Key points

Introduction

Early glottic squamous cell carcinoma—Tis, T1a, T1b, and T2 —carries a relatively good prognosis, whether treated surgically or nonsurgically with radiation therapy (RT). Epidemiologically, these tumors continue to be related to tobacco consumption and only exceptionally to human papillomavirus infection compared with oropharyngeal cancers. Surveillance, Epidemiology, and End Results data from the United States show that the incidence of laryngeal cancer has been decreasing by an average of 2.5% per year in the twenty-first century, with decreasing death rates ( http://seer.cancer.gov/statfacts/html/laryn.html ).

The main goal of conservation surgery is to optimize local control to avoid total laryngectomy. With optimum local control, overall survival is related to N stage, metastases, second primaries, and comorbidity. Due to the generally favorable outcomes of T1-T2 glottic tumors treated with different modalities, morbidity, voice quality, quality of life, and cost are issues to be considered when choosing a treatment modality for these early-stage tumors. This article covers the oncologic results related to surgical management of early glottic cancer, with voice quality covered in an article by Hartl DM and colleagues elsewhere in this issue.

Introduction

Early glottic squamous cell carcinoma—Tis, T1a, T1b, and T2 —carries a relatively good prognosis, whether treated surgically or nonsurgically with radiation therapy (RT). Epidemiologically, these tumors continue to be related to tobacco consumption and only exceptionally to human papillomavirus infection compared with oropharyngeal cancers. Surveillance, Epidemiology, and End Results data from the United States show that the incidence of laryngeal cancer has been decreasing by an average of 2.5% per year in the twenty-first century, with decreasing death rates ( http://seer.cancer.gov/statfacts/html/laryn.html ).

The main goal of conservation surgery is to optimize local control to avoid total laryngectomy. With optimum local control, overall survival is related to N stage, metastases, second primaries, and comorbidity. Due to the generally favorable outcomes of T1-T2 glottic tumors treated with different modalities, morbidity, voice quality, quality of life, and cost are issues to be considered when choosing a treatment modality for these early-stage tumors. This article covers the oncologic results related to surgical management of early glottic cancer, with voice quality covered in an article by Hartl DM and colleagues elsewhere in this issue.

Patient evaluation

The clinical and radiologic work-up for patients with glottic cancer is discussed in an article elsewhere in this issue. Particular attention should be given, however, to the evaluation of vocal fold mobility—normal, diminished, or fixed—due to the prognostic significance of this factor and the influence it may have on the surgical (or nonsurgical) treatment choice. Vocal fold mobility may be decreased (and the tumor classified then as T2) due to a bulky tumor but also due to paraglottic space invasion or invasion of the cricoarytenoid joint. Imaging is required to determine these deeper tumor extensions. These early-stage tumors have a low rate of thyroid cartilage invasion, but tumors with decreased vocal fold mobility have a higher risk of occult cartilage invasion. Laryngeal tumors are amenable to conservation surgery if the tumor can be resected with free margins (R0) while conserving 2 essential entities:

• •
  

  The functional integrity of the cricoid cartilage must be intact, keeping in mind that resection of the anterior arch is possible without destabilizing the cricoid ring. An unstable cricoid cartilage leads to laryngeal stenosis and permanent tracheostomy. The cricoid ring is the only complete cartilaginous ring in the airway and must be preserved in conservation surgery to prevent postoperative stenosis. Cricoid cartilage invasion is always a contraindication to conservation laryngeal surgery due to the impossibility of obtaining sufficient margins while maintaining a patent airway postoperatively. Tumors with anterior subglottic extension sparing the upper edge of the cricoid cartilage can be treated with conservation laryngeal surgery, and anterior subglottic extension up to, but not invading, the cricoid cartilage may be amenable to supracricoid partial laryngectomy with tracheohyoidoepiglottopexy (discussed later). Posteriorly, the cricoid cartilage is situated closely below the level of the vocal folds (a few millimeters), so that posterior tumors reaching the upper border of the cricoid cartilage are generally a contraindication to conservation laryngeal surgery.

  
  
• •
  

  At least 1 cricoarytenoid unit, comprised of the cricoid, an arytenoid cartilage, the cricoarytenoid joint and muscles, and the corresponding recurrent laryngeal nerve, must be preserved to preserve the sphincteric function of the larynx during swallowing, to avoid aspiration that can lead to pneumonia and death. The sphincteric function of the larynx (or neolarynx) also serves as the voice generator, with the mucosa generating sound waves.

