High-Risk Cutaneous Squamous Cell Carcinoma of the Head and Neck: A Clinical Review.

Background Given the rapidly evolving nature of the field, the current state of "high-risk" head and neck cutaneous squamous cell carcinoma (HNcSCC) is poorly characterized. Methods Narrative review of the epidemiology, diagnosis, workup, risk stratification, staging and treatment of high-risk HNcSCC. Results Clinical and pathologic risk factors for adverse HNcSCC outcomes are nuanced (e.g., immunosuppression and perineural invasion). Frequent changes in adverse prognosticators have outpaced population-based registries and the variables they track, restricting our understanding of the epidemiology of HNcSCC and inhibiting control of the disease. Current heterogeneous staging and risk stratification systems are largely derived from institutional data, compromising their external validity. In the absence of staging system consensus, tumor designations such as "high risk" and "advanced" are variably used and insufficiently precise to guide management. Evidence guiding treatment of high-risk HNcSCC with curative intent is also suboptimal. For patients with incurable disease, an array of trials are evaluating the impact of immunotherapy, targeted biologic therapy, and other novel agents. Conclusion Population-based registries that broadly track updated, nuanced, adverse clinicopathologic risk factors, and outcomes are needed to guide development of improved staging systems. Design and development of randomized controlled trials (RCTs) in advanced-stage HNcSCC populations are needed to evaluate (1) observation, sentinel lymph node biopsy, or elective neck dissection for management of the cN0 neck, (2) indications for surgery plus adjuvant radiation versus adjuvant chemoradiation, and (3) the role of immunotherapy in treatment with curative intent. Considering these knowledge gaps, the authors explore a potential high-risk HNcSCC treatment framework.