Introduction
Primary surgery with adjuvant radiotherapy has long been accepted as the standard treatment plan for cure for the majority of head and neck cancers, including oropharyngeal and supraglottic cancer. Although these open surgical approaches have yielded high rates of local and regional control, they carry the risk of significant and life changing morbidity. , This morbidity can have devastating effects upon the patient’s speech and swallowing, affecting their physical and mental well-being. , This functional and psychological cost to the patient has influenced the decision-making process of physicians and resulted in many patients being referred to a nonsurgical approach.
This nonsurgical approach has been supported by several phase III trials showing efficacy and safety. , , However, reviews of long-term outcomes of primary nonsurgical treatment have shown toxicity of treatment and poor functional outcomes. This lack of function preservation despite organ preservation has influenced multidisciplinary teams to reassess treatment algorithms. , , , ,
In the past 20 years, technological advances in light sources, fiberoptic endoscopes and end-effector energy sources such as LASER has encouraged surgeons to adapt to and adopt new minimally invasive operative techniques. These include transoral resection with headlight and loupes for magnification, transoral LASER microlaryngoscopic resection and transoral video assisted telescopic resection of tumors.
The development of surgical robotic systems and the introduction of transoral robotic surgery (TORS) has significantly improved visual access and reach with nontremulous wristed instruments. This has allowed safe and complete resection of tumors with reduced morbidity. , , ,
TORS was initially developed for otolaryngology, head and neck surgery in 2005 by Haus et al. in a porcine model. In the early 2000s, Weinstein and O’Malley demonstrated its use in the resection of T1 and T2 oropharyngeal carcinomas. , TORS was approved by the Food and Drug Administration (FDA) for selected lesions in 2009. Following this, its use has been integrated in the treatment matrix for head and neck carcinoma, and several large prospective studies conducted have demonstrated good functional and oncological outcomes. These improved outcomes have led to the reevaluation of the biologically different p16 positive human papillomavirus (HPV) 16–associated oropharyngeal cancer.
As patients enjoy increasing survivorship from head and neck carcinoma, issues surrounding quality of life are becoming more pertinent in the decision matrix.
Genden et al. conducted a nonrandomized prospective study demonstrating that TORS has a higher chance of returning a patient to baseline diet compared to chemoradiotherapy but showed no difference in oncological outcome. De Almedia et al. reported in a systematic review that patients undergoing TORS with adjuvant intensity-modulated radiation therapy (IMRT) or TORS alone had lower rates of long-term adverse events compared to chemoradiotherapy. Retrospective evaluation of radiotherapy such as the ICON-S study demonstrate good functional and oncologic outcomes with primary radiation. The recently published ORATOR trial was the first randomized, controlled phase-two clinical trial comparing IMRT (with or without chemotherapy) with TORS (with or without adjuvant radiation or chemoradiation). This trial reported a trend to better swallowing in the chemoradiation cohort but found no clinically meaningful difference in functional outcomes for similar oncological outcomes.
The current body of evidence is lacking high level evidence, with only one Cochrane review conducted in 2016 and numerous nonrandomized trials all providing no definitive evidence of superiority. There are several randomized, controlled studies currently being conducted that should report in the next few years. Some of these studies are examining the role of TORS in deescalating treatment, particularly for the cohort of patients who are nonsmokers with p16 positive/HPV 16 associated oropharyngeal cancer.
The current evidence suggests that TORS provides a good, safe treatment alternative for selected patients with suitable lesions and provides not only comparable oncologic results but is able to maintain an excellent functional outcome.
Anatomy
Understanding transoral surgical anatomy is vital to the safe practice of TORS. The most significant disadvantage for traditional open approaches to resection of head and neck tumors is the extensive dissection and potential damage to uninvolved anatomic structures and most pertinently to the muscles involved in swallowing. TORS has enabled access to the oropharynx, pharynx, and larynx with minimal damage to these surrounding structures.
