Transoral Robotic Surgery (TORS) for Primary Treatment of Oropharyngeal Cancer

Proprietary names: da Vinci® Surgical System, da Vinci STM Surgical System, da Vinci S High-Definition (HD)TM Surgical System, da Vinci SiTM HD Surgical System, EndoWrist® instrumentation, Intuitive® motion

Generic names: endoscopic instrument control system, endoscopic instruments and accessories, remote surgical manipulator, robotic surgical platform, robotic surgical system, robotic telemanipulator system, surgical robot, telerobotic surgery, telesurgical system

Procedure names: transoral robotic-assisted surgery, robotic-assisted surgery, minimally invasive endoscopic surgery

In 2009, da Vinci Surgical Systems (Intuitive Surgical, Inc.) received marketing clearance for use during transoral otolaryngology surgical procedures to treat benign and malignant tumors classified as T1 (i.e., ≤2 cm in greatest dimension) and T2 (i.e., >2 cm but ≤4 cm in greatest dimension). Since about 80% of oral tumors that clinicians treat with transoral robotic surgery (TORS) are oropharyngeal cancers (most often in late stages), the focus of this report is TORS for primary treatment of oropharyngeal cancer.1

Oropharyngeal cancer can occur at the base of the tongue, in the tonsillar region, in the soft palate, and in the posterior or lateral pharyngeal walls.2 Almost all oropharyngeal cancers are squamous cell carcinomas.2 Common risk factors for developing oropharyngeal cancer include human papilloma virus (HPV) infection believed to be transmitted through oral sexual contact, male gender (three to five times greater risk than females), tobacco use, and frequent, heavy consumption of alcohol.2-6 Symptoms of oropharyngeal cancer, which usually are not evident until late stages, include pain, dysphagia, weight loss, ear pain originating outside the ear, reduced ability to open the jaw, fixation of the tongue, bleeding, and presence of a neck mass.2 Clinicians must perform a biopsy to definitively diagnose oropharyngeal cancer.7 To determine the disease extent and plan treatment, imaging studies are often performed (e.g., chest x-ray, computed tomography CT, magnetic resonance imaging MRI, positron emission tomography PET, ultrasonography, PET/CT).5,7,8 Also, since patients with HPV-positive cancers may require a different management approach,9 determining HPV status is important.5

Clinicians initially classify oropharyngeal cancers according to a TNM system that describes the size of the primary tumor (Tis in situ through T4 advanced disease), the cervical node status (i.e., regional metastasis) (N0 none through N3 metastasis in a lymph node >6 cm in greatest dimension), and the presence or absence of distant metastasis (M0 none to M1distant metastasis).2,10 TNM measurements are used to further classify cancers as early stage (i.e., 0, I, II) or more advanced stage (i.e., III, IV).2 Staging helps the clinician develop a treatment plan, assess the likelihood of treatment success, and determine the prognosis.10

Primary treatment of oropharyngeal cancer depends on cancer type, stage, and location. According to National Comprehensive Cancer Network guidelines, treatment may include chemoradiotherapy, radiotherapy, surgery, or surgery followed by adjuvant chemoradiotherapy or radiotherapy.11 Open surgery, which is no longer routinely performed as a primary treatment for oropharyngeal cancer,8,12 requires a transcervical (i.e., ear-to-ear) incision across the throat or a lip-splitting mandibulotomy (i.e., splitting the jaw) and is associated with long-term or permanent speech and/or swallowing difficulties, disfigurement, damage to surrounding organs and nerves, significant pain, trauma, and a lengthy recovery.13,14 To avoid extensive surgery and in response to clinical study indicating poorer outcomes (i.e., survival, locoregional control) with primary treatment with radiotherapy alone compared with chemoradiotherapy,15 most clinicians have adopted chemoradiotherapy as the dominant primary treatment for advanced oropharyngeal cancer.1,12,16 However, the acute and severe late toxicity associated with chemoradiotherapy17 and the increasing incidence of HPV-positive oropharyngeal cancers in younger patients (aged 50 to 64 years) have led to interest in primary treatment of oropharyngeal cancers with minimally invasive surgery (i.e., transoral i.e., through the mouth techniques).18 Transoral laser microsurgery, a minimally invasive technique originally described in 1989, has not been widely adopted to treat oropharyngeal cancer due to limitations associated with access, field of vision, and instrument range of motion.12,18-20

Increasingly, surgeons are performing minimally invasive TORS as primary treatment for oropharyngeal cancers.12 According to advocates for this transoral approach, TORS provides "precise tailoring of postoperative adjuvant therapy (i.e., radiotherapy, chemoradiotherapy) based on pathologic staging information."18,21 In some cases, gaining pathologic information about the tumor and lymph nodes during TORS may reduce or eliminate the need for postoperative adjuvant therapy.22,23 Choosing the optimal postoperative adjuvant treatment option is especially important for patients with HPV-positive oropharyngeal cancers "who are expected to have a longer life span over which long-term treatment may occur."24

In 2011, 13,580 new cases of oropharyngeal cancer were reported in the United States.16

The overall incidence of oropharyngeal cancer has almost doubled in the past decade in the United States, while the incidence of smoking-related HPV-negative oropharyngeal cancers is declining.5,6 Furthermore, the number of individuals who present with late-stage disease is increasing. Between 1985 and 2007, the percentage of T1 and T2 cancers among late-stage oropharyngeal cancers almost doubled (33% in 1985 and 61% in 2007), and the overall percentage of early-stage oropharyngeal cancers dropped by half (30% in 1985 to 15% in 2007).25 These trends are primarily due to a dramatic increase in cases in otherwise...