Indications for Selective Neck Dissection: When, How, and Why
Indications for Selective Neck Dissection: When, How, and Why
ABSTRACT: Selective neck dissection is a procedure that is primarily indicated in patients with clinically negative nodal disease in which there is a high risk of occult metastases. Others have advocated its use for patients with positive nodes, although under very specific circumstances and in combination with postoperative radiation therapy. The type of selective neck dissection performed varies according to the site of the primary, because the pattern of metastases is unique in each case. This review presents the author’s philosophy on when, how, and why to employ the procedure, based on the location of primary cancers at oral, pharyngeal, laryngeal, cutaneous, thyroid, and salivary gland sites. [ONCOLOGY 14(10):1455-1464, 2000]
Selective neck dissection is an operative procedure designed to remove cervical lymph nodes at risk for involvement by metastatic disease and is characterized by the preservation of one or more lymph node groups that are routinely removed in radical neck dissections. According to the Committee for Head and Neck Surgery and Oncology of the American Academy of Otolaryngology/Head and Neck Surgery, selective neck dissection is one of four neck dissection procedures, and it includes four specific subtypes (Table 1). This committee also recommended terminology and defined boundaries to standardize the description of lymph node groups typically removed during neck dissection procedures (Table 2). The submental and submandibular lymph node groups are contained within level I. Levels II, III, and IV, respectively, include the superior, middle, and inferior jugular groups. Level V defines the posterior triangle nodes, and level VI contains the anterior compartment group (Figure 1).
Selective neck dissections are typically performed for occult or early metastases for which the removal of nonlymphatic structures (eg, sternocleidomastoid muscle, internal jugular vein, spinal accessory nerve) is thought not to be necessary. The procedure consists of compartmental removal of one or more levels containing lymph node groups determined to be at risk for metastatic cancer. Assessment of this risk is based on the size and location of the primary tumor. Thus, the compartments removed depend on the location of the primary lesion and its known pattern of spread.
The origin of the concept upon which selective neck dissection is based is unclear. Head and neck surgeons likely used this approach for several decades without describing the technique in a formal manner. For example, at the end of the 19th century, Kocher used limited neck surgery when resecting cancer of the oral cavity without clinically evident neck nodes. Later, a limited procedure known as suprahyoid neck dissection became popular as a means of removing occult lymphadenopathy associated with cancers of the oral cavity, particularly cancer of the lip.
Following Lindberg’s paper describing skip metastases that develop in level II and III nodes without affecting level I, suprahyoid neck dissection fell into disfavor and was replaced by supraomohyoid neck dissection. Suarez and Bocca et al described a modification of radical neck dissection for patients with laryngeal and hypopharyngeal cancers and clinically negative nodal disease. The procedure attracted much attention because it preserved the spinal accessory nerve, internal jugular vein, and sternocleidomastoid muscle. It became known as functional neck dissection, with the major emphasis being preservation of function.
Among the first to report the efficacy of limited neck surgery in a large series of patients, Jesse et al independently developed neck dissection modifications for cancers of the oral cavity and pharynx. They referred to the procedures collectively as modified neck dissections, in which there was also an emphasis on preserving level I neck nodes for pharyngeal cancers and level V nodes for cancers of the oral cavity.
Later, Byers promoted their work further and used the terms “anterior” and “supraomohyoid” neck dissection to describe the selective neck dissection procedures performed for cancers of the oral cavity and pharynx. The term “selective neck dissection” was not adopted to describe all the procedures encompassed within the sphere of limited dissection of the regional lymphatics until 1991.[1,8,9]
The general rationale for using selective neck dissections is based on the topographic distribution of lymph node metastases. This distribution appears to be predictable in patients with previously untreated squamous cell carcinoma of the head and neck, particularly in early disease. Indeed, anatomic studies by Rouviere and Fisch and Sigel demonstrated that lymphatic drainage of the mucosal surfaces of the head and neck follows relatively constant and predictable routes.
In 1972, a clinical study by Lindberg demonstrated that the lymph node groups most frequently involved in patients with carcinoma of the oral cavity are the jugulodigastric and midjugular nodes (levels II and III). In patients with carcinoma of the floor of the mouth, anterior oral tongue, and buccal mucosa, the nodes most frequently involved are in the submandibular triangle (level I). Lindberg also noted that cancers frequently metastasize to both sides of the neck and can skip the submandibular and jugulodigastric nodes, metastasizing first to the midjugular region.
The Lindberg study demonstrated that in the absence of metastases to the first echelon nodes, tumors of the oral cavity and oropharynx rarely involve the inferior jugular and posterior triangle nodes. Similar findings were reported by Skolnik et al in 1976, with a study of radical neck dissection specimens that found no metastases in the nodes of the posterior triangle of the neck, regardless of the site of the primary tumor, or the presence or absence of metastases in the jugular nodes.
Further evidence supporting the concept that lymph node metastases follow predictable patterns of spread was provided by Shah in a retrospective study of radical neck dissection specimens taken from patients with metastases from cancers of the oral cavity, larynx, and laryngopharynx. They concluded that cancers of the oral cavity metastasize most frequently to neck nodes in levels I, II, and III, whereas cancers of the oropharynx, hypopharynx, and larynx metastasize most frequently to the nodes in levels II, III, and IV.
As a general rule, selective neck dissection is performed in patients with cancer arising in the head and neck region who are considered at risk for metastatic disease in the regional cervical lymph nodes. The procedure is indicated primarily in patients who have no evidence of clinical metastases, who have a 15% to 20% risk of harboring occult metastatic disease, and for whom surgery is the preferred treatment of the primary lesion.
Additional indications include situations in which surgical access to the primary cancer extends to lymph node groups at risk for metastases and, more controversially, clinical evidence of nodal metastases confined to the first echelon nodes (usually N1 disease) when the primary is to be treated by surgical removal. In this setting, the patient will most likely receive postoperative radiation therapy, and the purpose of the selective neck dissection is to eradicate all gross disease.
Previous reports on selective neck dissection have typically approached the subject based on the specific type of neck dissection performed; eg, supraomohyoid vs lateral. For this article, I have chosen to review the issues based on the site of origin of the cancer. With this approach, an analysis can be made that is applicable to patients presenting with the full spectrum of the disease. Within each of the sites in the head and neck, the indications for selective neck dissection vary. Furthermore, there are important nuances that influence the strategic approach.