Durham, N.C. — The jury is still out on whether patients with high-risk cutaneous squamous cell carcinoma (CSCC) whose lymph nodes are clinically node-negative (N0) may benefit from elective neck dissection (END), according to Jonathan L. Cook, M.D., associate professor of medicine and director of dermatologic surgery, Duke University Medical Center, Durham, N.C. END, a diagnostic staging procedure, allows microscopic detection of subclinical nodal metastases.
Excision or destructive techniques cure most CSCC tumors, but some studies suggest that 1 percent to 3 percent eventually metastasize to regional lymph node basins. Since the presence of nodal metastasis is a key prognostic indicator for survival in CSCC, its prevention is an important goal. When nodal disease is present, surgeons usually excise the primary tumor, dissect the draining nodal basins, and consider adjunctive radiotherapy.
However, the advantages of excising the regional lymph nodes prophylactically in CSCC patients without apparent nodal disease are much less clear. There are few data on whether END is preferable to clinical observation, and no definite evidence of its survival benefit. Nodal dissections have become more selective, but the procedures are not without significant costs, operative risks and surgical morbidities. Finally, most N0 CSCC patients, even if not subjected to surgery to stage or treat the neck, do not go on to develop metastatic disease.
Scarcity of data
Since data on the use of END in CSCC is scarce, Dr. Cook and his colleague, Juan Carlos Martinez, M.D., a resident physician at Duke University, extrapolated data from studies of head and neck SCC (HNSCC), cautioning that HNSCC is an inherently more aggressive malignancy with higher rates of metastases and lower survival rates. Otolaryngologists ordinarily prescribe END for N0 HNSCC if the metastatic risk of a particular tumor exceeds 20 percent. However, no survival benefit has been shown in N0 HNSCC patients after undergoing END over patients initially staged as N0 who undergo therapeutic neck dissection after developing regional disease.
Higher risk areas
Lip tumors are at higher risk for metastases, particularly when on the upper lip, of sizes greater than 3 cm or depths greater than 6 mm, with poor cytologic differentiation or deep invasion into muscles, nerves or vessels. National Comprehensive Cancer Network clinical practice guidelines include a potential role for END in the management of large (T3 and T4) lip tumors. In three studies, the procedure revealed occult metastases in 7 percent to 20 percent of patients with lip SCC, but produced no significant survival benefits.
Like lip tumors, CSCCs on auricular or periauricular skin have higher rates of metastases (3 percent to 27 percent) than other CSCCs and can aggressively invade not only cervical nodes but the parotid gland. No data, however, exist on rates of occult metastases or survival when END has been performed on these tumors.
"The lack of proven survival benefit is the crux of the current controversy surrounding END's routine use," Dr. Cook explains.
Less invasive diagnostic methods
The risks incurred with END have spurred the development of less invasive diagnostic methods. Positron emission topography combined with either computed tomography or magnetic resonance imaging has improved both detection and localization of subclinical nodal metastasis. A histologic examination technique, ultrasound-guided fine needle aspiration biopsy (USgFNAB), has demonstrated a specificity of almost 100 percent and a sensitivity of up to 75 percent in detecting occult metastases in patients with N0 neck compared to pathologic specimens from neck dissections.
"Unfortunately, even these sophisticated techniques aren't sensitive enough to definitively exclude the presence of microscopically detectable metastatic disease. END is still the most accurate method for staging the neck."