The most important consideration is to understand the relationship of the carotid artery to the lateral pharyngeal structures. The position of the internal carotid artery in the neck must be understood from the preoperative scans and the surgeon must be aware of the possibility of an anomalous medially placed internal carotid artery. The relationship of the external carotid artery and its branches must similarly be understood in the preoperative imaging. The carotid vasculature usually lies deep and lateral to the styloglossus muscle and usually the tonsillar branch of the glossopharyngeal nerve can be identified during resection lying on the surface of the styloglossus.
Tongue base resection requires two considerations. First, it is important to recognize that in tongue base mucosectomy a clear surgical plane can be identified between the lymphoepithelial layer and the muscular layer of the tongue, and dissection proceeds in this surgical plane. Second, when resecting in a deeper muscular layer one must be aware of the lingual artery and the dorsal lingual branch of the lingual artery. The tongue is a very mobile structure and hence the arteries are tortuous and can be met on several occasions during the resection. The vessel and its branches require control with the application of a vascular clip.
The importance of understanding the anatomy of the lateral oropharyngeal wall is essential to ensure a safe, compartmentalized resection with clear margins.
Lateral oropharyngeal wall including tonsillar fossa
The lateral oropharynx is a compartment enclosed by the palatoglossus anteriorly and the palatopharyngeus posteriorly, respectively the anterior and posterior tonsillar pillars ( Fig. 43.1 ). The fossa produced by these two arches contains the palatine tonsils, which are lymphoid tissues covered medially by stratified squamous epithelium. The lateral surface of the tonsil is encased by dense fascial capsule, which is immediately related to the superior pharyngeal constrictor muscle. , Further lateral to the superior constrictor is the buccopharyngeal fascia, with a loose areolar plane separating these two layers ( Table 43.1 ). The buccopharyngeal fascia is the final barrier between the tonsillar fossa and the parapharyngeal space. The stylopharyngeus muscle lies lateral to the oropharynx as it arises from the styloid process attaching to the end of posterior border of the thyroid cartilage. The stylopharyngeus passes on the lateral surface of the superior constrictor, then between the superior and middle constrictor before reaching its attachment. At the superior and lateral aspect of the parapharyngeal space lies the medial pterygoid muscle, and at the inferior aspect lies the styloglossus muscle, upon which lies the tonsillar branch of the glossopharyngeal nerve.
| Layer | Landmarks | Muscles | Vessels | Nerves | Other Structures |
|---|---|---|---|---|---|
| First |
|
|
| Lingual branch of CN IX |
|
| Second |
|
|
|
|
|
| Third |
|
|
|
|
|
Vasculature and innervation
The palatine tonsil is supplied from the external carotid artery with its main branches approaching inferolaterally ( Fig. 43.2 ). The main supply is from the tonsillar branch of the facial artery; this pierces the superior pharyngeal constrictor muscle entering on the lateral surface of the tonsil. The facial artery is a close relation of the superior pharyngeal constrictor at this level before approaching the lateral border of the mandible. The tonsil also receives blood supply from the ascending pharyngeal artery as well as branches of both the internal maxillary artery and lingual artery. Both the internal and external carotid artery are close relations lateral to buccopharyngeal fascia. The tonsil is drained by the external palatine vein into the facial vein.
The glossopharyngeal nerve is the main afferent from the tonsillar fossa and the superior pharynx ( Fig. 43.3 ). The glossopharyngeal nerve exits from the jugular foreman passing between the internal jugular vein and internal carotid artery. It descends in front of the internal jugular vein before curving around the stylopharyngeus. It accompanies the stylopharyngeus between the superior and middle constrictor into the pharynx.
Lymphatics
The lateral oropharynx lymphatic drainage is directly into the deep cervical lymphatics, particularly the jugular digastric node. Hence, this is the usual pathway for metastatic spread in patients with tonsillar carcinoma. The soft palate superiorly drains to the retropharyngeal lymph nodes within the fat pad of the lateral wall of the pharynx anterior to the prevertebral fascia.
