Circulating cell-free DNA has a high degree of specificity to detect exon 19 deletions and the single-point substitution mutation L858R in non-small cell lung cancer
BACKGROUND Epidermal growth factor receptor (EGFR) mutations as prognostic or predictive marker in patients with non-small cell lung cancer (NSCLC) have been used widely. However, it may be difficult to get tumor tissue for analyzing the status of EGFR mutation status in large proportion of patients with advanced disease. PATIENTS AND METHODS We obtained pairs of tumor and serum samples from 57 patients with advanced NSCLC, between March 2006 and January 2009. EGFR mutation status from tumor samples was analyzed by genomic polymerase chain reaction and direct sequence and EGFR mutation status from serum samples was determined by the peptide nucleic acid locked nucleic acid polymerase chain reaction clamp. RESULTS EGFR mutations were detected in the serum samples of 11 patients and in the tumor samples of 12 patients. EGFR mutation status in the serum and tumor samples was consistent in 50 of the 57 pairs (87.7%). There was a high correlation between the mutations detected in serum sample and the mutations detected in the matched tumor sample (correlation index 0.62; P<0.001). Twenty-two of 57 patients (38.5%) received EGFR-tyrosine kinase inhibitors as any line therapy. The response for EGFR-tyrosine kinase inhibitors was significantly associated with EGFR mutations in both tumor samples and serum samples (P<0.05). There was no significant differences in overall survival according to the status of EGFR mutations in both serum and tumor samples (P>0.05). CONCLUSIONS Serum sample might be alternatively used in the difficult time of getting tumor tissue for analyzing the status of EGFR mutation status in patients with advanced NSCLC.