Robot-assisted thyroidectomy

Introduction

Thyroidectomy is commonly performed through a transcervical approach, a technique first described by Theodor Billroth in the late 19th century. ^, Since that early description, technological advancement and its application have seen a remarkable evolution in thyroidectomy techniques over the past 20 years. The endoscope was first utilized for parathyroidectomy by Gagner and then by Hüscher et al. for the thyroid lobectomy. ^, Several endoscopic techniques have since been described employing axillary, breast-axillary and transoral approaches. With the advent of robotic surgery and its application to the head and neck, interest has grown in employing this minimally invasive technology to endocrine surgery. The impetus for this has been avoiding a visible cervical scar, an inevitable component of the traditional approach. This has also been influenced by a societal emphasis on physical appearance.

The first robotic-assisted thyroidectomy was performed by Chung and colleagues via a transaxillary approach in 2007. This adopted a previously described endoscopic approach but afforded advantages of increased range of motion and eye-hand coordination. Since then, new approaches have been developed including a breast-axillary, retroauricular/facelift, and more recently a transoral technique. Although scar avoidance is the premise behind these approaches, the robotic surgeon needs to balance this with adequate exposure which continues to drive critics opposed to these techniques.

The American Thyroid Association (ATA) has recognized the role robotic surgery plays in thyroidectomy and published a position statement in 2016. Several important considerations were proposed, including patient selection, surgeon experience, cost, and technical challenges. Surgeon experience above all is the single most important factor in successful robotic-assisted thyroid surgery. Surgeons performing both high-volume traditional thyroid procedures as well as head and neck robotic procedures are best equipped to perform this surgery. Nuances such as appropriate patient selection, exposure requirements, and degree of technical difficulty only come through experience. Robotic-assisted thyroid surgery represents the next iteration in robotic head and neck surgery and is a safe technique for select patients performed by high volume head and neck institutions.

Indications and contraindications

There is a lack of consensus among surgeons performing robotic-assisted thyroidectomy as to its contraindications and this is reflected in the absence of established criteria in the literature. Patient factors such as fitness for general anesthesia (GA) and previous surgery or radiation therapy are contraindications that are agreed upon among most experienced surgeons. Furthermore, patient body mass index (BMI) needs to be taken into account for access purposes. Inconsistency, however, exists in other key criteria, including thyroid size, nodule/tumor size, thyroid pathology, and extent of disease. Thyroid size criteria varies considerably among authors. Some specify maximum allowable thyroid diameter, whereas others focus on total thyroid volume or dominant nodule size. Razavi and Russell reviewed the literature and proposed a 10-cm total thyroid diameter limit for robotic-assisted thyroidectomy. Furthermore, they felt that a total tumor or dominant nodule size of greater than 6 cm in indeterminate or benign pathology was a contraindication to robotic-assisted thyroidectomy.

There is some agreement that preoperative pathology needs careful consideration when proposing robot-assisted thyroidectomy. Well differentiated thyroid carcinoma greater than 2 cm in size is a relative contraindication to a robot-assisted technique. ^, Extrathyroidal extension (ECE), especially gross tracheal or esophageal invasion as well as patients with preoperative recurrent laryngeal nerve (RLN) palsy, should be considered for conventional surgery. Unless performed in high-volume centers, patients with poorly differentiated thyroid cancer or lymph node metastasis should also have traditional thyroid surgery.

Benign pathology including Hashimoto thyroiditis, Graves disease, and multinodular goiters, although not absolute contraindications to robotic-assisted thyroidectomy, need special consideration. Kang et al. considered poorly controlled and severe Graves disease as a contraindication to a robotic-assisted thyroidectomy. Bilateral thyroid disease is another special consideration, especially depending on the robotic approach used. Table 48.1 summarizes the key contraindications and special considerations for robotic-assisted thyroidectomy.

TABLE 48.1

Indications and Contraindications for Transoral Robotic Thyroidectomy

Adapted from Razavi CR, Russell JO. Indications and contraindications to transoral thyroidectomy. Ann Thyroid. 2017; 2(5):12. https://doi.org/10.21037/aot.2017.10.01 .

