PO124

Abstract

Worldwide, non-melanoma skin cancer (NMSC) has a high incidence. In 2020, Colombia, a Latin American country, had a NMSC incidence of 7.9 per 100.000 inhabitants. High Dose Rate (HDR) skin brachytherapy is a validated treatment option, with optimal and promising local control rates and cosmetic results, equivalent to surgical management and external radiation therapy. Nevertheless, this treatment technique may be scarce in Low Middle-Income Countries (LMICs), due to personnel training and technology requirements. We present the largest cohort of patients treated with HDR skin brachytherapy in Colombia, treated at the Colombian National Cancer Institute and a proposal for a low-priced, widely available, marker technique for Computed Tomography (CT) Simulation. This was a retrospective review of all patients with skin tumors treated with Ir-192 high dose rate (HDR) surface cast brachytherapy from January 1, 2019, to January 28, 2023 at the National Institute of Medicine. cancerology, Bogota - Colombia. 44 lesions (36 patients) were identified. The median age at diagnosis was 76 years (range = 50-98). The majority were basal cell carcinomas (82%, n = 36), squamous cell carcinomas (15%, n =7 ), and one cutaneous lymphoma (3%, n = 1). Most of the lesions were located in the head region. and neck. The most used RT dose was 40 Gy/8 interday fractions; all patients had individualized CT-based planning with alternative donut-type fiducial markers. Six months survival (OS) was 94% and 6-month progression-free survival (PFS) was 92%. Most of the deaths were from unrelated causes. Response was assessed in the clinic at 1 week and 2, 4, and 6 months after treatment. Our complete response (CR) rate was 97%, with partial response in one patient, we reported a local control (CL) rate at 6 months of 86%, and local recurrence in one patient. The procedure was well tolerated, with no grade 3-5 acute or late toxicities assessed on the RTOG and LENT/SOME scales. The median depth of the isodose line at 100% was 0.5 cm and the median surface dose = 120%. The median V 90 = 93%. Surface brachytherapy is an excellent alternative for the treatment of non-melanoma cancer, with response rates and effective local cancer control. In low-resource countries, treatments such as brachytherapy improve patient adherence, becoming future perspectives to be implemented. challenges in techniques, dosimetry, and casts provide challenges that evoke recursive solutions like our donut radiopaque fiduciary, thus demonstrating the skills of the radiation oncologist in the face of variability.