Homogeneity of EGFR Mutation in Patients with Resected Adenocarcinoma of the Lung

ABSTRACT Background Randomized phase III trials confirmed that patients with activating EGFR mutation treating with first-line EGFR TKI has better progression-free survival when compared with the standard platinum-based doublets. However, most of tumor samples for EGFR mutation detection are biopsy or fine needle aspiration. Mutation results rely on the homogeneity of EGFR mutation of the tumors. Heterogeneity of the EGFR genotype within a tumor might create the sampling error for the EGFR wide-type tumor. We conduct this study to evaluate the homogeneity of EGFR mutation in resected adenocarcinoma of the lung. Methods Chinese, non-smoking, treatment naive patients with the resectable adenocarcinoma of the lung are identified preoperatively between 2010 and 2011. If the resected tumor is confirmed to harbour EGFR mutation, the entire tumor specimen will be cut into smaller blocks. DNA of each block will be extracted and tested for EGFR mutations by direct sequencing. Results Total of eight Chinese patients with adenocarcinoma of lung harboring EGFR mutations were identified. The median age was 60 years (range 54–71; female 75%). Four patients (50%) had disease stage I diseases, two (25%) stage II and two (25%) stage III. All received lobectomy. Six patients remain in remission. Five patients had exon 21 L858R mutations, one had exon 19 deletion and two had rare exon 20 insertions. Multiple blocks of individual tumor were mapped for their EGFR mutation status by direct sequencing. The results showed homogeneity of EGFR mutation within the pulmonary adenocarcinoma. Conclusions Our result showed homogeneity of EGFR mutation within the resected adenocarcinoma of lung. Even fine needle aspiration can extract the representative tumor cells for EGFR mutation detection. However, in the metastatic lung cancer, different tumor sites might harbor different genotypes. Hence, the result of the EGFR mutation assay depends on where the biopsy is taken.