ESTRO 2025 - Abstract Book

S1508

Clinical – Mixed sites & palliation

ESTRO 2025

References: 1. 1.5 T MR-guided and daily adapted SBRT for prostate cancer: feasibility, preliminary clinical tolerability, quality of life and patient-reported outcomes during treatment. Alongi et al., Radiat Oncol. 2020. 2. Feasibility and safety of 1.5 T MR-guided and daily adapted abdominal-pelvic SBRT for elderly cancer patients: geriatric assessment tools and preliminary patient-reported outcomes. Mazzola et al., J Cancer Res Clin Oncol. 2020 3. 1.5 T MR-Guided Daily Adapted SBRT on Lymph Node Oligometastases from Prostate Cancer. Nicosia et al., J Clin Med. 2022 4. MRI-Linac – Based Radiotherapy — Promising or Hype? Roach et al., JAMA Oncol 2024

2074

Digital Poster Clinical safety and efficacy of palliative Simultaneous Integrated Boost Lattice RT in patients with advanced cancers: A prospective analysis Preetha Umesh 1 , Kratika Bhatia 1 , Kundan Singh Chufal 1 , Irfan Ahmad 1 , Alexis Andrew Miller 2 , Harsh Vyas 1 , Munish Gairola 1 1 Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India. 2 Radiation Oncology, Illawarra Cancer Care Centre, Wollongong, Australia

Purpose/Objective: To evaluate palliative SIB-Lattice RT for bulky metastatic tumors.

Material/Methods: This prospective IRB-approved study (2021 – 2024) enrolled patients with metastatic cancer of any primary or histology who met these criteria: (A) ECOG PS 3 – 4; (B) progressive/refractory disease on standard-of-care systemic treatments; (C) expected survival <3 months with further systemic treatment/best supportive care (BSC); and (D) primary complaint (breathlessness, pain, or neuropathy) attributable to a target lesion sufficiently large for Lattice RT planning. Multi-specialty clinic approval and informed consent were obtained prior to treatment. Symptom burden was assessed pre- and 4 weeks post-RT using the modified Medical Research Council (mMRC) scale for dyspnea and numeric pain rating scale (NPRS). Toxicity was evaluated with CTCAE v5. Target lesion volumetric response was assessed opportunistically during routine CT or PET-CT imaging. Overall survival (OS) was calculated from the start of RT. Briefly, the target lesion (GTVp) was contoured and given a 5mm inner margin, within which 2cm high-dose spheres (GTVs1, GTVs2, etc) were placed (center-to-center separation > 3cm and 1cm away from OARs). A 3mm outer expansion was given to the target lesion (PTVp) and spheres (PTVs1, PTVs2, etc). PTVp was prescribed 20-30Gy in 5 10Fx; the high-dose sphere(s) PTV was prescribed a SIB boost of 30-45Gy in 5-10Fx. VMAT treatment planning and delivery was performed on Eclipse v15 and TrueBeam, respectively (figure 1). The primary endpoints were change in symptom burden and toxicity, while volumetric response was a secondary endpoint. Two-sided paired Wilcoxon signed-rank test and paired t-test were used for symptom burden comparison and volumetric change assessment, respectively. Significance was set at < 0.05.