ESTRO 2023 - Abstract Book

S1834

Digital Posters

ESTRO 2023

The use of WBRT in patients with metastases reduces the risk of disease progression, helping to improve the quality of life of the patients. Our findings indicate that techniques currently available, such as VMAT irradiation, allow for the treatment of the PTV with simultaneously protecting the hippocampus in order to maintain the patient's normal mental processes.

PO-2058 Dosimetric Comparison Of Dose&Volume Change By Different Planning Techniques In Hodgkin Lymphoma

A. ALTAY 1 , M. Kurt 1 , P. Çona 2 , S. Tunç 1 , C. Demiröz Abakay 1 , S. Kahraman Çetinta ş 1

1 Bursa Uluda ğ University Medical Faculty, Radiation Oncology, Bursa, Turkey; 2 Bursa City Hospital, Radiation Oncology, Bursa, Turkey Purpose or Objective To investigate the target volumes, the doses received by heart and carotid arteries exposed to the different radiation doses using three-dimensional conformal radiotherapy (3DCRT), helical tomotherapy (HT), and volumetric arc therapy (VMAT) techniques in patients with early supradiaphragmatic Hodgkin lymphoma (HL). Materials and Methods Treatment plans of patients were reconstituted retrospectively. The target volumes, the doses received by the heart and carotid arteries when 20 Gy and 30 Gy radiation doses that were given according to the definition of involved field (IFRT) and involved node (INRT) using 3DCRT, HT and VMAT techniques in patients with HL, were obtained. Plans were also taken for CMS XIO 5.00 for 3DCRT, MONACO 5.1 for VMAT, and HiART TPS for HT. In VMAT planning, 2 full arches were used in the presence of axillary involvement, and butterfly technique was used in those without involvement. Results There were a total of 19 patients (13M ,6F). There was a significant difference between 3DCRT, HT and VMAT techniques for V95%, Dmean, D2% in PTVIFRT at both doses given (p<0.001). HT created more conformal plan compared to other techniques, and VMAT technique both kept the maximum possible dose to a minimum providing more homogeneous dose distribution (p<0.001; p<0.001). The VMAT technique for conformity index was better (p<0.001), while the HT technique provided more homogeneous dose distribution (p<0.001) according to the PTVINRT. There was no statistically significant difference in the Dmean, V10, V15, V20 values of the heart between the two doses used. While the prescribed doses was 20 Gy and 30 Gy, there was a statistically significant difference for the right carotid artery Dmean according to the definition of IFRT (p=0.006 and p=0.005, respectively), and a more appropriate DVH was obtained usingVMAT technique. No statistically significant difference was found according to the definition of INRT. With VMAT and HT techniques, 18% and 28% reductions were obtained compared to 3DCRT with all dose values for the heart, respectively. When the volume to be irradiated was kept constant and the dose given was reduced from 30 Gy to 20 Gy, a decrease in Dmean value of the heart was achieved by 33%, 33% and 35% in 3DCRT, HT and VMAT techniques, respectively. Similarly, when the defined dose was kept constant and the irradiated volume decreased, the Dmean value of the heart decreased. With regard to the carotid artery doses, the mean values of the carotid arteries were reduced by 53%, 45% and 53% for 3DCRT, HT and VMAT, respectively. Conclusion In all techniques, the target volume received the desired dose, but with the HT technique, PTV’s were ensured to receive the most appropriately prescribed dose, while the max dose was obtained at minimum in VMAT technique. Although advanced rotational techniques such as HT and VMAT can be chosen for cardiac side effects, the INRT technique, which provides volume reduction, has been found to be more effective in preventing long-term side effects. 1 West University of Timisoara, Faculty of Physics, Timisoara , Romania; 2 "Dr. Gavril Curteanu" County Hospital, Radiotherapy, Oradea, Romania; 3 West University of Timisoara, Faculty of Physics, Timisoara, Romania; 4 University of Oradea, Faculty of Informatics & Science, Oradea, Romania; 5 University of South Australia, Cancer Research Institute, Adelaide, Australia Purpose or Objective Stability and reproducibility in radiotherapy are mandatory for tumor control, for healthy tissue protection and for an effective treatment. In view of this, the evaluation of the factors contributing to setup errors and the calculation of setup margins for the planning target volume should be stringent clinical requirements. This work presents the effect of breast board inclination and body mass index (BMI) on patient setup and dosimetry during conformal as well as intensity modulated radiotherapy techniques. Materials and Methods The immobilization system used for patient setup was a Quest breast board which allowed different inclination of the patient, hand and arm holders and a bottom stopper. Three groups of patients positioned in supine were evaluated: group A immobilized on 7.5° inclination, group B immobilized on 0° inclination (no inclination) and group C which was immobilized on both inclinations (0° and 7.5°). Patient position was evaluated with weekly orthogonal and tangential portal images to assess the systematic ( Σ ) and random ( σ ) errors for standard coordinates (right-left, superior-inferior and anterior-posterior) and also for some tangential image parameters: central lung distance (CLD), central beam edge to skin distance (CBESD) and central caudal distance (CCD). Three sets of treatment plans were completed for all patients (3DCRT, IMRT and VMAT techniques) using conventional dose prescription (50Gy in 25 fractions) and error simulations were performed on Monaco PO-2059 The impact of breast board and body mass index on setup errors during breast cancer radiotherapy I.-.C. Costin 1 , I. Costin 2 , L.G. Marcu 3,4,5