Suitability of transbronchial brushing cytology specimens for next-generation sequencing in peripheral lung cancer

Next-generation sequencing (NGS) enables the diagnosis of large numbers of gene aberrations during one examination, and precision medicine has been developed for patients with advanced non-small cell lung cancer (NSCLC). However, peripheral lung lesions account for the majority of advanced lung cancers, especially lung adenocarcinoma. In these cases, it is difficult to obtain tissue samples which contain sufficient tumor cells by transbronchial biopsy (TBB) with forceps. Even when the target lesions are quite small, bronchial brushing can obtain enough tumor cells by endobronchial ultrasonography using guide sheath (EBUS-GS). In this study, we investigate the suitability of bronchial brushing cytology specimens obtained by EBUS-GS-TBB to evaluate the correlation between the success rate of NGS and extracted DNA/RNA yields according to biopsy method. We prospectively collected 222 tumor samples obtained from patients with advanced lung cancer. All patients were enrolled in a prospective nationwide genomic screening project for lung cancer (LC-SCRUM-Japan/Asia). Genomic data were obtained from the clinico-genomic database of LC-SCRUM-Japan/Asia. The extraction yields of DNA/RNA from samples obtained by EBUS-GS-TBB were relatively low compared with tissue samples. The success rate of DNA sequencing for EBUS-GS-TBB was 97.9%, with no significant differences between biopsy methods. The success rate of RNA sequencing for EBUS-GS-TBB was 80.4%, which was relatively low compared with surgical biopsy samples (P = 0.069). However, some rare oncogenic driver aberrations were detected from these specimens. This study demonstrated that cytology samples obtained by transbronchial brushing with EBUS-GS-TBB were suitable for NGS analysis.