Endoscopic thyroidectomy (ESTC) has evolved steadily over the last 20 years, and the improvements in cosmesis and quality of life make it a popular choice for young patients. With the emergence of TOETVA, the cosmetic effects of thyroid surgery have been further optimized and the disadvantages of large trauma in ESTC have been minimized. However, the promotion of TOETVA for the treatment of PTC requires more clinical data and operational experience sharing. In this study, we evaluated the safety and feasibility of TOETVA for PTC.
Regarding the safety of TOETVA, the main concern for surgeons is the protection of nerves. To better protect the nerves during the dissection of the thyroid gland, some technical points need to be addressed. During TOETVA, difficulties are routinely encountered in exposing the superior pole of the thyroid, increasing the probability of SLN injury. Partial sternothyroid amputation does not normally affect the quality of life of patients but is conducive to the successful exposure and protection of the SLN. Additionally, the RLN is usually located at the larynx entry point; therefore, "tunnel" exploration is recommended at the larynx entry point through the use of separating pliers for quick and accurate identification of the RLN. Furthermore, the thyroid closely approximates the RLN at the larynx entry point; thus, bipolar electrocoagulation is recommended for complete resection of the thyroid at the larynx entry point and to protect the RLN. Using these neuroprotection techniques, transient SLN palsy and transient RLN palsy only occurred in three (4.0%) and five patients (6.7%) in this study, respectively. The probability of temporary nerve injury in this study was similar to that in other reports on open surgery [25–29]. More importantly, permanent nerve injury did not occur in the present study.
We used the extent of CND to evaluate the feasibility of TOETVA for the treatment of PTC. The boundary for CND was marked with forward dissection to the sternum and lateral dissection to the carotid artery. The number of lymph nodes removed with TOETVA in this study was 6.8 ± 3.9, which was no less than that in open surgery , and no tumor recurrence was found during the follow-up period, suggesting that TOETVA is effective for CND. As another parameter, the operating time for TOETVA, which was reported in previous studies to be significantly longer than that in open surgery , was used to judge the feasibility of the procedure. In this study, although the average operating time was 140 minutes, the time gradually decreased with consecutive TOETVA operations (Fig. 7), demonstrating that the operating time can be reduced with the improvement of surgical proficiency through more experience.
In this study, the average tumor size removed with TOETVA was only 0.83 ± 0.66 cm, mainly because TOETVA was offered to patients with tumors smaller than 2 cm during the preoperative imaging workup. Four patients who had tumors larger than 2 cm in this study demanded TOETVA despite dissuasion from the surgeon. Factually, the tumor size determined with postoperative pathology is often smaller than that determined with preoperative ultrasound in our center.
There are several caveats related to the TOETVA procedure. Firstly, the operating space for TOETVA is quite narrow at the beginning of the operation and may suitably accommodate the electric hook due to its small size and flexibility. We believe that reasonable use of an electric hook, especially the electric cutting function, will help expedite the process of initial space establishment in TOETVA. Secondly, carbon nanoparticles can be injected into the inferior pole of the thyroid in order to solve the problem of finding the inferior parathyroid gland. Thirdly, because of the surgical difficulties and complications, TOETVA should be performed by a surgeon with extensive experience in ESTC. Beginners should strictly follow the standard operating procedures and be familiar with neuroprotection techniques. Despite the fact that our surgeon had completed more than 1000 cases of ESTC over a period of more than 10 years, the mean operating time for TOETVA was around 140 min, which is still much longer than that of open surgery.
The limitations of the study are as follows: First, the clinical data for the patients who underwent open surgery were not included in this study as a comparable reference to improve the level of evidence. Secondly, the mean follow-up period for patients with PTC was only 15.6 ± 10.9 months, which is too short to draw conclusions regarding the effectiveness of TOETVA in the treatment of PTC.
In summary, based on our operational savvy on neuroprotection, we believe that the safety and short-term clinical outcomes for TOETVA are comparable to those of open surgery in our hands. However, whether TOETVA can be upheld as one of the choices for PTC should be further tested and verified with well-designed clinical trials. For now, the TOETVA procedure should be performed on carefully selected patients by experienced surgical endoscopists.