Preclinical feasibility of bronchoscopic fluorescence-guided lung sentinel lymph node mapping

Abstract

Objective: Lung sentinel lymph node mapping, where peritumorally injected material is tracked through the lymphatics, aims to find the first potential sites of nodal metastasis. We sought to evaluate the preclinical feasibility of bronchoscopic fluorescence-guided sentinel lymph node mapping.

Methods: Healthy Yorkshire pigs were used; sentinel lymph node mapping was performed with indocyanine green. The primary fluorescence imaging method was an ultrathin composite fiberscope placed in the bronchoscope working channel. Secondary methods used a fluorescence thoracoscope placed in the trachea (rigid bronchoscopy) and pretracheal fascial plane (mediastinoscopy) to validate ultrathin composite fiberscope settings for sentinel lymph node detection. A tracheostomy was created, and the pig was placed in a lateral decubitus position. Transbronchial intraparenchymal indocyanine green injection was performed primarily in the right lower lobe. Ultrathin composite fiberscope and rigid bronchoscopy were performed with (n = 6) or without (n = 2) mediastinoscopy, with the former group guiding dose and ultrathin composite fiberscope optimization. Fluorescent targets were interrogated by endobronchial ultrasound before ultrathin composite fiberscope-guided transbronchial needle aspiration. Specimen fluorescence was documented before creating cytological smears. Pigs were killed postprocedure for nodal dissection.

Results: A total of 100 μL of 10 mg/mL indocyanine green generated strong transbronchial fluorescence with low risk of indocyanine green contamination. Fluorescence was detectable by 10 minutes postinjection. There was concordance among ultrathin composite fiberscope, rigid bronchoscopy, and mediastinoscopy. Except for 1 pig with airway contamination, ultrathin composite fiberscope-guided endobronchial ultrasound transbronchial needle aspiration obtained fluorescent material in all pigs. Specimen fluorescence was associated with specimen adequacy.

Conclusions: Bronchoscopic fluorescence-guided sentinel lymph node mapping was feasible, with specimen fluorescence providing real-time feedback on sentinel lymph node biopsy success. If translated to clinical practice, attention must be paid to minimizing indocyanine green leakage.

Keywords: endobronchial ultrasound; indocyanine green; lung cancer; near-infrared; sentinel lymph node.