Image guidance improves freedom from recurrence rate after superficial radiation therapy for non-melanoma skin cancer

Background and purpose: This is the first study to quantify the 2-year freedom from recurrence for individuals with non-melanoma skin cancer (NMSC) such as basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and squamous carcinoma in-situ (SCCIS) treated with image-guided superficial radiation therapy (IGSRT) versus SRT without image guidance.Materials and methods: This retrospective cohort study evaluates the 2-year freedom recurrence rate of NMSCs treated by IGSRT (March 2016 to January 2022) and compares it to existing data on NMSCs treated by SRT via one sample proportion tests. Individuals > 18 years old with biopsy-proven SCC, SCCIS, and/or BCC treated with IGSRT were included in the study. 1602 patients/2,880 treated lesions were followed until 1/14/2022. SRT literature was identified through an Ovid Medline search.Results: All NMSCs treated by IGSRT in this cohort had an aggregate 2-year freedom from recurrence of 99.23%. The recurrence rate for BCC (N=1382) was 1.1%, for SCC (N=904) 0.8% and for SCCis (N=594) 0.0%. These recurrence rates are significantly improved compared to a pooled study that evaluated NMSCs across histology (Cognetta) and BCCs alone (Silverman) treated without image guidance (standard SRT) (p < 0.001).Conclusion: IGSRT offers a paradigm-shifting treatment option for patients with NMSCs – offering statistically significantly improved outcomes compared to standard SRT, and a more desirable toxicity profile to surgical options. This study demonstrates that IGSRT is associated with remarkably low recurrence rates, which are statistically significantly improved from the previous generation of SRT, and in line with modern outcomes for Mohs micrographic surgery.