ESTRO 2023 - Abstract Book

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ESTRO 2023

The median follow-up was 16.1 months (0 - 55.8 Mo.). Fractionated SRT with 27 Gy in 3 fractions was the most common dose prescription in p.o. SRT group compared to single fraction radiosurgery with 20 Gy in def. SRT arm due to the larger target volume (21.8 vs. 5.6 cc). The difference in median overall survival was not statistically significant with 18.6 Mo. and 10.1 Mo. (p=0.34) in p.o. and def. SRT groups, respectively (Figure 1). There was no significant difference in the local or distant intracranial recurrences in both groups. However, leptomeningeal spread was seen exclusively in p.o. SRT arm (3 vs. 0 in def. SRT). No higher-grade toxicities ( ≥ 3 CTCAE V4.0) were observed in both groups. Radiation necrosis was seen on MRI in 3 P. after p.o. whereas in 1 P. after def. SRT. Surgical intervention was not necessary for the necrosis. Extracranial tumor progression remained the main cause of death in both groups.

Conclusion The survival and toxicity results were comparable in both groups. Selection bias can account for the relatively better overall survival in p.o. SRT cohort. The risk of leptomeningeal spread needs to be considered during volume definition after tumor resection.

PO-1136 Reirradiation by stereotactic radiotherapy of brain metastases in case of local recurrence

F. Lucia 1 , R. Touati 1 , V. Bourbonne 1 , G. Dissaux 1 , G. Goasduff 1 , O. Pradier 1 , R. Seizeur 2 , U. Schick 1

1 University Hospital of Brest, Radiation Oncology, Brest, France; 2 University Hospital of Brest, Neurosurgery, Brest, France

Purpose or Objective The aim of this study was to evaluate the efficacy and safety of a second course of SRT (SRT2) treatment for local recurrence of brain metastases previously treated with SRT (SRT1), using Hypofractionated Treatment Effects in the Clinic (HyTEC) reporting standards. Materials and Methods From December 2014 to May 2021, 32 patients with 34 brain metastases received salvage SRT2 after failed SRT1. A total dose of 21 to 27 Gy in 3 fractions or 30 Gy in 5 fractions was prescribed to the periphery of the PTV (99% of the prescribed dose covering 99% of the PTV). After SRT2, multiparametric MRI, sometimes combined with 18F-DOPA PET-CT, was performed every 3 months to determine local control (LC) and radionecrosis (RN). Results The median interval between SRT1 and SRT2 was 12 months. The median delivered dose (BED with an α / β ratio of 10) at 100% of GTV at SRT2 was 40.89 Gy (range 24.87-50.36 Gy). The median cumulative delivered dose (BED) at 100% of GTV was 81.78 Gy (range 76.59-91.25 Gy). After a median follow-up of 12 months (range 1-37 months), the crude LC and RN rates were 68% and 12%, respectively, and the median overall survival was 25 months. In multivariate analysis, the performance of surgery was predictive of a significant better LC (p = 0.002) and survival benefit (p = 0.04). The volume of normal brain receiving 5 Gy during SRT2 (p = 0.04), dose delivered to the PTV in SRT1 (p = 0.003), and concomitant systemic therapy (p = 0.04) were associated with increased risk of RN.