BackgroundAlthough transbronchial diagnostic procedures are sometimes difficult to perform because of the patient’s respiratory or general conditions, endoscopic ultrasound with bronchoscope-guided fine-needle aspiration (EUS-B-FNA), a known transesophageal diagnostic procedure, might be useful for such cases. We conducted this prospective three-center observational study to evaluate the safety and efficacy of EUS-B-FNA in suspected lung cancer patients with poor respiratory or general conditions.MethodsPatients with suspected lung cancer with respiratory failure, Eastern Cooperative Oncology Group performance status of 2 or higher, or severe respiratory symptoms, were enrolled. The primary endpoints were the diagnostic yield of lung cancer and its safety, and the secondary endpoints were the success rate of molecular and programmed death ligand 1 (PD-L1) analyses, and the 6-month survival rate in patients with lung cancer.ResultsWe enrolled 30 patients, of which 29 were included in the analysis. Among them, 26 were eventually diagnosed with lung cancer. The diagnostic yield for lung cancer was 100% (26/26). There were no adverse events associated with EUS-B-FNA requiring procedure discontinuation. The success rates of molecular analysis forEGFR,ALK,ROS-1, andBRAFwere 100% (14/14), 100% (11/11), 100% (9/9), and 75% (6/8), respectively. The success rate of the PD-L1 analysis was 100% (15/15). The 6-month survival rate in patients with lung cancer was 53.8% (95% confidence interval [CI]: 33.4–76.4), and the median overall survival (OS) was 196 days (95% CI: 142–446).ConclusionsEUS-B-FNA is a safe and effective diagnostic method, even in patients with suspected lung cancer with poor respiratory or general conditions.Trial registrationThis clinical trial was registered athttps://www.umin.ac.jp/ctr/index.htm(UMIN000041235, approved on 28/07/2020).