A modified cryobiopsy specimen retrieval method using a thin bronchoscope and small guide sheath for the diagnosis of peripheral pulmonary lesions.

Abstract

Background: Retrieval of 1.1-mm ultrathin cryobiopsy specimens through a large guide sheath (GS) enables specimen collection without removal of the therapeutic bronchoscope and GS; however, this approach remains limited to selected patients because therapeutic bronchoscopes have restricted access to the peripheral bronchi. To expand the applicability of cryobiopsy to more peripheral pulmonary lesions (PPLs), we applied a modified cryobiopsy specimen retrieval approach, termed the ultrathin CRYObiopsy specimen with Guide sheath en bloc RetrievAl THrough a bronchoscoPe channel (CRYO-GRATHP) method using a thin bronchoscope. This study evaluated the efficacy and safety of this procedure.

Methods: We retrospectively analyzed patients with PPLs who underwent bronchoscopic cryobiopsy using the CRYO-GRATHP method at Okayama Medical Center between April 2023 and March 2026. Lesions were localized using an endobronchial ultrasound with a small GS and a thin bronchoscope, followed by small forceps biopsy and ultrathin cryobiopsy using a 1.1-mm cryoprobe. The primary endpoint was diagnostic yield, and the secondary endpoints included safety, procedure duration, specimen size, sampling success by freezing time, and biomarker testing success.

Results: A total of 28 patients were included. All patients underwent additional cryobiopsy because rapid on-site cytological evaluation of small forceps biopsy specimens was negative. The median target lesion size was 17 mm, and most lesions were in the upper lobes (79%). The overall diagnostic yield was 75.0%, and a specific diagnosis was achieved in 77.3% of upper-lobe lesions. The median specimen size was 3.73 mm² for cryobiopsy and 1.00 mm² for forceps biopsy (P<0.001). Regarding safety, bleeding was limited to grade 0-2 in all cases, with no grade ≥3 bleeding, and no pneumothorax was observed. Nineteen (68%) procedures were performed without endotracheal intubation.

Conclusions: In this pilot study, the CRYO-GRATHP method appeared to be a feasible and safe cryobiopsy technique for small PPLs, particularly those located in the upper lobe.