ESTRO 36 Abstract Book

S764 ESTRO 36 _______________________________________________________________________________________________

with cervical cancer (CC) were treated with radical radiochemotherapy. 17 pts with CC were treated palliative with radiotherapy , 10 pts with hepatic lesions (1 HCC and 9 meta ad hepar) treated with chemotherapy, 7 pts with pancreatic ca treated with chemotherapy, 2 breast ca treated with chemotherapy ( 1 with RT and 1 with CT), 11pts with lung ca treated with chemotherapy , 7 pts with rectal ca. treated with radiotherapy, 4 pts with ca. of sigmoid colon treated with chemotherapy, 2 pts with gastric ca. treated with chemotherapy and 1 with radiotherapy. The Celsius TCS hyperthermia system, an electro-hyperthermia, with a maximum output of up to 500 Watts was used. Two different electrode sizes were applied externally by physical means to the region with tumour in a targeted and controlled manner. The aim was to increase the temperature to 41 o C - 42 o C, one session lasted 60min. It was combined with either chemotherapy or radiotherapy twice per week. Toxicity of the skin was evaluated at every session with RTOG/EORTC classification system. The tolerance of treatment was ranged as Group 1: very good if there were 1-2 pauses because of discomfort with no other symptoms, Group 2: good- 3-4 pauses because of discomfort and skin toxicity Grade 1, Group 3: poor- > 4 pauses or shortening of hyperthermia course because of itching and skin toxicity>=Gr 2. Results Local deep hyperthermia was easily tolerated. 78 pts didn’t report any problems and were assigned to Group 1. 16 pts were assigned to Group 2 and only 2 pts to the group “poor”. Toxicity was generally mild and never of grade 3. 1/10 pts felt pain in the last few minutes of the session. Acute radiation toxicity was the same with or without hyperthermia. There was a reduced tolerance of hyperthermia in obese persons, with folds of skin on the abdomen. This is primarily due to the fact that between folds of skin sweat is collected what increases negative impression from temperature. All patients with tumours located in pelvis, reported pressure on the coccyx. We haven’t observed any increased vaginal bleeding during radical and palliative treatment of CC. Conclusion Tolerance associated with hyperthermia was very good and most patients felt comfortable during this treatment. Acute toxicity of the skin during the treatment was low. EP-1432 Advantage of butterfly-vmat versus vmat in mediastinal tumors J. Luna 1 , A. Ilundain 1 , S. Gómez-Tejedor 1 , D. Esteban 1 , M. Rincón 1 , J. Olivera 1 , W. Vásquez 1 , I. Prieto 1 , L. Guzmán 1 , J. Vara 1 1 Fundación Jiménez Díaz, Radiation Oncology, Madrid, Spain Purpose or Objective There is a growing concern about the risks of late adverse effects in young people who receive mediastinal radiotherapy. The amazing technical advance has achieved better planned treatments. At present, the new focus of interest is to minimize the low doses in organs at risks (OARs) Material and Methods We present our first results of a new protocol in our Department for mediastinal radiotherapy. This protocol includes the comparison of two treatment plannings for every patient: volumetric modulated arc therapy (VMAT), and Butterfly VMAT (a technique developed by the University of Turin, Radiation Oncology Unit). VMAT was performed with a double arc of 360º. B-VMAT consisted of 2 coplanar arcs of 60º (gantry starting angles 150º and 330º) and 1 no-coplanar arc of 60º (gantry starting angles 330º, couch angle 90º).

Until now, five patients have been included: Three mediastinal lymphomas in young women (total dose 36 Gy in two cases and 30 Gy in the other one), one patient diagnosed of hemangiopericytoma located at internal mammary chain (total dose 50 Gy) and the fifth patient diagnosed of thymoma (54 Gy) In the dose- volume histogram, regarding the PTV, the parameters analyzed were V95, V98, V107, Medium dose, Homogeneity index (HI) and conformity index (CI). For OARS- (heart, lung and breast) and body, several dosimetric parameters were registered. Results Our results show similar data in PTV coverage, IH and CI. Regarding the OARs, dosimetric parameters were equivalent in lung, heart and body. However, breast doses were clearly lower with B-VMAT, mainly the lowest doses (V4 and V10). For V4 , the medium value was 45.6% (7.8% – 63.1%) for VMAT and 21.5 % (0.7%- 60.1%) for B-VMAT. For V10, the VMAT medium value was 23.2% (0%- 37.2%) and the B-VMAT medium value was 8.9% (0%- 24.4%). Conclusion B-VMAT for mediastinal tumors is clearly superior to usual VMAT for breast doses, mainly the low doses, and equivalent in the rest of dosimetric parameters. Although the inclusion of more patients is needed, our preliminary results show B-VMAT like a great technical advance in mediastinal radiotherapy. Electronic Poster: Physics track: Basic dosimetry and phantom and detector development EP-1433 Photoneutron Flux Measurement via NAA in a Radiotherapy Bunker with an 18 MV Linear Accelerator T. Gulumser 1 , Y. Ceçen 1 , A.H. Yeşil 1 1 Akdeniz University- School of Medicine, Department of Radiation Oncology, Antalya, Turkey Purpose or Objective In cancer treatment, high energy X-rays are used which are produced by linear accelerators (LINACs). If the energy of these beams is over 8 MeV, photonuclear reactions occur between the bremsstrahlung photons and the metallic parts of the LINAC. As a result of these interactions, neutrons are also produced as secondary radiation products (γ,n) which are called photoneutrons. The study aims to map the photoneutron flux distribution within the LINAC bunker via neutron activation analysis (NAA) using indium-cadmium foils. Material and Methods The radiotherapy bunker hosts a Philips SLI-25 LINAC which is used for experimental studies. The measurements are taken at the highest energy of the LINAC which corresponds to 18 MeV bremsstrahlung photons. Indium and cadmium foils were used at 91 different points within the bunker. Neutron activation was performed by irradiating the room with 10000 monitor units (MU) at different gantry angles. The field was 40x40 cm 2 open. The activated indium foils are then counted in a High Purity Germanium (HPGe) detector system. Since indium has a high absorption cross section for thermal and epithermal neutrons, bare indium foil irradiation results in flux information of that region. However cadmium has high absorption cross section in the epithermal and fast region. If one filters the indium foils by cadmium coatings, the difference in the count yields thermal fluxes which are of interest for the doses to the patients in radiotherapy. Results Result of the analysis shows that the maximum neutron flux in the room occurs at just above of the LINAC head towards to gun direciton. This is expected since most of