Long-Term Efficacy and Safety of Superficial Radiation Therapy in Subjects With Nonmelanoma Skin Cancer: A Retrospective Registry Study.

Background: Low-dose superficial radiation therapy (SRT) effectively treats nonmelanoma skin cancer (NMSC) without requiring invasive excision. SRT is especially safe and effective among the elderly who comprise most patients with basal cell and squamous cell carcinomas (BCCs and SCCs). Objective: To demonstrate the long-term safety and efficacy of SRT for treating NMSC with a new generation device. Methods: A retrospective chart review was performed at four clinical study sites. The study population included male and female patients (N=516) treated with SRT for NMSC (N=776) including BCCs (n=448) and SCCs (n=328) prior to January 2015 with long-term follow-up records. Results: The overall mean (SD) total treatment dosage was 4652.33 (366.34) cGy (range, 3636.6 to 5455 cGy) administered over a mean of 12.3 (1.85) sessions. The overall Kaplan-Meier survival probability estimate (95% CI) was 0.989 (0.980, 0.998) at 24 months, 0.989 (0.969, 1.000) at 60 months, and 0.989 (0.942, 1.000) at 85 months. There were six recurrences of BCCs (n=4) and SCCs (n=2). The most common adverse event was hypopigmentation. Limitations: Retrospective study design and some incomplete data. Conclusion: It is estimated that 98.9% of nonmelanoma skin cancers will not recur after 85 months following superficial radiation therapy. J Drugs Dermatol. 2020;19(2)163-168. doi:10.36849/JDD.2020.4647