ESTRO 2024 - Abstract Book

S810

Clinical - CNS

ESTRO 2024

included the macroscopic tumor and the resection cavity. The clinical target volume (CTV) included the GTV with 5mm margin towards the brain tissue as well as 15mm margin along the meningeal surface. In addition, the CTV was expanded whenever there was suspected bony invasion as well as abnormal PET uptake. All CTVs were adapted to natural anatomical barriers. To create the planning target volume, all CTVs were expanded by 3 mm. CTV volume ranged from 34 to 394 cc (median, 76.5). Toxicity was assessed according to Common Terminology Criteria for Adverse Events version 4.0. Clinical evaluation and serial brain imaging studies (MRI) were requested every 3-6 months for 2 years, annually between 3 and 5 years after PT and once every two years thereafter. Median follow-up (FU) time was 28 months (range, 4-61). Death (by any cause) was the event for overall survival (OS), local relapse or progression were events for local control (LC). LC and OS were calculated using the Kaplan-Meier estimates. The log – rank test was used to compare different survival functions according to predefined stratifications and was based on a two-sided significance level, p £ 0.05. All pts completed the treatment without breaks. Registered acute side effects include grade 1 (15%) and grade 2 (6%) skin erythema/hyperpigmentation, grade 1 (17%) and grade 2 (58%) alopecia, grade 1 (44%) and grade 2 (6%) fatigue, grade 1 (4%) and grade 2 (4%) conjunctivitis, grade 1 (12%) and grade 2 (4%) headache, grade 1 (10%) and grade 2 (8%) nausea. Grade 3 conjunctivitis was registered in 2% of pts. There were no further grade 3 or higher acute toxicities. Registered late side effects include grade 1 (10%) and grade 2 (27%) alopecia, grade 1 (4%) fatigue, and grade 1 (4%) headache. During follow-up 5 pts (10%) experienced radiation-induced radiological abnormalities (RIA): symptomatic grade 3 radiation necrosis (RN - diagnosed at imaging) in 2 pts (4%) and grade 1 RIA in 3 pts (6%). Grade 1 RIA were managed with clinical/radiological monitoring and resolved without intervention. Pts with RN received steroids therapy with clinical/radiological monitoring. Due to only minor clinical and radiological improvement, both pts received Bevacizumb with moderate clinical and near complete radiological improvement. There was no further grade 3 or higher late toxicities. The 3- and 5-year actuarial LC was 81% and 67%, respectively. On univariate analysis, timing of PT (adjuvant vs at progression after surgery, p=0.16) and tumor location (skull base vs other locations, p=0.27) were not significant prognosticators for LC. Moreover, relief of symptoms recorded before irradiation occurred in 35% of pts. A total of 6 pts died during the FU period; 4 were deemed tumor related as a result of recurring and/or progressively growing tumor, while 2 deemed to different events. The 3- and 5-year actuarial OS was 100% and 67%, respectively. On univariate analysis, timing of PT (adjuvant vs at progression after surgery, p=0.31) and tumor location (skull base vs other locations, p=0.41) were not significant prognosticators for OS. Results:

Conclusion:

High-dose PT is safe and effective treatment for pts with AM. Longer follow-up is necessary to confirm safety and efficacy.

Keywords: Brain, Atypical meningioma, Proton Therapy

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