ESTRO 2023 - Abstract Book

S17

Saturday 13 May

ESTRO 2023

1 Gemelli Molise Hospital – Università Cattolica del Sacro Cuore, Radiation Oncology Unit, Campobasso, Italy; 2 Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Fondazione Policlinico Universitario A. Gemelli, IRCCS, UOC Radioterapia Oncologica, Roma, Italy; 3 Vito Fazzi Hospital, Radiation Oncology Unit, Lecce, Italy; 4 Gemelli Molise Hospital - Università Cattolica del Sacro Cuore, Oncology Unit, Campobasso, Italy; 5 Vito Fazzi Hospital, Oncology Unit, Lecce, Italy; 6 "Federico II" University, Radiation Oncology Unit, Napoli, Italy; 7 Fondazione Policlinico Universitario A. Gemelli IRCCS, Department of Woman, Child and Public Health, Roma, Italy; 8 Fondazione Policlinico Universitario A Gemelli IRCCS, UOC di Radioterapia Oncologica, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Roma, Italy; 9 Università Cattolica del Sacro Cuore, Istituto di Radiologia, Roma, Italy Purpose or Objective The benefit of surgery and maintenance treatment with Poly (ADP-ribose) polymerase inhibitors (PARPi) has been recently shown in ovarian cancer (OC) recurrence. The management of oligometastatic progression (OMP) during PARPi maintenance is unclear and continuing the treatment beyond progression could be an option. Furthermore, the efficacy and safety of stereotactic body radiation (SBRT) in patients with metastatic, persistent, and recurrent OC are proven. The aim of this observational, retrospective, multicenter study (Epimetheo) was to define the activity and safety of the SBRT in a real- world data set of patients with OMP during PARPi maintenance. Materials and Methods Patients treated with PARPi in maintenance setting received SBRT if OMP occurred. OMP was assessed by either Computed Tomography (CT)-scan or PET/CT scan, and in the case of < 5 lesions, SBRT was prescribed. Maintenance treatment was continued until the extensive progression of the disease. The endpoints of the study were the rate of complete response (CR) to SBRT plus concomitant PARPi therapy and acute toxicity profile assessment. The objective response rate (ORR) included CR and partial response (PR). Toxicity was evaluated by the Common Terminology Criteria for Adverse Events (CTCAE) scale. Results From May 2019 and May 2022, SBRT was used to treat 57 OC patients with a total of 115 lesions (70 lymph nodes and 45 parenchyma lesions) under PARPi maintenance. The patient characteristics and some treatment details are shown in Table 1. Olaparib, Niraparib, and Rucaparib were administered to 45.6%, 45.6%, and 8.8% of patients, respectively. Treatment response was assessable in 109 lesions with a median time to the best response of 5 months (1-14 months): CR, PR, and stable disease were observed in 71 (65.1%), 30 (27.5%), and 6 (5.5%) lesions respectively. Two lesions (1.8%) progressed. Out of 42 adverse effects, 34 were Grade 1, four were Grade 2, and four were Grade 3. Concerning severe acute toxicities 2 (pain flare and upper gastrointestinal toxicity) occurred in the same patient who was treated for a retro- esophageal lymph node recurrence with 35 Gy in 5 fractions, the third was an anemia and the fourth was a skin toxicity in a patient previously undergone in-field radiotherapy. Patients achieving complete response on a 'per lesion' basis experienced a 1-year actuarial local control rate of 94.2% versus 82.3% in lesions not achieving complete response (p: 0.140).

Conclusion This study confirms the activity and safety of SBRT in patients in association with PARPi in this clinical setting. The toxicity rate in this series is consistent with that described in the literature on the stereotactic technique, and the addition of the PARP inhibitor did not worsen the toxicity. MO-0050 Feasibility of the determination of the molecular-integrated risk profile in the PORTEC-4a trial A. van den Heerik 1 , N. Horeweg 1 , L. Lutgens 2 , D. Haverkort 3 , S. Kommoss 4 , A. Staebler 5 , F. Koppe 6 , M. Nowee 7 , H. Westerveld 8 , M. de Jong 9 , D. Cibula 10 , P. Dundr 11 , J. Cnossen 12 , J.W. Mens 13 , C. Chargari 14 , C. Genestie 15 , S. Bijmolt 16 , C. Gillham 17 , C. O’Riain 18 , T. Stam 19 , I. Jurgenliemk-Schulz 20 , M. Hamann 21 , V. Smit 22 , T. Bosse 22 , C. Creutzberg 1 1 Leiden University Medical Center, Radiation Oncology, Leiden, The Netherlands; 2 Maastricht Radiation Oncology Clinic, Radiation Oncology, Maastricht, The Netherlands; 3 Radiotherapy Group, Radiation Oncology, Arnhem, The Netherlands;