ESTRO 2023 - Abstract Book

S203

Saturday 13 May

ESTRO 2023

Figure 1: VAS average.

Figure 2: WOMAC evolution.

Conclusion 3 Gy is non inferior to 6 Gy in knee and hip arthritis. There was no presence of grade 3-4 skin toxicity in both arms. The decrease of analgesics consumption analysis is in progress. OC-0267 Long-term results of an SBRT dose-escalation trial for bone and lymph node metastases (NCT03486431) C. Mercier 1,2 , C. Billiet 1,2 , I. Joye 1,2 , P. Meijnders 1,2 , D. Nevens 1,3 , P. Ost 1,4 , D. Verellen 1,2 , P. Dirix 1,2 1 Iridium Netwerk, Radiation Oncology, Antwerp, Belgium; 2 University Antwerp, Integrated Personalised and Precision Oncology Network, Antwerp, Belgium; 3 University Antwerp, Integrated Personalised and Precision Oncology Network, Ghent, Belgium; 4 Ghent University, Department of Human Structure and Repair, Antwerp, Belgium Purpose or Objective To present long-term results of a stereotactic body radiotherapy (SBRT) trial for non-spine bone and lymph node oligometastases, comparing toxicity and efficacy of the three most used fractionation (i.e. 5, 3 or single fraction) schedules (NCT03486431). Materials and Methods This was a prospective non-randomized trial including patients with 3 or less non-spine bone and/or lymph node metastases. In the first, second and third cohort of each 30 patients, all detected metastases were treated to 5 x 7 Gy, 3 x 10 Gy or 1 x 20 Gy, respectively. SBRT could be combined with standard of care systemic treatment. The primary endpoint was 6- month dose-limiting (grade ≥ 3) toxicity (DLT) rate (previously published) and secondary endpoints were late toxicity, local failure (LF) and progression-free survival (PFS). The study opened in July 2017 and closed in December 2018. In the current report, long-term follow-up was analyzed through September 2022. Results Ninety patients received SBRT to 101 metastases. Median age was 69 (IQR 62-75) and the majority of patients (74%) were male. The most common primary tumor types were prostate (n=52; 58%), breast (n=13; 14%) and lung (n=8; 9%). The three groups were well-balanced for patient and tumor characteristics. The primary endpoint was previously reported after a median follow-up of 17.2 months. At that time, no DLT was observed in any of the treatment arms. Median follow-up for the current analysis was 50 months. Rates of grade 2 SBRT-related acute or late toxicity were 13%,7 % and 10% in cohort 1 through 3, respectively (p=0.9). No grade 3-5 toxicities were observed. LF occurred in 9% vs 3% vs 6% of lesions for the first, second and third cohort, respectively (p=0.5). Overall estimated 4-year local control rate was 93%. There was no difference in local control rates between schedules (Figure 1).