ESTRO 2021 Abstract Book

S570

ESTRO 2021

Differences in OS at 2, 3, or 5 years were not statistically significant when comparing the different OMD states. However, it appeared that better OS was observed in the “de novo OMD” group. The OS according to primary tumor is illustrated in Figure 1 (A-C). Overall, OS was significantly influenced by primary tumor type, with superior OS observed for prostate cancer and worst OS observed for lung cancer.

Conclusion This systematic review demonstrates large heterogeneity in reporting of SBRT for OMD and inclusion of heterogeneous patient cohorts into most studies. To facilitate future meta-analyses and comparison of individual studies, comprehensive reporting of OMD characteristics using standardized terminology is recommended, as proposed by the ESTRO/EORTC consensus. PD-0742 Prognostic Value of The ESTRO EORTC Classification System of Oligometastatic Disease J. Willmann 1 , E. Vlaskou Badra 1 , S. Adilovic 1 , M. Ahmadsei 1 , S.M. Christ 1 , M.C. Mayinger 1 , M. Guckenberger 1 , N. Andratschke 1 1 University Hospital Zurich, Department of Radiation Oncology, Zurich, Switzerland Purpose or Objective Oligometastatic disease (OMD) describes a state of limited metastatic spread in which patients might benefit from metastases-directed local therapy in addition to standard of care systemic therapy. The OligoCare project of the European Society for Radiotherapy and Oncology (ESTRO) and European Organisation for Research and Treatment of Cancer (EORTC) recently proposed an OMD classification system with standardized OMD reporting and nomenclature (Guckenberger et al. 2020). The current study aims to apply the OMD