Recurrence of keratinocyte cancers after superficial radiation therapy

Superficial radiation therapy (SRT) is a noninvasive treatment that uses low-energy X rays (50-150 kV) to treat skin cancers. SRT is used by dermatologists due to its accessibility and safety profile. Higher-energy radiation therapies are typically used by radiation oncologists. This narrative review aimed to evaluate the long-term clearance rates of keratinocyte cancers (KCs) treated with SRT. A literature search of MEDLINE, PubMed and Embase was performed in May 2024 and identified 12 studies that used SRT to treat KCs. The 12 studies included 6027 patients and reported a total of 9157 lesions treated with SRT. All studies were of a retrospective cohort design. No prospective cohort studies or randomized controlled trials (RCTs) were available for inclusion. Patients with KCs treated with SRT had a mean recurrence rate of 4.6% at the 3-year follow-up, with longer follow-up durations linked to higher recurrence rates (R² = 0.486). Recurrence rates for squamous cell carcinomas and basal cell carcinomas treated with SRT were 5.0% and 3.9%, respectively. The outcomes for SRT are encouraging; however, with the lack of head-to-head trial data in the form of RCTs, the evidence is of poor quality. These results justify the consideration of prospective studies, including RCTs, to compare the efficacy and safety of SRT with other established approaches. While SRT shows promise as a treatment option for KCs, the limited strength of the available evidence makes this conclusion uncertain.