ESTRO 2025 - Abstract Book

S1701

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

2910

Digital Poster ULTRA-HIGH DOSE RATE SINGLE FRACTION FOR SQUAMOUS AND BASAL SKIN CANCER (ULISSE TRIAL) Giovanni Gadducci 1,2 , Taiusha Fuentes 1,2 , Noemi Giannini 1,2 , Alessandra Gonnelli 1,2 , Fabio Di Martino 2,3,4 , Andrea Cavalieri 2,5 , Luigi Masturzo 2,6 , Mariagrazia Celentano 4,6 , Jake Harold Pensavalle 2,6 , Simone Capaccioli 2,5,6 , Nicolò Mori 1,7 , Agata Janowska 1,7 , Marco Romanelli 1,7 , Cristian Scatena 5,8 , Antonio Giuseppe Naccarato 5,8 , Beatrice D’Orsi 2,9 , Giulia Rosini 9 , Giuseppe Felici 10 , Paola Puccini 1 , Monica Naso 1 , Cecilia Trippa 1 , Katsiaryna Kharkauskaya 1 , Stefano Ursino 1,2,11 , Fabiola Paiar 1,2,5 1 Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy. 2 Centro Pisano ricerca e implementazione clinica Flash Radiotherapy (CPFR@CISUP), Presidio S. Chiara, ed. 18 via Roma 67, Pisa, Italy. 3 Unit of Medical Physics, Pisa University Hospital “Azienda Ospedaliero-Universitaria Pisana”, via Roma 67, Pisa, Italy. 4 National Institute of Nuclear Physics (INFN), Section of Pisa, Pisa, Italy. 5 Center for Instrument Sharing of the University of Pisa (CISUP), University of Pisa, Pisa, Italy. 6 Department of Physics, University of Pisa, Pisa, Italy. 7 Unit of Dermatology, University of Pisa, Pisa, Italy. 8 Division of Pathology, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy. 9 Institute of Neuroscience, Italian National Research Council, Pisa, Italy. 10 SIT Sordina, IORT Technologies, Aprilia (LT), Italy. 11 Department of Radiation Oncology, Pisa University Hospital “Azienda Ospedaliero-Universitaria Pisana”, via Roma 67, Pisa, Italy FLASH effect has been demonstrated in different animal models, and in different tissue including skin. However clinical evidence remains limited. Therefore, it is crucial to develop a clinical protocol to validate the data obtained from preclinical experiments in humans. Currently, the only available ultra-high dose rate(UHDR) electron linacs can only deliver low-energy electrons, as very-high-energy electrons (VHEE) has not yet been implemented. For this reason, the first clinical setting in which the effectiveness of FLASH RT can be appreciated is the treatment of superficial tumors like non-melanoma skin cancer (NMSC). NMSC is the most common type of cutaneous cancer worldwide. For patients unfit for surgery or who choose to avoid surgical resection, definitive radiotherapy is considered a valid alternative as a curative treatment approach. AIMS : The objective of this study is to compare the effects of exclusive FLASH-RT versus CONV-RT in patients with early stage SCC and BCC. Material/Methods: The ULISSE trial is a single-center, Phase II, randomized study. Patients will be randomized into two groups: FLASH-RT (average dose rate 800 Gy/s) and CONV-RT (average dose rate 3 Gy/min). Both arms will enroll at least 40 patients. The tumor will be irradiated with a dose of 22 Gy at the 90% isodose in a single fraction. Inclusion criteria are: histological diagnosis of SCC or BCC, stage cT1cN0 , not eligible for surgery, over 60 years old, and Performance Status Scale score of <3. Patients may also be eligible if they have received previous radiotherapy and/or surgical treatments within 3 cm of the new tumor site. After radiotherapy, patients will be monitored for 6 months using coherent radiation optical tomography, ultra-high frequency ultrasound, macroscopic evaluation, blood sampling, and biopsy. Both radiotherapy treatments modalities will be performed using a triode-gun-based ElectronFlash LINAC, which will allow us to switch from CONV to FLASH modality keeping energy spectrum and the others beam parameters unchanged. Purpose/Objective: BACKGROUND :

Results: The clinical trial has been submitted to the Ethics Committee for approval.

Conclusion: The treatment of skin with low-energy electrons may play a pioneering role in the future implementation of VHEE, as healthy skin represents a primary organ at risk for the treatment of deep tumors. The skin also serves as an effective