ESTRO 2025 - Abstract Book

S1537

Clinical – Mixed sites & palliation

ESTRO 2025

2842

Digital Poster Clinical Implementation And Outcomes Of SRT/SBRT With Linac-Based VMAT Technique In A Less Resourced Country- A Single Center Experience Md Abdul Mannan, Ahammad Al Mamun Sweet, Md. Jobairul Islam, Qamruzzaman Chowdhury, Md. Arifur Rahman, Ehteshamul Hoque Radiation Oncology, Labaid Cancer Hospital & Super Specialty Centre, Dhaka, Bangladesh Purpose/Objective: This study evaluates the clinical implementation and outcomes of SRT/SBRT using Linac-based Volumetric Modulated Arc Therapy (VMAT) for brain, lung, and liver lesions, with a focus on advanced imaging and rigorous quality assurance. Material/Methods: The study involved 25 patients: 10 with intracranial lesions treated with 27 Gy in 3 fractions, 10 with lung lesions treated with 50 Gy in 5 fractions, and 5 with liver lesions treated with 35 Gy in 5 fractions at Labaid Cancer Hospital & Super Specialty Center, Dhaka, Bangladesh from May 2023 to August 2024. Gross Tumor Volume (GTV), Internal Target Volume (ITV), and Planning Target Volume (PTV) were delineated following RTOG guidelines. MRI was fused with planning CT scans for enhanced tumor delineation where needed. Treatments were delivered using 6X Flattening Filter-Free (FFF) photon beams on Varian TrueBeam accelerators with Millennium 120 MLC. VMAT plans were optimized in the Eclipse Treatment Planning System (AAA algorithm, 1.25 mm grid resolution). Dosimetric parameters, including Conformity Index (CI), Gradient Index (GI), Heterogeneity Index (HI), and Quality of Coverage (QRTOG), were analyzed. Treatments were executed by 80% isodose line. Hot Spot was allowed 120 – 150 % of prescribed dose. Patient-specific QA was performed using portal dosimetry and Octavius 4D phantom. Treatment set-up verification was done by doing mandatory IGRT with CBCT. Results: A total of 25 patients were included (Table 1). Most patients were male (76%, n=19). Median age was 43 years (range 35-59). ECOG performance status was 0-1 in 21 patients (84%). The majority of patients 13 had metastatic disease(stage IV: 13 (52%)). OAR doses remained within tolerance limits, and QA results demonstrated excellent agreement between planned and delivered doses, achieving gamma pass rates of 99.3%±0.68 (3%/1mm) for octavius 4D and 99.6%±0.4 for portal dosimetry. Median follow-up was 12 months (range 3-18 months). Notably, treatment responses were excellent, with no local residual/recurrences observed. Though there was four patient who developed new site of recurrences. Among 4 patients 2 died of distant recurrences. 1yr Local Control (LC), Progression-Free Survival (PFS) and Overall Survival (OS) were 100%, 84% and 92%, respectively. No G3 acute toxicities were observed.