Clinical Significance Of Detection Of Plasma-Based EGFR And KRAS Mutations In Patients With Advanced NSCLC

Objective: In this study, we attempted to detect EGFR and KRAS mutations in plasmaof patients with advanced NSCLC by pyrosequencing, investigate whether plasma DNAcould be used as a substitute for tumor tissues for detecting gene mutations, and study thecorrelation of EGFR/KRAS mutations with the efficacy of the epithelial growth factorreceptor-tyrosinekinase inhihitor (EGFR-TKI) as well as their correlation with survival inTKI-treated patients.Method: Blood was obtained from146patients with advanced NSCLC and tumortissues were obtained from64patients, of whom40patients had plasma and matched tissue.The exon2of KRAS was amplified by nested-PCR, and exons19,20and21of EGFR inplasma were amplified by mutant-enriched PCR using selective restriction enzymedigestion. Then mutations were detected by pyrosequencing. The association betweenmutations and the patients’ survival was analyzed using Kaplan-Meier.Results:1. EGFR mutations were detected in22(34.38%) tissues and KRAS mutations weredetected in3(4.69%) tissues among the64tumor tissues from patients with advancedNSCLC.2. EGFR mutations were detected in24(24.24%) tissues and KRAS mutations weredetected in9(6.16%) tissues among the99and146patients with advanced NSCLC,respectively. No statistical significance was found in EGFR/KRAS mutations betweenplasma and tumor tissues (P=0.16; P=0.919).3. The same EGFR mutations were observed in plasma and its matched tissue in tenpatients (consistency:85%).The sensitivity of detection of circulation EGFR mutations is71.42%and the specificity is92.31%.There was only1KRAS mutation detected in the40 patients tissue, but no mutation was detected in the matched plasma (consistency:97.5%).4. Significant correlation existed between EGFR mutations in tumor tissue frompatients with advanced NSCLC, and a smoking history (P=0.013), and histopathologictypes (P=0.022). No significant association was observed between EGFR mutations and sex(P=0.090), age (P=0.913), PS score (P=0.702), tumor stage (P=0.164). There was nosignificant correlation between EGFR/KRAS mutations in plasma and clinical parameters(P>0.05).5. No significant correlation was found between KRAS mutations in plasma andtumor tissues and clinical parameters (P>0.05).6. Among the38TKI-treated patients, the disease control rate (DCR) and objectiveresponse rate (ORR) were90%and60%, respectively, in patients with EGFR mutation inplasma, and53.57%and17.86%, respectively, in patients with wide-type EGFR (DCR,P=0.059; ORR, P=0.019).7. The DCR and ORR were66.67%and33.33%, respectively, in patients withwide-type KRAS in plasma, and40%and0%, respectively, in patients with KRASmutation.But there was no statistical significance was found (DCR, P=0.337; ORR,P=0.295)8. The overall median PFS of the38TKI-treated patients was6months. Patients withEGFR activating mutations in plasma had a favoring median PFS of10.5months,significantly longer than the patients with wild-type EGFR (5.0months)(P=0.228). Themedian PFS was2.5months for patients with KRAS mutation and9months for patientswith wild-type KRAS, respectively (P=0).Conclusion:1. A high consistency of85%and97.5%,respectively exists between EGFR mutationand KRAS mutation detection in plasma and in tumor tissues. Plasma DNA could be usedas a substitute for tumor tissues for detecting gene mutations.2. It is feasible to detect EGFR and KRAS mutations in plasma DNA bypyrosequencing, which is simple and high-throughput. The detection sensibility of EGFRmutations can be increased by ME-PCR, facilitating choosing patients for TKI treatment.3. EGFR mutations in tumor tissues of patients with advanced NSCLC are morecommon in nonsmoking female adenocinoma patients. 4. EGFR and KRAS mutations in plasma are highly associated with the treatmentresponse and prognosis of TKI-treated patients.