S1036
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
Conclusion: Electron Flash-radiotherapy using a modified C-arm linac was safe, which demonstrated fundamental proof-of-principle for broader implementation of this technology in clinical trials and routine. The limited toxicity observed in this trial is supportive of the Flash sparing effect even in fractionated and mixed-modality radiotherapy, which requires further validation. References: [1] dal Bello R, et al., Radiotherapy and Oncology, Volume 187, 2023,109822, ISSN 0167-8140[2] dal Bello R, et al., Technical preparation for a phase i clinical study of e-Flash radiotherapy for palliative treatment of superficial skin lesions of malignant melanomas. 2024 [cited 2025 May 23rd]; Available from: https://scholar.google.com/citations?view_op=view_cit ation&hl=en&user=Dl5Wt6QAAAAJ&sortby=pubdate&c itation_for_view=Dl5Wt6QAAAAJ:GnPB-g6toBAC. Keywords: Flash, UHDR (ultra-high dose rate), melanoma Radiotherapy with nivolumab (RADNIV) as a rechallenge for heavily pretreated patients with metastatic malignant melanoma: a pilot study Rafal Suwinski 1 , Katarzyna Galwas 1 , Adam Idasiak 1 , Marcin Rajczykowski 1 , Gra ż yna Kaminska-Winciorek 2 1 Radiotherapy and Chemotherapy Clinic and Teaching Hospital, Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice, Poland. 2 Skin Tumor Unit, Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice, Poland Purpose/Objective: A synergistic effect of immunotherapy and radiation therapy is not only based on spatial cooperation of these modalities but also on abscopal immunological responses that can be triggered by irradiation. We hypothesize that the resistance to immunotherapy alone acquired during initial therapy of patients with metastatic malignant melanoma (MMM) can be reversed by combining immunotherapy and radiation therapy in subsequent treatment lines. Material/Methods: Twenty-two patients with MMM (15 BRAF V600E wild type and 7 mutated) who progressed with standard systemic therapies and exhausted common therapeutic options were enrolled in the study (2018 - 2024). This included 10 patients who had ipilimumab/nivolumab combination, 8 patients with pembrolizumab monotherapy, 3 treated with BRAF inhibitors, and one with nivolumab used as first-line therapy. Subsequent therapies included Digital Poster 1829 immunotherapy in 4 patients, BRAF inhibitors in 3 and chemotherapy in 4. According to the RADNIV study
protocol, five 4.0 Gy fractions (the total dose of 20.0 Gy) were administered every 2 weeks simultaneously with 240 mg of nivolumab. GTV included the largest malignant tumor (metastatic or primary) detected on CT scans at the time of MMM progression. For those patients who did not progress up to 4 weeks after radiotherapy nivolumab (480 mg every 4 weeks) was continued until disease progression or unacceptable toxicity. Progression-free survival (PFS) was measured from the start of radiotherapy until disease progression or death, overall survival (OS) was measured from the start of radiotherapy until death of the patient from any cause. Results: The median number of nivolumab courses was 5 (range 1-21). 14 patients discontinued nivolumab due to disease progression, 2 due to immune-related toxicity, and 4 due to other issues. One patient is still on nivolumab. The median actuarial PFS was 3.5 months. The median OS was 6.5 months (16.7 months for wild-type BRAF and 5.4 months for BRAF mutant), 3-year actuarial OS at 3 years in a whole group was 20% -Fig. 1. Out of three patients who survived more than 2 years, all were wild-type BRAF.
Conclusion: Radiation therapy with nivolumab can provide a meaningful therapeutic effect in a proportion of patients with heavily pretreated MMM. Although the therapeutic group is too small to draw any definitive conclusions, the proposed schedule of radio- immunotherapy rechallenge appears to be of interest for BRAF wild-type patients who exhausted all standard therapeutic options. The 3-year OS is such a group treated according to RADNIV protocol may reach approximately 20%. References: 1. D’Andrea MA Systemic Antitumor Effects and Abscopal Responses in Melanoma Patients Receiving Radiation Therapy. Oncology 2020;98:202–2152. Okwan-Duodu D, Pollack BP, Lawson D, Khan MK. Role of radiation therapy as immune activator in the era of modern immunotherapy for metastatic malignant melanoma. Am J Clin Oncol. 2015;38:119–25.3. Kropp
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