ESTRO 2020 Abstract Book

S815 ESTRO 2020

Purpose or Objective The purpose of the study is to present the result of comparison of the automatic optimization using the RapidPlan with manual optimization, and to present the configuration and training process of the estimation model, its evaluation of geometric and dose components, and the algorithm evaluation. Material and Methods The calculations were made in the Ecpice planning system ver. 15.6. Dose constraints from the RapidPlan estimation algorithm were used for optimization. The plans were made for the True Beam HD accelerator, for FF 6MV beams. The model consisted of 258 plans covering all types of prostate radiation therapy, i.e. 1 / prostate alone, 2 / with vesicles, 3 / with lymph nodes. The model includes plans with the conventional dosing of 2Gy / 1.8Gy and the hypofractionated 2.5Gy for the prostate area alone. The three targets have been defined: PTV1 – the prostate, PTV2 – the vesicles, and PTV3 – the nodes. 10 OARs have been defined: the Rectum, the Bladder, the Femoral Heads, the Intestines, the Esica, the Rectus, the Penile Bulb, the Marrow, the Large Blood Vessels, and the Bones. The model was trained on the plans after an iterative tuning, i.e. the re-optimization of base plans with a model based on these plans, each time creating a new model, etc. At the training stage, approx. 35% of Outliers were obtained for each of the OARs. Most were the geometric deviations due to an inconsistent contouring and a diverse population. Results The 258 plans were evaluated. For each of them a model plan was created and compared with the corresponding plan created by the physicist. For PTV1 , the average difference between the automatic model and the clinical plan (AM) was V98 -0.20% at STD 0.27, for ΔV2 0.76% at STD -0.17, for ΔSTD 0.26 at STD -0.05. PTV2 ΔV98 -0.22% at STD -1.11, for ΔV2 0.83% at STD 0.08, for ΔSTD 0.18 at STD -0.43. PTV3 -1.24% at STD -0.01, for ΔV2 0.21% at STD 0.25, for ΔSTD 0.37 at STD -0.28. Rectum ΔDmean -2.85%, at STD 0.44, Bladder ΔDmean -5.33%, STD -3.78, Femoral heads ΔDmean = -6.33%, STD -3.14, Intestines ΔDmean (%) = -5.42%, STD -1, 37, Anus ΔDmean = -5.49%, STD -2.96. The number of plans with lower average doses in the population of the analyzed plans (Manual / Automatic) was 71/197 for rectum, 36/232 for bladder, 11/83 for intestines, and 20/81 for anus. Conclusion For all the critical organs, the average population dose is lower in the automatic planning compared to the manual planning. The model generates similar quality (V98 rating) dose distributions for PTV1 and PTV2. For PTV3 a slightly understated dose was observed for the automatic planning but within tolerance ranges. More consistent plans were achieved - population less different, as indicated by a smaller standard deviation. Shorter treatment planning times have been observed. The use of the automatic planning also suggests a reduction in the likelihood of human random errors. The RapidPlan guarantees versatility for all prostates regardless of the contouring range. PO-1510 Cardiopulmonary Sparing During Breast RT with Personalized Breast Holder and Proton Beam Therapy R. Wang 1 , T.H. Chen 1 , M.Y. Chung 2 , D.C. Tien 2 , K.H. Tseng 2 , J.F. Chiou 1,3,4 , L.S. Lu 1,5 1 Taipei Medical University Hospital, Radiation Oncology, Taipei, Taiwan ; 2 National Taipei University of Technology, Electrical Engineering, Taipei, Taiwan ; 3 Taipei Medical University, Radiology- School of Medicine- College of Medicine, Taipei, Taiwan ; 4 Taipei Medical University, Taipei Cancer Center, Taipei, Taiwan ; 5 Taipei Medical University, Graduate Institute of Biomedical Materials and Tissue Engineering, Taipei, Taiwan

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 Twenty left-sided breast cancer patients, ten with mastectomy and ten with lumpectomy, were selected