ESTRO 2023 - Abstract Book

S205

Saturday 13 May

ESTRO 2023

divided by the prescription dose. Under-coverage was defined as CCI < 0.90. The potential association between CCI and outcomes (LR and PFS) was evaluated. Results A total of 549 lesions from 381 patients were assessed. Mean CCI was 0.88 (95% confidence interval [CI], 0.86-0.89), and 196 (36%) lesions were under-covered. The highest mean CCI (0.95; 95% CI, 0.93-0.97) was seen in non-spine bone lesions (n=116), while the lowest mean CCI (0.71; 95% CI, 0.69-0.73) was seen in spine lesions (n=104). On multivariable analysis, CCI < 0.90 did not predict for worse local recurrence or progression-free survival. Conclusion Under-coverage of the PTV is not associated with worse local recurrence and progression-free survival rates in this large, population-based phase II trial. Combined with low rates of toxic effects, this study supports the practice of prioritizing OAR constraints during SABR treatment planning for oligometastases. OC-0269 Early toxicity of SBRT for oligometastatic cancer patients in the EORTC/ESTRO OligoCare cohort F. Alongi 1 , U. Ricardi 2 , M. Scorsetti 3 , L. Livi 4 , P. Balermpas 5 , Y. Lievens 6 , P. Braam 7 , B.A. Jereczek-Fossa 8 , K. Stellamans 9 , I. Ratosa 10 , J. Widder 11 , H. Peulen 12 , P. Dirix 13 , L. Verbeke 14 , S. Ramella 15 , H. Hemmatazad 16 , K. Khanfir 17 , X. Geets, 18 , P. Jeene 19 , T. Zilli 20 , B. Fournier 21 , C. Fortpied 22 , F.B. Oppong 23 , P. Ost 24 , M. Guckenberger 25 1 IRCCS Sacro Cuore Don Calabria Hospital & University of Brescia, Advanced Radiation Oncology, Negrar (Verona), Italy; 2 Università degli Studi di Torino, Torino, Italy, Radiation Oncology, Torino, Italy; 3 Humanitas University, Department of Biomedical Sciences, Pieve Emanuele (Milan), Italy; 4 Azienda Ospedaliero-Universitaria Careggi , Radiation Oncology, Florence, Italy; 5 University Hospital Zürich, University of Zürich , Radiation Oncology, Zurich, Switzerland; 6 Radiation Oncology Department, Ghent University Hospital and Ghent University, Radiation Oncology, Ghent, Belgium; 7 Radboud University Medical Center Nijmegen, Radiation Oncology, Nijmengen, The Netherlands; 8 European Institute of Oncology and University of Milan, Oncology and Hemato-oncology department, Milan, Italy; 9 Campus Kennedylaan, AZ Groeninge Kortrijk , Kortrijk , Belgium; 10 Istitute Of Oncology, Radiation Oncology, Ljubljana, Slovenia; 11 Universitaetsklinikum Wien, Radiation Oncology, Wien, Austria; 12 Catharina Ziekenhuis, Radiation Oncology, Eindhoven, The Netherlands; 13 Iridium Network, Radiation Oncology,, Wilrijk , Belgium; 14 Onze-Lieve-Vrouw Ziekenhuis, Radiation Oncology, Aalst, Belgium; 15 Policlinico Universitario Campus Bio-Medico- Oncology Center, Policlinico , Radiation Oncology, Roma, Italy; 16 Bern University Hospital (Inselspital), Radiation Oncology, Bern, Switzerland; 17 Hopital de Sion, Hopital du Valais , Radiation Oncology, Sion, Switzerland; 18 Cliniques Universitaires Saint-Luc, -, Brussels, Belgium; 19 Radiotherapiegroep, - , Deventer, The Netherlands; 20 Hôpitaux universitaires de Genève - HUG - site de Cluse-Roseraie, , Radiation Oncology, Geneve, Switzerland; 21 European Organisation for Research and Treatment of Cancer (EORTC) , Headquarters, Brussels, Belgium; 22 European Organisation for Research and Treatment of Cancer (EORTC) , Headquarters, Brussels, Belgium; 23 (European Organisation for Research and Treatment of Cancer (EORTC) , Headquarters, Brussels, Belgium; 24 Iridium Network, Radiation Oncology, Wilrijk, Belgium; 25 University Hospital Zürich, University of Zürich, Radiation Oncology, Zürich, Switzerland Purpose or