“A topic ceases to be interesting when it is no longer controversial.”

One of the first controversies faced by the clinician during the process of determining whether to perform an elective neck dissection is the value of imaging studies of the neck. Admittedly, determination of the status of the lymph nodes of the neck by clinical examination is not always accurate in patients with cancer of the head and neck. Various imaging modalities have been shown to be more accurate in detecting minimal enlargement of lymph nodes in the neck.1–3 A clinician may be more inclined to recommend elective treatment of the neck when one or more enlarged nodes are demonstrated by an imaging study, as the probability of an enlarged lymph node containing metastasis is higher. However, not all enlarged lymph nodes contain metastatic deposits. More importantly, a negative ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) scan cannot be relied on to withhold elective treatment of the neck, because none of these techniques can depict small tumor deposits within a lymph node. The presence of radiolucency within a lymph node, considered a very reliable criterion for the presence of metastasis, is not very useful in evaluating the N0 neck, because necrosis seldom occurs in micrometastases. Furthermore, the size criteria currently used to consider a node positive on CT or MRI (largest diameter <10 or 15 mm) are not optimal, especially for nodes in the submandibular triangle, a frequent site of metastases from cancers of the oral cavity. Recently, DiNardo⁴ studied the lymph nodes of the submandibular triangle in patients with floor-of-mouth cancer. DiNardo found that 88% of the nodes harboring metastatic carcinoma were < 10 mm in diameter. The UCLA group has reported a similar study of neck dissection specimens, which showed that 67% of lymph nodes containing metastasis were 6 10 mm in diameter.⁵ Yuen et al.⁶ recently studied neck dissection specimens by whole-organ sectioning at 3-mm intervals. Among 2826 lymph nodes examined, these investigators found that the median size of the metastatic foci was 3 mm and occupied a median of 6% of the cross-sectional area of the involved nodes. Clearly, ultrasound, CT, and MRI scans are unable to detect metastases of this size in a lymph node of any size, nor can they differentiate between reactive enlargement of a lymph node and enlargement caused by metastasis.

Multidirectional ultrasonography scanning has shown promise for improved preoperative evaluation of the N0 neck.⁷ In experienced hands, this technique permits fine-needle aspiration of lymph nodes as small as 3 mm in diameter. Using this technique, Snow⁸ and several other investigative groups in the Netherlands^{1, 9} have reportedly been able to identify 75 to 77% of patients with occult lymph node metastases. Despite the success reported by these groups and the results of a prospective multi-institutional study in the Netherlands, which showed that the results with ultrasound-guided fine-needle aspiration biopsy (FNAB) are not as investigator dependent as is often suggested,⁹ this technique has not gained wide acceptance outside Europe. Perhaps it is because the technique is demanding in terms of equipment and personnel time. More importantly, long-term assessment of the outcome in patients deemed node-negative by ultrasonography and FNA cytology, in whom an elective neck dissection was not performed, has only recently been published. These results are not as encouraging as was hoped. In a study of 92 patients whose necks were staged N0, and which were cytologically negative, followed for 1 to 3 years, 19 (21%) subsequently developed a neck node metastasis. Six of these 19 patients (32%) died of distant metastases or of loco-regional recurrence.¹⁰

It is hoped that positron emission tomography (PET) will be a more useful imaging technique for detecting metastases in the lymph nodes, without their removal and histopathologic examination. It relies on abnormal tissue metabolism to detect neoplasms. Myers and Wax¹¹ recently reported that PET permitted accurate determination of the presence or absence of metastasis in a small group of 11 patients with squamous cell carcinoma of the oral cavity. These patients were staged clinically N0 and underwent 19 neck dissections. PET scans were positive in all 7 instances in which the neck dissection had histologically confirmed metastasis and were negative in all 12 cases in which there was no histologic evidence of metastasis. Unfortunately, these investigators do not report examining the lymph nodes by more than one section. Although the results of this first study are encouraging, evaluation of this technique awaits studies of larger numbers of patients. These may not be forthcoming because of the limited accessibility to this technology and its prohibitive cost.11

Is Sentinel Node Biopsy a Substitute for Elective Neck Dissection?

Another controversy surrounding elective neck dissection concerns the value of sentinel node biopsy. Considering the experience with this technique in patients with melanoma and breast cancer, it is anticipated that gamma probe-directed biopsy of the sentinel node may be useful in the management of the N0 neck in patients with squamous cell carcinoma of the head and neck. To that end, a recent study of 5 patients conducted by Koch et al.¹² showed that identification and biopsy of the sentinel node are feasible in these patients. However, a number of substantial problems were identified: (1) the proximity of the primary tumor obscures the lymphoscintigram, particularly when the tumor is located in the oral cavity; (2) intramucosal injection of the radiolabeled material is more difficult than intradermal injections and the isotope often extrudes into the saliva; and (3) some sites in the head and neck are inaccessible, and the technique is limited in patients who have been previously irradiated. According to these investigators, their observations “cast doubt on the general applicability and utility of the technique” for squamous cell carcinoma of the head and neck.¹²

When Should the Neck Be Treated Electively?

