Application of Carbon Nanoparticles in Transoral Endoscopic Thyroidectomy Vestibular Approach for Unilateral Papillary Thyroid Cancer

Background: Transoral endoscopic thyroidectomy vestibular approach (TOETVA) is newly applied technology. Carbon nanoparticles (CNs) are novel lymph node tracers that have been widely used in China to help remove central lymph nodes (CLNs) and protect the parathyroid glands (PGs) in open thyroid cancer surgery. This study is to evaluate the effectiveness and safety of CNs in TOETVA. Materials and Methods: A total of 158 patients who underwent TOETVA with unilateral papillary thyroid carcinoma were enrolled in this study from March 2019 to February 2022. The participants were divided into a CNs group (n=88) and a control group (n=70), based on whether they received a intraoperative injection of CNs or not. Meanwhile, the CNs group were additionally divided into 2 subgroups, leakage subgroup (n=26) and standard subgroup (n=62). The 2 groups and subgroups were compared in terms of patient characteristics, perioperative clinical results, and postoperative outcomes. Results: All common metrics had no significant differences were found between the CNs group and the control group (P>0.05). The standard subgroup of CNs group had advantage over the control group on PGs identification (59/62 vs. 59/70 for superior PG, 56/62 vs. 52/70 for inferior PG, P<0.05). Moreover, the standard subgroup harvested more CLNs than the control group (8.97 +/- 2.96 vs. 7.47 +/- 2.93, P<0.05). More operation time was spent on the leakage subgroup of CNs group than the control group (160.00 +/- 17.61 vs. 140.00 +/- 13.32, P<0.05). Meanwhile, the leakage subgroup had disadvantage on intraoperative hemorrhage (26.15 +/- 10.80 vs. 21.21 +/- 7.09, P<0.05) and hospital durations (4.96 +/- 0.72 vs. 4.57 +/- 0.69, P<0.05). Furthermore, the leakage group identified fewer inferior PG than the control group (7/26 vs. 52/70, P<0.05). Contrary to the standard subgroup, the CLNs of the leakage subgroup was also unsatisfactory compared with the control group (4.96 +/- 1.84 vs. 7.47 +/- 2.93, P<0.05). Conclusions: The application of CNs suspension tracing technology has a definite effect in TOETVA. It can improve the thoroughness of lymph node dissection in the central region and enhance recognition of the PG. However, refined extracapsular anatomy is indispensable to prevent CN leakage. Leaked CNs will also be counterproductive to the operation.