ESTRO 2023 - Abstract Book

S2051

Digital Posters

ESTRO 2023

1 Azienda Ospedaliero Universitaria delle Marche, Radiotherapy Department, Ancona, Italy; 2 Azienda Ospedaliero Universitaria delle Marche, Medical Physics, Ancona, Italy Purpose or Objective Despite modern techniques, large pendulous breasts often cause problems in the simulation, planning, and treatment during radiotherapy (RT) of breast cancer patients (pts) after conservative surgery, including increased skin toxicity and incidental lung and cardiac doses. We report our experience with pts with large pendulous breasts treated with a Bra during RT and the impact on treatment reproducibility, acute skin toxicity, and pulmonary and cardiac dosimetry. Materials and Methods From August 2020 to April 2022, twelve large-breasted pts (6 right and 6 left) underwent RT after breast conserving surgery. During simulation, pts put on Chabner XRT® Radiation Bra (Bra) custom-fit adapted to ensure that the breast tissue was contained entirely within the Bra cup. The shoulder straps have been adjusted and all points of Velcro® attachment have been indexed. Thermoplastic polyurethane windows allowed visibility of skin and bony landmarks essential for repeatable position. Two mm slices-Computed Tomography scan was acquired with and without Bra in supine position on a breast board immobilization device, with both arms raised above the head and extended from the mandibular angle to the diaphragm. RT was performed using 3-dimentional RT (3DCRT) in 6 pts and volumetric modulated Arc therapy (VMAT) in 6 pts. In 4 pts with unfavorable anatomy or comorbidities deep inspiration breath hold (DIBH) technique was used. All pts received 40,05 Gy in 15 fractions to whole breast (WB) with a sequential or simultaneous integrated boost in hypofractionated regime; only one pt underwent RT to WB plus regional lymph nodes in conventional fractionation due to an autoimmune disease. Selected dose constraints were: Dmean ≤ 5Gy, V8Gy ≤ 30%, D5% ≤ 16 Gy to the heart; V16Gy ≤ 20%, V8Gy ≤ 35%, V4Gy ≤ 50% to the ipsilateral lung. Toxicities were evaluated using Common Terminology Criteria of Adverse Events (CTCAE) version 5.0 scale.

Results 3DCRT or VMAT technique planning and Bra device allowed dose homogeneity, less lateral breast displacement with less heart and lung involvement, compared to plan without Bra. The dosimetric parameters were in all pts: heart V8Gy ≤ 8%, D5% ≤ 10 Gy Dmean ≤ 4 Gy; ipsilateral lung V16Gy ≤ 19%, V8Gy ≤ 33%, V4Gy ≤ 44%. Daily IGRT showed optimal reproducibility. RT was well tolerated: all pts presented Grade 1 fatigue, disappeared after 1 month of follow-up; 9 pts Grade 1 and 3 pts Grade 2 erythema. Conclusion In our preliminary experience, the use of Bra improved simulation, planning, daily reproducibility, and cosmetic outcome. This device application also reduced the dose to the heart and ipsilateral lung. More cases are needed to confirm the effectiveness of the device in terms of treatment reproducibility and improvement in dosimetric parameters. M. Buglione di Monale 1 , L. Spiazzi 2 , A. Guerini 3 , S. Nici 2 , F. Vaccher 4 , C. Toraci 2 , D. Bazzana 3 , S. Barucco 3 , S. Riga 5 , R.G. Pellegrini 6 , C. Cozzaglio 3,2 , S.M. Magrini 1 , D. Farina 7 1 University and ASST Spedali Civili, Radiation Oncology, Brescia, Italy; 2 ASST Spedali Civili, Medical Physics, Brescia, Italy; 3 ASST Spedali Civili, Radiation Oncology, Brescia, Italy; 4 University of Brescia, Radiology, Brescia, Italy; 5 ASST Spedali Civili, Medical Phyiscs, Brescia, Italy; 6 Elekta AB, Medical Affairs, Stockholm, Sweden; 7 University and ASST Spedali Civili, Radiology, Brescia, Italy Purpose or Objective MR has higher contrast resolution than CT imaging and, for this reason, is the preferred imaging modality in brain and head and neck (HN) tumors. Contouring and treatment planning in RT are usually based on CT simulation imaging. The acquisition of MR images for both simulation and planning on a dedicated MR scanner could improve the delineation of target volumes and organs at risk (OARs) and the dose optimization process. The integration of MR simulation in radiotherapy treatment workflow could thus optimize treatment quality and give prognostic and predictive information. The abstract describes the defined workflow and analyze the outcome of the first month of use. PO-2281 MRgRT with an MR scanner for simulation: benefits for patients treated with MRL/conventional LINAC

Materials and Methods