Partial Pharyngectomy
Giuseppe Spriano
INTRODUCTION
The pharynx has a tubular configuration. It takes part in the pharyngeal phase of swallowing and deglutition and contributes to phonation mainly by determining the resonance characteristics of the voice. Squamous cell carcinoma accounts for more than 90% of malignant tumors originating in this region. The relevant steps involved in the proper coordination of pharyngeal activity, the possible impact of surgery on the quality of life, explain why more surgical salvage procedures have been reported over the years since the 1950s adopting organ preservation protocols. However, a wide range of surgical procedures, from transoral tonsillectomy to transmandibular pharyngectomy, are still considered valid oncologic approach in the management of cancer of the oropharynx. These procedures always consist of excision of the primary cancer and neck dissection. Segmental mandibulectomy, as currently performed, was reported by Slaughter et al. and by Ward and Robben half a century ago, and the main step of the procedure has not changed.
HISTORY
Development of cancer in this region is strictly related to the use of tobacco and alcohol products and to the infection of human papillomavirus (HPV). The patient may complain of dysphagia, otalgia, or evidence of a cervical mass. The history should include information about the patient’s sexual habits. The majority of patients are initially found to have stage III or IV cancer.
PHYSICAL EXAMINATION
The head and neck surgeon must perform a detailed history and physical examination of the head and neck as the first step in establishing the correct diagnosis, staging, and treatment planning of a pharyngeal cancer. This must include inspection and bimanual palpation of the oral cavity, floor of the mouth and tongue, direct fiberoptic examination of the pharynx, and laryngeal structures. Palpation of the neck is critical in the correct staging of the patient.
The patient is routinely prepared with blood samples and coagulation tests, urine tests, electrocardiogram, and chest radiography. The health conditions of the patient and the present risks of undergoing surgery under general anesthesia must also be evaluated. Low performance status and malnutrition may interfere with healing and expose the patient to infections.
Any previous surgery or radiation to the area must be taken into consideration for adequate treatment planning because it can interfere with the choice of reconstructive techniques. Blood units are screened, typed, and crossed or autologous blood is drawn if more than 500 mL of blood loss is estimated.
INDICATIONS
a. Low-stage cancers (T1, T2, N0-N1):
1. Tumor excision (treatment of choice)
2. Surgical salvage, in case of residual cancer after radiation or chemoradiation (selected N1 cases)
b. High-stage cancers (T3, T4a, N0-1; any T, N2-N3):
1. Surgical salvage for residual cancer following organ preservation protocols
2. Primary treatment
c. Recurrent cancer
Pharyngectomy for oncologic reasons must always obtain adequate cancer free margins, at least 2 cm wide because of the tendency of these cancers to have submucosal spread, to prevent microscopic residual disease (R1) at the surgical margins.
CONTRAINDICATIONS
Comorbidities and invasion of the prevertebral fascia by the primary cancer are the main contraindications to this surgery.
PREOPERATIVE PLANNING
Imaging Studies
Imaging studies include computed tomography (CT) and magnetic resonance imaging (MRI) of the skull base and neck with and without contrast. Imaging studies, particularly MRI/CT, are useful to detect invasion of the mandibular infiltration or the distance between the cancer and the mandible. CT scan of the chest will be required especially for stages III and IV cancer.
Physical examination, including inspection and palpation, remains one of the most important aspects of the preoperative evaluation. Resectability of cancer of the posterior pharyngeal wall is determined by the size and degree of fixation of the cancer. Endoscopy under general anesthesia, performed for bioptic mapping of the lesion, is considered a mandatory procedure. Radiologic evaluation of the patient includes MRI, which proves to be the most sensitive modality for tissue definition in evaluating cancers involving the base of the tongue. Diagnosis of gross tissue invasion of the preepiglottic space and the depth of infiltration into the base of the tongue may be determined by obtaining sagittal MRI scans. The high signal intensity of the preepiglottic adipose tissue can usually be distinguished from the dense fibers of the hyoepiglottic ligament, musculature of the base of the tongue, lingual lymphoid tissue, and cancer.
A barium pharyngoesophagram can often be helpful in assessing mobility of these cancers. Ultrasonography of the neck is performed to identify metastasis to cervical lymph nodes to complete the staging. CT of the chest is also done in order to detect primary or metastatic cancer of the lungs. The structure of the oropharynx and hypopharynx plays a key role in swallowing. Temporary aspiration is a predictable postoperative occurrence. The patient’s functional status, especially cardiopulmonary performance, must be considered in patient selection.
