ESTRO 2022 - Abstract Book

S55

Abstract book

ESTRO 2022

Conclusion Patients treated with SBRT with ORD can achieve long-term STFS. SBRT for ORD might be an alternative treatment in patients who either cannot receive systemic therapy due to comorbidities or to defer systemic therapy in patients with a perceived low cancer activity. However, the impact on overall survival remains uncertain. Prospective randomized trials are needed to determine if a holiday from systemic therapy after SBRT is safe and feasible for ORD patients.

PD-0078 Three-year update of outcomes for SABR-treated extracranial oligometastases: A real world experience

M.K. Abutaleb 1 , W. Croxford 1 , A. Fatimilehin 1 , S. Bowen-Jones 1 , M. Bewley 1 , R. Colaco 1 , R. Hall 2 , P. Whitehurst 2 , R. Wooder 2 , G. Radhakrishna 1 , D. Woolf 1 1 The Christie NHS Foundation Trust, Clinical Oncology Department, Manchester, United Kingdom; 2 The Christie NHS Foundation Trust, Clinical Medical Physics and Engineering, Manchester, United Kingdom Purpose or Objective We present real-world data from a single institution demonstrating longer term treatment outcomes in patients who have received SABR for oligometastases in addition to standard of care management. We compared our treatment outcomes and safety and safety against published data. Materials and Methods We retrospectively collated 5-year outcomes for patients with oligomatastases treated with SABR from February 2016 to September 2021. Inclusion criteria were as per the UK SABR Consortium Guidelines 1 . Prescribed doses ranged between 25- 60Gy in 3-8 alternate day fractions. The primary endpoints were: local in-field control rate (LC), distant relapse (DR) for Years 1, 2 and 3, median overall survival (OS), progression free survival (PFS) and median time to further subsequent treatment (TFST). Tumour biologically effective dose (BED) was calculated using α / β ratio of 10. When applicable, endpoints were estimated from SABR treatment end date. Toxicity data ( ≥ G3) was collected and assessed using CTCAE v5.0. Results A total of 142 patients received 152 treatments (10 patients had SABR for 2 sites). Patients’ characteristics are shown in table-1 . Mean tumour BED was 96.4 Gy (range 43.2-180) for the prescribed doses. Median follow up was 33 months (range 0-65), Median LC for years 1, 2 and 3 was 89.4%, 83.5% and 82.2% respectively. OS for years 1, 2 and 3 was: 89.1%, 77.8% and 72.4% respectively. Median OS is not yet reached ( Fig-1 ). DR was 66.4%, 52.6% and 47.3% for years 1, 2 and 3 respectively. Median times to: local in-field recurrence (LR) and DR were 10 and 9 months respectively. Median local and distant PFS was 19 months. Median TFST was 12 months (range 0-36). G3 toxicities observed in 1.4% (2/142) (spinal fracture and fatigue). No ≥ G4 toxicities.