Base of tongue
The tongue is attached to the hyoid bone, mandible, styloid process, and pharynx (see Fig. 43.1 ). Anatomically it consists of intrinsic muscles that are in three tangential planes and the extrinsic muscles. The extrinsic muscles are the genioglossus, hyoglossus, styloglossus, and palatoglossus. The embryological origin of the tongue defines the anatomical division into the oral and pharyngeal part. The pharyngeal component or tongue base is the area of interest for TORS. The pharyngeal component or tongue base begins posterior to the circumvallate papilla and projects posteriorly to form the anterior wall of the oropharynx. The tongue base is covered by lymphoid tonsillar tissue which is contiguous with the palatine tonsil at the glossotonsillar sulcus. Deep to this are the intrinsic muscles of the tongue. The root of the tongue consists of the floor of the mouth which includes genioglossus muscle resting above the geniohyoid and mylohyoid muscles. Transoral access to these areas can be difficult due to exposure. This is an important consideration in TORS.
Vasculature and innervation
The lingual artery arises from the external carotid artery at the level of the hyoid bone, travelling laterally to the middle constrictor. At this point it is crossed by the hypoglossal nerve passing deep to the hyoglossus muscles where it runs on the superior surface of the hyoid bone. At this junction it can be damaged during transoral base of tongue surgery. Following this critical point, the artery gives off a suprahyoid branch, dorsal lingual artery, the sublingual artery, and the arteria profunda. The arteria profunda passes between the genioglossus muscle and inferior intrinsic tongue. The tongue is drained by lingual veins which pass to internal jugular vein.
The hypoglossal nerve provides motor supply to the tongue. The nerve exits the base of the skull from the hypoglossal canal, descending posterior to the internal carotid artery, the glossopharyngeal nerve, and vagus nerve. It travels between the internal carotid artery and internal jugular vein, passes anterior to lie in front of the vagus nerve before looping in front of the internal and external carotid artery and lingual artery. A small branch of the occipital artery supplying the sternocleidomastoid muscle crosses the nerve inferior to the posterior belly of the digastric muscle. The nerve travels over the hyoglossus muscle travelling on the superior border of the hyoid bone, deep to the digastric and mylohyoid muscles. This landmark is the most at risk for transoral base of tongue surgery. The nerve divides into its terminal divisions between the mylohyoid and genioglossus muscle before supplying the tongue.
Lymphatics
The base of tongue has a dense lymphatic supply draining to submental, submandibular, jugulodigastric and jugulo-omohyoid nodes. The lymphatics are extensive and communicate to bilateral drainage pathways.
Preoperative assessment
The importance of accurate preoperative assessment cannot be overstated in setting up the surgeon and patient for success. Weinstein and O’Malley in 2009 reported a multiinstitutional retrospective review which was utilized by the United States FDA to help certify the use of TORS. However, not all patients are appropriate candidates for TORS. In 2014, the FDA restricted its use to benign lesions and T1 or T2 lesions. While there have been numerous studies since this demonstrating its effectiveness as a treatment modality for a wider group of patients, appropriate case selection is vital to deliver a successful TORS program. The contraindications to TORS as a treatment modality can be broken down into patient-related factors and tumor-related factors. ,
Patient considerations
Patient selection for TORS surgery is based upon maximizing exposure while minimizing surgical morbidity. The ultimate purpose would be for patients to avoid tracheostomy, pharyngotomy, and free flap reconstruction. Due to the fact that TORS requires healing by secondary intention, operative candidates must be able to withstand potential complications such as bleeding, airway compromise, dehydration, and malnutrition. Comorbidities such as immunosuppression, congestive cardiac failure, chronic obstructive lung disease, connective tissue or rheumatological disease, and bleeding diathesis may serve as relative or absolute contraindications. ,
Adequate access and exposure are vital in enabling successful TORS procedures. Rich et al. identified 8Ts of the preoperative assessment to ensure adequate transoral access. , These included:
- 1.
Trismus
- 2.
Transverse dimension (mandibular)
- 3.
Teeth
- 4.
Tori
- 5.