SURGICAL TECHNIQUE
Effective prophylaxis is obtained by intravenous (IV) infusion of a broad-spectrum antibiotic within 30 minutes of the beginning of the surgical procedure. Nasotracheal or orotracheal intubation may be considered, when tracheostomy is not required. All patients are operated in the supine position with a pillow under the shoulder to achieve hyperextension of the head. Tracheostomy is performed at the beginning of the operation, and a nasogastric feeding tube is inserted.
If CO2 laser surgery is being planned, precautions for laser must be carried out.
In case the transoral approach is to be used, a fiberoptic headlight is worn by the surgeon.
Surgical techniques involving the oropharynx may be categorized according to the surgical approach or the disease location (subsite[s] involved). In the former category, there are three principal approaches that can be used in performing pharyngectomy as described:
1. Transoral: surgical excision of the pharyngeal cancer, through the oral cavity. This approach is reserved for limited benign tumors or small, superficial cancers of the lateral, superior (soft palate), and posterior pharyngeal wall. Advances in technology using various devices such as the CO2 laser and robotic surgery
have extended the indications for this procedure to cancers that may involve other subsites such as the base of the tongue, and valleculae, and in some cases even more advanced cancers, which may be adequately exposed and safely excised in this manner.
have extended the indications for this procedure to cancers that may involve other subsites such as the base of the tongue, and valleculae, and in some cases even more advanced cancers, which may be adequately exposed and safely excised in this manner.
2. Transpharyngeal or transcervical: Resection is achieved by a cervical, submandibular approach, which exposes the mass through a lateral and/or anterior pharyngotomy. This approach does not allow wide exposure compared to transmandibular surgery; nevertheless, it guarantees en bloc cancer resection and neck dissection while preserving continuity of the mandible.
3. Transmandibular: defines all pharyngectomies achieved through the mandible—the mandible may be preserved (mandibulotomy) or excised with the cancer via a composite resection (mandibulectomy) depending on the stage (T4abone) and/or subsite of the cancer. The transmandibular approach allows wide exposure of the oropharyngeal lumen from the base of the tongue to the tonsil fossa and the posterior pharyngeal wall. Hence, the resection may be performed under direct visual control of the cancer, the carotid artery and/or internal jugular vein. Continuity may be maintained between the oropharyngeal resection and the neck dissection. The reconstruction is achieved by using a pedicle or a free flap.
Tracheostomy and nasogastric feeding tube are always required in transpharyngeal and transmandibular pharyngectomy but can be avoided in limited transoral procedures.
After the excision, reconstruction by means of pedicled or free flaps is performed in a single-stage procedure in order to
Divide the pharyngeal lumen from the neck spaces
Restore organ function as much as possible
Support wound healing with healthy tissue transposition or transfer, particularly in case of salvage surgery following radiation or chemoradiation
Transoral Approach
This technique has been introduced at the beginning of the 20th century for removal of hypertrophy of the tonsil and since then adapted for excision of cancer involving this subsite.
Despite the effectiveness of nonoperative organ preservation protocols for cancer involving the tonsil and tonsil fossa, surgery remains a valid treatment with limited functional sequelae. Management of cancer of the oropharynx by transoral resection, and elective neck dissection, may spare the patient adverse effects of full-dose radiation therapy or chemoradiation. In addition, minimally invasive procedures, using CO2 laser and robotic surgery, are being recognized as effective micromanipulation instruments over conventional procedures. Surgical indications for the tonsil region may differ considering the size and site of limited cancers.
The transoral approach has advantages but also very strict limitations, including a narrow visual field of operation and an angled position of the lateral oropharyngeal wall.
Pros
Avoids an external incision
Early recovery of swallowing function with limited neural disability
Reduced hospitalization time
Cons
Limited or inadequate visualization of anatomic landmarks in case of bulky tumor
No visual control of deep neck vessels during the excision
No possibility of performing en bloc resection of the pharyngeal lesion and neck dissection
Resection of the Posterior Pharyngeal Wall
This procedure consists of the transoral excision of limited cancers of the posterior pharyngeal wall that do not involve the prevertebral fascia and do not reach the lateral pharyngeal walls. Adequate visualization is essential when choosing this approach.
