Accuracy of epidermal growth factor receptor gene mutation analysis by direct sequencing method based on small biopsy specimens from patients with non-small cell lung cancer: analysis of results in 19 patients

Background. The importance of an epidermal growth factor receptor (EGFR) gene mutation has been recognized in patients with non-small cell lung cancer (NSCLC), and many reports have indicated that the presence of somatic mutations in the EGFR gene is a strong predictor of both clinical and in vitro sensitivity to EGFR tyrosine kinase inhibitors; thus necessitating the standardization of a mutation screening system based on the sources of tissue samples. Methods. In this study, we compared the results of EGFR mutation analyses in 19 small biopsy specimens with results obtained in surgical materials from the same patients with NSCLC. We used a laser microdissection method and a direct sequencing method, and we confirmed the accuracy of EGFR mutation analysis with small biopsy specimens. Results. The results obtained from the biopsy specimens were identical to those obtained from the surgical materials in 18 of the 19 patients analyzed. For the 1 patient in whom the results obtained from the two sets of materials were not identical, the number of cancer cells in one bronchoscopic specimen was insufficient to perform analyses of all three exons of interest (i.e., exons 18, 19, and 21), and so only exon 19 was sequenced, and no mutation was demonstrated. Conclusion. We conclude that satisfactory accuracy can be achieved by the genomic analysis of a small biopsy specimen from a patient with NSCLC and we note that it is possible to conduct prospective clinical trials that include patient assignment for treatment based on the results obtained.