ESTRO 2023 - Abstract Book

S31

Saturday 13 May

ESTRO 2023

SHARON BONE involved 4 Italian RT units. Patients (pts) aged at least 18 years with ECOG PS ≤ 3 candidates for palliative RT on painfully complicated bone metastases were eligible. We randomly allocated pts to either 30 Gy in 10 daily fractions (over two weeks), or 20 Gy in 4 fractions twice a day (in two consecutive days). Allocation was not masked because of the nature of the intervention. The primary endpoint was pain relief one month after treatment. Pain relief, toxicities, and Quality of Life questionnaires were also assessed at 2, 3, 6, and 12 months after RT. This trial is registered at clinicaltrials.gov (NCT03503682). Results Between February 2018 and December 2021, 83 pts were enrolled (30 Gy: 41; 20 Gy: 42). Pts characteristics are summarized in Table 1. Five patients on the standard RT schedule versus none in the experimental arm did not complete RT. Moreover, due to early death, the primary endpoint was not evaluable in 5 pts (1 and 4 pts from the standard and experimental arm, respectively). Overall, the primary endpoint was evaluable for 73 pts (35 and 38 pts for standard and experimental arms respectively). Complete pain response (NRS=0) at 1 month was 22.9% and 28.9% in the 30 and 20 Gy arms, respectively (p: NS). The overall pain response rates (complete plus partial) were 82.9% and 86.8% in the 30 and 20 Gy arms, respectively (p: NS). Both treatments were well tolerated, with 12.2% and 4.8% pts experiencing G ≥ 2 toxicity in standard and experimental arms, respectively. In the 30 Gy arm, two vertebral fractures were recorded.

Conclusion 20 Gy in 4 fractions twice a day is non-inferior to the standard 30 Gy in 10 fractions for pain relief in complicated bone metastases, and it is at least as safe in terms of acute toxicity, with a lower rate of RT definitive interruptions. PD-0064 Metastases-directed SRT combined with systemic therapy: 2y results of the TOaSTT real-world database S. Kroeze 1 , J. Schaule 2 , M. Spaas 3 , K.H. Kahl 4 , J.J. Verhoeff 5 , F.L. Schneiders 6 , O. Blanck 7 , F. Lohaus 8 , S. Rogers 9 , D. Kaul 10 , S. Benavente 11 , S.E. Combs 12 , G. Skazikis 13 , K. Baumann 14 , I. Popp 15 , F. Koppe 16 , H. Geinitz 17 , K.E. de Jaeger 18 , S. Siva 19 , S. Stera 20 , A. Wittig-Sauerwein 21 , V. Lewitzki 22 , F. Eckert 23 , M.M. Schymalla 24 , M. Guckenberger 2 1 Kantonsspital Aarau, Radiation Oncology, Aarau, Switzerland; 2 University Hospital Zürich, Radiation Oncology, Zürich, Switzerland; 3 Ghent University Hospital, Radiation Oncology, Ghent, Belgium; 4 Universitätsklinikum Augsburg, Radiation Oncology, Augsburg, Germany; 5 University Medical Center Utrecht, Radiation Oncology, Utrecht, The Netherlands; 6 University Medical Center Amsterdam, Radiation Oncology, Amsterdam, The Netherlands; 7 University Medical Center Schleswig-Holstein, Radiation Oncology, Kiel, Germany; 8 Technische Universität Dresden, Radiation Oncology, Dresden, Germany; 9 Kantonsspital Aarau , Radiation Oncology Center KSA-KSB, Aarau, Switzerland; 10 Charité-University Hospital Berlin, Radiation Oncology, Berlin, Germany; 11 Vall d'Hebron University Hospital, Radiation Oncology, Barcelona, Spain; 12 Technical University Munich, Radiation Oncology, Munich, Germany; 13 Schwarzwald-Baar Klinikum, Radiation Oncology, Villingen-Schwenningen, Germany; 14 Klinikum Stuttgart, Radiation Oncology, Stuttgart, Germany; 15 University of Freiburg, Radiation Oncology, Freiburg, Germany; 16 Instituut Verbeeten, Radiation Oncology, Tilburg, The Netherlands; 17 Ordensklinikum Linz, Radiation Oncology, Linz, Austria; 18 Catharina Hospital, Radiation Oncology, Eindhoven, The Netherlands; 19 Peter MacCallum Cancer Centre, Radiation Oncology, Melbourne, Australia; 20 University Hospital Frankfurt, Radiation Oncology, Frankfurt, Germany; 21 University Hospital Jena, Radiation Oncology, Jena, Germany; 22 University Hospital Würzburg, Radiation Oncology, Würzburg, Germany; 23 University Hospital Tübingen, Radiation Oncology, Tübingen, Germany; 24 Philipps-University Marburg, Radiation Oncology, Marburg, Germany Purpose or Objective Metastases-directed stereotactic radiotherapy (SRT) is frequently performed in patients receiving immunotherapy (IT) or targeted therapy (TT), with different clinical goals like obtaining a durable control of resistant metastases, a prolongation of progression free survival or the prevention of a systemic therapy switch. Due to a lack of prospective data on this topic, our aim was to prospectively collect real-world data and examine the safety and efficacy of metastases-directed SRT combined with targeted therapy or immunotherapy. Materials and Methods Patients treated with metastases-directed SRT performed concurrent ( ≤ 30d) to any type of TT or IT were included in the international multicenter prospective register trial (TOaSTT). Patients received SRT of brain metastases (BM) or extracranial lesions. Overall survival (OS), progression free survival (PFS) and time to discontinuation (TTD) of systemic therapy after SRT were analyzed using Kaplan-Meier survival curves and log rank testing. Treatment-related toxicity was measured using the CTCAE v4.03 criteria. Results