ESTRO 2025 - Abstract Book

S2848

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

Keywords: Lattice radiotherapy, VMAT, IMRT, Lung cancer

References: Grams MP, Deufel CL, Kavanaugh JA, Corbin KS, Ahmed SK, Haddock MG, Lester SC, Ma DJ, Petersen IA, Finley RR, Lang KG, Spreiter SS, Park SS, Owen D. Clinical aspects of spatially fractionated radiation therapy treatments. Phys Med. 2023 Jul;111:102616. doi: 10.1016/j.ejmp.2023.102616. Epub 2023 Jun 11. PMID: 37311338.

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Digital Poster Evaluation of the feasibility of implementing the VMAT-TBI procedure, considering differences in patient anatomy Joanna Litoborska 1 , Weronika Kijeska 1 , Agnieszka Skrobała 1,2 , Agata Jodda 1 , Maria Radomiak 1 , Sara Styś 1 , Justyna Kosmowska 1 , Wiktoria Sońska 1 , Magdalena Fundowicz 3 , Małgorzata Żmijewska-Tomczak 3 1 Medical Physics Department, Greater Poland Cancer Center, Poznan, Poland. 2 Department of Electroradiology, Medical University, Poznan, Poland. 3 Radiotherapy Department, Greater Poland Cancer Center, Poznan, Poland Purpose/Objective: Total body irradiation (TBI) combined with chemotherapy is one of the preparative methods used prior to bone marrow transplantation in patients with hematologic malignancies. This procedure is increasingly being performed using advanced dynamic techniques such as VMAT. The VMAT-TBI technique requires special procedures due to the large irradiation volume, field size limitations, the need for planning with multiple isocenters, and precise patient positioning. The aim of the study is to summarize and evaluate the feasibility of implementing VMAT-TBI procedure developed by the authors in a cohort of 54 patients with diverse anatomy. Material/Methods: The analysis was conducted on 54 patients aged 3 to 70, including 26 women, 22 men and 6 children. Two types of immobilization were used: vacuum bags for 29 patients and a dedicated plate for 25 patients. For each patient, two computed tomography (CT) were acquired, one from the top of the head to the lower thigh and another from the toes to the upper thigh. For the upper body, plans were created using the VMAT technique based on 4 isocenters for 3 patients, 7 isocenters for 14 patients and 9 isocenters for 37 patients. The lower body was irradiated using 3DCRT technique. Patient positioning was verified using 2DkV images for each isocenter, CBCT (in the chest area) and body surface tracking. Four different irradiation regimens were used depending on the diagnosis and general condition of the patient): 2Gy for 18 patients, 4Gy for 5 patients, 8 Gy for 5 patients and 12Gy (with a dose limited to 9Gy in lung) for 26 patients. Results: The following parameters were evaluated: the coverage of 95% (D 95 ) and 2% (D 2 ) of PTV volume with the prescribed dose, the mean dose to the lungs, and the dose in 2% of the whole body volume. The D 95 was, on average 95.8% (range 91.1% - 96.9%), while D 2 did not exceed 105.6% on average (103.4% - 110.2%). The mean dose to the lungs averaged 8.73Gy (8.06Gy - 8.99Gy). The dose of 2% of the total body volume average did not exceed 118.5% of the prescribed dose (103.3% - 145.8%). Conclusion: In conclusion, implementing the VMAT-TBI procedure in this group of 54 patients demonstrates that the developed technique meets established criteria for total body irradiation in both pediatric and adult patients. The procedure is robust and adaptable to variations in patient anatomy (e.g., volume and length of the PTV) while enabling effective lung dose reduction.

Keywords: TBI, VMAT, multi-isocentric technique