The decision to recommend elective treatment of the neck nodes depends mainly on the location and stage of the primary tumor and on a few other potential factors.

ORAL CAVITY

Elective treatment of the neck is indicated in patients with T2, T3, and T4 cancers of the oral cavity, regardless of the site of origin. Possible exceptions are T2 tumors of the buccal mucosa, in which the associated rate of lymph node metastases is low,¹³ and T1 tumors of the oral tongue, because some surgeons believe, as we do, that elective neck dissection is desirable in these patients,^{14, 15} particularly when the lesion is thicker than 1.5 to 2 mm.^{16, 17} An increasing number of clinical, histologic, biochemical, and genetic factors are under study as potential predictors of the propensity of a tumor to metastasize to the lymph nodes. Their role remains sufficiently unclear to recommend their use in routine treatment planning.

OROPHARYNX

Tumors of the oropharynx have a high propensity to metasta-size to the regional lymph nodes even in early stages. Therefore, the regional lymph nodes should be treated electively, regardless of the stage of the primary tumor. With the exception of early, well-lateralized tumors, tumors of the oropharynx have a tendency to metastasize to both sides of the neck, often indicating treatment of both sides of the neck. Dissection of the retropharyngeal nodes should be considered particularly for tumors extending onto the pharyngeal walls, as retropharyngeal nodal metastasis occurred historically in up to 44% of cases.¹⁸

GLOTTIC CANCER

For glottic tumors staged T1 and T2, elective treatment of the neck is generally not indicated because the incidence of metastases is low. There are possibly two exceptions: (1) when tumor is found in a delphian node during the course of a partial laryngectomy, as the reported rate of lateral neck metastases in such cases is about 40¹⁹; and (2) when treating recurrent T1-T2 tumors, because of the reported risk of occult metastases is about 20%. The need to dissect the neck in patients with T3 glottic tumors remains controversial. However, because lymph node metastases have been observed in 17 to 22% of cases, we believe that elective treatment of the neck is appropriate.^{20, 21} Elective dissection of the neck is clearly indicated in patients with T4 tumors.²²

SUPRAGLOTTIC CANCER

Elective treatment is warranted in all stages of supraglottic cancer. A possible exception may be T1 tumors of the suprahyoid epiglottis. Furthermore, treatment of the neck should include the lymph nodes at risk on both sides of the neck, with as many as 75% of the recurrences in the neck occuring in the “undissected” contralateral side.²³

SUBGLOTTIC CANCER

Elective treatment of the lateral compartments of the neck does not seem warranted in patients with subglottic cancer. The reported incidence of metastases to these nodes is only 10%.^{24, 25} By contrast, the paratracheal lymph nodes are involved more frequently and should be treated bilaterally.^{26, 27}

Is Elective Treatment Preferable to Observation and Therapeutic Neck Dissection?

The value of elective treatment of the neck is not universally accepted. The notion of watching the neck and treating it only when metastases become clinically apparent is allegedly supported by two prospective randomized studies.^{28, 29} In both studies, the survival of patients with cancer of the oral cavity who underwent “elective” neck dissection was not significantly better than the survival of patients who underwent a therapeutic neck dissection. Unfortunately, these studies have not resolved the controversy. In fact, they have been criticized because the number of patients studied was insufficient to arrive at a conclusive opinion.

The efficacy of elective treatment of the neck in patients with larynx cancer has been recently compared to that of therapeutic neck dissection at the time metastases become clinically apparent in an interesting retrospective study by Gallo et al.30 From a population of 1808 patients with cancer of the larynx treated at the University of Florence, two groups of patients were selected for comparison. The first group of 76 patients had clinically an N0 neck, underwent elective neck dissection, and had histologically positive nodes. The second group consisted of 96 patients who were initially staged N0 but who subsequently developed lymph node metastases and underwent therapeutic neck dissection. Postoperative radiation to the neck was given to 11% of the patients in the first group and to 20.8% in the second group (P = 0.178). The criteria used to determine when patients were selected for one group or the other were not established a priori. However, Gallo and colleagues state that patients were “usually” selected to undergo elective neck dissection when they had an advanced tumor (T3-T4); had a fat, short, or muscular neck that was not easy to evaluate clinically; had a low educational level; and poor follow-up was anticipated. In this study, there was not a statistically significant difference between the two groups of patients in overall determinant and actuarial survival rates, with a minimum follow-up of 5 years. This is surprising because patients who underwent delayed therapeutic neck dissection had a significantly higher incidence of distant metastases, multiple positive nodes, and extracapsular tumor spread.³⁰ Other retrospective studies have found that elective neck dissection decreases the neck recurrence rates significantly in patients treated for N0 supraglottic carcinoma.³¹

Self-examination by the patient and reliable follow-up evaluation are essential for watchful waiting to succeed in the management of the N0 neck. Unfortunately, a significant number of the patients who do not undergo elective neck dissection cannot be salvaged later, when they present with palpable metastases, because the disease is too far advanced.²⁹

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