The quantitatively analysis of epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) and its correlation with response rate of EGFR tyrosine kinase inhibitors (TKI)

Abstract

Abstract Background and Purpose: Lung cancer is the most frequent malignant tumor in China. Epidermal growth factor receptor (EGFR) had been validated as one of the most important therapeutic targets of non-small cell lung cancer (NSCLC), and tyrosine kinase inhibitors (TKI) have improved the overall outlook and quality of life for most of EGFR mutation positive NSCLC patients; however, the fact that 30% of EGFR mutation positive patients still do not response to TKIs. The current diagnostic test qualitatively measures the overall EGFR mutation status of the cancer tissue, ignored the impacts of nonmutated, TKI-unresponsive cancer cells. 274 NSCLC patients were recruited for the study to carry out the mutation analysis and its correlation with the response rate to EGFR TKIs with a novel quantitative methodology. Experimental Procedures: 1) Selection of paraffin sections of each recruited patients by pathologist to ensure the tumor cells exceeds 70% of total tissue; 2) Extraction of genomic DNA from paraffin sections; 3) Construction of plasmids of both mutated transcripts and wild-type transcripts for each mutation to be analyzed; 4) Real-time PCR amplification of extracted genomic DNA samples with both mutated probes and wild-type probes, and measurement of mutated copy numbers and wild-type copy numbers of each sample with standard curves made by mutated plasmids and wild-type plasmids respectively; 5) Confirmation of the mutation status of each sample with sequencing; 6) Calculation of the percentage of mutated EGFR copy numbers among the total EGFR copy numbers to derive quantitatively mutation data of each patient sample; 7) Observation of EGFR mutations and its demographic features with quantitative data; 8) Evaluation of the outcomes of the therapy with EGFR TKIs (including gefitinib and erlotinib) and analysis of the correlation of increased EGFR mutated transcripts with response rate to EGFR TKIs Summary of New Data: 1) 94 recruited samples was detected with EGFR mutation among total samples, the mutation ratio various from 5% to 90%; 2) The most frequently detected EGFR mutations among the 94 samples are deletions of Exon 19 (56 cases) and L858R (23 cases); 3) The mutation positive NSCLC patients are divided into 4 groups: a) low mutation rate + gefitinib; b) high mutation rate + gefitinib; c) low mutation ratio + erlotinib; d) high mutation rate + erlotinib. There are significant differences between group a and group b, group c and group d. 4) There is no significant difference between various EGFR mutation types against response rate to TKIs. Conclusions: 1) The EGFR mutation ratios in NSCLC patients are various; 2) The EGFR mutation ratio is significant correlated with the response rate to TKIs. This talk is also presented as Poster B36.