Multi-gene analyses from waste brushing specimens for patients with peripheral lung cancer receiving EBUS-assisted...

Although flexible bronchoscopy with the assistance of miniature radial-probe endobronchial ultrasound (EBUS) is increasingly employed to diagnose peripheral lung cancer, transbronchial biopsies typically offer an insufficient amount of tissue to conduct additional molecular analysis. We evaluated the feasibility of multi-gene analyses from waste brushing samples obtained by EBUS-assisted bronchoscopy.

For lung cancer patients with positive brushing cytology, analysis of EGFR, K-ras and EML4-ALK fusions were carried out, utilizing reverse transcription-polymerase chain reaction and Sanger sequencing on the cell-derived RNA retrieved from waste brushing samples.

EBUS-guided brushings were judged positive for tumor cells in 84 (68.9%) of the 122 patients with peripheral lung cancer receiving flexible bronchoscopy. Genotyping of EGFR and K-ras was successfully implemented in 80 (95.2%) of the 84 cytology-proven brushing samples, along with satisfactory yields to detect EGFR (55.0%) and K-ras (2.5%) mutations. The results of EGFR genotyping from the brushing specimens were highly concordant with those provided from other corresponding samples (concordance rate: 94%, kappa: 0.92). Of the 19 patients with adenocarcinoma or non-small cell lung cancer not otherwise specified harboring wild-type EGFR and K-ras, two cases (10.5%) were identified to harbor EML4-ALK fusions.

Our results suggest that multi-gene analyses from waste brushing specimens using RNA-based Sanger sequencing is highly feasible. This approach offers an opportunity to overcome the dilemma of flexible bronchoscopy in molecular diagnostics for lung cancer, and could potentially recruit more patients for targeted therapy according to the molecular characteristics of the tumor cells.