ESTRO 2021 Abstract Book

S878

ESTRO 2021

Conclusion Our data, according to bibliography, shows an excellent LC and OS with low toxicity. We are not able to draw any firm conclusions from such a small data set, but we have not detected association between LC and potential risk factors in multivariate analysis. The change of treatment system does not seem to have influenced the results either. The association detected in univariate analysis between LC and previous surgery, and LC and tumor volume, will be analyzed in depth in the future. PO-1055 Fractionated stereotactic radiotherapy in optic nerve meningioma L. Paisán 1 , M.R. Magallón Sebastián 1 , M.I. García Berrocal 1 , J. Romero Fernández 1 , I. Zapata Paz 2 , B. Gil Haro 2 , R. Benlloch Rodríguez 3 , J.F. Obeso Herrero 2 , O. Engel 2 , A. Valcárcel Díaz 1 , S. Santana Jiménez 2 , P. Sarrión Rubio de la Torre 2 1 Puerta de Hierro University Hospital , Radiation Oncology, Madrid, Spain; 2 Puerta de Hierro University Hospital, Radiation Oncology, Madrid, Spain; 3 Puerta de Hierro University Oncology, Radiation Oncology, Madrid, Spain Purpose or Objective Optic nerve meningioma (ONM) is a rare tumor and the optimal management still remains controversial. A late diagnosis and inappropriate treatment lead to a progressive loss of vision. The purpose of this retrospective study is to assess the effectiveness of early treatment with fractionated stereotactic radiotherapy for the ONM. Materials and Methods Between January 2010 and April 2020, 300 patients with intracranial meningioma were treated at the department of Radiation Oncology of the Hospital Universitario Puerta de Hierro, Madrid. Among them, only 9 patients (3%) were diagnosed with ONM and were included in the present study. Fractionated stereotactic RT was administrated to a PTV including tumor plus 2-3 mm margin up to a total dose of 50.4 Gy in 28 fractions of 1.8 Gy with non-coplanar fixed fields and image-guided intensity-modulated radiotherapy planning (IG-IMRT) Results In our series, 8 patients were female. Mean age at diagnosis was 39 years (range 31-50). Mean post-treatment follow-up was 61months (range 2-108). Tumor control rate, considered as absence of progression in RMN studies, was 100%. Six patients improved their visual acuity and none of the remaining three patients with total vision loss at diagnosis improved it. No patients in our study experienced acute or late toxicity. Conclusion These findings support the use of radiation therapy for ONM. It is a safe noninvasive modality that stabilize or