Plasma epidermal growth factor receptor mutation analysis and possible clinical applications in pulmonary adenocarcinoma patients treated with erlotinib.

Tumor epidermal growth factor receptor (EGFR) mutation analysis is significant for making treatment decisions for metastatic pulmonary adenocarcinoma. However, less than half of patients have adequate tumor samples for mutation analysis. Patients with adenocarcinoma of the lungs who were due to receive erlotinib treatment were included in the present study. Tumor EGFR mutation status was analyzed using DNA sequencing. Plasma specimens from the patients were collected prior to erlotinib treatment. The plasma-free DNA EGFR mutation status was analyzed using the PCR clamp method. A total of 54 consecutive patients were included in the study. The plasma-free DNA EGFR mutation status of the 54 patients was analyzed. Only 30 patients had adequate tumor samples for EGFR analysis, including 15 with activating mutations (exon 19 deletions or L858R). EGFR-activating mutations were detected in the plasma-free DNA in 25 of 54 patients. The response rate was 86.7 and 33.3% in patients with and without tumor activating mutations, respectively (p=0.002). The response rate was 68 and 31% based on the patients' plasma-free DNA EGFR mutation status, respectively (p=0.013). No significant difference in progression-free survival (PFS) was observed between patients with and without EGFR-activating mutations, according to data from tumor tissue or plasma-free DNA analysis, although the median PFS time was longer for those patients with EGFR-activating mutations in plasma samples. Plasma EGFR mutation analysis is useful for adenocarcinoma patients who have no or inadequate tumor samples available for EGFR examination. Patients with plasma EGFR-activating mutations had an improved response rate and a statistically insignificant longer PFS.