ESTRO 2022 - Abstract Book

S529

Abstract book

ESTRO 2022

OC-0604 Early toxicity after SABR of oligometastatic bony metastases in the BONY M phase II trial

N.J. Spindler 1 , M.V.O. Felter 1 , O. Hansen 2 , T.B. Nielsen 3 , M.H. Suppli 4 , M. Josipovic 4 , L.Ø. Poulsen 5 , F. Gaard-Petersen 1 , H.M.B. Sand 5 , T.M. Abramova 6 , M. Johansen 6 , J.S. Kornerup 7 , M.D. Alsaker 7 , E. Serup-Hansen 1 , P. Geertsen 1 , I.R. Vogelius 8 , C. Behrens 1 , G.F. Persson 9 1 Copenhagen University Hospital - Herlev and Gentofte, Department of Oncology, Herlev, Denmark; 2 Odense University Hospital, University of Southern Denmark, Department of Oncology, Department of Clinical Research, Odense, Denmark; 3 Odense University Hospital, Laboratory of Radiation Physics, Department of Oncology, Odense, Denmark; 4 Copenhagen University Hospital - Rigshospitalet, Department of Oncology, Copenhagen, Denmark; 5 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; 6 Ålesund Hospital, Department of Radiotherapy, Clinic of Oncology, Ålesund, Norway; 7 St. Olavs University hospital, Department of Radiotherapy, Clinic of Oncology, Trondheim, Norway; 8 Copenhagen University Hospital - Rigshospitalet, Faculty of Health, University of Copenhagen, Department of Oncology, Department of Clinical Medicine, Copenhagen, Denmark; 9 Copenhagen University Hospital - Herlev and Gentofte, Faculty of Health, University of Copenhagen, Department of Oncology, Department of Clinical Medicine, Herlev, Denmark Purpose or Objective Stereotactic ablative radiotherapy (SABR) of bone metastases is rapidly emerging into standard practice but is still considered investigational and not without risk. When applied to patients with oligometastatic disease (OMD), lasting local control is important. The multicenter prospective phase II trial, BONY-M, evaluated the efficacy and safety of SABR to bone metastases in patients with OMD. Patient characteristics and preliminary early toxicity data are presented. Materials and Methods Patients eligible for the study had at least one bony metastasis and OMD defined as a maximum of five metastatic lesions or oligo-progressive disease (OPD) defined as a maximum of three metastatic lesions. Maximum diameter of each bone metastasis ≤ 5cm. Ablative treatments, including surgery of all metastatic sites, should be possible and planned. Patients with spinal metastases and a Bilsky score ≥ 1b were excluded. The primary endpoint was 1-year local control rate. Secondary endpoints include toxicity (CTCAE v.5.0), change in pain score, quality of life, efficacy, and survival measures. At least 67 patients were planned to be included. SABR was delivered in three fractions of 37.5Gy or 30Gy to the GTV, with 80% and 67% isodose coverage of CTV and PTV, respectively. Dose distribution within the target area was non-homogenous, with steep dose gradients outside the GTV. Dose constraints to selected organs at risk (OAR) were predefined and prioritized over target coverage. Radiotherapy parameters were accessed through the national radiotherapy collaboration system (DcmCollab), CRF data were accessed through the protocol’s redcap database. Results The BONY-M trial opened in December 2019 and finished recruiting the 67 patients in late October 2021. At abstract submission, 66 patients from six centers across Norway and Denmark had finished treatment and had a median follow-up of 6.8 months (range 0.1-22.9). Patient and treatment characteristics are listed in Table 1 and 2. Early CTCAE toxicity records were accessible for 43 patients (64%), of whom five (~7%) experienced treatment-related G2 and one (~1.5%) G3