Image-Guided Superficial Radiation Therapy for Basal and Squamous Cell Carcinomas Produces Excellent Freedom from Recurrence Independent of Risk Factors

<b>Background/Objectives</b>: Basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) are non-melanoma skin cancers (NMSCs) and the most prevalent cancers in the United States. Image-guided superficial radiotherapy (IGSRT) is a relatively new treatment option that uses high-resolution dermal ultrasound integrated with superficial radiotherapy to improve tumor visualization. IGSRT is a clinically equivalent non-surgical alternative to Mohs micrographic surgery at 2 years of follow-up in early-stage NMSC, but larger cohort studies with longer follow-up periods that allow for analysis of patient outcomes by demographic and disease characteristics are needed. <b>Methods</b>: This large, retrospective cohort study was conducted to determine the effect of risk factors (tumor location, tumor stage, and sex) on 2-, 4-, and 6-year freedom from recurrence rates in 19,988 NMSC lesions treated with IGSRT, including lesions with complete treatment courses. <b>Results</b>: Overall freedom from recurrence rates were 99.68% at 2 years, 99.54% at 4 years, and 99.54% at 6 years; rates did not differ significantly by tumor location (head/neck versus other locations, <i>p</i> = 0.9) or sex (male versus female, <i>p</i> = 0.4). In contrast, there was a significant difference in freedom from recurrence rates when analyzed by tumor stage (<i>p</i> = 0.004). <b>Conclusions</b>: There was no significant effect of tumor location or sex on freedom from recurrence in IGSRT-treated NMSC. Although there was a significant difference according to tumor stage, freedom from recurrence rates exceeded 99% at all stages.