ESTRO 2025 - Abstract Book

S1729

Clinical - Sarcoma & skin cancer & malignant melanoma

ESTRO 2025

4375

Poster Discussion Clinical Outcomes of Postoperative Stereotactic Radiotherapy Combined with Systemic Treatment for Resected Melanoma Brain Metastases Maiwand Ahmadsei 1 , Sheela Aidoo 1 , Sebastian M. Christ 1 , Nicolaus Andratschke 1 , Matthias Guckenberger 1 , Reinhard Dummer 2 , Joanna Mangana 2 , Panagiotis Balermpas 1 1 Department of Radiation Oncology, University Hospital and University Zurich, Zurich, Switzerland. 2 Department of Dermatology, University Hospital and University Zurich, Zurich, Switzerland Purpose/Objective: Melanoma Brain metastases (MBM) have a high incidence, present in 20–40% of patients already at diagnosis 1 . Prior to the advent of immunotherapy and tyrosine kinase inhibitors (TKI), MBM have been associated with poor overall survival (OS), with a median of 4 months 2,3,4 . Yet, the overall results and any additional benefit of a combination of postoperative SRS/SRT and simultaneous treatment with ICI/TKI for MBM remain unclear. The aim of this study was to evaluate clinical response in patients under active ICI/TKI therapy treated with postoperative SRT to the resection cavity. Material/Methods: A retrospective single-center analysis was performed to patients with MBM under ICI/TKI treated with SRT/SRS for the resection cavity between 2014 and 2023. Clinical, radiological, and radio-oncological data were extracted from medical records (KISIM™), imaging (IMPAXX™), and radiation oncology information system (ARIA®). Descriptive statistics and univariate/multivariate analyses were conducted. Kaplan-Meier methods were employed to calculate oncological outcomes. Results: 71 patients meeting the inclusion criteria were included in this analysis. The median age was 59.3 (16.7-85.5) years, 20 patients (28.2%) were female. The majority of patients (84.5%) showed metachronous metastases, while 11 patients had synchronous metastases. Details of timing and sequence of systemic therapy are described in table 1. The most common dose prescription (n=55, 77.5%) was 30 Gy to the encompassing isodose delivered in six fractions. The median follow-up was 1.67 years (range: 0.02–8.7 years). The 1- and 2- year local control rates were 83% and 70% respectively. Intracranial control rates were 41% at 1 year and 34.5% at 2 years, with a median intracranial control duration of 0.39 years (95% CI: 0.27–1.42). Median OS was 2.27 years (95% CI: 1.34–3.85). Univariate analysis identified no significant predictors of local recurrence or reduced survival. However, multiple lines of prior systemic therapies (HR 1.24, 95% CI: 1.04–1.46, P = 0.012) and BRAF-mutated primary tumors (HR 2.0, 95% CI: 1.13–3.6, P = 0.018) were significantly associated with an increased risk of intracranial failure. Five cases (7%) of asymptomatic radiation necrosis were observed.