Discussion

Classic total laryngectomy is a transcervical procedure requiring a large skin incision, transection of the strap muscles and excision of the hyoid bone. The location of the tumour determines the surgical steps used to save as much healthy tissue as possible. Therefore, open laryngeal surgery approaches the tumour from the “blind side” and, lacking the depth of information that can be extracted intra-operatively, the surgeon is not able to recognize the lesion until the late stages of the procedure.^{Reference Tsetsos, Poutoglidis, Vlachtsis, Stavrakas, Nikolaou and Fyrmpas2}

In contrast, transoral robotic surgery total laryngectomy provides immediate exposure of the tumour and helps the surgeon to save as much mucosa as possible. The strap muscles and hyoid bone are not violated. The field is magnified and tissues maintain a standard position. Theoretically speaking, all these modifications may lead to lower rates of pharyngocutaneous fistulas and better cosmetical and functional outcomes.^{Reference Smith, Schiff, Sarta, Hans and Brasnu12,Reference Hans, Chebib, Chekkoury-Idrissi, Distinguin, Circiu and Vialatte de Pemille15} It should be noted that narrow field total laryngectomy also does not violate the hyoid bone and the integrity of the strap muscles.

Neck involvement is often in laryngeal SCC, making neck dissection imperative in cases with cN1+ neck. In addition, almost every primary total laryngectomy for SCC should be accompanied by at least ipsilateral neck dissection, even in cN0 cases.^{Reference Tsetsos, Poutoglidis, Vlachtsis, Stavrakas, Nikolaou and Fyrmpas2} Therefore, the advantage of the short incision during transoral robotic surgery total laryngectomy cannot be exploited in cases requiring neck management. According to our systematic review, transoral robotic surgery total laryngectomy has never been performed in cases where neck management was mandatory. Indications of transoral robotic surgery total laryngectomy include salvage cases for selected cT3 or less, N0M0, dysfunctional larynx after organ preservation strategies, and some rare laryngeal neoplasms of the larynx with very low regional metastatic potential such as low-grade adenoid cystic carcinomas and low-grade chondrosarcomas. Most T3 and almost all T4a tumours should not be considered for transoral robotic surgery total laryngectomy, because the infiltration of laryngeal cartilages, pre-epiglottic space invasion, and every extralaryngeal extension are absolute contradictions.^{Reference Dowthwaite, Nichols, Yoo, Smith, Dhaliwal and Basmaji11–Reference Hans, Chebib, Chekkoury-Idrissi, Distinguin, Circiu and Vialatte de Pemille15}

Surgical time is a major limitation in transoral robotic surgery total laryngectomy. The presented data report time ranges from 226 to 370 minutes.^{Reference Dowthwaite, Nichols, Yoo, Smith, Dhaliwal and Basmaji11–Reference Hans, Chebib, Chekkoury-Idrissi, Distinguin, Circiu and Vialatte de Pemille15} Classic open total laryngectomy without neck dissection is a much shorter procedure.^{Reference Laccourreye, Crevier-Buchman, Hacquart, Naudo, Muscatello and Brasnu17} However data should be interpreted carefully. The specimens of transoral robotic surgery total laryngectomy are much smaller than they are in classic open surgery.^{Reference Hans, Chebib, Chekkoury-Idrissi, Distinguin, Circiu and Vialatte de Pemille15} A smaller specimen limits the application of transoral robotic surgery to smaller tumours but offers the advantage that a prophylactic flap is not required. Preserved strap muscles consist of a natural enhancement of the neopharynx. Because most cases of transoral robotic surgery total laryngectomies are salvage cases or cases with a dysfunctional larynx after radiation failure, the time of a classic open procedure often included the routine use of a regional flap.^{Reference Guimarães, Aires, Dedivitis, Kulcsar, Ramos and Cernea18} Therefore, the time to harvest a prophylactic flap is saved.

Pharyngocutaneous fistula formation after total laryngectomy is a serious and dangerous complication with high morbidity.^{Reference Rao, Arora, Singh, Nagarkar and Aggarwal19} It is related to multiple predisposing factors (prior radiation therapy, low haemoglobin levels, diabetes, positive surgical margins, tension in pharyngeal closure and/or T-closure of neopharynx). Intra-oral transoral robotic surgery total laryngectomy eliminates some of these predisposing factors by saving healthier mucosa than is done using traditional transcervical total laryngectomy. The strap muscles are preserved, and the pharyngeal closure is easier to be performed in a more horizontal fashion, limiting the tension in the neopharynx. According to the literature, the rate of pharyngocutaneous fistula formation is very high in salvage cases even when a prophylactic flap is recruited.^{Reference Süslü, Senirli, Günaydın, Özer, Karakaya and Hoşal20,Reference Hasan, Dwivedi, Gunaratne, Virk, Palme and Riffat21} Our results demonstrate a risk of 20 per cent in transoral robotic surgery salvage total laryngectomies, but the data are not adequate to draw safe conclusions. This percentage should be considered high if we have in mind that the procedure is indicated in a selected group and promises certain advantages.

The achievement of negative surgical margins of resection is the cornerstone of the surgical oncologic practice. Positive surgical margins are always associated with lower survival rates. Transoral robotic surgery total laryngectomy resulted in negative margins in every reported case. However, in the series of Hans et al.^{Reference Hans, Chebib, Chekkoury-Idrissi, Distinguin, Circiu and Vialatte de Pemille15}, one patient developed a local recurrence of chondrosarcoma. This phenomenon was attributed to contamination of the field due to the close incision of the thyroid and cricoid cartilage.

Although there is much enthusiasm for the adaptation of transoral robotic surgery in head and neck procedures, there is still scepticism about the cost. The use of transoral robotic surgery is not free, and surgeons must be aware of this. According to a study by Dombrée et al.,^{Reference Dombrée, Crott, Lawson, Janne, Castiaux and Krug22} transoral robotic surgery total laryngectomies are significantly more expensive than the traditional open procedures. Specifically, the overall cost of a transoral robotic surgery total laryngectomy was calculated at approximately €6767 compared to €3581 for an open approach. The authors stated that the cost is mainly affected by equipment purchase and maintenance.^{Reference Dombrée, Crott, Lawson, Janne, Castiaux and Krug22}

Our systematic review has certain limitations. Firstly, the included studies are retrospective and present limited cases. Sparse data in the literature reflect the difficulty of transoral robotic surgery total laryngectomy and its restricted indications. The limited data make it difficult to compare transoral robotic surgery total laryngectomy results to those of large cohort studies of traditional total laryngectomies. In addition, the presented studies had significant differences in important surgical steps and therefore did not use the same technique to excise the larynx. These differences reduce the homogeneity of our data. Finally, the lack of information on swallowing outcome, follow-up status and voice rehabilitation restricts our conclusion regarding some very critical and interesting outcomes of this procedure.