ESTRO 2020 Abstract book

S865 ESTRO 2020

Twenty left-sided breast cancer patients, ten with mastectomy and ten with lumpectomy, were selected randomly from all breast cancer patients receiving radiotherapy from 2017 to 2018 at our institution. Patients were prescribed 50 Gy to the CTV. All patients were treated with forward planned tangential and supraclavicular step-and-shoot 6 MV fields and with combined 18 MV fields used for larger breasts. 17 of the patients were treated in deep inspiration breath-hold. For each patient an additional plan was generated, using two 6 MV VMAT fields in a butterfly configuration (each arc spanning 40-70 degrees). A skin flash of 1cm was used to ensure robustness. Dose planning was done in pinnacle 16.0 in the Auto-Planning module. Mean doses to organs at risk, the relative volume receiving 90% of the prescribed dose (V90%) for supraclavicular and IMN region and V95% for breast were compared using paired t-tests. Results Mean doses to the organs at risk and the V90% and V95% to the target areas are shown in the table. The mean dose to Ipsilat lung, contralat lung and contralat breast was statistically significant higher with the automated plans, whereas the heart dose remained similar dose. The automated plans showed statistically significant higher coverage of the all the target volumes. Conclusion The left-sided breast radiotherapy with VMAT plans in Pinnacle with Autoplan allowed plans with good coverage to the target regions. Compared to the manual plans the VMAT plans had statistically significant better coverage to the target regions without introducing significantly higher dose to the heart but with a small significant increased dose to the ipsilat lung dose and contralateral - lung and breast. But all OAR doses were clinically acceptable and meet the dose constraints suggested by DBCG (www.DBCG.dk). PO-1512 VMAT based TBI using a novel rotatable tabletop C. Losert 1 , R. Shpani 1 , R. Kießling 1 , P. Freislederer 1 , M. Li 1 , F. Walter 1 , M. Niyazi 1 , M. Reiner 1 , C. Belka 1 , S. Corradini 1 1 LMU Munich, Department of Radiation Oncology, Munich, Germany Purpose or Objective VMAT techniques have recently been implemented in clinical practice for total-body irradiation (TBI). To date, most techniques still use special couches, translational tables, or other self-made immobilization devices for dose delivery. Aim of the present study was to report the first results of a newly developed rotatable tabletop designed for VMAT-TBI. Material and Methods The VMAT-TBI technique theoretically allows the use of standard equipment in the standard linac room. Nevertheless, the main problem is that patients taller than 120cm cannot be treated in one position due to the limited cranio-caudal couch shift capacities at the linac. Therefore, patients are usually turned from a head-first supine position (HFS) to a feet-first supine position (FFS) to overcome this limitation. The newly developed rotatable tabletop consists completely of carbon fiber, including the ball bearing within the base plate of the rotation unit. The patient can be turned 180° from a HFS to a FFS position within a few seconds, without the need of repositioning.

Purpose or Objective Heart and lung exposure to ionizing radiation is a significant risk factor for late complications during whole breast irradiation (WBI). We have reported a tailor-made device (PERSonalized BReAst holder, PERSBRA) to decrease cardiac and lung radiation exposure for patients receiving left-sided WBI. In this research, we explore cardiopulmonary sparing performance of PERSRA in the setting of proton beam therapy (PBT). Material and Methods The 10 patients referred for left sided WBI were enrolled in this study. The breast contours in her modified forward bending pose were acquired with an OpenNI-compatible scanner. The images were processed into a stereolithography file followed by 3D printing with thermoplastic elastomer to fabricate PERSBRA. PERSBRA is a holder device to reproducibly increase the distance between left breast and the heart. CT simulation images with or without PERSBRA were acquired. Pinnacle version 9.8 and Ray station version 8B were used to generate treatment plans with photon and proton beams. Statistical significance (S.S.) of differences between means was defined by p<0.01 with paired sample T-test. Results The 10 patients with DCIS or invasive ductal carcinoma had a median age of 59 years old and clinical stages between 0 and IIIA. The prescribed doses were homogenously 50 Gy to left breast and supraclavicular fossa if indicated. The dosimetric parameters below were expressed in mean ± standard deviation. Consistent with previous reports, PERSBRA resulted in dose reduction of heart mean dose, left lung V20Gy and left lung V10Gy in photon plans. When comparing PBT plans to photon plans in simulation CT images with PERSBRA, both plans were comparable in terms of PTV coverage (PBT vs photons, PTV V 95% 99±0.58 vs. 97.81±1.06, N.S.), left lung V 20Gy (7.72±1.12 vs. 10.00±1.03 cGy, N.S.), and left lung V 10Gy (12.82±1.53 vs. 13.7±1.31 cGy, N.S.). PBT plans have superior performance over photon plans in heart mean dose (71.80±5.53 vs. 365.33±42.77 cGy, S.S.), left anterior descending artery mean dose (613.3±69.61 vs. 1559.57±198.30 cGy, S.S.), left anterior descending artery maximal dose (3213.50±326.16 vs. 4773.56±98.48 cGy, S.S.), left lung V 5Gy (17.80±5.77 vs. 21.3±4.92 cGy, S.S.), and right breast maximal dose (0±0vs. 281.63±49.37 cGy, S.S.). Conclusion Our data support that combined use of PERSBRA with PBT reinforces heart and lung sparing during left sided WBI. Lung sparing with PERSBRA in terms of V 10Gy and V 20Gy appears comparable to what proton plans can offer, although the latter is slightly better in V 5Gy . It warrants further investigation to analyze health economics of the two cardiopulmonary sparing techniques. PO-1511 Automatic treatment planning for left sided breast cancer with lymph nodes. K.H. Engstroem 1 , I. Hazell 1 , K.L. Gottlieb 1 , V.N. Hansen 1 , E. Van Veldhuizen 1 , E.L. Lorenzen 1 1 Odense University Hospital, Radiofysisk laboratorium, Odense, Denmark Purpose or Objective Conventional treatment of the breast is tangential forward planed beams including segments and wedges. However, the coverage of the internal mammary lymph nodes (IMN) can be hard to achieve for some patients. Helical techniques such as Thomotherapy and VMAT can used to increase the conformity but may introduce a low dose bath in the surrounding normal tissue. In the present study, we evaluate VMAT in a butterfly field configuration using Pinnacle Autoplan module in comparison with clinical plans with tangential radiotherapy. Material and Methods