Abstract book - ESTRO meets Asia

S4 ESTRO meets Asia 2018

76.12% in the V40 compare to the FB-SBRT plans. In this study we have not removed the PTV from the ipsilateral lung volume, hence compare to the other studies higher mean dose were documented. Conclusion DIBH-SBRT plans are much superior due to smaller PTV due to its capability of immobilizing the target motion during the treatment within the threshold window. In this study we also found that the DIBH based SBRT significantly reduces the doses to the ipsilateral lung due to lung inflation, which will results in less lung toxicity compare to the FB based SBRT. We need well equipped advanced CT simulator with gating system and image guidance tool to practice safe DIBH based SBRT treatment. OC-014 Evaluation of a New Commercial Automated Breast Planning Software: A first experience in Japan N. Mizuno 1 , R. Yamauchi 1 , S. Fukushima 1 , S. Kashiyama 1 , T. Itazawa 1 , J. Kawamori 1 1 St. Luke's International Hospital, Department of Radiation Oncology, Tokyo, Japan Purpose or Objective Automated breast treatment planning (ABP) may bring intensity-modulated radiation therapy (IMRT) into routine clinical practice for a large number of patients with breast cancer, without causing excessive effort for the treatment planning. The purpose of our study was to validate a new commercial ABP software for tangential IMRT and compare ABP plans with clinical treatment plans by standard manual planning. Material and Methods We prospectively enrolled 150 patients with Stage 0-І breast cancer who underwent breast-conserving surgery at our institution between September 2016 and August 2017. The study protocol was approved by an institutional review board, and all patients provided informed consent before CT-simulation for treatment planning of whole- breast irradiation. In clinical treatment plans, 142 patients received two-field tangential irradiations using a forward-planned field-in-field (FIF) technique. Clinical treatment plans were performed with a total dose of 42.56 Gy in 16 fractions (n = 98) or 50 Gy in 25 fractions (n = 44). All plans were retrospectively re-planned using an ABP software, with the same planning CT images as obtained for clinical plans. The setting for the ABP software included whole-breast and breast-coverage modes for all patients. For both clinical and ABP plans, each beam parameter was recorded for isocenter location, gantry angle, collimator angle, and JAW opening. The number of segments, total monitor units, and planning time were compared for each plan. The dose-volume data were analyzed with respect to 90% of prescribed dose-volume overlap, homogeneity index (HI) of target, lungs, heart (for left-sided breasts only), and maximum dose of irradiated volume. Furthermore, three experienced radiation oncologists reviewed the ABP plans. Results Beam parameters differed based on the technique (i.e., simple FIF technique and tangential IMRT) used in clinical plans vs. ABP plans. However, the adverse clinical impact seems to be small. The planning time significantly decreased in ABP plans than in clinical plans (clinical plans: 53.1 ± 6.7 min, ABP plans: 4.8 ± 1.4 min, P < 0.001). The dice similarity coefficient of 90% of prescribed dose- volume overlap was 0.80–0.90 in most patients (0.84 ± 0.05). The HI of CTV was significantly smaller in ABP plans than in clinical plans (clinical plans: 0.110 ± 0.031, ABP

plans: 0.077 ± 0.019, P < 0.001). V20 Gy of the lungs, Dmean of the heart, and D2 CC of the irradiated volume in ABP plans were 4.2 ± 1.2%, 115.3 ± 76.5 cGy, and 105.8 ± 1.7% (prescribed dose: 100%), respectively. Experienced radiation oncologists deemed 136 ABP plans (95.8%) to be clinically usable. Conversely, six ABP plans (4.2%) were rejected due to the coverage of target volume (n = 2, 1.4%) or the heart dose (n = 4, 2.8%). Conclusion ABP software demonstrated a high clinical acceptability, and the cost-efficiency of planning was dramatically improved. ABP software is a useful tool for delivering high- quality treatment to a large number of patients. OC-015 Dosimetric Influence of Jaw tracking in IMRT and VMAT for Carcinoma of Cervix M.A. Muneem 1 , N. Sultana 2 , T. Hossain 2 , T. Basharat 2 , K.R. Mani 1 1 United Hospital Ltd, Department of Radiation Oncology, Dhaka, Bangladesh 2 Dhaka University, Deaprtment of Biomedical Physics & Technology, Dhaka, Bangladesh Purpose or Objective To Study the dosimetric advantage of the Jaw tracking technique in Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) for carcinoma of cervix patients. Material and Methods We retrospectively selected ten previously treated Cervix patients in this study. All the ten patients under went CT simulation along with immobilization and positional devices. Targets and organ at risk (OAR) were delineated slice by slice for all the patients. All the patients were planned for IMRT and VMAT with intend to deliver 50 Gy in 25 fractions. All the plans were planned with 6 MV photons using Millennium 120 MLC using the TrueBeam linear accelerator. IMRT and VMAT plans were performed with jaw tracking (JT) and with static jaw (SJ) technique by keeping the same constraints and priorities for the target volumes and critical structures for a particular patient. For standardization all the plans were normalized at the target mean of the planning target volume. All the plans were accepted with the criteria of bladder mean dose < 40 Gy, rectum mean dose < 40Gy and cauda maximum point dose < 45 Gy without compromising the target volumes. Target conformity, dose to the critical structures and low dose volumes were recorded and analyzed for IMRT and VMAT plans with and without jaw tracking for all the patients. Results The conformity index average of all patients followed by standard deviation (x̄ ± s x̄ ) of the JT-IMRT, SJ-IMRT, JT- VMAT and SJ-VMAT were 1.176 ± 0.14, 1.174 ± 0.14, 1.193 ± 0.22 and 1.23 ± 0.19 and homogeneity index were 0.089 ± 0.02, 0.085 ± 0.02, 0.102 ± 0.016 and 0.100 ± 0.016. In low dose volume JT-IMRT shows a 5.4% (p-value < 0.001) overall reduction in volume receiving at least 5 Gy (V5) compare to SJ-IMRT, whereas 1.2% reduction in V5 volume in JT-VMAT compare to SJ-VMAT. JT-IMRT shows mean reduction in rectum and bladder shows of 1.34% (p-value < 0.001) and 1.46% (p-value < 0.001) compare to SJ-IMRT, while only 0.30% and 0.03% reduction were observed between JT-VMAT and SJ-VMAT. JT-IMRT plans also shows considerable dose reduction to bowel, right femoral head, left femoral head and cauda compared to the SJ-IMRT plans.