In vivo imaging characterization of basal cell carcinoma and cutaneous response to high-dose ionizing radiation therapy: A prospective study of reflectance confocal microscopy, dermoscopy, and ultrasonography

Background: Radiation therapy (RT) is a treatment option for select skin cancers. The histologic effects of RT on normal skin or skin cancers are not well characterized. Dermoscopy, high-frequency ultrasonography (HFUS), and reflectance confocal microscopy (RCM) are noninvasive imaging modalities that may help characterize RT response. Objectives: To describe changes in the tumor and surrounding skin of patients with basal cell carcinoma (BCC) treated with RT. Methods: The study was conducted between 2014 and 2018. Patients with biopsy-proven BCCs were treated with 42 Gy in 6 fractions using a commercially available brachytherapy device. Dermoscopy, HFUS, and RCM were performed before treatment and at 6 weeks, 3 months, and 12 months after RT. Results: A total of 137 imaging assessments (RCM 1 dermoscopy 1 HFUS) were performed in 12 patients. BCC-specific features were present in 81.8%, 91%, and 17% of patients imaged with dermoscopy, RCM, and HFUS at baseline, respectively, before treatment. After treatment, the resolution of these features was noted in 33.4%, 91.7%, and 100% of patients imaged with the respective modalities. No recurrences were seen after a mean of 31.7 months of follow-up. Limitations: Small sample size and no histopathologic correlation. Conclusion: Dermoscopy and HFUS were not as reliable as RCM at characterizing BCC RT response.