Superselective Neck Dissection for Upper Aerodigestive Tract Carcinoma
K. Thomas Robbins
INTRODUCTION
The superselective neck dissection (SSND) is a lymphadenectomy procedure in which there is compartmental removal of the lymph node-bearing tissue from two or less levels of the neck. It is viewed as a subcategory of the selective neck dissection (SND), which itself is defined as a lymphadenectomy that preserves the nonlymphatic structures of one or more levels of the neck.
Variations in neck dissections are common and have been practiced throughout the history of the procedure. Even Crile, who is credited the most for describing the radical neck dissection, in his landmark article included variations comparable to the contemporary SND. However, it was not until the 1970s that such operations were reported as a separate entity and referred to as a modified neck dissection, which ultimately encouraged a new philosophy in the management of metastases to the neck resulting in the SND procedure becoming the procedure of choice for the majority of neck dissections being performed today.
The SND is based on the patterns of lymphatic spread by metastatic cancer. In most situations, it involves the removal of lymph nodes from at least three neck levels because the risk is usually high for this number of levels. However, under more specific conditions, the number of levels of the neck at high risk may be less than three. In this situation, a more targeted neck dissection that encompasses less than three levels may be feasible. Thus, the SSND would be a surgical option.
HISTORY
It is important to rule out any symptoms indicating that the patient is not a surgical candidate. This would include complaints suggestive of extensive cancer at the primary site such as intractable pain, referred otalgia, severe dysphagia, and marked weight loss. One should look for clinical evidence of distant metastases such as complaints related to the chest.
PHYSICAL EXAMINATION
Whereas unresectable cancer in the primary site, extension of neck metastasis to involve the deep muscles of the neck or encasing the carotid artery, and evidence of distant metastases are all important exclusions to make on physical examination, definitive evidence is usually provided by imaging studies.
INDICATIONS
When used as a component of the primary treatment, the most common application of the SSND is in the treatment of supraglottic carcinoma. Tumors arising from this site have a high propensity to metastasize to the regional lymph
nodes in levels IIA and III. Studies have shown that patients with supraglottic cancer, regardless of the T classification, rarely have evidence of metastases outside of these two levels provided that there is no clinical evidence of neck metastases at the time of diagnosis. Ambrosh et al. performed neck dissections limited to levels II and III in the majority of patients with cancer of the supraglottic larynx and a clinically negative neck undergoing transoral laser resection although it was only later that this targeted procedure became referred to as an SSND. When SSND is used as part of the primary treatment, it is important to point out that the presence of positive lymph node metastasis found within the neck dissection specimen is an indication for postoperative adjuvant radiation therapy.
nodes in levels IIA and III. Studies have shown that patients with supraglottic cancer, regardless of the T classification, rarely have evidence of metastases outside of these two levels provided that there is no clinical evidence of neck metastases at the time of diagnosis. Ambrosh et al. performed neck dissections limited to levels II and III in the majority of patients with cancer of the supraglottic larynx and a clinically negative neck undergoing transoral laser resection although it was only later that this targeted procedure became referred to as an SSND. When SSND is used as part of the primary treatment, it is important to point out that the presence of positive lymph node metastasis found within the neck dissection specimen is an indication for postoperative adjuvant radiation therapy.
In addition to the SSND being applicable as a component of the primary treatment for head and neck cancer, it also has a role in patients whose primary treatment approach is nonsurgical, namely, radiation therapy combined with chemotherapy. The use of chemoradiation has expanded over the past decade to become a common treatment approach for patients with advanced cancer of the head and neck. However, there remains an ongoing uncertainty related to the optimal management of metastases to the neck associated with cancer of the head and neck. Initially, the common philosophy was to perform a neck dissection on all patients who presented with bulky lymph node metastasis regardless of the response to the initial chemoradiation, the socalled planned neck dissection. However, after reports emerged indicating a high rate of control of metastasis to the neck when neck dissection was not performed among patients who had a clinical complete response to chemoradiation, the use of the planned neck dissection came into question. Thus, there is an emerging trend to perform neck dissection only for patients who do not achieve a clinical complete response in the neck. Under such circumstances, the procedure is referred to as a salvage neck dissection.
