ESTRO 2023 - Abstract Book

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ESTRO 2023

Meningiomas are the most common CNS tumors and the majority is regarded as benign. However, a subset of patients presents with complex tumors involving several anatomic compartments of the skull base - eluding concepts of gross total resection. Proton therapy (PT) is applied as definitive treatment for primary or recurrent disease or postoperatively following subtotal resection.

We report on the first 100 adult patients treated with PT at MedAustron Ion Therapy Center

Materials and Methods All patients were enrolled in the prospective registry trial. Target volume definition was based on CT, MR and DOTA-PET/CT. CTV1 included tumour (GTVMR/PET), and 5mm margin along the meninges, CTV2 was limited to GTVMR/PET. PT PBS treatment plans were generated by applying the SFIB-optimisation method and utilizing 2-4 beams per plan with a beam spacing of >30°. Prescribed doses to PTV1 were 50.49Gy_RBE at 1.87Gy_RBE/fr and 54.0Gy_RBE at 2.0Gy_RBE/fr to PTV2 in overall 27 fractions. Follow up status was assessed with MRI at 6, 12 months post treatment and annually thereafter, side effects were assessed using CTCAE v4.0. and quality of life (QoL) using EORTC-C30 and BN20 questionnaires. The scores entered by the patients were added and normalized to 0-100 scale according to previously described protocols. Results Between 08/2017 and 04/2021, 100 patients were treated, 22% (n=22) male and 78% (n=78) female patients. Median age at therapy was 54a (25a-82a). In 57% (n=57) PT was the definitive treatment (no surgery or surgery >12 mo prior to PT). 43% (n=43) underwent at least one surgery (range 1-3) prior to PT, with median time between surgery and start of PT of 6mo (3mo-11mo). 89% (n=89) meningiomas were located in the skull base with involvement of multiple anatomic compartments. The median GTV was 24cc (1cc-226cc) and the median CTV 41cc (2cc-352cc), respectively. At median follow-up of 36.5 month (12.7mo- 54.1mo), 1 local in-field failures were observed resulting in local control of 97.8% (95%CI: 91.5-99.5) At 3 years. No > grade 2 acute toxicity was observed. During follow-up two grade 3 toxicities occurred: One patient developed symptomatic radiation induced brain lesion (RIBL) which resolved within 12 month; one patient was hospitalized for new onset of epilepsy without corresponding radiographic findings. The general QoL including the global health status and all functioning domains was not compromised following proton radiotherapy. Conclusion First clinical data demonstrate that PT based on SFIB is a safe and efficient treatment of anatomically complex, low grade meningiomas. Acute and late toxicity incidences in our series were low with excellent, prospectively assessed preservation of QoL. A. Castaño Cantos 1 , M. Rodriguez Roldan 2 , E. González del Portillo 1 , I. Garrido Botella 1 , M. Teja Ubach 3 , M. González Cantero 1 , R. Rosel Aller 1 , B. Debén Méndez 1 , R. Matute Martín 4 , R. Morera López 1 1 Hospital Universitario La Paz, Radiotherapy Oncology, Madrid, Spain; 2 Hospital Universitario La PAz, Radiotherapy Oncology, Madrid, Spain; 3 Hospital Universitario la Paz , Radiotherapy Oncology, Madrid, Spain; 4 hospital Universitario La Paz, Radiotherapy Oncology, Madrid, Spain Purpose or Objective Pituitary adenoma (PA) is a histologically benign lesion and constitutes approximately 10% to 20% of primary intracranial tumours. Its management is a therapeutic challenge due to their location. Effective treatment should be decided by a multidisciplinary committee consisting of endocrinologists, neurosurgeons, ophthalmologists, radiologists and radiation oncologists. Our purpose is to analyse our experience of treatment with conventionally fractionated radiotherapy (CFRT) or hypofractionated stereotactic radiotherapy (HSRT) using VMAT technique. Materials and Methods Seventeen patients evaluated in the Complex Pituitary Pathology Unit of the Hospital Universitario La Paz, from 2015 to 2022. The mean age at diagnosis was 47 years. Sixteen patients were diagnosed with macroadenoma and only one with microadenoma by MRI. Thirteen of them were hormone-secreting PA and underwent medical treatment and subsequent surgery after failing to achieve reduction and/or hormonal normalisation. All of them required radiotherapy treatment due to tumour growth during follow-up. Five patients had non-functioning AP and treatment consisted of surgery and radiotherapy at follow-up due to relapse. All patients received radiotherapy using VMAT technique: 5 patients received CFRT (50.4Gy/28 fractions) and 11 patients received HSRT (25Gy/5 fractions). Hypofractionated stereotactic radiotherapy was administered on the Infinity linac accelerator with Hexapod system, robust immobilization stereotactic frames/masks and daily volumetric image-guidance in order to reduce movements and volume margins without compromising tumour control. Results With a median follow-up of 80 months, patients had no tumour progression after radiotherapy treatment. The control rate for HA is around 90% and 95% for non-functioning HA, according to the literature. No grade 3-4 side effects were observed during radiotherapy treatment. In the long term no severe side effects have been detected. PO-1123 Fractionated stereotactic radiotherapy with volumetric modulated arc therapy for pituitary adenoma

Conclusion