ESTRO 2023 - Abstract Book

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ESTRO 2023

3.01), p=0.50, I2=0%). In the reirradiation vs combination therapy group (Table 2); combination therapy improved OS (14 studies, 805 participants; HR 0.60 (0.48-0.75), p<0.0001, I2=29%) and PFS (5 studies, 259 participants; HR 0.48 (95%CI 0.35 0.65), p<0.00001, I2=0%), and combining reirradiation with bevacizumab reduced radionecrosis (3 studies, 129 participants; RR 0.04 (95%CI 0.01-0.23, p=0.0002, I2=0%). Subgroup analysis of studies accounting for confounders through methodology or multivariate analysis reaffirmed these results. A meta-analysis could not be conducted on QoL outcomes due to insufficient reporting.

Conclusion Combination therapy may improve OS and PFS with acceptable toxicity in select patients with rHGG. Limitations of current literature include the small number of studies, selection bias and confounders. RCTs accounting for these factors are required for further investigation. Additional studies comparing QoL outcomes are also required.

PO-1138 Proton therapy re-irradiation of intracranial meningiomas failing after previous radiation therapy

D. Scartoni 1 , I. Giacomelli 1 , S. Vennarini 2 , P. Feraco 3 , L. Picori 4 , L. Annicchiarico 5 , S. Sarubbo 6 , D. Amelio 1

1 APSS Trento, Proton Therapy Center, Trento, Italy; 2 Fondazione IRCCS Istituto Nazionale dei Tumori - Milano, Pediatric Radiotherapy Unit, Milano, Italy; 3 APSS Trento, Radiology Department, Trento, Italy; 4 APSS Trento, Nuclear medicine Department, Trento, Italy; 5 APSS, Neurosurgery Department, Trento, Italy; 6 APSS Trento, Neurosurgery Department, Trento, Italy Purpose or Objective Re-irradiation of intracranial meningiomas (MS) is often difficult due to the limited radiation tolerance of the surrounding tissue. Aim of this analysis is to report safety and efficacy of proton therapy (PT) for re-irradiation of recurrent MS.