ESTRO 2020 Abstract book

S861 ESTRO 2020

select the clinically optimum balance of trade-offs for a selected calibration patient. Automated planning of new patients is then possible with the employment of algorithms designed to ensure trade-off balancing for a novel patients is consistent with that selected during calibration. The purpose of this work was to quantitatively assess whether or not a single patient’s calibration parameters are sufficient to generated automated plans for new patients of the same treatment site. Material and Methods 19 randomly chosen prostate seminal vesicles (PSV) patients previously treated at Velindre Cancer Centre were selected for this study. A previously calibrated EdgeVcc automated planning protocol, which included seven MCO parameters, was used as a base protocol. For each patient, an experienced operator used EdgeVcc’s MCO functionality to create a patient specific gold standard plan (GS). To simplify the MCO problem, four of the criteria were held constant across all plans (bowel dose volume, PTV homogeneity, and max dose objectives to bladder and rectum). The three criteria navigated (average dose to rectum, average dose to bladder, and PTV conformality) were considered to have the most clinically interesting trade-off relationships. For each patient, two additional plans were generated automatically with EdgeVcc using the following calibration methodologies: 1) calibration based on MCO navigation of a single randomly selected patient which was independent of the original set of 19 patient (SP), 2) calibration based on the average results of the GS MCO navigation using a leave-one-out validation methodology (Av). Results A summary of key dosimetric parameters for the three sets of plans can be found in Table 1. Compared to GS, SP yielded statistically significant increases in rectum V24.3 Gy and mean dose, and decreases in bladder V40.5Gy and mean dose. No differences found were deemed clinically significant.

Conclusion The two KB models used for planning allow an homogeneous plan quality and some dosimetric gains. Further investigations will be carry out to improve the models. Firstly, it will be performed an external validation of the two models by different centers. Then, an evaluation plans data-set will be generated internally by less experienced planner. Sequentially, sub-KB models will be developed splitting right and left breast cases. Finally, twins A and B models will be generated without the optimization structures. Up to our knowledge, these are the first KB models taking into account whole-breast irradiation comprehensive of nodal station. This KB approach effectively refine plans optimization and could be helpful in clinical practice, in particular in a centre where there are planners with different expertise, in order to standardize and improve the quality of the plans. PO-1504 Pareto navigation guided automated planning: is a single patient enough to calibrate a solution? I. Foster 1 , P. Wheeler 2 , E. Spezi 1 , J. Staffurth 3 , A. Millin 2 1 Cardiff University, School of Engineering, Cardiff, United Kingdom ; 2 Velindre Cancer Centre, Medical Physics, Cardiff, United Kingdom ; 3 Cardiff University, School of Medicine, Cardiff, United Kingdom Purpose or Objective EdgeVcc is an automated planning methodology developed in Raystation (RaySearch Laboratories, Stockholm, Sweden) that is calibrated using multi-criteria optimisation via Pareto navigation (MCO) [1]. For a given treatment site, an operator will use MCO techniques to

Conclusion This study shows evidence that a single patient is sufficient for calibrating an automated solution for PSV using MCO. Although there may be some statistical differences between GS and SP, those differences are considered clinically negligible. Whilst averaging calibrations over multiple patients (Av) may offer an improvement to SP, it is considered this improvement is not large enough to warrant the investment of obtaining more data.