ESTRO 2025 - Abstract Book

S1705

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

2953

Digital Poster Outcomes of stereotactic radiotherapy as first-line local treatment of melanoma patients with brain metastases Aneta Maria Borkowska 1,2 , Piotr Błoński 1 , Dorota Kiprian 2,3,4 , Michał Czerwiński 2 , Piotr Rutkowski 1 , Mateusz Jacek Spałek 1,2 1 Department of Soft Tissue/Bone Sarcoma and Melanoma, Maria Skłodowska-Curie National Research Institute of Oncology, Warsaw, Poland. 2 Department of Radiotherapy I, Maria Skłodowska-Curie National Research Institute of Oncology, Warsaw, Poland. 3 Gamma Knife Center, Gamma Knife Center, Warsaw, Poland. 4 Department of Head and Neck Cancer, Maria Skłodowska-Curie National Research Institute of Oncology, Warsaw, Poland Purpose/Objective: Study aimed to evaluate efficacy of stereotactic radiotherapy (SRT) as first-line treatment of melanoma brain metastases (BMs). Material/Methods: In retrospective study, we evaluated melanoma patients with BMs. We included patients, who underwent SRT as first-line treatment for BMs. SRT was administered in 5-24Gy fractions (Table1). In GammaKnife (GK) all patients received single fraction, and in linear accelerator (LINAC) 1, 3, or 5 fractions. We evaluated pattern of progression of disease after SRT and influencing factors. Results: 142 pts were included in the study, 83 were treated with LINAC and 59 with GK. Median age was 64 years (22-89), 73 were males (51.4%), BRAF V600 mutation was present in 75 (52.8%) cases. One, 3 and 5 fractions were administered in 80 (56.3%), 41 (28.9%), and 21 (14.8%) pts, respectively. 68 pts had SRT on one target lesion (33 pts in GK, and 35 pts in LINAC). In most cases (80 pts, 56.3%) first progression occurred in non irradiated lesions. Among them, 39 patients had new intracranial lesions, whereas 41 had exclusively extra-cranial progression. Only 26 pts (18.3%) experienced first progression in previously irradiated volume (12 of them simultaneously developed new brain metastases). Before SRT, most frequent systemic treatment was immunotherapy (IT)(75pts, 52.8%), followed by BRAF/MEK targeted therapy (33pts, 23.2%). 20 pts was systemic treatment naive before the SRT, 8pts received chemotherapy, 6 pts were enrolled in clinical trials. Significantly longer PFS and OS times were achieved in pts treated in clinical trials, the shortest in chemotherapy group (median OS 40.6vs4.2months). Results of other groups were similar (median for IT, BRAF/MEK and no-treatment was 13.4, 9.3, and 12.25months, respectively). Median EQD2 (α/β ratio=2.5Gy) was 69 Gy (42-141Gy) and pts with higher than median EQD2 had superior OS (median OS: 15.2vs10.7months, p=0.036). Neither OS nor PFS was influenced by patients’ sex, BRAF mutation status, or age. One fraction SRT had superior PFS(p=0.023) and OS(p=0.012) compared to 3 and 5 fractions. Patients with one target lesion had superior PFS(p=0.012) and OS(p=0.024) than pts with multiple lesions.