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

February 2020 | Volume 19 | Issue 2 | Original Article | 163 | Copyright © February 2020


Published online January 17, 2020

William Roth , Robert E. Beer , Vivek Iyengar , Thomas Bender , Isabelle Raymond

aDermatology and Dermatological Surgery, Boynton Beach, FL bBalfour Dermatology, Brentwood, CA cDermatology Associates, Tinley Park, IL dAdvanced Dermatology and Skin Care Centre, Mobile, AL eSensus Healthcare, Boca Raton, FL

Abstract
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

INTRODUCTION

Nonmelanoma skin cancer (NMSC) comprises basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and numerous less common skin tumors.1 NMSCs are the commonest form of malignancy among Caucasians2 and its incidence continues to rise worldwide.3 Although Mohs surgery has traditionally been regarded as the gold-standard for treating NMSC,4 it may not be suitable for the elderly due to frailty, limited life-expectancy, and comorbidities.5-7

Superficial radiation therapy (SRT) comprises low energy X-rays produced by units generally operating in the 50 to 150 kV range. SRT was the standard of care for office-based radiation treatment of NMSCs for more than 100 years but declined during the 1980s due to an increase in the popularity of Mohs micrographic surgery and because there were no new devices to replace older ones;8 however, the use of SRT is currently seeing a resurgence following the reintroduction of newer, easy-to-use SRT equipment.9 Low-dose SRT effectively treats NMSC without requiring invasive excision.10 SRT can be performed as an office procedure without anesthesia,11 minimal risk of infection and superior cosmetic outcomes.12 Recovery is rapid with no or minimal downtime or lifestyle restrictions. SRT has been shown to be safe and very effective among elderly who comprise the majority of patients with NMSC.8,13

The objective of this retrospective chart review was to further demonstrate the long-term efficacy of SRT for treating NMSCs with a new generation device.

METHODS

Seven clinical centers across the US that treated NMSCs with SRT for at least 5 years were contacted to participate. Sites were required to have treated at least 50 patients with ≥5-year follow-up. Three sites declined or did not respond. The study was therefore conducted in four clinical practices, where three of the four investigators were also Mohs surgeons. Retrospective chart reviews identified 516 subjects treated for 776 histologically confirmed, primary, cutaneous NMSC lesions. Relevant clinical