High-dose conformal proton therapy for clinical perineural invasion in cutaneous head and neck cancer.

Non-melanomatous skin cancer (NMSC) is the most common malignancy worldwide. Perineural invasion (PNI) is an uncommon (<5%), high-risk feature observed with NMSC more commonly seen in those with squamous cell carcinoma. One-third of these patients will have clinical PNI, which refers to tumor cell invasion extensive enough to cause clinically detectable deficits of the involved nerve. Uncontrolled disease within the skull base can be debilitating and, if not eradicated, fatal. The primary management options including radiotherapy with or without surgery, with local control rates exceeding 50%. Given the overwhelming influence of local control on disease control and survival, dose escalation and complication mitigation through hyperfractionated and high-dose conformal skull-base proton therapy are strategies to improving the therapeutic window in patients with cutaneous head and neck cancer with clinical PNI.