Feasibility of Non-Invasive Sentinel Lymph Node Identification in Early-Stage NSCLC Through Ultrasound Guided Intra-Tumoral Injection of ^99mTc-Nanocolloid and Iodinated Contrast Agent During Navigation Bronchoscopy

Background: As the first sentinel lymph nodes (SLN) in lung cancer are most likely to harbor metastasis, their non-invasive identification could have a significant role in future treatments. We investigated the feasibility of adding an SLN procedure to a diagnostic navigation bronchoscopy. Methods: Thirty-one patients were included for injection of ^99mTc-nanocolloid and an iodinated contrast agent intra-/peritumorally and assessment of tracer dissipation via SPECT and CBCT imaging. Injections were performed endobronchially using a multi-modal catheter (Pioneer Plus), combining radial ultrasound and an angulated retractable needle to place injections under fluoroscopy and real-time ultrasound. Results: The injection of an imaging tracer was feasible in all cases using the catheter. Ultrasound visualized 29/30 tumors, and tracer injection was performed in 100% of patients. An SLN was subsequently identified in 10 out of 31 cases (32.3%) via SPECT/CT imaging. Iodinated contrast agent injection under CBCT imaging prior to ^99mTc nanocolloid injection visualized dissipation pathways and enabled needle relocation for subsequent ^99mTc-nanocolloid injection. Conclusions: Performing imaging tracer injections with a multi-modal catheter provided safe and local depot placement immediately following diagnostic navigation bronchoscopy. SPECT/CT imaging using ^99mTc-nanocolloid showed inconsistent results for SLN identification.