Elective neck dissection in oral carcinoma: a critical review of the evidence.

More than 50% of patients with squamous cell carcinoma of the oral cavity have lymph node metastases and histological confirmation of metastatic disease is the most important prognostic factor. Among patients with a clinically negative neck, the incidence of occult metastases varies with the site, size and thickness of the primary tumour. The high incidence rate of occult cervical metastases (> 20%) in tumours of the lower part of the oral cavity is the main argument in favour of elective treatment of the neck. The usual treatment of patients with clinically palpable metastatic lymph nodes has been radical neck dissection. This classical surgical procedure involves not only resection of level I to V lymph nodes of the neck but also the tail of the parotid, submandibular gland, sternocleidomastoid muscle, internal jugular vein and spinal accessory nerve. It is a safe oncological surgical procedure that significantly reduces the risk of regional recurrences, however it produces significant post-operative morbidity, mainly shoulder dysfunction. Aiming to reduce morbidity, Ward and Roben described a modification of the procedure sparing the spinal accessory nerve to prevent post-operative shoulder morbidity. Several clinical and pathological studies have demonstrated that the pattern of metastatic lymph node metastases occurs in a predictable fashion in patients with oral and oropharyngeal carcinoma. The use of selective supraomohyoid neck dissection as the elective treatment of the neck, in oral cancer patients, is now well established. However, its role in the treatment of clinically positive neck patients is controversial. Some Authors advocate this type of selective neck dissection in patients with limited neck disease at the upper levels of the neck, without jeopardizing neck control. The main factors supporting this approach are the usually good prognosis in patients with single levels I or II metastasis independent of the extent of neck dissection, and the low rates of level V involvement in oral cavity tumours. Furthermore, the high incidence of clinically false-positive lymph nodes in oral cavity cancer patients is well recognized. In selected cases, supraomohyoid dissection could be extended to level IV, and followed by radiotherapy when indicated. Several reports have confirmed the usefulness of minimally invasive sentinel lymph node biopsy in melanoma and breast tumours. However, only preliminary data testing the feasibility of the method exist regarding the management of oral and oropharyngeal squamous cell carcinoma. The complexity of lymphatic drainage and the presence of deep lymphatics of the neck make application of this method difficult. This attractive concept has recently been explored by several investigators who examined the feasibility of identifying the sentinel lymph node in primary echelons of drainage from oral cavity squamous carcinoma. The current knowledge of sentinel lymph node biopsy does not allow avoiding the indication of elective neck dissection in clinical practice. Sentinel lymph node biopsy cannot be considered the standard of care at this time. However, there are multi-institutional clinical trials testing this approach. Management of occult neck node metastasis continues to be a matter of debate. The role of imaging methods such as ultrasound-guided needle biopsy, sentinel node biopsy and positron emission tomography-computed tomography are still being evaluated as alternatives to elective neck dissections. Whether one of these techniques will change the current management of cervical node metastasis remains to be proved in prospective multi-institutional trials.