A similar setup described for resection of the tonsil is used in this procedure. The extent of the lesion must be evaluated by MRI for any evidence of involvement of the prevertebral fascia. Staging will consider retropharyngeal lymph node involvement as well.
The traditional cold knife excision has largely been replaced by devices such as monopolar cauterization, coblation, radiofrequency ablation, and CO2 laser, which produce good hemostasis.
Description of Technique
After tracheostomy, which is always suggested for airway safety, the patient is placed in the Rose position and the lesion is visualized using a mouth gag. The margins of excision are delineated, according to the lesion (benign/malignant) that is going to be excised. The depth of the lesion is outlined, the incisions made, and blunt dissection is performed and completed along the prevertebral fascia. The specimen is oriented for pathologic examination. Once the specimen is removed, it is sent for frozen section evaluation to assure free margins of resection. Bleeding is controlled by electrocauterization, bipolar cautery, or other surgical tools such as coblation or laser.
If the defect is not reconstructed, purse string sutures are placed between the mucosa of the defect and the underlying prevertebral fascia. In other cases reconstruction is performed using a split-thickness skin graft or a microvascular free flap transfer, such as the radial forearm free flap, which is anastomosed with microsurgical technique to the neck host vessels, after bilateral neck dissection. A nasogastric feeding tube is inserted at the end of the procedure.
Transpharyngeal Approach
This technique consists of a transcervical, submandibular pharyngectomy. It has been used as the standard approach to treat oropharyngeal cancers, not involving the larynx or mandible. It is indicated for early (T1-T2) cancer of the oropharynx, T2-T3 cancer of the soft palate extending to the lateral pharyngeal wall, base of the tongue and small cancers of the posterior pharyngeal wall. Cancer extending to the vallecula, tonsil, or supraglottic larynx and large cancers of the posterior pharyngeal wall are not suitable for resection by this approach.
It is used in median pharyngectomy, via supra or subhyoid approach, and lateral pharyngectomy. The former is indicated to treat of the base of the tongue and the posterior wall, the latter to excise cancer of the tonsil and subtonsillar fossa.
Median Pharyngectomy
The suprahyoid approach is a simple technique that allows for adequate exposure of the base of the tongue and the posterior pharyngeal wall with complete tumor control, preservation of function, and minimization of cosmetic deformity. The excellent exposure of the oropharynx offers a precise macroscopic identification of tumor margins and minimizes possible injuries to vital neurovascular structures. The open wound can usually be closed primarily without the need of flap reconstruction.
The traditional excision of the tumor is being gradually substituted by more recent techniques, such as robotic surgery, which appears to be able to excise radically oropharyngeal tumors arising on the anterior and posterior walls in those cases they do not deeply infiltrate the organ.
Some authors reported oncologic success in the treatment of T3 squamous cell carcinoma of the base of the tongue with this approach together with supraglottic laryngectomy. The occurrence of delayed deglutition and chronic aspiration limits the use of the procedure to selected cases.
Description of Technique. The skin incision depends on the extension of the operation. A superiorly based apron flap or a horizontal linear skin incision in a skin crease is outlined to perform bilateral neck dissections (Fig. 31.1).
After elevating the subplatysmal flap, a suprahyoid muscle flap is harvested and rotated downward, after its dissection from the hyoid bone. The laryngopharyngeal complex is isolated to identify the vascular and neural structures. Care must be taken laterally around the greater cornu of the hyoid bone to avoid injury to the hypoglossal nerve, when it is free from disease, and the lingual artery. The preepiglottic space is dissected, keeping its connection to the hyoid bone. The lateral pharyngeal wall is exposed together with the hypoglossal nerve and superior laryngeal vessels and nerves. Superior retraction of the separated suprahyoid tongue musculature will define the hyoepiglottic ligament, which extends from its broad hyoid origin to its narrow insertion into the epiglottis. Pharyngotomy represents the key point of the procedure. It must be performed far from the cancer to avoid residual disease and neoplastic intraoperative dissemination. When the cancer is located close to the vallecula, laryngotomy in the supraglottic subsite is a safe approach to the base of the tongue. In this case, the epiglottis is removed together with the hyoid bone and preepiglottic space. When there is no involvement of the vallecula, an incision through the mucosa just above the superior edge of the hyoid bone provides entry into the pharynx (Figs. 31.2
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