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Sentinel node biopsy for oral cancer

Cancer of the oral cavity is the most frequently diagnosed form of head and neck cancer. Though head and neck cancer accounts for slightly less than 10 percent of all cancers diagnosed in the United States annually, nearly one-half of these (30,000) develop in the oral cavity.¹

Squamous cell carcinoma is the type of cancer found in about 95 percent of patients diagnosed with cancer of the head and neck. Tobacco and alcohol consumption are the factors usually implicated in its development, although excessive sun exposure has an etiologic role for those oral cancers arising on the lips.

Regional lymph node metastases
The five-year, disease-free survival (cure) rate for oral cancer is about 40 percent overall. The potential for cure depends on the particular oral subsite involved as well as the clinical stage of the disease. The presence or absence of regional lymph node metastases is the single most important factor affecting prognosis in patients with oral cancer. Cure rates for oral cancer are decreased by approximately 50 percent in patients having cervical lymph node metastasis.²

A large portion of patients with oral cancer may have no cervical lymph node metastases detectable by examination or radiographic imaging study, yet they may still have clinically occult cervical lymph node metastases. Though this is site and stage dependent, regional node metastasis occurs in 20 percent to 50 percent of oral cancer patients.^3,4

Treatment
Patients with proven neck metastases usually are treated with a complete neck dissection (radical or modified radical) or, sometimes, with radiation therapy if the neck disease is at an early stage (N1). The treatment of the primary oral cavity lesion often will determine how the early stage neck will be treated; i.e., the neck is treated with the same modality as the primary lesion.

The issue of managing the clinically negative neck that, nevertheless, is thought to harbor occult metastases remains controversial. This situation can be handled with elective neck dissection, elective radiation therapy or close observation only. Proponents and data supporting each one of these approaches can be found in the medical literature.

This controversy is not unique to head and neck squamous cell carcinoma. The same controversy about what constitutes the best management for possible micrometastases led to the approach of intraoperative localization of primary draining lymph node(s), or sentinel lymph node(s), using a vital blue dye for cutaneous melanoma.⁵ Currently, however, intraoperative localization using radio-lymphoscintigraphy has been found to be more sensitive than the blue dye technique. A single injection of Tc-99m mini sulfur colloid to the primary melanoma site results in focal accumulation in sentinel lymph nodes within 20 minutes and persists for at least 18 hours. A hand-held gamma probe can then be used to guide dissection and identification of the sentinel lymph node(s).

The concept of intraoperative radiolymphoscintigraphy and sentinel lymph node biopsy for head and neck squamous cell carcinoma has not yet adequately been investigated. Its potential for the identification of micrometastases, as it has done for melanoma, is promising. If biopsy of sentinel lymph nodes could be proven to be a sensitive indicator of regional cervical lymph node metastases, many unnecessary elective lymph node dissections could be avoided.

A trial currently is under way at Ellis Fischel Cancer Center to determine whether intraoperative radiolymphoscin-tigraphy and sentinel lymph node biopsy is a sensitive, reliable method for identifying micrometastases in patients with head and neck squamous cell carcinoma. The subsite that most readily lends itself to this approach is the oral cavity.

The trial is limited to patients having cancer at this subsite. Preliminary results of data accrued over the first 12 months of this trial indicate that the concept of sentinel lymph node biopsy may be applicable to head and neck squamous cell carcinoma of the oral cavity.

Summary
Efforts continue to be directed toward finding a better way to manage the clinically negative neck among head and neck cancer patients. The traditional approach has been to treat all necks at significant risk of having occult lymph node metastases. Unfortunately, this approach often involves the unnecessary treatment of necks that ultimately prove to be pathologically free of cancer. Intraoperative radiolympho-scintigraphy and sentinel lymph node biopsy may prove to be a better way of determining when cervical lymph nodes should be treated.

References

1. Rice DH, Spiro RH: Carcinoma of the oral cavity. Current Concepts in Head and Neck Cancer. The American Cancer Society; 1989:17-28.

2. Johnson JT, Barnes L, Myers EN etal: The extracapsular spread of tumors in cervical node metastasis. Arch Otolaryngol Head Neck Surg. 1981;107:725-729.

3. Friedman M, Mafee MF, Pacella BL et al: Rationale for elective neck dissection in 1990. Laryngoscope. 1990;100: 54-59.

4. Spiro JD, Spiro RH, Shah JP et al: Critical assessment of supraomohyoid neck dissection. Am J Surg. 1988;156:286-289.

5. Morton DL, Wen DR, Wong JH et al: Technical details of intraoperative lymphatic mapping for early stage melanoma. Arch Surg. 1992;127:392-399.