This study reviewed the outcomes of 26 patients who received definitive or postoperative proton therapy for nonmelanoma skin cancer with clinical perineural invasion. The 3-year overall and disease-free survival rates were 59% and 60%. The 3-year local control, local regional control, and distant metastasis-free survival rates were 80%, 65%, and 96%, respectively.

Grade 3+ late toxicities occurred in 13 patients (50%) and the most common toxicities included grade 3+ keratitis of the ipsilateral eye, which occurred in 4 patients (15%) and grade 3+ brain necrosis in 4 patients (15%). This study concluded that PT is effective in the management of nonmelanoma skin cancer with clinical perineural invasion.

Although disease control and complication rates compare favorably to those previously published for photon-based radiation therapy, the risk for late toxicity is significant and patients should be appropriately counseled.