ESTRO 2023 - Abstract Book

S2109

Digital Posters

ESTRO 2023

Conclusion If the CBCT scan length is reduced it is possible to reduce the risk of LAR in OAR (Organ at risk) in the thorax region. If the distance from the OAR and to the edge of the CBCT is increased by 3 cm, the radiation dose can be reduced up to 85%. If it is not possible to spare the OAR based on the irradiated area, a daily ISO centre move before CBCT can be used to spare other OAR.

PO-2343 quantification of organ motion with magnetic resonance in carbon ion therapy of the abdominal tumors

L. Anemoni 1 , M. Serantoni 1 , M.E. Piazzolla 1 , M.S. Cadeo 1 , A. Vai 2 , C. Paganelli 3 , E. Orlandi 1 , S. Tampellini 1

1 National Center for Oncological Hadrontherapy (Fondazione CNAO), Radiotherapy, Pavia, Italy; 2 National Center for Oncological Hadrontherapy (Fondazione CNAO), Medical Physics, Pavia, Italy; 3 Politecnico di Milano, Elettronica, Informazione e Bioingegneria, Milano, Italy Purpose or Objective Imaging plays a key role in hadrontherapy, being fundamental for the study of breathing motion and its impact on treatment with thermoplastic mask.The objective of the Study is to support the clinical component in the identification of organ motion at the abdominal level both inter and intra fraction,using 4D magnetic resonance imaging,and the contouring of target and organ at risk in order to suggest optimal strategies for customizing treatment. Inter-fraction evaluation:segmentation of liver,kidney and hepatic dome in VIBE sequence acquired in MRI. The mass center of the planning and revaluation CT has been calculated,the result was compared with the mass center data of the vibe sequences to establish the movement of liver and kidney. Intra-fraction evaluation:segmentation of liver and right kidney in reconstructed 4DMRI sequence.The phase 1= end Exhale,that is the phase of end exhalation and the phase 5=end-inhale,that is the phase of end inhalation, have been surrounded .The center of mass was calculated by comparing phase 1 and phase 5 data. Results The intra-fraction movement,calculated as the difference between EX and IN phase of 4DMRI,is 1.48mm(std 0.67mm)for liver and 1.30mm(std 0.65mm)for kidney. Similarly,inter-fraction motion,measured on both CT and MRI imaging, and calculated between repeated acquisitions ,is contained on all patients and it is below the maximum voxel of MRI imaging(i.e. 5mm). Conclusion The motion compensation technique,based on compression mask,is able to limit intra and inter-fraction motion,providing accurate dose delivery even in abdominal district organs subject to respiratory motion.It is important to remember that we refer to the maximum dimension of the voxel because this is the minimum dimension and therefore the movement that you can solve. M. Mahe 1 , A. Beddok 1 , V. Calugaru 2 , F. Goudjil 3 , G. Créhange 3 , L. Feuvret 4 , S. Bolle 5 , R. Dendale 6 , C. Ala Eddine 7 , C. Le Tourneau 8 , L. Champion 8 1 Institut Curie Paris, Radiothérapie , Paris, France; 2 Institut curie Paris, Radiothérapie, PARIS, France; 3 Curie Paris, Radiothérapie, PARIS, France; 4 East Group Hospital. Hospices Civils , Radiotherapie, LYON, France; 5 Gustave Roussy, Radiothérapie, Villejuif, France; 6 Curie Orsay, Radiotherapie, Orsay, France; 7 Curie Paris, Radiotherapie, paris, France; 8 Curie Paris, Oncology, Paris, France Purpose or Objective Re-irradiation (reRT) for local relapses of head and neck adenoid cystic carcinoma (HNACC) is a challenge. The objective of the present study was to analyze the outcomes and toxicity following this treatment Materials and Methods Methods: We retrospectively analyzed the records of 10 patients reirradiated with proton ther-apy (PT) or IMRT at Institut Curie regarding pattern of failure. control and survival rates and toxicity. Results Results: Patient received a median dose of 72Gy at reRT after a median RT-interval of 53.5 months. Median follow up was 26 months. the 1-. 2- and 3-year LFFS were 66.7%. 55.6%. and 41%. respectively. Six patients had locoregional failures (LRF) which occurred in-field for four patients (66.6%). Over the follow-up period. eight patients died. The 1-. 2- and 3- year OS were 77.8%. 66.7%. and 44.4%. respectively. LFFS and OS were significantly better in the subgroup of sinusal tumors (p = 0.013) and the subgroup of patients reirradiated more than two years after the first course (p = 0.01). Toxicity was acceptable with almost only grade 1-2 acute adverse events and rare late toxicities with 2 grade 3-4 adverse events (radionecrosis). Conclusion Materials and Methods A group of 10 patient was considered both for inter-fraction and intra-fraction evaluation. PO-2344 Curative reRT for patients with recurrent head and neck adenoid cystic carcinomas