ESTRO 2021 Abstract Book

S1160

ESTRO 2021

or lymphovascular invasion that makes adjuvant treatments necessary. Traditionally, brachytherapy has been delivered with radioactive isotopes as Iridium -192. However,electronic brachytherapy is an innovative type of brachytherapy, which causes lighter penumbra. This, together with its mobility capacity, can be critically important when treating locations where there is minimal space for additional margin. Apart from this advantage, lower radioprotection and shielding is required. Materials and Methods Data on patients who are candidates for treatment with surface electronic brachytherapy have been collected prospectively. Histology, tumor size and risk factors, the intention of brachytherapy treatment as well as its prescription have been studied. During the follow-up, the toxicities (CTCAE v5), aesthetic and oncologic results observed were noted. The size of the applicator used were 10, 20, 35 or 50mm. Treatment with electronic brachytherpy was performed with the Xoft Axxent System. X-ray source is placed directly into a skin applicator close to the surface and provides the prescription dose in the treatment area to a 2-3mm depth. Results Between July and December 2020 35 treatments with electronic brachytherapy have been performed. 66% were male and 34% female with an average age of 76.3 years. The intentionality of the radiotherapy treatment was radical in 49% of patients, adjuvant after surgery in 34% and palliative with hemostatic purpose in 17%. The histology of the lesions treated was basal cell carcinoma 54%; squamous cell carcinoma 14%; melanoma, lymphoma and Kaposi's sarcoma 9%; squamous eccrine ductal carcinoma in one patient; and keloid in another. Most of the lesions treated were located in the forehead (26%) and nasal area (23%). The majority were treated to 40-50 Gy using 8 to 10 fractions. Applications occurred 1-2 times a week with 48 hours between treatments. Toxicity observed at treatment completion was in the form of radiodermatitis in 65.7% of patients. Only 3 patients presented grade 3 toxicity. At the one-month post-treatment review, skin toxicity was observed in only 8 patients (23%) in the form of radiodermatitis and hyperpigmentation, none of them greater than grade 2. With a median follow-up of 4.6 months, hemostatic intent in palliative patients was 100% successful in the first month. During follow-up, 100% complete response was achieved in patients treated with radical intention. No recurrence was observed in patients treated with surgery and adjuvant radiotherapy. Conclusion Electronic brachytherapy appears to be an alternative to Iridium-192 HDR -brachytherapy in terms of effectiveness, with acceptable toxicities. Continued follow-up of these patients is necessary to assess long- term toxicities and effectiveness. PO-1412 Superficial radiotherapy in the treatment of non-melanoma skin cancer M. Cerrolaza 1 , P. Sanagustin 1 , R. Ibañez 1 , A. Campos 1 , S. Flamarique 2 , C. Garcia 2 , C. Escuin 1 , V. Navarro 1 , A. Lanuza 2 , M. Lanzuela 2 1 University Hospital Miguel Servet, Radiation Oncology, Zaragoza, Spain; 2 University Hospital Miguel Servet , Radiation Oncology, Zaragoza, Spain Purpose or Objective Non-melanoma skin cancer (NMSC) includes mainly keratinocytic neoplasms such as basal cell and squamous cell carcinoma. The development of these tumors is related to age, ultraviolet exposure, fair skin and immunosuppression. Although surgical management remains the "Gold Standard" treatment for NMSC, radiotherapy may be a treatment option in patients who are not surgical candidates or if the location is a cosmetically sensitive area that may cause some type of disfigurement. Radiotherapy is also used for NMSCs as adjuvant therapy when excision is incomplete and re-excision is not feasible, or when there are risk factors for tumor recurrence. Materials and Methods Patients diagnosed with basal cell and squamous cell carcinoma treated between January 2016 and September 2020 in our department were retrospectively recorded. The treatment was administered with the Therapax 150 orthovoltage machine with cylinders and cones between 1-15 cm and filters adapted to administer between 80-120 Kv. Characteristics of patients, location, size and histology of the lesions, fractionation, and oncologic results, as well as toxicities evaluated with the CTCAE v.5 scale were collected. Results 731 treatments were performed in 647 patients. In 66 patients more than one treatment was administered. With a median age of 82.45 years, 54% of the patients were male and 46% female. A total of 484 treatments were performed on basal cell carcinomas (66%) and 247 on squamous cell carcinomas (34%) with a mean size of 2.9 cm. The lesions were in very heterogeneous regions but the most frequently treated were the nasal region (24%), fronto-parietal region (22%) and auricular region (11%). Also, the dose fractionation used (between 12 and 75 Gy) differed considering various factors such as age, performance status or site of the lesion. The most used fractionation schemes were 55 Gy in 11 fractions of 5 Gy (14%), 50 Gy in 10 fractions of 5 Gy (12.6%), 50 Gy in 5 fractions of 10 Gy (7.5%) and 60 Gy in 12 fractions of 5 Gy (7.3%). The kilovoltage applied was 80 Kv in 75%, 100 in 19% and 120 in 5%. The available follow-up data were analyzed for 73% of the patients at 3 and 6 months, 1, 2 and 3 years after completion of treatment, 93% of whom presented complete response/no recurrence during the treatment. Partial response was the best response in 40% of patients. No major grade 2 acute or chronic toxicities were observed throughout follow-up. Conclusion Adjuvant radiotherapy after surgery or with radical intent in the treatment of non-melanoma skin cancer is a well-tolerated treatment with low acute and late toxicities. It is especially indicated in elderly patients or those who are inoperable due to its effectiveness and patient comfort.