Transoral robotic surgery for hypopharyngeal and supraglottic tumor resection

Introduction

The hypopharynx and supraglottic larynx are unique parts of the upper aerodigestive tract. These sites are critical to the functions of airway, speech, and swallowing. Therefore malignancy at these sites requires careful assessment and consideration of treatment options.

Controversy reigns as to the optimal treatment option for early cancers of the hypopharynx and larynx. Although more than 90% of these malignancies are squamous cell carcinomas, there is a variation in the behavior and treatment response of cancers at these sites within this histological diagnosis. Cancers at these sites may be exophytic and demonstrate good response to either radiation or partial laryngeal and pharyngeal resection. However, some early cancers may be deeply infiltrating and, in patients with a significant history of cigarette smoking and alcohol consumption, single modality treatment may not be sufficient to provide enduring locoregional control and cure. Furthermore, hypopharyngeal cancers may have submucosal spread of disease, which can extend one to three centimeters from the primary site, and this needs to be factored into consideration when designing resection and or radiation margins. Patients’ professional and social demands further compound the factors that need to be considered when making treatment decisions.

The response to radiation of early cancers and the lack of experience with, and the poor swallowing outcomes associated with, previous external partial laryngeal surgery, often directed clinicians to offer treatment with nonsurgical protocols. Although these cancers are radiosensitive, because of the high rate of nodal metastases, radiation requires a wide field of radiation, including both necks. Surgical options with minimal morbidity to speech, swallowing, and the airway provide an opportunity to avoid the early and late toxicities associated with radiation and chemoradiation protocols. This is particularly important as an option for the younger patient, who prioritizes early return to employment, social and family responsibilities, and avoidance of the late toxicities of chemoradiation protocols.

The advent of transoral LASER and transoral robotic surgery (TORS) has provided an option of minimally invasive organ preservation surgery. There is evidence in the literature of equivalent or better swallowing and speech outcomes for suitably identified and accessible cancers, when performed by trained surgeons in high volume surgical centers.

Anatomy of the supraglottic larynx and hypopharynx

The larynx and hypopharynx are intimately associated and share anatomical boundaries. The pharynx can be considered as a three-walled structure which opens anteriorly to an air containing space. The pharynx is divided into the nasopharynx, the oropharynx. and the hypopharynx. The nasopharynx has a posterior wall upon which lies the adenoid tissue, and its two lateral walls contain the nasopharyngeal openings of the eustachian tubes. The nasopharynx opens anteriorly to the air containing posterior choanae of the nose. The oropharynx extends from the level of the soft palate to the level of the vallecula. It has a posterior pharyngeal wall that contains lymphoid tissue, and these are sometimes prominent laterally as the lateral pharyngeal bands. The lateral walls of the oropharynx contain the palatine tonsils and opens anteriorly to the airspace of the oral cavity.

The hypopharynx is the longest segment of the pharynx, extending widely above from the vallecula at the level of the hyoid and narrowing down toward the post cricoid ring leading into the esophagus at the level of the cricoid. The hypopharynx opens anteriorly to the air containing larynx.

It has a distinct posterior wall and expands laterally into the pyriform sinuses. These lateral expansions have an intimate relationship with the larynx. The medial wall of the hypopharynx is a lateral relation of the posterior larynx ( Fig. 44.1 ). It is important to recognize that the lateral wall of the hypopharynx near its apex occupies and lies medial to the posterior third of the thyroid cartilage. The division of the hypopharynx into theses subsites is important in determining the stage of the cancer and when planning resection of hypopharyngeal cancers ( Fig. 44.2 ). Cancers limited to one subsite are ideal candidates for transoral resection.

The critical subsite is the postcricoid region of the hypopharynx which is a complete ring leading into the esophagus (see Fig. 44.2 ). Cancers involving this region require a total laryngopharyngectomy and reconstruction of a neopharynx with a tubed free vascularized flap (e.g., Radial Forearm flap or Antero-Lateral Thigh flap) or a pedicled regional flap (e.g., pectoralis major myocutaneous flap) or a vascularized tube such as a free jejunal flap.

The larynx is divided into three sections: the supraglottis, the glottis, and the subglottis.

The supraglottic larynx extends from above, along the free edge of the epiglottis and aryepiglottic folds and the arytenoid cartilages to a horizontal plane that extends through the midpoint of each laryngeal ventricle. The external skeleton of the supraglottic larynx is the hyoid bone, the thyrohyoid membrane, and the thyroid cartilage ( Fig. 44.3 ). Lying between the mucosa covering the supraglottic larynx and the external contour of the larynx is a “horseshoe-shaped” space filled with fat, lymphatic capillaries, and a rich vascular capillary network, known as the preepiglottic space. This midline preepiglottic space is in continuity with the paraglottic space on each side, lying between the vocal ligament and the thyroid cartilage. The supraglottic larynx and the pharynx are both embryologically derived from the fourth branchial arch; their lymphatic drainage is similar, with the primary drainage nodes being in levels II and III.