While the traditional philosophy was to remove lymph node groups in all five neck levels, more recent reports have demonstrated efficacy of the SND. Proponents of SND rely on the concept that the pattern of lymph node metastases in the cervical region is predictable and that neck levels that were not involved prior to treatment are very unlikely to harbor residual metastasis following chemoradiation. With this growing acceptance of the postchemoradiation SND, the rationale for its use presents the opportunity to include the option of performing a more targeted SND, namely, the SSND, one that removes the lymph nodes only at the levels in the neck, which are at the greatest risk for harboring clinically positive disease. For example, in patients for whom the residual lymph node metastasis is limited clinically to a single neck level following chemoradiation, there is evidence to indicate that removing only the lymph nodes in that level is feasible and safe.
CONTRAINDICATIONS
In addition to the general contraindications for undergoing surgery based on the medical status of the patient, the SSND should not be performed based on factors specific to the disease process. In its application for use as part of the primary treatment for patients with N0 disease, there is no evidence to support its efficacy for cancers arising in upper aerodigestive tract sites other than the supraglottic larynx. However, it is possible that its use may be expanded to other primary sites should additional data indicate lymph node metastasis confined to two or less levels of the neck. For patients with N+ disease, the SSND is contraindicated when used as part of the primary therapy.
In the context of using SSND following chemoradiation, the data do not support its use if there is residual nodal disease in multiple neck levels. Additionally, the procedure should be used with caution among patients whose initial lymph node metastasis involved more than two levels prior to therapy even though the residual adenopathy following chemoradiation may be confined to only one level in the neck.
PREOPERATIVE PLANNING
Routine laboratory investigation is important to rule out any systemic disease that may require special consideration. Imaging studies are also critical: computed tomography (CT) scans with contrast; magnetic resonance imaging studies may be indicated to substitute or complement CT scans; and FDG-PET studies. Typically, the FDG-PET is fused with CT scans in which case contrast can also be given to improve the imaging studies on CT alone. Specific analysis is necessary to define the cancer at the primary site as well as metastasis in the neck and to rule out any distant metastatic deposits. For patients who are being considered for SSND as part of the primary treatment concurrent with surgical removal of the primary lesion, the imaging studies should demonstrate the absence of metastatic cancer in the neck. However, for patients who are being considered for SSND following chemoradiation, the evidence of residual disease in the neck by imaging studies must be either absent or confined to a single level of the neck.
SURGICAL TECHNIQUE
As with most neck dissections, the patient is placed in the supine position with a shoulder role and draped in a manner to expose the important landmarks such as the suprasternal notch, clavicle, inferior auricle, mastoid
process, and mentum. If the dissection involves both heminecks, each side is draped in a fashion to expose the landmarks on each side. The incision itself does not have to be as long as the ones used for the more traditional neck dissections, including SND. However, it should be placed in a manner by which it could be extended if the need arises during the procedure to convert the SSND into a more extensive procedure. Since the majority of SSNDs are performed for metastases associated with carcinoma arising in the pharynx and larynx, the neck levels most frequently targeted are II and III. Therefore, the following description is specific for this procedure.
process, and mentum. If the dissection involves both heminecks, each side is draped in a fashion to expose the landmarks on each side. The incision itself does not have to be as long as the ones used for the more traditional neck dissections, including SND. However, it should be placed in a manner by which it could be extended if the need arises during the procedure to convert the SSND into a more extensive procedure. Since the majority of SSNDs are performed for metastases associated with carcinoma arising in the pharynx and larynx, the neck levels most frequently targeted are II and III. Therefore, the following description is specific for this procedure.
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