Tongue
- 6.
Tilt
- 7.
Treatment (prior radiotherapy)
- 8.
Tumor
While the above list relates specifically to endoscopic transoral laser microsurgery, they can be applied for TORS. There has been further work to expand the preoperative considerations specifically for TORS on the work originally done by Rich et al. These include , :
- 9.
Morbid obesity
- 10.
Micrognathia
- 11.
Microstomia
- 12.
Craniofacial abnormalities
These four additions have been recognized to impair TORS access. While there is no specific body mass index that prevents TORS, a BMI greater than 40 has served as a relative contraindication. Micrognathia and microstomia are both subject to the skill of the physical examiner and may be subjective, hence, difficult to apply consistently. Arora et al. attempted to produce more specific anatomical characteristics and dimensions by assessing 51 cadavers. The group assessed mandibular body length, mandibular body height, hyoidmental distance, sternomental distance, thyromental distance, cricomental distance, and neck circumference. The significant results are demonstrated in Table 43.2 .
| Parameter | Site | Visualization | Mean | T | P Value |
|---|---|---|---|---|---|
| Mandibular body height | Base of tongue | Adequate | 2.6 | 2.18 | 0.03 |
| Suboptimal | 2.2 | ||||
| Epiglottis | Adequate | 2.7 | 2.64 | 0.01 | |
| Suboptimal | 2.2 | ||||
| Hyoid-mental distance | Base of tongue | Adequate | 5.5 | 2.41 | 0.02 |
| Suboptimal | 4.8 | ||||
| Epiglottis | Adequate | 5.5 | 2.02 | 0.05 | |
| Suboptimal | 4.9 | ||||
| Neck circumference | Base of tongue | Adequate | 38.7 | −2.08 | 0.04 |
| Suboptimal | 42.1 | ||||
| Epiglottis | Adequate | 36.8 | −2.10 | 0.04 | |
| Suboptimal | 41.2 |
The greater mandibular body height, longer hyoid-mental distance, and narrower neck circumference all were beneficial to adequate visualization. The remaining anthropometric measurements did not significantly influence visualization. Preoperative imaging has been utilized to help determine whether anatomical characteristics can predict access. The characteristics found to be of statistical significance include:
- 1.
Distance from posterior pharyngeal wall to hyoid: ≤30 mm
- 2.
Angle between epiglottis and vertical plain of larynx: ≥130 degrees
- 3.
Distance from posterior pharyngeal wall to soft palate: ≤8.1 mm
Preoperative assessment of the patient and imaging is important to recognize contraindications to surgery. Specific patient comorbidities are important in surgical planning.
Tumor considerations
Tumor location, characteristics, and involvement of surrounding anatomical structures are important parts of assessing the candidacy of a patient for TORS. Furthermore, the extent of resection to enable clear margins must also be estimated by the surgeon. The pioneers of TORS, Weinstein et al. and O’Malley, presented three categories of contraindications: vascular, functional, and oncological. ,
Vascular contraindications :
- 1.
Tonsillar cancer with a retropharyngeal carotid artery
- 2.
Epicenter of tumor is in the midline of the tongue base or vallecular, which would put both lingual arteries at risk
- 3.
Tumor is adjacent to carotid bulb or internal carotid artery, which will result in intraoperative exposure of vessel
- 4.
Encasement of carotid artery by primary tumor (T4b) or by metastatic neck node
- 1.
Functional contraindications :
- 1.
Tumor resection requiring more than 50% of deep tongue base musculature
- 2.
Tumor resection requiring more than 50% of the posterior pharyngeal wall
- 3.
Tumor resection requiring up to 50% of the tongue base as well as the entire epiglottis
- 1.
Oncological contraindications :
- 1.
All T4b cancers
- 2.
Posterolateral fixation of tonsillar cancers to prevertebral fascia
- 3.
Unresectable neck disease
- 4.
Neoplastic related trismus
- 5.
Multiple distant metastasis
- 6.
Involvement of mandible or hyoid
- 7.
