The Relationship Between EGFR Gene Mutations And The Response Of Tyrosine Kinase Inhibitors In Patients With Advanced Non-small-cell Lung Cancer

Background: Epidermal growth factor receptor(EGFR) is an important molecule target in targeted therapy in non-small-cell lung cancer(NSCLC).EGFR tyrosine kinase inhibitors Iressa (gefitinib)and Tarceva(erlotinib) block the activity of EGFR by competing ATP biding the ATP-bingding pocket on EGFR ,EGFR as their targets,and they are hotspots in the field of treatment of advanced NSCLC .Researches had reported that the mutation rate of EGFR gene was much higher in Iressa responsers than in non-responders.The tumor relief rate was much higher in patients with EGFR mutions than in those without EGFR mutations.The overall survival of NSCLC patients with EGFR mutations had a longer trend than that of patients without mutations, but had no stastical significance. About 90% of EGFR mutations were clusered within exon 19 and exon 21 of EGFR gene, all of which were heterozygous mutations and were activating mutations. Now the most common method to detect EGFR gene mutations was direct sequencing, expensive and time consuming, which didn't fit clinical screening.Aim : The study was to evaluate the mutations in the exon 19 and exon 21 of EGFR gene in a series of Chinese patients with bronchioloalveolar carcinoma and advanced NSCLC and to evaluate the relationship between EGFR gene mutations and effects of Iressa and Tarceva in advanced NSCLC patients.Method: We collected paraffin-embedded tumor tissue samples from 59 patients with advanced NSCLC ,34 of which were treated with Iressa monotherapy and 25 of which were treated with Tarceva monotherapy, as well as 55 patients with bronchioloalveolar carcinoma. We detected mutations in exon 19 by nested PCR,PAGE electrophoresis and direct sequencing ,and detected mutations in exon 21 by PCR-RFLP method identified by direct sequencing.Results: The activating EGFR tyrosine kinase domain mutations was detected in 22 patients out of the 59 patients treated with Iressa or Tarceva(22/59,37.3%) and in 24 patients out of 55 patients with bronchioloalveolar carcinoma(24/55,43.6%). Mutations in exon 19 were in-frame deletions resulting in amino acid changes ,and mutations in exon 21 were mutation in exon 21(L858R) resulting in amino acid substitutions. From the patients receiving monotherapies, 7 patients had in-frame deletions in exon 19,13 patients had L858R,and 2 patients had both of them. The mutation rates were higher in females,non-smokers and patients with adenocarcinoma rather than in males,smokers and patients with non-adenocarcinoma respectively. The response rate was higher in patients with mutations than those without mutations and there was stastical significance(41.7% vs 15%, p=0.012). Patients with EGFR gene mutations had a higher response rate than those without mutations while receiving Iressa monotherapy and there was statistic significance(p=0.012).When treated with Tarceva the response rate seemed to be higher in patients with EGFR gene mutations than those without mutations, but there was no stastical significance(p=0.063) and we couldn't conclude that EGFR gene mutations correspond to response of Tarceva. Patients with EGFR gene mutations had a higher disease control rate than those without mutations(86.4% vs 54.1%,p=0.011). Patients with EGFR gene mutations had a higher disease control rate than those without mutations while receiving Tarceva monotherapy and there was statistic significance(p=0.027).When treated with Iressa the disease control rate seemed to be higher in patients with EGFR gene mutations than those without mutations, but there was no stastical significance(p=0.153) and we couldn't conclude that EGFR gene mutations correspond to disease control rate of Iressa.Conclusion:The activating mutations in exon 19 and exon 21 of EGFR gene was highly associated with the response rate and disease control rate of EGFR tyrosine kinase inhibitors(Iressa and Tarceva).Methods to detect deletion mutations in exon 19 of EGFR gene by nested PCR and PAGE identified by direct sequencing and to detect missense mutations in exon 21 of EGFR gene by PCR-RLFP method followed by direct sequencing were the fast,simple,correct ones to detect the common mutations in EGFR gene.