ESTRO 37 Abstract book

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ESTRO 37

Purpose or Objective To automate optimization process in RayStation treatment planning system (TPS) for head and neck treatments by means of specific Phyton script. Material and Methods Genetic algorithm (GA) was implemented for head and neck VMAT treatments. The chromosomes of the algorithm were max equivalent uniform dose functions (maxEUD) for: larynx, oral cavity, both parotid glands and inner ears. Ten initial couples were randomly generated and a maximum of five reproductions were permitted. The fitness function included coverage of PTVs and mean dose of parotid glands, larynx, oral cavity and inner ears with different weights. The script was tested for five patients and two different dose prescriptions (both simultaneous integrated boost): four patients with three dose levels (70 Gy, 63 Gy and 54 Gy) in 35 fractions; one with two (66 Gy, 59.4 Gy) in 33 fractions. A comparison with corresponding plans created with Monaco TPS (M, Elekta) was carried out. M plans had the same initial template with active multicriterial function for OARs. All the plans were evaluated with a score of PlanIQ (Sun Nuclear) in terms of target coverage, conformity index of PTVs and constraints of OARs. Results In figure are reported the totals scores (TS) obtained. Script plans scores were always higher to M ones (mean TS: 78.7±27.7 for GA and 73.3±28.1 for M). Mean score of PTV1.1 coverage (max = 15) was 12.0±6.7 for GA and 11.5±6.5 for M. The values of other PTVs were (max = 10): for PTV1.2, 8.1±1.9 for GA and 4.1±3.2 for M; for PTV1.3, 9.4±1.0 for GA and 9.5±0.5 for M. Maximum doses of spinal cord, brainstem and optic pathways were always below the requested value both for GA and M. For parallel OARs, GA spared parotid glands more (average score of summed parotid glands: 5.6±2.0 for GA and 4.4±2.5 for M). For other OARs, the results obtained with GA and M were very similar to each other.

Purpose or Objective Breast tangents remain as one of our field's dominant non-VMAT/IMRT treatment techniques. Modern treatment and optimization techniques are, in many ways, suboptimal for the treatment of tangential superficial disease and may lead to higher low-dose to the lungs and larger volumes of patient receiving radiation that would otherwise be avoided through standard breast tangents. A new approach (Trajectory Optimization in Radiotherapy Using Sectioning (TORUS)) to the treatment of superficial disease has been developed and has been shown to produce plans of higher quality than VMAT and IMRT, with shorter delivery times for sites including chest wall and scalp. In this study, we extend TORUS to generate automated radiation trajectories for left and right sided, intact, breast cancers and compare to conventional tangents, VMAT and IMRT. Material and Methods TORUS avoids degradation of 3D dose optimization quality by mapping the connectedness of target regions from the BEV perspective throughout the space of deliverable coordinates. This connectedness information is then incorporated into a graph optimization problem to define trajectories. The unique usage of two distance functions in this graph optimization permits the TORUS algorithm to generate efficient dynamic trajectories for delivery. 3D dose optimization is performed for trajectories using Aria's Photon Optimizer (version 15.5.1). In this work a new technique for improving coverage of trajectories has been incorporated into the TORUS approach. Results In this study we perform trajectory optimizations for 3 intact breast cases, two left and one right sided. Optimizations were performed for which dynamic collimator and gantry motion were permitted, with couch motion constrained to static arrangements. In all cases, TORUS has outperformed VMAT and IMRT with improved organ at risk sparing, conformality, and homogeneity. TORUS has inferred a characteristic class solution with small deviations in starting and stopping positions and couch rotation between cases. Conclusion The TORUS algorithm is able to automatically generate trajectories for breast treatment which have improved plan quality and delivery time than standard IMRT and VMAT treatments. TORUS offers an exciting and promising avenue forward toward increasing the dynamic capa- bilities of radiation delivery, and may offer improvement over standard breast tangents in difficult to plan cases involving excessive lung and/or heart proximity. EP-1896 Is robust optimization better than virtual bolus method to achieve skin flash in breast VMAT plans? D. Nguyen 1 , C. Corbet 1 , G. Largeron 1 , F. Josserand- Pietri 1 , S. Yossi 2 , M. Khodri 1 1 orlam Macon, Saone Et Loire, Macon, France 2 orlam Charcot, Rhone, Lyon, France Purpose or Objective In this study, we evaluate the virtual bolus method and the Robust Optimization (RO) functionality in Raystation 6.0.24 (RS) treatment planning system to take into account the setup uncertainties and anatomic variations, for Breast VMAT (Volumetric Modulated Arc Therapy) irradiation. Material and Methods Five patients with advanced stage breast cancer were randomly selected for this study. The prescription dose was 50 Gy in 25 fractions. Dosimetric planning goals were determined from normal tissue tolerances and from the clinical experience of radiation oncologists in our clinic. To assess the efficiency of each method, we created VMAT (Nominal), virtual bolus-VMAT and Robust-VMAT treatment plans for each patient. A setup uncertainty of

Conclusion Automatic planning gives results clinically comparable with manual ones reducing considerably the workload and increasing the overall quality of plans. These preliminary results must be confirmed by further ongoing investigation with a larger Head and Neck plans dataset and planned with already available commercial versions of automated treatment planning solution by different vendors, too. EP-1895 Automated Trajectory Planning for Breast Treatment Using TORUS C. Locke 1 , K. Horst 1 , K. Balazy 1 , K. Bush 1 1 Stanford Cancer Center, Radiation Oncology, Stanford, USA