Tumor extension into soft tissue of neck
- 8.
Eustachian tube involvement
- 1.
Patients may not demonstrate tumor contraindications for TORS but still not be suitable candidates for intervention. While tumor features are favorable for resection, functional consequences and surgical morbidity are vital in surgical planning; hence, it is necessary to be aware of situations where the morbidity and functional deficits will not be minimized.
Return to preoperative swallow function is an important recovery goal of TORS. Increased TNM stage has been demonstrated to produce worse postoperative swallowing outcomes. A recent review of quality-of-life outcomes for 81 patients demonstrated that those patients greater than 55 years old were five times more likely to need long-term gastrostomy tubes. The same study further showed that resection of more than one oropharyngeal subsite resulted in a greater than fivefold increase in gastrostomy tube insertion.
While functional outcomes are an important consideration, the impact of adjuvant radiotherapy or chemoradiotherapy on quality of life must also be considered (Baskin). While the aim of first line therapy is to ensure either no or deescalated therapy, this may not always be possible due to tumor characteristics. Zevallos et al. performed a multivariate analysis of 369 TORS patients that demonstrated individuals with T2 tumor and those with N2 disease were far more likely to have positive margins. In conjunction with potential extracapsular extension, deescalated therapies may not be possible. Adjuvant therapy has been well known to produce poorer quality of life outcomes.
Anesthesia considerations
Airway management
Airway management is critical within TORS due to the shared airway. Most institutions opt for a nasal intubation to ensure clear passage of the oral cavity with improved surgical access once the gag is placed, some preferring a reinforced endotracheal tube (ETT). , However, an oral tube has been used within the literature with good success and secured to the tongue or other oral structures. Advanced airway equipment, such as a videolaryngoscope or a fiberoptic scope, prevents trauma to the primary pathology and limits bleeding. Consideration must be taken in choosing tube location based on tumor location, size, and the potential use of laser equipment intraoperatively.
Anesthesia
Most institutions utilize a bispectral index-guided total intravenous anesthesia using target-controlled infusions of propofol and remifentanil for induction and maintenance. , However, use of volatile gases with or without fentanyl or remifentanil has been utilized. Invasive monitoring is usually recommended and, if central venous access is required, some institutions recommend femoral access; however, subclavian access is also suitable. ,
Neuromuscular blockade is important not only to facilitate intubation but also during gag placement. It is necessary to ensure sufficient muscular flaccidity is present to allow placement of the gag and ensure cough risk reduction throughout the procedure. Some institutions have recommended neuromuscular blockade infusions to produce optimal surgical conditions; however, they require reversal at the end of surgery. Throughout surgery, neuromuscular blockade monitoring is recommended.
It is recommended that all venous access be placed on the contralateral side to the robotic patient cart. , Positioning of the patient requires adequate neck extension and this should be taken into consideration when securing the endotracheal tube ETT. All infusion pumps should be placed at the end of the operating table and an extra-long anesthetic circuit is utilized. All infusion lines and circuit should be placed on the contralateral side of the robotic surgical cart. Once the patient is secured and surgeon is about to commence, inspired oxygen should be reduced to maintain adequate oxygen supply. , This decreases the risk of potential airway fire if there is cuff leak with diathermy closely applied.
Intraoperative analgesia is multimodal and includes nonsteroidal anti-inflammatory drugs, opiates, antibiotics, and dexamethasone. In the context of postoperative airway edema judicious use of opiates should be considered to avoid oversedation. Antiemetic therapy should be used to minimize the risk of postoperative nausea and vomiting. Intraoperative fluid management should be conservative to mitigate the development of postoperative edema. Sympathetic stimulation from the continual pressure of surgical gag can be overcome with deepening of anesthesia or analgesia. , Intraoperative utilization of remifentanil target-controlled infusions in conjunction with propofol is used; however, other options include intermittent boluses or infusions of opiates, beta-blockers.
