ESTRO 2024 - Abstract Book

S1996

Clinical - Mixed sites, palliation

ESTRO 2024

fracture with no evidence of local relapse. 6-months and 1-year DPFS were 65.1%, and 35.7%, respectively, with a median DPFS of 9 months. 34 patients had a sequential oligometastatic disease (SOMD). Polymetastatic disease (PMD) occurred after median 36 months (8.6-38), and the 1- and 2-year PMD were 64.2%, and 51.4%. At the univariate analysis, prostate cancer metastases were associated with improved PFS (p=0.04). No toxicity events grade > 3 were recorded.

Conclusion:

Spinal SBRT is an effective approach in oligometastatic patients. Dose boost could be safely administered to improve significantly LC. Among oligometastatic patients, those with prostate histology had an improved PFS.

Keywords: SBRT; spinal metastases; oligometastases

2884

Mini-Oral

MR-guided stereotactic radiotherapy of abdominal metastases: toxicity and dosimetric predictors

Mette v Felter 1 , Pia K Møller 2 , Mirjana Josipovic 3 , Susanne N Bekke 1 , Uffe Bernchou 2 , Eva Serup-Hansen 1 , Kasper Madsen 1 , Parag Parikh 4 , Joshua Kim 4 , Poul Geertsen 1 , Claus P Behrens 1 , Ivan R Vogelius 3 , Mette Pøhl 3 , Tine Schytte 2 , Gitte F Persson 1 1 Herlev Hospital, Department of Oncology, Herlev, Denmark. 2 Odense University Hospital, Department of Oncology, Odense, Denmark. 3 Rigshospitalet, Department of Oncology, Copenhagen, Denmark. 4 Henry Ford Hospital, Department of Radiation Oncology, Detroit, USA

Purpose/Objective:

Recommendations for organs at risk (OAR) constraints to avoid ≥ grade 3 treatment -related adverse events (TRAEs) are mostly based on results from studies performed 10-20 years ago [1-3]. As technology advances, it is crucial to continuously collect and report TRAEs to update and challenge normal tissue complication probability (NTCP) recommendations. The SOFT (Stereotactic ablative radiotherapy (SABR) of infra-diaphragmatic sOFT tissue metastases) trial is a prospective, multicenter, phase-2 trial investigating magnetic resonance-guided stereotactic ablative radiotherapy (MRgSABR) for abdominal oligometastases disease (OMD) (NCT04407897). We report the 1 year TRAEs and explore gastrointestinal (GI) dose-response relationships.

Material/Methods:

Inclusion criteria included genuine or induced OMD from any solid cancer with up to five metastases, all accessible for ablation, and at least one abdominal metastasis. MRgSABR was planned with a risk-adapted strategy, where fixed OAR constraints were prioritized over target coverage. Fractionation schemes were 45-67.5 Gy in 3-8 fractions