Introduction
The most favorable management of oropharyngeal cancer is still controversial. In the past, oropharyngeal cancers were treated with surgery followed by radiation. Surgical resection usually required mandibulectomy or mandibulotomy and removal of pharyngeal musculature, which resulted in significant morbidity. Because of the functional and cosmetic impairments and current development of organ preservation regimens, chemoradiation has become the treatment of choice in many patients with cancer of the oropharynx. Furthermore, studies have demonstrated an increased incidence of human papilloma virus (HPV)-related cancer of the oropharynx, particularly among young adults who have a better prognosis. There are emerging data that less aggressive treatment can be performed in this group of patients without sacrificing the good cure rate.
The oropharynx is the middle part of the throat that extends from the junction of the soft and hard palate superiorly to the superior edge of the epiglottis and the hyoid bone inferiorly, circumvallate papillae of the tongue anteriorly, and pharyngeal wall posteriorly. It includes the base of the tongue, the soft palate, the lateral and posterior pharyngeal walls, the tonsils, and tonsil pillars. The function of this region is crucial in swallowing, respiration, and speech. It is noteworthy that the swallowing function is adversely affected both by surgical resections and chemoradiation. Dysphagia and poor speaking may result in social problems, but aspiration may cause life-threatening complications. Therefore appropriate selection of the type of surgical approach is quite important in the management of cancer of the oropharynx.
The prognosis and treatment of cancer of the oropharynx are strongly related to the involvement of cervical lymph nodes. The incidence of lymphatic metastasis is relatively high, depending on the subsite. Even in patients with no adenopathy at the time of diagnosis, elective ipsilateral or bilateral neck treatment is required either through a neck dissection or by radiation therapy. In addition, the tonsillar fossa and base of the tongue are known as the most common potential mucosal sites in unknown primaries. There is also a risk for metastasis to the retropharyngeal lymph nodes in cancer of oropharynx, particularly in those patients in whom the posterior pharyngeal wall or the soft palate is involved. These nodes are beyond the classical neck dissection. The majority of those patients are required to have adjuvant radiotherapy. In such instances, radiation therapy is rational as a single treatment modality for primary and lymphatic metastasis, as well. Otherwise, transoral surgery is a feasible option in selected early limited cancer, in which the need for adequate exposure is fundamental.
Transoral resection of cancer of the oropharynx was first described by Huet in 1951. This technique eliminates the morbidity created by the mandibular swing or composite resection. In addition, this minimally invasive surgery may avoid adverse consequences of chemoradiation with comparable outcome. Moreover, it provides pathologic staging for further adjuvant treatment. Transoral surgery is generally indicated in early-stage cancer of the oropharynx. This can be done either via transoral robotic surgery or endoscopy-based transoral laser microsurgery. The transoral approach has been expanded with the development of transoral robotic surgery. This technological improvement provides three-dimensional visualization for precise dissection and safety of margins. There are some advantages of robotic surgery, including shorter hospitalization, rapid functional recovery, avoidance of tracheostomy, and reduced need for nasogastric tube feeding. We favor transoral robotic surgery in carefully selected patients.
Key Operative Learning Points
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Careful patient selection
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Accurate assessment of tumor extension and lymph node involvement
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Surgical anatomy of the carotid artery and association pharyngeal structures
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Special training for robotic surgery if transoral robotic surgery is preferred
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Ipsilateral or bilateral neck dissection is necessary. It can be done either simultaneously or separately. We prefer concurrent neck dissection following transoral resection.
Preoperative Period
History
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History of present illness
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Persistent sore throat, throat discomfort
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Neck mass
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Odynophagia, referred otalgia with swallowing, globus sensation
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Trismus, dysphagia, bleeding, difficulty moving the tongue
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Past medical history
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Tobacco use, alcohol consumption, betel quid chewing
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HPV exposure
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Radiation exposure
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Comorbid diseases, including systemic diseases and hemorrhagic diatheses
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Medications and herbal products being used
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Physical Examination
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Oral cavity—oropharynx
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Must include all mucosal surfaces to evaluate a second primary or extension of the primary tumor to surrounding structures
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Any dentures should be removed during the inspection.
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Palpation for size, deep fixation, and mobility of the lesion
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Assessment of cranial nerves, particularly cranial nerve IX, X, and XII
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Endoscopy
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Both flexible and rigid endoscopic evaluation
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Endoscopy under general anesthesia. This is preferred before definitive treatment in order to evaluate for the adequate exposure and availability of the tumor for transoral approach.
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Neck
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Palpation of the both necks
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Recording of the levels of lymph node involvement
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Imaging
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Computed tomography (CT), for bony invasion of the skull base, mandible, and status of the lymph nodes, particularly retropharyngeal lymph nodes
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Magnetic resonance imaging (MRI) for the depth of tumor invasion, perineural infiltration, and association with vital structures, particularly the carotid artery
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Positron emission tomography–computed tomography (PET-CT) to discover distant metastasis, especially in cases of advanced cancer. Not required in all cases
Indications
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Primary or recurrent cancer of the oropharynx, which can be excised transorally depending on the surgeons’ experience and patients’ condition and wishes
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Generally indicated in T1 and T2 cancers of the soft palate ( Fig. 33.1 ), posterior pharyngeal wall, tonsil and anterior pillar, the base of the tongue, and uvula ( Fig. 33.2 )
Fig. 33.1
Superficial carcinoma of the soft palate.
Fig. 33.2
T2 sagittal section of magnetic resonance imaging showing the tumor of the base of the tongue (arrow) accessible for transoral surgery.
Contraindications
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Trismus
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Inadequate exposure
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In robotic surgery, cancer requiring resection of more than 50% of the base of the tongue or more than 50% of the posterior pharyngeal wall ( Fig. 33.3 )
Fig. 33.3
Tumor invasion with more than 50% of the base of the tongue is a contraindication for transoral surgery.
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Close association of the tumor with carotid artery
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Invasion into the parapharyngeal space
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Bone invasion
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Tumor fixation of prevertebral fascia
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Invasion of the vital structures by the primary cancer
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Unresectable lymph node metastasis regardless of the primary cancer
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Poor exposure due to patients anatomic situation, such as micrognathia, cervical spine injury, macroglossia
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Inability to convert to open surgery intraoperatively
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Patients preference for another treatment modality
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Comorbid diseases with increased risk for general anesthesia
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Distant metastasis. Adenoid cystic carcinoma with limited pulmonary metastasis may be an exception.
Preoperative Preparation
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Biopsy to confirm the diagnosis
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Review any biopsies or tissue from previous surgery
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Routine laboratory tests and preparation of red blood cell suspension for probability of transfusion during surgery
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Cessation of antiplatelets/anticoagulant drugs
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Evaluation of the patient’s dentition is essential to prevent osteoradionecrosis due to probable postoperative radiotherapy.
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Dental consultation with prosthodontist for temporary postoperative palatal prosthesis in patients who need partial resection of the palate
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Counseling of the patient about the probable needs for temporary tracheostomy and/or nasogastric tube
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Cervical lymph node dissection is a part of the treatment of cancer of the oropharynx even in N0 neck; thus the patient should be informed about neck dissection.
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