Human factors and situational awareness are critical in TORS as nonverbal cues and direct visualization are limited between the surgeon and anesthetist. Being a shared airway, clear communication between the surgical team and anesthetic team is always required. Emergency undocking and removing of the robotic is a necessary skill required by all staff present within the case.
Intraoperative planning
As with any surgery, TORS requires a highly effective team with clear communication between all members, including the surgical assistant, anesthetist, and nursing staff. Ensuring all team members are properly and appropriately trained in TORS is essential to ensure a well-functioning team. It should be emphasized that while staff may be trained for robotic surgery in other specialties, it is necessary that all members of the team are specifically trained for TORS. It is important to ensure that all equipment is available and instrumentation setup is complete with emergency equipment accessible and present within the operating theatre. This is particularly important due to the potential airway risk in TORS patients.
Robotic devices
The robotic systems currently approved for use with TORS are the da Vinci Standard, S (no longer being manufactured), Si (no longer being manufactured), X and Xi Surgical Systems made by Intuitive Surgical Inc. (Sunnyvale, CA).
Equipment and instrumentation
While individual equipment and instrumentation is important, the first hurdle is to ensure that the operating room is large enough to accommodate all the equipment. The primary equipment necessary for the operation ( Fig. 43.4 ) includes:
- 1.
Robotic system: da Vinci robotic system, consisting of three modules: patient side cart, surgeon console, and vision cart
- 2.
Laryngoscopy tray with appropriate rigid laryngoscopes
- 3.
Emergency airway tray, including tracheostomy tray
- 4.
General surgical tray
- 5.
Secondary video tower
- 6.
Procedural case tray, inclusive: mouth gag and retractors, (monopolar) cautery spatula, and the Maryland dissector or Maryland bipolar dissector if the 8mm arms are utilized
Further equipment required:
- 1.
Thirty-degree surgical endoscope
- 2.
Zero-degree surgical endoscope
- 3.
Sequential compression device or pneumatic calf compressors
- 4.
Cautery unit
- 5.
Two surgical suctions: preferably pediatric Yankauer suction—this thinner profile enables improved positioning
- 6.
Surgical light source
The other additional ear, nose, and throat (ENT) specific equipment that is required includes:
- 1.
Lip retractor and teeth protectors
- 2.
Needle holder
- 3.
Debakey and Gillies forceps
- 4.
Hemostats
- 5.
Metzenbaum and suture scissors
- 6.
Small and medium vascular clips with appropriate applicators
Retractors for transoral robotic surgery
TORS has enabled that the more invasive, aggressive surgical approaches such as mandibulotomy and lateral pharyngotomy can be avoided. However, while TORS is a viable alternative, success requires adequate exposure to enable visualization and access for excision of the lesion. To enable success, multiple retractor systems have been created specifically for minimally invasive work in the oropharynx, hypopharynx, and larynx ( Table 43.3 ).
| Retractor | Features | Primary Indications | Limitations |
|---|---|---|---|
| Crowe-Davis | Open lateral frame, easily accessible, familiar | Oral cavity, oropharynx | Limited base of tongue, hypopharynx, and larynx exposure |
| McIvor | Easily accessible, familiar, useful in edentulous patient | Oral cavity, oropharynx | Limited base of tongue, hypopharynx, and larynx exposure, closed frame |
| Dingman | Wide frame, cheek retractors, tie down points, accessible | Oral cavity, oropharynx (especially palate) | Limited base of tongue, hypopharynx, and larynx exposure, closed frame |
| FK/FK-WO | Wide frame, various blades designed for exposure of specific areas, integrated suction, modified for TORS (FK-WO) | Oropharynx, hypopharynx, larynx | Closed frame, expense? |
| LARS | Designed for laryngeal procedures, curved frame, various blades, vertically adjustable blades, instrument attachments | Larynx, oropharynx, hypopharynx | Closed frame, expense? |
| Medrobotics Flex (FRS) | Designed for TORS, curved frame various blades, blade adjustment in multiple planes, integrated suction | Oropharynx, hypopharynx, larynx | Closed frame, expense? |
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