S1035
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
(2x 9 Gy, average dose rate 216 Gy/s) followed by one fraction of conventional electron RT (1x 9 Gy, average dose rate 0.17 Gy/s) (Figure 1). The primary endpoint was safety, which was defined as a maximum of two patients developing dose limiting toxicity (DLT). DLT was defined as any skin toxicity grade >III or skin toxicity grade >II for >2 weeks (CTCAE V5.0) during or within six weeks (day 42) of Flash-RT. Secondary objectives were technical feasibility, relief of symptoms, response of irradiated metastases and late side effects. The study allowed recruitment to an expansion cohort. Flash-RT was delivered using 9 MeV UHDR (ultra-high dose rate) electrons on a converted TrueBeam with FLEX extension (Varian Medical Systems, Inc.) [1].
after ART. Recurrence rates were high in those with multiple risk factors. These findings emphasise the need for enrolment into prospective clinical trials such as SCC-AFTER, which will inform optimal management strategies in this high-risk group. References: 1.Lansbury L et al. Interventions for nonmetastatic squamous cell carcinoma of the skin: systematic review and pooled analysis of observational studies BMJ 2013;347:f61532.Ruiz ES et al. Performance of the American Joint Committee on Cancer Staging Manual, 8th Edition vs the Brigham and Women's Hospital Tumor Classification System for Cutaneous Squamous Cell Carcinoma JAMA Dermatol 2019;155(7):819- 253.Schmitt AR et al. Staging for cutaneous squamous cell carcinoma as a predictor of sentinel lymph node biopsy results: meta-analysis of American Joint Committee on Cancer criteria and a proposed alternative system JAMA Dermatol 2014;150(1):19-24 Keywords: cSCC, adjuvant radiotherapy, risk factors Flash-Skin I: A Phase I Clinical Study of LINAC- based Electron Flash Radiotherapy for Palliative Treatment of Malignant Melanoma Skin Lesions Jens von der Grün 1 , Riccardo Dal Bello 1 , Fernanda G Herrera 2 , Serena Psoroulas 1 , Jerome Krayenbuehl 1 , Debra Lauer 1 , Egle Ramelyte 3 , Joanna Mangana 3 , Joshua McNeur 4 , Lena Tirpak 4 , Wendy Smith 4 , Marta Vilalta 4 , Ricky A Sharma 4 , Vidhya Krishnamurthi 4 , Patrick Kupelian 4 , Matthias Guckenberger 1 , Stephanie Tanadini-Lang 1 , Panagiotis Balermpas 1 1 Department of Radiation Oncology, University Hospital Zurich, University of Zurich, Zurich, Switzerland. 2 Department of Radiation Oncology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland. 3 Department of Dermatology, University Hospital Zurich, and Faculty of Medicine, Zurich, Switzerland. 4 Varian Medical Systems, Varian Inc., Palo Alto, California, USA Mini-Oral 1765 Purpose/Objective: Until today, only case reports exist on the use of electron Flash-RT (eFlash-RT) in humans and no data on utilizing a conventional C-arm linear accelerator (linac) for this treatment. Here, we report a prospective clinical trial of eFlash-RT for treatment of melanoma skin metastases using a converted linac. Material/Methods: The study was a single-center, phase I trial, approved by the national authorities and local ethics (NCT06549439). Patients with metastatic melanoma and ≥ 1 skin/subcutaneous metastases were treated with a radiotherapy schedule of 3x 9 Gy (2x / week). Lesions were treated with two fractions of eFlash-RT
Results: Between January and June 2025, seven patients (five female) were treated. Median age was 80 years (range: 55-96), six metastases were located in the extremities, one below the clavicle, with a median diameter of 11 mm (5-23). All fractions were delivered successfully with dose accuracy within 4.6% for single UHDR fractions and within 2.8% for total dose [2]. Median follow up at the time-point of analysis was 197 days (49 – 245), with one patient deceased due to metastatic progression. No patients experienced grade III dermatitis or any other skin toxicity at any time-point. Five patients experienced grade I-II skin toxicity (Figure 2). No other study-related adverse events were observed except for one patient reporting grade I pain in the treated region. One complete remission and three partial responses were observed with three lesions reported as stable.
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