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From the Department of Head & Neck Surgery, Roswell Park Cancer Institute, Buffalo, New York.
Correspondence: Address correspondence to: Thom R. Loree, MD, FACS, Department of Head and Neck Surgery, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, New York; Fax: (716) 845-8646; e-mail: thom.loree{at}roswellpark.org
The article by Ross et al. in the July issue addresses an important and timely problem in head and neck surgical oncology.1 The management of the clinically negative neck in patients with squamous cell carcinoma of the oral cavity is a challenging problem. For early stage primary lesions, the incidence of occult metastases to the cervical lymph nodes is significant. It ranges from 20% to 30%.2
It is well known that the presence of cervical lymph node metastases is the most important prognostic factor relating to survival and recurrence rates associated with squamous cell carcinoma of the head and neck. Combining these two facts leads to the problem of the clinical N0 neck. It is logical to assume that early diagnosis and treatment of occult cervical lymph node metastases would result in improved local-regional disease control and survival.
Over the past several decades there has been a gradual progression in the management of this problem. Initially, a strategy of observation was employed. Following surgical extirpation of the primary lesion, the neck was kept under close observation. Patients who developed detectable cervical lymph node metastases were treated with neck dissection and/or radiotherapy. Even today, it is still difficult to demonstrate that this approach is definitely inferior to the more modern, more aggressive, proactive approaches. Despite this, it is currently accepted that it is better to stay ahead of cancer than to chase it.
As observation fell into disfavor, management by routine radiotherapy after resection of the primary tumor or radical neck dissection at the time of primary tumor resection was advocated. Both strategies were flawed. Both approaches require unnecessary treatment with potentially significant morbidity for the majority of patients. In response to this problem, the concept of the selective neck dissection for staging developed. The appropriate selective neck dissection was based upon studies from comprehensive neck dissection series that identified the pattern of cervical lymph node metastases from various primary sites.
For the oral cavity, supraomohyoid neck dissection (SOHND), which removes levels I, II, and III, was shown to be an appropriate elective staging dissection for the N0 presentation.3 At many institutions, SOHND has become the standard of care. For clinical N0 patients, it performed for virtually all T2 lesions and selected T1 and T3 lesions. Patients in whom pathologic review of the neck specimen reveals lymph node metastases (multiple nodal involvement and/or extracapsular extension) are candidates for adjuvant radiotherapy. Despite the wide acceptance of this strategy, there remain some detractors. SOHND is associated with a lower risk for morbidity than radical neck or even modified radical neck dissection. However, it still proves to be an unnecessary procedure in most patients (those who have no nodal metastases). In addition, SOHND can miss some cases with occult nodal metastases (those with occult metastases at level IV but not in levels I, II, or III).4
It appears that sentinel lymph node biopsy (SLNB) may be the next step in the progression of management of the clinically N0 neck in early stage squamous cell carcinoma of the oral cavity. The technique may eliminate some of the concerns surrounding elective neck dissection (ELND). Potentially, the procedure involves less morbidity than neck dissection. However, the most important question is whether or not it is as accurate as a staging procedure as ELND. SLNB has been validated and accepted as a useful and accurate method for lymph node staging in cutaneous melanoma and, more recently, in the management of breast cancer. Given the behavior of squamous cell carcinoma, it is reasonable to assume that SLNB would be useful and accurate in the management of squamous cell carcinoma of the oral cavity.
The appropriate way to validate SLNB as a staging procedure is to perform the procedure with ELND and correlate the pathologic findings. SLNB may prove to be more accurate than ELND. It is easier to subject a single lymph node specimen (or a few) to intensive pathologic examination by multiple sectioning and immunohistochemical staining than it is an entire ELND specimen. SLNB may also identify those few patients who have lymph node metastases limited to areas outside the boundaries of the usual selective ELND. On the other hand, SLNB may prove to be less accurate than ELND if it is shown that there are a significant number of cases in which the identified sentinel lymph nodes do not harbor occult disease but disease is present in nonsentinel lymph nodes within the ELND specimen.
The results of this study are noteworthy. The study reports on a large number of cases, and it combines the experience of several different centers. Therefore, the results may be similar to results obtained if SLNB were to be employed routinely at all institutions. The results presented in the article by Ross et al. in this issue support the viewpoint that SLNB is more accurate than ELND. In only three patients (of 45) did SLNB fail to identify occult disease. However, in five patients SLNB identified disease that would have been missed if SOHND had been used for staging. Unfortunately, in over half of their patients, SLNB was performed alone and cannot be correlated with ELND. With a follow-up of only 2 years, time will tell whether or not the reported sensitivities remain valid.
The authors have shown that SLNB is less accurate for floor-of-mouth tumors than for tumors at other sites in the oral cavity. As others have found, the majority of sentinel nodes are identified with the gamma probe. Use of blue dye is less accurate but may be unnecessary.5
As this current article shows, the European head and neck community has embraced the concept of the SLNB in the management of oral cavity cancer and many advocate the procedure as a stand-alone alternative to ELND.6 The authors are to be congratulated on their pioneering work on this subject. Their results suggest that stand-alone SLNB may well prove to be a valid replacement for (and improvement over) ELND. However, it is perhaps premature to adopt SLNB as the standard of care at this time.
Further efforts to validate SLNB as a stand-alone staging procedure are ongoing. These efforts include multi-institutional trials involving the performance of SLNB with ELND under protocol control.7 Over the next few years, the results of these trials should allow a definitive resolution of this issue.
Received for publication May 19, 2004. Accepted for publication June 7, 2004.
REFERENCES
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