Individual patients must also meet certain requirements for conservation laryngeal surgery, be it by transoral resection or open surgery. Comorbidities and tolerance of general anesthesia must be evaluated. Pulmonary function testing is recommended if open surgery or extended resection (arytenoid) is planned, and the risk of postoperative aspiration requires that patients have sufficient pulmonary reserve to withstand this possible complication in the immediate postoperative period. Procedures having little effect on the sphincteric function of the larynx, such as cordectomy, are of low risk in the elderly whereas a hemilaryngectomy or a supracricoid partial laryngectomy alters the sphincteric function of the larynx and, therefore, is considered a high-risk procedure in elderly patients. Conservation surgery has been performed for malignant and benign laryngeal tumors in children for whom the same oncologic and functional principles apply. Voice considerations and patient preferences should be discussed as well and are addressed in another article of this issue.

In historical series of T1-T2 glottic tumors treated with small-field RT without prophylactic treatment of the neck, reported rates of nodal recurrence were approximately 4%. In surgical series, the rate of occult neck metastases for early glottic cancer was less than 10%. It is now generally agreed that prophylactic treatment of the neck is not necessary if the tumor is classified radiologically as cN0.

Transoral laser microsurgery

The carbon dioxide laser beam with a wavelength of 10,600 nm is absorbed by water, limiting the depth of extension in human tissues and thus allowing cutting precision without widespread thermal damage to surrounding tissues. Transoral laser resection via suspension microlaryngoscopy was first developed in the 1970s by Strong and Jako, with the first laser cordectomy reported in 1975. Extension of the technique to include resection of laryngeal structures other than the vocal fold was promoted by Eckel and Thumfart, Rudert, Steiner and Ambroch, and otherss in the 1980s and widespread use of the technique appeared in the 1990s. In the past 25 years, TLM has largely supplanted open conservation laryngeal surgery, with pioneers of the technique showing early on that complete, oncologically sound resection is possible transorally with low morbidity and without diminished oncologic outcomes. Technological advances in laryngeal microscopy and lasers have facilitated access to this type of surgery, which is now considered the gold standard for treatment of early glottic cancer.

Transoral laser resection is based on à la carte resection, after tumor spread and sparing noninvolved structures, contrary to other techniques in which resection follows anatomic landmarks rather than following the tumor itself. In most cases, tracheotomy is not required, simplifying the postoperative course. Limits to the technique include patients whose morphology limits exposure of the larynx transorally and short neck, small oral aperture, large tongue base, retrognathism, and/or tooth mobility or dental prosthetic work in the anterior maxillary region. Exposure of the larynx may be facilitated by resection of the false vocal fold (vestibulectomy) and/or by partial resection of the epiglottis, particularly the petiole of the epiglottis for exposure of the anterior commissure.

Today the European Laryngological Society classification for transoral laser resection of glottic cancers is largely used. It takes into account depth of resection in the vocalis muscle and extent of resection, including the anterior commissure and supraglottic and subglottic structures (particularly suited to T2 lesions). Table 1 summarizes this classification.

Robot-assisted transoral laryngeal surgery

The width of the robotic arms and difficulty with triangulation in the limited laryngeal space are main factors contributing to the slow take-off of robot-assisted transoral surgery for early glottic cancer, the supraglottic larynx being more accessible with the surgical robot in its current configuration. Exposure of the larynx may be facilitated with tongue retraction and partial epiglottectomy. Another limiting factor, until recently, was the degree of thermal injury inflicted on the glottis by the monopolar cautery used with robotic surgery. Recently, this problem has been addressed by the development of a CO ₂ laser fiber, which decreases the depth and width of thermal dissemination to adjacent tissues. The role of robotic assistance for early glottic cancer remains to be fully explored. The considerations of this transoral resection are the same as those for TLM, mainly the significance of close or positive margins, anterior commissure involvement, and outcomes for tumors with decreased vocal fold mobility or deep paraglottic invasion.

Open surgery

Open conservation laryngeal surgery (partial laryngectomy) is performed less and less for early glottic cancer particularly due to the accessibility of TLM and its comparable oncologic outcomes, with much lower morbidity. The use of nonsurgical organ preservation with RT or chemoradiation has also contributed to the decline in open surgery. Contemporary knowledge of tumor extensions and modern imaging techniques have also contributed to the decline in open surgery for these early tumors: the low rate of thyroid cartilage invasion in particular makes wide cartilage resections most often unnecessary for these early tumors.

Many different techniques have been described for open resection of T1-T2 glottic cancer, which can be globally classified into vertical partial laryngectomies—entailing a vertical thyrotomy, with open cordectomy, frontolateral vertical partial laryngectomy, vertical hemilaryngectomies, and frontal anterior vertical partial laryngectomy—and horizontal partial laryngectomies, essentially represented by the family of supracricoid partial laryngectomies with cricohyoidoepiglottopexy, cricohyoidopexy, or tracheocricohyoidoepiglottopexy.

