Vitamin B2 as a Tracer for Intraoperative Pulmonary Sentinel Node Navigation Surgery

Background: We investigated whether fluorescent agents, especially vitamin B2, can act as tracers for intraoperative pulmonary sentinel node mapping. Materials and Methods: Vitamin B2, fluorescent beads, and green fluorescent protein (GFP) were each injected into pulmonary parenchyma in 4 pigs (experiment 1). The safety of each tracer was also verified in 12 rats (experiment 2). Results: Experiment 1: In all groups, the sentinel lymph node was identified in 3 out of the 4 pigs (75%). Speed of agent dispersion: vitamin B2>GFP >fluorescent beads. Level of fluorescence judged as: vitamin B2>GFP=fluorescent beads. Experiment 2: In all groups, all rats survived until sacrifice without complications. In the fluorescent beads group, the fluorescent beads remained in the blood vessels. Conclusion: Vitamin B2 is inexpensive, safe and easy to apply. It is anticipated that clinical application of vitamin B2 for intraoperative pulmonary sentinel node mapping will become possible. The standard surgical therapy for lung cancer is lobectomy and systematic lymph node dissection. However, in 80% of clinical stage IA patients, mediastinal lymph node metastases are not seen on postoperative pathological examination (1). Lymph node dissection is highly useful for an accurate diagnosis of the pathological stage, but in most cases it is not a curative treatment and in some cases, it can even be harmful for patients. The possibility of damage to nerves or vessels during lymph node dissection increases with the extent of the dissection, and the frequency of pulmonary or cardiovascular complications increases. Therefore, it is important to determine which lymph nodes do not need to