ESTRO 2023 - Abstract Book

S1297

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ESTRO 2023

Median follow-up was 43.3 (0.0 – 53.7) months. No grade (G) ≥ 3 acute toxicity was observed. Two pts experienced G1 back pain; other two pts suffered from nausea, one G1 and the other G2. No late toxicity was observed. Overall Survival (OS) at 12-, 24- and 36- months was 82.1%, 67.7% and 60.2% respectively. Distant metastases free survival (DMFS) was 57.7% at 12 months, 44.4% at 24 months and 35.5% at 36 months. Kaplan Meier estimates of local relapse free survival (LRFS) was 88.3% at 12 months, and 24 months, and 77.3% at 36 months (See Fig. 1).

Before treatment 8 pts were symptomatic, and after SBRT a complete pain response was observed in all of them.

Fig. 1: Local Relapse Free Survival after salvage stereotactic re-irradiation for bone relapses.

Conclusion Stereotactic bone re-irradiation appears feasible, with low acute and late toxicity despite the proximity of organs at risk, in particular spinal cord for the spine metastases. Further studies are needed to confirm these results.

PO-1597 Stereotactic Arrhythmia Radioablation for Ventricular Tachycardia: Single Center Experience

F. Colombo 1 , F. Salaroli 2 , I. Renna 2 , E. Lattanzi 2 , G. Ceccon 2 , S. Gianni 2 , C. Grondelli 2 , M. Bergamini 2 , C. Dell'Anna 2 , M. Galaverni 2 , G. Benecchi 3 , G. Gonzi 4 , M.F. Notarangelo 4 , A. Palumbo 5 , C. Ghetti 3 , N. D'Abbiero 2 , N. Simoni 2 1 Azienda Ospedaliero Universitaria di Parma - Scuola di Specializzazione UNIMORE, Radiation Oncology Unit, Parma, Italy; 2 Azienda Ospedaliero Universitaria di Parma, Radiation Oncology Unit, Parma, Italy; 3 Azienda Ospedaliero Universitaria di Parma, Medical Physics Unit, Parma, Italy; 4 Azienda Ospedaliero Universitaria di Parma, Cardiology Unit, Parma, Italy; 5 Azienda Ospedaliero Universitaria di Parma, Radiology Unit, Parma, Italy Purpose or Objective Stereotactic Ventricular Arrhythmia Radioablation (STAR) has emerged as a promising treatment option to precisely ablate the arrhythmogenic substrate of scar-related refractory ventricular tachycardia (rVT), in patients at prohibitive risk for catheter ablation (CA). Materials and Methods We present the experience with the first 2 patients treated with STAR for rVT at our Institution. The first patient treated was an 87-years-old man, hospitalised for rVT requiring ICD interventions, unresponsive to antiarrhythmic drugs. The second patient was a 60-years-old man, with rVT secondary to ischemic cardiomyopathy, presenting to the emergency department in VT storm requiring multiple ICD shocks and not responsive to maximal antiarrhythmic therapy. Both patients were considered not eligible for CA due to high intraprocedural risks. For target localization, high-density substrate electroanatomic cardiac mapping, cardiac computed tomography (CT) and magnetic resonance (MR) were acquired. To manage cardiac motion, a four-dimensional (4D) CT-simulation was adopted. Target volume definition was defined by Radiation Oncologists in cooperation with Electrophysiologists and dedicated Radiologists.

Results STAR was delivered using 3 co-planar arcs configuration Volumetric Modulated Arc Therapy (VMAT). A photon energy of 6MV, flattening filter free (FFF) technique, and a dose rate of 1400 MU/min were used for both treatments. The prescribed dose was 25 Gy in single fraction to the Planning Target Volume, with a Dmax of 32 Gy to the arrhythmogenic substrate. To optimize image-guidance, a Cone Beam CT (CBCT) was performed before each arc delivery, and a respiratory-gated