Objective Several randomized phase II trials have reported improved outcome if local ablative therapies were added to standard-of- care treatment of oligometastatic cancer patients with very low rates of toxicity. In this analysis, based on the first patients included in the ongoing ESTRO/EORTC E ² -RADIatE OligoCare cohort, we report on the early toxicity for patients treated with SBRT for oligometastatic cancer. Materials and Methods The analysis is based on a snapshot of the database on October 10th 2022 including only the first 1100 enrolled patients. A total of n=1002 were included in this analysis after exclusion of non-eligible patients or patients with incomplete data. The current update reports the patient characteristics and adverse events observed within 6 months of the start of SBRT, using the CTCAE v5 scale. Only events of grade 3 or higher related to radiotherapy are reported. Results Patients were treated with SBRT at 32 centers across 9 European countries for oligometastatic breast (n=163), colorectal (n=183), non-small cell lung (n=198) or prostate cancer (n=458). The majority of patients had a good performance status (WHO 0-1: 82.4%). In 97% of cases, less than 4 metastases were irradiated, with most patients receiving radiotherapy for a single metastasis (67.2%). The most common organ sites irradiated were non-vertebral bones (22.9%), lung (20.8%), non- regional lymph nodes (18.3%) and spine lesions (15.8%). The median clinical target volume was 3.7cc (Q1-Q3: 1.2-12.8cc). The median number of fractions was 5 (range 1-11) with a median dose of 9.4 Gy per fraction (Q1-Q3: 7.5-12.2Gy). The median dose per fraction was highest for metastases from colorectal primaries at 13.1Gy per fraction, followed by NSCLC (10.2Gy), breast (8.6Gy) and prostate cancer (8.5Gy). The median BED, using an α / β of 10, delivered was 73 Gy (Q1-Q3 (59.7-104.4). SBRT was delivered in combination with systemic therapy in 38.3% of cases. There were only 0.5% of patients with grade 3 or higher adverse events reported. In total 4 cases of grade 3 toxicity were reported (pain: 1, empyema: 1, pneumonia: 1, decreased appetite: 1) and 1 grade 5 toxicity (pneumonitis). In total, 6 patients (0.6%) were diagnosed with a new primary malignancy and 27 patients died (2.7%) within the first 6 months of follow-up. Conclusion Very few grade 3 or higher toxicity are being observed in the OligoCare cohort, with the vast majority of patients being alive at 6 months follow-up. Up-to-date data will be presented at the ESTRO congress. OC-0270 Metastases-directed SRT and systemic therapy: EORTC-ESTRO OligoCare delphi consensus recommendations S. Kroeze 1 , M. Pavic 2 , K. Stellamans 3 , Y. Lievens 4 , C. Becherini 5 , M. Scorsetti 6 , F. Alongi 7 , U. Ricardi 8 , B. Jereczek 9 , P. Westhoff 10 , J. But-Hadzic 11 , J. Widder 12 , X. Geets 13 , S. Bral 14 , M. Lambrecht 15 , C. Billiet 16 , I. Sirak 17 , S. Ramella 18 , I.G. Battista 19 , S. Benavente 20 , A. Zapatero 21 , F. Romero 22 , T. Zilli 23 , K. Khanfir 24 , H. Hemmatazad 25 , B. De Bari 26 , D. Klass 27 , S. Adnan 28 , H. Peulen 29 , J. Salinas Ramos 30 , M. Strijbos 31 , S. Popat 32 , P. Ost 33 , M. Guckenberger 2 1 Kantonsspital Aarau, Radiation Oncology, Aarau, Switzerland; 2 University Hospital Zürich, Radiation Oncology, Zürich, Switzerland; 3 AZ Groeninge Kortrijk , Radiation Oncology, Kortrijk, Belgium; 4 Ghent University Hospital and Ghent University, Radiation Oncology, Ghent, Belgium; 5 Careggi University Hospital, Radiation Oncology, Florence, Italy; 6 IRCCS Humanitas Research Hospital, Radiation Oncology, Milan, Italy; 7 IRCCS Sacro Cuore don Calabria Hospital, Radiation