Contraindications	Special Considerations
Patient unfit for a GA Previous neck surgery or radiotherapy Preoperative RLN palsy A total thyroid diameter of >10 cm Dominant nodule/tumor >6 cm if benign/indeterminate pathology OR Dominant nodule >2 cm if Bethesda Very suspicious or confirmed DTC. Extrathyroidal extension Poorly differentiated thyroid cancer Large multinodal goiter Sub/retrosternal goiter Poorly controlled Graves disease	Patient BMI Hashimoto thyroiditis Lymph node metastasis Bilateral disease

Contraindications

Special Considerations

Patient unfit for a GA
Previous neck surgery or radiotherapy
Preoperative RLN palsy
A total thyroid diameter of >10 cm
Dominant nodule/tumor >6 cm if benign/indeterminate pathology
- OR
- Dominant nodule >2 cm if Bethesda Very suspicious or confirmed DTC.
Extrathyroidal extension
Poorly differentiated thyroid cancer
Large multinodal goiter
Sub/retrosternal goiter
Poorly controlled Graves disease

Patient BMI
Hashimoto thyroiditis
Lymph node metastasis
Bilateral disease

BMI, Body mass index; DTC, well-differentiated thyroid carcinoma; ETE, extrathyroidal extension; GA, general anesthesia; MNG, multinodular goiter; RLN, recurrent laryngeal nerve.

Preoperative assessment

Patient evaluation

A thorough head and neck history and examination should be performed routinely in any patient considered for robotic thyroid surgery. The history should focus on previous head and neck surgery and radiation therapy to the neck or upper mediastinum. Cervical/thoracic spine abnormalities or a history of spinal surgery should be established, as this impacts access. A history of breast or axillary surgery should also be asked when considering a transaxillary approach. As with any thyroid history, symptoms and signs of hyper/hypothyroidism, voice change, airway symptoms, and a family history of thyroid cancer should be determined.

The physical examination (PE) should concentrate on patient factors which may limit robotic surgical access. For transoral robotic thyroidectomy (TORT) this may include poor neck extension, limited mouth opening or trismus, and retrognathia. Poor dental hygiene with abscess is a contraindication to TORT. The presence of axillary or retroauricular scars may exclude these approaches for thyroidectomy. The other key element to the PE is assessment of the extent of thyroid disease. This includes palpation of the thyroid to assess goiter size, retro/substernal extension, or in the setting of thyroid cancer whether this is locoregionally advanced. A large firm fixed mass may indicate significant extranodal extension (ENE). Palpation for central and lateral neck disease also provides vital information for staging purposes but importantly in most institutions necessitates a neck dissection through a cervical incision, thus abolishing any benefit from robotic thyroidectomy. The PE should be completed with a dedicated voice assessment and laryngoscopy to evaluate vocal cord function. Vocal cord paralysis may indicate locally invasive thyroid cancer or in the setting of benign disease confirm a relative contraindication to robotic surgery.

Imaging

Thyroid ultrasound (US) is mandatory prior to consideration of any surgical procedure on the thyroid. Specifically for robotic thyroid surgery it defines total thyroid diameter and volume along with nodule size and characteristics. In well trained hands it can also be useful in defining ENE or central/lateral neck lymphadenopathy. In conjunction with fine needle aspiration (FNA), the information gathered from US helps to plan the correct thyroid surgery for patients and more importantly assists in defining patients eligible for a robotic approach.

Although not mandatory, cross-sectional including computed tomography (CT) or magnetic resonance imaging (MRI) of the neck may be useful in large goiters, especially with sub/retrosternal extension. The extent of gross ENE can also be defined; however, these are situations in which robotic thyroidectomy is contraindicated. Posteriorly based lymphadenopathy may also be evaluated. Routinely, CT and MRI do not tend to add any further information that US does not already provide and so has a limited role in the preoperative workup of potential robotic thyroidectomy candidates. US is the most important modality for thyroid workup, and cross-sectional imaging techniques should be reserved for situations where US expertise is not available.

Fine needle aspiration

The role of FNA is no different in robotic thyroid surgery from conventional surgery. It may assist the surgeon in counseling patients for surgery, in particular, the extent of surgery planned. The ATA guidelines on thyroid nodules and differentiated thyroid cancer best summarizes the role of FNA in thyroid nodule evaluation and treatment.

Laboratory testing

Thyroid function testing, especially thyrotropin (TSH), should be performed in all patients with a thyroid nodule being evaluated for surgery as recommend by the ATA. Free T3 and T4 is also important prior to surgery to assess secretory activity of the thyroid. Graves disease robotic thyroidectomy is best performed by experienced robotic thyroidectomy surgeons.