Background: Activated carbon nanoparticle (CNP) is a novel tracer that may facilitate nodal dissection in clinically nodal positive (cN1) papillary thyroid carcinoma (PTC). The present study compared the nodal yield and surgical outcomes between surgery with CNP and without CNP.
Methods: Patients who underwent total thyroidectomy with therapeutic nodal dissection for cN1 PTC were given the option of intraoperative CNP injection. Among those who received CNP, 0.2 mL CNP suspension was injected in both thyroid lobes before dissection. Study endpoints included number of total and metastatic lymph nodes, inadvertently removed parathyroid glands (PGs), postoperative parathyroid hormone, calcium, and post-6-month thyroglobulin (Tg). Biochemical complete response (BCR) was defined as Tg ≤ 1 ng/mL and/or stimulated Tg ≤ 2 ng/mL.
Results: One-hundred and twenty patients (58.3%) received CNP, while 86 (41.7%) had surgery without CNP. Demographics, tumor characteristics, and operative time were comparable between the two groups. However, total mean number of normal and metastatic lymph nodes retrieved were significantly greater in CNP group (10.0 vs. 8.1, p = 0.032 and 4.5 vs. 2.7, p = 0.002, respectively). Rate of inadvertently removed PG was significantly less in CNP group (13.3% vs. 23.3%, p = 0.042). Postoperative Tg level and BCR were significantly lower in CNP group (9.9 ng/mL vs. 14.7 ng/mL, p = 0.297 and 82.4% vs. 72.9%, p = 0.002, respectively). However, large-sized ( ≥ 3 cm) PTCs had a significantly lower nodal staining rate than smaller-sized PTCs (10.3% vs. 69.4%, p < 0.001).
Conclusions: CNP injection can facilitate therapeutic central nodal dissection by increasing the nodal yield rates and reducing inadvertent PG removal. To enhance its utility, a greater volume of CNP might be necessary in larger-sized (> 3 cm) PTCs.