Open cordectomy and the frontolateral vertical laryngectomy are the open equivalents of the type IV and type Va endoscopic resections (see Table 1 ). Neither technique requires a tracheostomy, but, as for TLM, the complete resection of the vocalis muscle is a major factor in voice quality (see article elsewhere in this issue for details). TLM allows tailoring of the resection to the depth of invasion of the tumor, which open surgery does not. Initial local control for T1a glottic tumors treated with these techniques ranges from 90% to 100% and is comparable to TLM. With these open procedures, swallowing should be monitored closely, because some patients may have temporary low-grade clinical aspiration (in particular elderly patients). Speech and oral feeding can start on postoperative day 1. Subcutaneous emphysema can develop and can be managed conservatively by reopening the wound and replacing a nonsuction drain, with or without a compression dressing. Laryngeal granuloma is rarely obstructive and usually heals spontaneously or with oral steroid treatment. A further issue with these 2 types of open procedures—as with TLM in the region of the anterior commissure—is anterior glottic web formation, another factor influencing voice quality. A reconstruction procedure, pulling the false vocal fold down to cover the cartilage defect (a false vocal fold flap) has been described and shown to decrease granuloma and web formation in open frontolateral partial laryngectomies.

Vertical hemilaryngectomy is essentially an equivalent of a type Vc TLM resection associated with resection of part of the thyroid cartilage. The standard vertical partial laryngectomy or standard hemilaryngectomy entails resection of the entire vocal fold, the entire ventricle and false vocal fold, part of the thyroid ala, and the vocal process of the arytenoid cartilage. It is generally indicated for T2 glottic tumors with normal or impaired vocal fold mobility. Resection of the thyroid ala allows more extensive resection of the paraglottic space for tumors with deep muscular invasion, but the posterior part of the paraglottic space lateral to the arytenoid is not resected with this technique. Extended hemilaryngectomies involve the same resection as the standard hemilaryngectomy but also if necessary entail resection of the ipsilateral arytenoid with disarticulation and/or resection of the entire anterior commissure.

The frontal anterior laryngectomy corresponds to an extended type VI resection with TLM but including thyroid cartilage resection. It remains an excellent indication for glottic carcinoma with extension to the anterior commissure, due to the wide cartilaginous resection that this technique provides at this level, the simple postoperative course, and the satisfactory voice quality. This technique does not address tumor extension superiorly to the preepiglottic space, however, which is resected in the supracricoid procedures.

Supracricoid partial laryngectomies allow total removal of the thyroid cartilage for excellent control of anterior commissure and ventricular tumors. The entire paraglottic space is removed bilaterally. One arytenoid cartilage can be removed, allowing for resection of glottic and supraglottic tumors extending posteriorly. The major portion of the preepiglottic space, excluding the lateral horns, can be safely resected. The entire cricothyroid membrane and anterior subglottis are resected. The preservation of the epiglottis (supracricoid partial laryngectomy with cricohyoidoepiglottopexy) is determined by the proximity of the tumor to the petiole of the epiglottis and the extension to the preepiglottic space.

For these extensive resections, the restrictions to conservation laryngeal surgery for glottic cancer—a stable cricoid and a functional cricoarytenoid unit—apply to all the different techniques, keeping in mind that for resections extending beyond cordectomy or frontolateral partial laryngectomy, some aspiration is expected postoperatively. Thus, pulmonary function should be normal. Patients with chronic respiratory insufficiency or decreased pulmonary reserve should not undergo this type of surgery. Heart disease, uncontrolled severe diabetes, or other severe comorbidities and age greater than 70 are relative contraindications to extended vertical and supracricoid partial laryngectomies as well.

Local control with open surgery for T1 carcinomas ranges from 90% to 100% and for T2 from 69% to 100%. Comparing historical cohorts, for T2 tumors, supracricoid partial laryngectomies seem to provide higher rates of local control and laryngeal preservation than vertical hemilaryngectomies (69%–78% for hemilaryngectomies vs 83%–100% for supracricoid laryngectomies), particularly for T2 tumors with decreased vocal fold mobility. This is most likely due to the lack of resection of the posterior paraglottic space in a classic vertical hemilaryngectomy, which is addressed by supracricoid resections, but also possibly to a higher rate of occult thyroid cartilage invasion, which may be missed by radiologic assessment.

The postoperative course after open conservation laryngeal surgery (except cordectomy and frontolateral partial laryngectomy) is complex, requiring management of the tracheostomy and feeding tube. Hospitalization is 1 to 3 weeks on average, whereas for TLM it is less than 1 to 2 days. Recovery of efficient swallowing is long, particularly after supracricoid partial laryngectomies, with 42% of patients still demonstrating clinical aspiration after 1 month but 97% recovering swallowing without aspiration at 1 year. In large published series by specialized centers, the rate of permanent gastrostomy was 2% to 3%, permanent tracheostomy less than 1%, and total laryngectomy for intractable aspiration 2%. The advantage of open surgery is to allow more extensive resection for more extensive tumors, with epiglottoplasty or cricohyodopexies to reconstruct a functional larynx, in terms of both swallowing and voice.