Neuroaxis Radiation for pediatric tumors (Medulloblastoma and Atypical teratoid/rhabdoid tumor) with VMAT (volumetric modulated arc therapy) and IMRT (intensity modulated radiotherapy) in Radiation Oncology Department in Bank of Cyprus Oncology Center. Marilena Theodorou, MD 1, , Andriana Peratikou, MSc, DABR, 2 , Stefani Stefanou MSc,CSI, MIPEM, 2, , Lora Ioannou, MSc, CSI, MIPEM, 2,, Efthymiou Themos MSc, 2, Erato Stylianou MSc, 2,,Ali Vehbi Artikan MSc, DABR, 2 Aristotelis Giannos MSc 2, Demetrios Andreopoulos, MD,PhD 1 1 Radiation Oncology Department, Bank of Cyprus Oncology Center, 2 Medical Physics Department, Bank of Cyprus Oncology Center, Contact: marilena.theodorou@bococ.org.cy Radiation Oncology and Radiodiagnostics, Banc of Cyprus Oncology Center, Nicosia, Cyprus , www.bococ.org.cy Introduction A 10-years old boy with a Medulloblastoma WHO IV after total resection with a KI=70% due to astathia and diplopia, referred for the neuroaxisradiation and boost to the tumor bed according to Medulloblastoma protocol. .An 11-y old girl with an atypical teratoid/rhabdoid tumor (AT/RT) left frontotemporal who referred to us for the neuroaxisradiation and boost to the post-OP tumorrest according to the EU-RHAB protocol. The KI=90% without neurological deficits. . Methods The planning-CT in 3mm thin slights, was acquired with the patient in the supine position, contrast agent was given i.v., while a thermoplastic mask was used for fixation. For the definition of clinical target volumes (CTV), the pre- and post-operative MRIs and pre- and post-operative CTs were fused using the Oncentra Master Plan software. For the contouring we used the Tomotherapy Richtlinie for Neuroaxis-radiation. The CTV1 (clinical target definition) included the brain up to Foramen magnum plus 1cm margin in all directions adapted in both eyes and 2cm caudal. The CTV2 included the Cervical Spine with 1cm margin in all directions. The CTV3 included the Thoracic Spine with 1cm cranial/caudal and 1.5cm medial/lateral, anterior/posterior margin. The CTV4 included the Lumbar and Sacral Spine with 1cm cranial/caudal and 2cm medial/lateral, anterior/posterior margin. The planning target volume (PTV) included the 4 CTVs. The gross tumor volume (GTV) was the macroscopic tumor in the Pre-Operative-MRI and the CTV was the OP-cavity in the Post-Operative-Planning-MRI and CT. The Boost-PTV included the GTV+CTV+1cm margin in all directions adapted in anatomical structures such as brainstem. The VMAT-technique offered high coverage of all five targets. 95% of dose covered 97,4 % of PTV1, 100% of PTV2, 99,14% of PTV3, 99,7 % of PTV4 and 99,7 % of Boost-PTV. From the Sum-Plan for Phase I and II as observed in the cumulative dose of the summation plan good sparing was achieved for the organs at risk (OAR) such as Nervii opticii, Chiasm, Brainstem, Eyes, Lens, Internal ears, Pituitary gland, Thyroid gland, Lungs, Cor, Stomach, Intestinum, Kidneys, Liver, Bladder, Rectum. The IMRT plan had also 99% coverage of all PTVs. Results The children tolerated the treatment well without significant side effects or complications except of fatigue and alopecia. The treatment was daily ambulance. The further FUs gave no late side effects. B Example 1: VMAT plan, 23,4 Gy neuroaxis, boost tumor bed 54 Gy Example 2: IMRT plan, 36 Gy Neuroaxis, 54 Gy tumor bed, 59,4 Gy tumorrest, Conclusion and summary In conclusion we can suggest the Neuroaxis Radiation using the VMAT technique for pediatrics tumor due to the high coverage of the targets, the safety for the OAR and the short time radiation especially for little children in order to avoid sedation PROS 2017 (Congress of the international society of paediatric oncology , New York