555 Practice changing landmark study- multi-institutional analysis of image guided superficial radiotherapy (IGSRT) for the treatment of non-melanoma skin cancer (NMSC)

Abstract

Practice changing landmark study- multi-institutional analysis of image guided superficial radiotherapy (IGSRT) for the treatment of non-melanoma skin cancer (NMSC). NMSC is generally treated in dermatology offices using surgical techniques. This study presents the largest multi-institutional retrospective modern series of Image Guided Superficial Radiotherapy (IGSRT) for Non-Melanoma Skin Cancer (NMSC). Between July 2013 and December 2019, 2424 NMSC lesions treated with IGSRT at 3 clinics in Texas and 1 clinic in NY were analysed. All lesions received 50, 70 or 100 kiloVoltage(kV) energy IGSRT 2-4 times weekly. KV energy selection was determined by ultrasound depth measurements and/or tumor characteristics. Patients returned 3-6 weeks after completion of therapy for dermoscopy/clinical evaluation and ultrasound imaging to confirm complete tumor clearance. Patients were then followed every 2-12 months thereafter. Any lesions in the treatment site suspicious for residual or recurrent tumor were biopsied. Exclusion criteria included tumors greater than 4 cm in diameter or non-movable tumors adherent to deeper structures. Follow-up ranged from 0.1-62.8months. At a mean follow up of 15.8 months, 29 patients with 77 lesions expired, all without recurrence. Kaplan-Meier (KM)Tumor control rates at 1, 2 and 5 years were 99.5%, 99.4% and 99.4% respectively. One, 2 and 5 year KM Overall-Survival (OS) for the entire group was 97.6%, 95.8% and 85.8% and unaffected by disease status or treatment. This study represents the largest study of NMSC treated with non-invasive IGSRT. The 99% cure rate is comparable to the best cure rates of other invasive modalities such as Mohs micrographic surgery. This innovative non-surgical technology with its high cure rate in the treatment of NMSC has the potential to transform the practice of dermatology with regard to treatment of NMSC.