Sentinel Lymph Node Biopsy for Cutaneous Squamous Cell Carcinoma of the Head and Neck

Nonmelanoma skin cancer is the most commonly diagnosed malignancy in the United States, with cutaneous squamous cell carcinoma (cSCC) representing about 20% of those cases. It is estimated that there are 700,000 patients diagnosed each year in the United States and the incidence has been increasing worldwide. Most tumors are found within the sun-exposed areas of the head and neck. The vast majority require only local treatment, however there is a subset of patients who present with regionally metastatic disease. Retrospective reviews have determined factors associated with recurrence, metastasis, and disease-specific death include tumor size ≥ 2 cm, location on lip and ear, perineural and lymphovascular invasion, poorly differentiated histology, tumor extension beyond fat and immunosuppressed patients.

There have been multiple proposed staging schemes, including the American Joint Committee on Cancer (AJCC) and recently the Brigham and Women's Hospital (BWH) tumor staging. AJCC staging utilizes the size for early stage tumors, T1 < 2 cm and T2 ≥ 2 cm and less than 4 cm. Advanced tumors, T3 and T4 are stratified by aggressive features, including invasion beyond fat, perineural invasion (PNI), or bone/skull base erosion. BWH aimed to better stratify tumors by the number of aggressive features, T1 tumors with 0 features, T2a tumors with 1 feature, T2b with 2-3 features, and T3 with 4 or more features. High-risk features include tumor diameter ≥ 2 cm, poorly differentiated histology, PNI, tumor invasion beyond fat, or bone erosion. In a recent study, and found BWH provided superior prognostication for patients with localized cSCC as compared to AJCC7. However, BWH does not address regional or distant metastasis and therefore current treatment guidelines are based on BWH staging scheme. AAJCC systemCurrently, there is a general paucity of prospective data that can provide a consensus on risk-stratification of cutaneous squamous cell carcinomas and subsequent treatment algorithm. A consensus on risk-stratification for high-risk cSCC is lacking; consequently, treatment algorithm for primary tumors and nodal disease is not clear.

There is a subset of tumors with increased risk of local recurrence, nodal and distant metastasis which has yet to be elucidated. Data has shown metastasis to regional lymph nodes is the strongest predictor of recurrence and survival, and risk of nodal metastasis is noted to be 6% for all-comers and upwards of 20% for high-risk tumors. Therefore, detecting subclinical metastatic disease is extremely important for staging aggressive skin cancers and optimizing treatment.Imaging, including CT, MRI and PET, are considered for high-risk tumor. Data has demonstrated a higher risk of developing local recurrence, nodal metastasis and death from disease in patients that did not receive pre-treatment imaging as compared those who underwent imaging.

Guidelines recommend surgical excision of the primary tumor as first line treatment for cutaneous squamous cell carcinoma. Both Moh's micrographic surgery (MMS) and standard excision are both considered feasible surgical options. Available literature on management of lymph node metastasis largely limited to retrospective reviews and case series. Therefore, optimal management of regional lymph nodes for high-risk tumors remains unclear.

Sentinel lymph node biopsy (SNLB) is a common procedure utilized in multiple oncologic surgeries, especially dermatology. SLNB is recommended for aggressive skin cancers including melanoma and Merkel cell carcinoma. There is limited data on the utility of SLNB in nonmelanoma skin cancers, including cutaneous SCC. To date, there have been no prospective trials and current data comes from small retrospective studies. Therefore, the impact of SLNB on management and outcomes with high-risk cSCC remains unknown. Therefore, the impact of SLNB on cSCC remains unclear. The purpose of this study is to evaluate the rate of occult metastasis utilizing sentinel lymph node biopsy in clinically node-negative intermediate and high-risk cSCC.