ESTRO 36 Abstract Book

S515 ESTRO 36 2017 _______________________________________________________________________________________________

control and the D 90 (p=0.08 and 0.025 respectively) were observed, no significant relationship between point A dose and local control probability could have been established (Figure). Moreover, a trend towards an inverse relation was observed. After sorting patients according to 3 levels of doses, highest local control rates werereported in patients with D 90 CTV HR ≥85 Gy, whereas the patients with point A doses ≥ 70 Gy had the worst outcomes. CTV HR and CTV IR

Conclusion In patients treated with IGABT, point A dose is not predictive of local control, and nor correlated to D 90 . It tends to be inversely related to D 90 and therefore to be a surrogate of the irradiated volume. The pertinence of reporting point A dose should be questioned. PO-0939 Comparison of brachytherapy sources of endometrial cancer: Electronic brachytherapy source and 192Ir S. Lozares 1 , J.A. Font Gómez 1 , A. Gandía Martínez 1 , A. Miranda Burgos 2 , A. Méndez Villamón 2 1 Hospital Universitario Miguel Servet, Medical Physics and Radiation Protection Department, Zaragoza, Spain 2 Hospital Universitario Miguel Servet, Oncologic Radiotherapy Department, Zaragoza, Spain Purpose or Objective To compare 29 endometrial cancer patients treated in our center with cylindrical applicators and Axxent (Xoft Inc.) electronic brachytherapy with an equivalent planning 29 patients previously treated with Axxent (50 kV source) have been replanned with Ir-192 source. The calculation for both types of sources were performed on BrachyVision (Varian Inc.) treatment planning system. The prescription was 5 Gy per fraction applied in 3 fractions or 5 fractions depending on previous radiotherapy treatment. The planning parameters of the planning target volume (PTV) countoured from the cylinder surface to 5 mm along the active length were evaluated. V150 and V200 data for PTV and D2cc, V50% and V35% for organs at risk (OAR) were evaluated, the percentage of the volume receiving 35% and 50% of the prescription dose, respectively, and D2cc, highest dose to a 2 cubic centimetre volume of an OAR. Results for bladder, rectum and sigmoid are showed. Results made for Ir-192 source. Material and Methods

We may observe a reduction in dose at V35% and V50% in all OAR and also a reduction in D2cm 3 occurs (Table 1). PTV parameters increase in the case of Axxent, as reported previously, but very few cases of vaginal mucositis have been reported in our center as is showed in another clinical abstract. All patients were treated between 2015 and early 2016, enough time to develop early problems. Conclusion Preliminary results are very optimistic about the adequacy of Xoft equipment for treatment of endometrial cancer with a clear reduction of the physical dose in organs at risk and very few development of acute mucositis despite the considerable increase V150 in the treatment volume. Further studies will be necessary to take into account the RBE in treatments with such sources. PO-0940 3D mapping for precise definition of GTV, CTV and their correlation in cervix cancer BT (EMBRACE) S. Banerjee 1 , R. Pötter 2 , C. Kirisits 2 , K. Majercakova 2 , M.P. Schmid 2 , S.K. Shrivastava 3 , U. Mahantshetty 3 1 Medanta The Medicity, Radiation Oncology, Gurgaon, India 2 Vienna General Hospital- Medical University of Vienna, Departmentof Radiation Oncology, Vienna, Austria 3 Tata Memorial Hospital, Department of Radiation Oncology, Mumbai, India Purpose or Objective Image Guided adaptive Brachytherapy (BT) for cervix cancer is based on MRI and gynaecologic examination (GE) at diagnosis (D) and at BT to define the HR CTV. For documentation of disease at D and at BT schematic mapping diagrams (SMD) are used indicating values for maximum dimensions of GTV at D and at BT. For comprehensive assessment of available volumetric information through MRI at D and at BT an advanced schematic 3D mapping diagram (3DMD) was developed to provide precise reproducible topographic and quantitative information (Fig1). This was used to evaluate the topographic and quantitative relation between GTVD, HR CTV and IR CTV. Material and Methods 42 proven cervical cancer FIGO IIB-IIIB patients from Vienna and Mumbai were selected, mean age was 52 years. All were enrolled in the EMBRACE study and completed the planned treatment with MRI at D and at BT. SMDs from GE with individual tumour contours and dimensions as prescribed for EMBRACE were available. A 3DMD in axial, coronal and sagittal orientation was used with a scale (grid with 10 mm distance) for the precise documentation of available volumetric information