ESTRO 2023 - Abstract Book

S679

Monday 15 May 2023

ESTRO 2023

of them can experience a poli-progression after a local ablative treatment (LAT). The purpose of this study was to retrospectively identify predictive factors of poli-progression in patients receiving SBRT for OMD. Materials and Methods Data from a monocentric database were retrospectively analysed. Patients treated with SBRT for OMD and who developed progression after LAT were selected. Patients were categorized as oligo or poli-progressive according to the number of new/progressing metastases (< or > 5). Herein, we analyzed data about patients’ characteristics, oligometastatic presentation and radiation treatment characteristics to evaluate their relation with kind of progression. Univariate and multivariate Cox regression (backward conditional) model were used for this purpose. Results From 2013 to 2021, data from 1306 patients treated in our institution were collected. Of those, 700 progressing patients were retrospectively selected for this analysis. Baseline patients’ and treatment characteristics are summed in table 1.

During follow up 227 patients (32,4%) experienced a poli-progression; median time to poli-progression was 7.72 months (range 1-79.6).

Five variables predictive of poli-progression were found to be statistically significant at the univariate analysis: performance status (p<0.001), site of primary tumor (p=0.016), ablative dose (p = 0.002), treated site (p=0.002), single or double organ (p=0.03). Of those, four variables retained their significant predictive value on the multivariate analysis (table 2).

Conclusion Our study identified four predictive factors associated with poli-progression in patients with OMD receiving SBRT. According to literature, OMD patients may have various clinical presentations, heterogeneity about the course of disease and outcomes. Our data may support comprehensive characterization of OMD, better understanding of factors associated with progression and eventually improve the management of specific subgroups of patients.

PD-0807 Single-fraction PSMA-PET- and multiparametric MRI-guided SBRT for prostate cancer local recurrences

F. Ehret 1 , T. Hofmann 2 , C. Fürweger 2 , M. Kufeld 3 , M. Staehler 4 , A. Muacevic 3 , A. Haidenberger 5

1 Charité - Universitätsmedizin Berlin, Radiation Oncology, Berlin, Germany; 2 European Radiosurgery Center Munich, Medical Physics, Munich, Germany; 3 European Radiosurgery Center Munich, Radiosurgery, Munich, Germany; 4 Ludwig- Maximilians-University Munich, Urology, Munich, Germany; 5 European Radiosurgery Center Munich, Radiation Oncology, Munich, Germany

Purpose or Objective