Utility of activated carbon nanoparticle (CNP) during total thyroidectomy for clinically nodal positive papillary thyroid carcinoma (PTC)

Abstract

Introduction: Activated carbon nanoparticle (CNP) is a novel operative tracer that can potentially facilitate the appropriate extent of nodal dissection during thyroidectomy in papillary thyroid carcinoma (PTC). Shortly after peri-tumoral injection of CNP, regional lymphatics and nodes are stained dark to help to guide the surgeon on the extent of nodal dissection. The present study aimed to evaluate the benefits of intraoperative CNP injection during total thyroidectomy by comparing the surgical and oncological outcomes between those who received intraoperative CNP injection and those did not receive it in clinically nodal PTC. Materials & Methods: Among 503 patients with PTC, 206 (41.0%) underwent a total thyroidectomy with nodal dissection for a clinically nodal positive (cN1) PTC. Among those receiving CNP injection, 0.2mL of CNP suspension was injected in the thyroid close to the tumor with the injected site pressed for 3 minutes before dissection began. For those who underwent surgery without CNP, a standardized procedure was performed. All patients were operated by one surgical team. Study endpoints included operative time, rate of inadvertently-removed or auto-transplanted parathyroid glands (PGs), number of total and metastatic lymph nodes, postoperative parathyroid hormone and calcium levels and postoperative thyroglobulin (Tg) level. Biochemical complete response (BCR) was defined as suppressed Tg ≤1ng/mL and/or stimulated Tg ≤2ng/mL. Results: Patient demographics, tumor characteristics and operative time were comparable between the two groups. However, the total mean number of normal and metastatic lymph nodes excised were significantly greater in the CNP group (11.0 v. 6.4, p=0.021 and 5.9 vs. 3.4, p=0.039). Meanwhile, the rate of inadvertently removed or auto-transplanted PG was also significantly less in the CNP group (16.2% vs. 21.9%, p=0.042). The postoperative Tg level and BCR rate were also significantly lower in the CNP group (9.9ng/mL vs. 14.7ng/mL, p=0.297 and 82.4% vs. 72.9%, p=0.002, respectively). However, in terms of rate of lymph node staining, large-sized (≥ 3cm) tumors had significantly lower rate than smaller-sized PTCs (10.3% vs. 69.4%, p<0.001). Conclusion: CNP injection can potentially facilitate nodal dissection during thyroid surgery in PTC by increasing the normal and metastatic nodal yield rates while reducing the rate of inadvertent PG removal. To improve the utility of CNP further, a greater volume of CNP injection might be necessary for larger-sized (>3cm) PTCs.