Transoral Laser Microsurgery of Supraglottic Cancer
The treatment of supraglottic cancer may include surgery or radiotherapy, as single-modality therapy or combined treatment. If surgery is part of the treatment protocol, the open transcervical and the endoscopic transoral approach are available for access to the primary tumor. The open supraglottic laryngectomy was first described by Justo Alonso in 1947. The procedure consists of resecting the entire supraglottis including the epiglottis, the preepiglottic adipose tissue, and the ventricular folds together with the thyroid cartilage superior to the glottic plane. The conventional supraglottic resection may be extended posteriorly to include resection of the arytenoid, anteriorly to the base of the tongue and laterally to the piriform sinus.
With regard to these requirements, open supraglottic partial laryngectomy can be indicated for T1, T2, and selected T3 and T4 cancers. The management of the primary cancer has evolved over the last decades, and transoral approaches came into use. On condition that the supraglottis can be exposed adequately, cancers meeting the requirements for open supraglottic resections can be resected endoscopically as well. Vaughan from Boston was the first to describe supraglottic partial laryngectomy via transoral laser microsurgery. Steiner in 1979 used CO2 laser technique for transoral endoscopic treatment of glottic and selected supraglottic cancers. Subsequently, Davis et al. and Zeitels et al. published the results of laser microsurgery in selected patients with supraglottic cancer. In recent years, the transoral approach became increasingly popular because of less morbidity and earlier and better swallowing rehabilitation compared to open supraglottic laryngectomy and simultaneous chemoradiation. T1 and T2 as well as selected T3 and T4 cancers were treated with this method.
Supraglottic cancers usually do not produce early symptoms. Patients may present with odynophagia, persistent dysphagia, otalgia, or chronic cough. Hoarseness, the typical early symptom of vocal cord cancer, can also occur with supraglottic cancer, though usually later in the disease state. Many patients notice a mass in the neck as a first sign of supraglottic cancer. Stridor and airway obstruction occur late.
Physical examination must include fiberoptic laryngoscopy with adequate documentation. The spread of cancer within the larynx and to the adjacent organs, in particular piriform fossa and base of tongue, is determined. Special attention to the movement of the vocal cords is needed. A careful examination of the neck by palpation, ultrasound, and ultrasound-guided fine needle aspiration cytology is required to detect spread of cancer to the cervical lymph nodes. Computed tomography (CT) scans or magnetic resonance imagings (MRIs) of the neck are done to further determine the extent of the disease, both in the larynx and in the neck. This is followed by a direct laryngoscopy with biopsies.
Prior to surgery, a routine clinical examination including blood tests, chest radiography, electrocardiogram, and ultrasound of the abdomen is done. Pulmonary function tests may be useful in patients with preexisting chronic obstructive pulmonary disease. These tests are not routinely performed, since they are not predictive for postoperative outcomes. In my practice, the indication for transoral laser microsurgery is not influenced by the results of the pulmonary function tests. Second primary cancers, particularly in the head and neck region, the lung, and the esophagus, should be excluded preoperatively.
Prerequisite for a laser supraglottic laryngectomy is the adequate exposure of the supraglottis with a bivalved laryngoscope. Cancers of the epiglottis and/or ventricular fold(s) without infiltration of the preepiglottic adipose tissue (T1 and T2 tumors) and cancers with spread to the preepiglottic adipose tissue with mobile vocal folds (T3 tumors) are usually resectable with the laser. Cancers with impaired vocal cord mobility or vocal cord fixation due to spread of the cancer to the paraglottic space or fixation of the arytenoid cartilage can be resected along with parts of the vocalis muscle and/or the arytenoid cartilage. In more advanced cancers, parts of the base of tongue, piriform sinus, or one arytenoid cartilage can be included in the resection. The extent of laser resection is limited by the patient’s ability to regain adequate swallowing function.
Inadequate exposure of the supraglottis with a bivalved laryngoscope is a contraindication to endoscopic resection. Extensive infiltration of the soft tissues of the neck, bilateral extensive infiltration of the base of tongue, and cartilage destruction should also be regarded as contraindications to transoral laser microsurgery. Bilateral fixation of the vocal cord and/or arytenoid cartilage and excision of the cancer across the posterior commissure to the opposite arytenoid are also contraindications. These findings usually mandate a total laryngectomy.
The routine use of CT scans is unnecessary in early supraglottic cancer, located at the free edge of the epiglottis or the ventricular fold. All other supraglottic cancers should be staged with either CT or MRI in order to detect any infiltration of the pre- and/or paraglottic space and cartilage invasion. MRI is particularly useful for detecting spread of submucosal spread of cancer and invasion of the preepiglottic adipose tissue. Imaging studies should always be performed prior to diagnostic microlaryngoscopy and biopsy.
Flexible Laryngoscopy and Staging Microlaryngoscopy
The accurate staging of a supraglottic cancer should include flexible laryngoscopy with adequate documentation. Detailed assessment of vocal cord mobility should be carried out. The extent of the cancer is determined with indirect and direct laryngoscopy. Angled rigid scopes are useful for evaluating the anterior commissure and the ventricles. Biopsy with histopathologic confirmation of cancer is necessary before a partial laryngeal resection is carried out. A carefully performed biopsy does not alter the clinical aspect of the tumor. Panendoscopy, staging microlaryngoscopy, and biopsy can be done at the same time as the definitive surgery, and we feel comfortable with frozen section confirmation of squamous cell carcinoma.
Therapeutic outcome of supraglottic cancer is influenced strongly by the presence of lymph node metastases. An accurate preoperative staging of the regional lymphatics must be performed. The lymph nodes of the neck are examined by ultrasound and ultrasound-guided fine needle aspiration biopsy. The majority of patients with supraglottic cancer are staged by the use of imaging techniques primarily indicated for staging of the primary cancer. With regard to the early detection of lymph node metastases, the use of MRI has added little to the diagnostic accuracy of contrast-enhanced CT.
The patient is placed under general endotracheal anesthesia with paralytic agents. The carbon dioxide laser can be used with special endotracheal tubes like the Laser-Shield II (Xomed-Treace), an aluminum- and Teflon-coated silicone tube, or the Laser-Flex (Mallinckrodt), a spiral metallic tube with two cuffs. For years, we have been using the MLT Tube (Mallinckrodt) made of polyvinyl chloride, preferring a tube with a 6-mm inside diameter for most applications. The cuff of the tube is filled with air, and the endotracheal tube is secured in the left oral commissure if the surgeon is right handed. Ointment is placed in both eyes and the eyelids taped shut.