ESTRO 2021 Abstract Book

S568

ESTRO 2021

Conclusion MF-SRS at a dose of 27 Gy or 24 Gy in 3 daily fractions seems to be an effective and safety treatment modality for brain metastases, associated with better local control and a reduced risk of radiation-induced RN as compared with SF-SRS at dose ranged from 21 Gy to 24 Gy. PD-0739 PET-imaging integration in recurrent glioblastoma treatment planning: impact on patient outcomes A. Robertson 1 , I. Yakushev 2 , D. Bernhardt 1 , S. Combs 1 1 Klinikum rechts der Isar, Radiation Oncology, Munich, Germany; 2 Klinikum rechts der Isar, Nuclear Medicine, Munich, Germany Purpose or Objective Recurrent glioblastoma is a neurological malignancy with poor patient outcomes, owing to its aggressive nature, and a lingering median overall survival between 7.5 to 9.5 months. Conventional definition of re- irradiation treatment volumes is dependent on MRI, which itself relies on non-specific blood brain barrier disturbances for contrast enhancement. This enhancement can exclude glioma tumour extension, and poorly differentiates post-therapeutic changes commonly seen in recurrent glioma, thus resulting in an imperfect treatment volume which can adversely affect patient outcomes. Amino-acid PET (AA-PET) has been shown to have a higher sensitivity and specificity in glioma diagnosis and delineation than MRI. A small body of evidence suggests superior overall survival in recurrent glioma when PET-imaging is incorporated into treatment planning. This single center, retrospective evaluation sought to determine the impact AA-PET integration in treatment planning has on overall survival (OS) and local control (LC) in recurrent glioblastoma. Materials and Methods 173 patients treated for recurrent glioma at the Klinkum rechts der Isar between 2002 and 2020 were analyzed. Inclusion criteria included local recurrence of histologically confirmed glioblastoma and having received previous radiotherapy for primary glioma. The median age was 57, with a functional ability of KPS ≥ 80 in 91 patients (52.6%). Radiotherapy was performed in an adjuvant setting following surgical resection (n = 93, 53.8%) or as primary therapy (n = 46.2%). Target volumes were delineated based on conventional CT and MRI (n = 56, 32.4%) or with 18F-Fluoroethyltyrosine (FET)-PET integration (n = 117, 67.6%). Patients were treated with stereotactic fractionated or intensity modulated radiotherapy with a median total dose of 36 Gy and a dose per fraction of 3 Gy respectively. Results A median follow-up of 4.5 months was obtained (range 0-52.7 months). Mean OS in the non-PET group was 7.4 months, compared to 8.6 in the PET-group. Regarding LC, non-PET LC was with 3.8 months versus 4.0 in the PET group. When sub-analyzed by functional status KPS ≥ 80, the non-PET mean OS was 9.8 versus 14.4 in the PET group (p = 0.033). Univariate and multivariate analyses suggested a significant impact on overall survival in this group (multivariate HR = 0.59, p = 0.019). Conclusion These results suggest PET-integration in treatment planning is associated with a significantly increased OS in functional patients with recurrent glioblastoma. PD-0740 Real-world patient & treatment characteristics of oligometastatic disease: results of OligoCare M. Guckenberger 1 , U. Ricardi 2 , M. Scorsetti 3 , P. Balermpas 1 , Y. Lievens 4 , F. Alongi 5 , L. Livi 6 , P. Braam 7 , B.A. Jereczek-Fossa 8 , K. Stellamans 9 , L. Verbeke 10 , H. Peulen 11 , K. Khanfir 12 , S. Ramella 13 , T. Zilli 14 , X. Geets 15 , H. Hemmatazad 16 , G.B. Ivaldi 17 , I. Ratosa 18 , P. Jeene 19 , B. Fournier 20 , C. Fortpied 20 , P. Ost 4 1 University Hospital Zürich, University of Zürich , Department of Radiation Oncology, Zürich, Switzerland; 2 Università degli Studi di Torino, Radiation Oncology, Torino, Italy; 3 Humanitas University, Pieve Emanuele (Milan), IRCCS Humanitas Research Hospital, Rozzano and Department of Biomedical Sciences, Milan, Italy; 4 Universitair Ziekenhuis Gent, Radiation Oncology, Gent, Belgium; 5 University of Brescia and IRCCS Sacro Cuore Don Calabria Hospital, Negrar, Radiation Oncology, Negrar, Italy; 6 Azienda Ospedaliero-Universitaria Careggi Florence, Radiation Oncology, Florence, Italy; 7 Radboud University Medical Center Nijmegen, Radiation Oncology, Nijmegen, The Netherlands; 8 University of Milan, Milan, Italy and Division of Radiotherapy, IEO European Institute of Oncology, IRCCS, Department of Oncology and Hemato-oncology, Milan, Italy; 9 Campus Kennedylaan, AZ Groeninge Kortrijk , Kortrijk, Belgium; 10 Onze-Lieve-Vrouw Ziekenhuis, Radiation Oncology, Aalst, Belgium; 11 Catharina Ziekenhuis, Radiation Oncology, Eindhoven, The Netherlands; 12 Hopital de Sion, Hopital du Valais , Sion, Switzerland; 13 Universitario Campus Bio-Medico- Oncology Center, Policlinico , Roma, Italy; 14 Hôpitaux universitaires de Genève - HUG - site de Cluse-Roseraie, Radiation Oncology, Geneva, Switzerland; 15 Cliniques Universitaires Saint-Luc, Radiation Oncology, Brussels, Belgium; 16 Inselspital, Universitätsspital , Radiation Oncology, Bern, Switzerland; 17 Istituti Clinici Scientifici Maugeri, Radiation Oncology, Pavia, Italy; 18 Division of Radiation Oncology, Institute of Oncology , Ljubljana, Slovenia; 19 Radiotherapiegroep, Deventer, the Netherlands, Radiotherapiegroep, Deventer, the Netherlands, Deventer, The Netherlands; 20 European Organisation for Research and Treatment of Cancer (EORTC) , Headquarters, Brussels, Belgium Purpose or Objective Oligometastatic disease (OMD) has been recognized as a heterogeneous cancer state, and optimal multimodality treatment strategies remain unknown. This is explained by the limitations of the currently available evidence, mostly small prospective trials and retrospective studies, which lack standardization and sufficient statistical power for subgroup analyses. The OligoCare project aims to identify patient, tumor, staging and treatment characteristics influencing overall survival after radical radiotherapy for oligometastatic breast, colorectal, prostate and non-small-cell lung cancer (NSCLC). Poster discussions: Poster discussion 3: Oligometastatic disease