0.3719), less RRM1+ (24% vs 35%, p=0.4142), more TS- (93% vs 86%, p=0.4478), lower class III beta tubulin (45% vs 57%, p=0.4515). CONCLUSIONS: A difference in expression of chemotherapeutic target markers has been detected in differing EGFR genotypes, although its significance has been dampened by our small patient population, and larger patients groups will be needed to evaluate the impact of different chemotherapies on survival of the different EGFR genotype tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3867. doi:10.1158/1538-7445.AM2011-3867