ESTRO 37 Abstract book

S1021

ESTRO 37

EP-1883 Class-solution for Pinnacle Autoplan using dual arc VMAT for head and neck cancer J. Van Santvoort 1 , D. Reijtenbagh 1 , H. Rozema 2 , M. Van Dalum 2 , R. Gangabisoensingh 2 , M. De Goede 1 , R. Wiggenraad 2 , M. Mast 2 1 Haaglanden Medical Centre, Medical Physics, Leidschendam, The Netherlands 2 Haaglanden Medical Centre, Radiotherapy, Leidschendam, The Netherlands Purpose or Objective Automated planning (Autoplan) can play a significant role to improve efficiency and plan quality and consistency, but a class-solution is important for successful implementation. High target coverage and adequate Organ At Risk (OAR) sparing must be achieved, each with the right priorities, making fine tuning afterwards unnecessary. Pinnacle Autoplan was used during the introduction of Volumetric Arc Therapy (VMAT) for head and neck (H&N) cancer patients in our clinic. We developed a class- solution to create dual arc VMAT plans with a Simultaneously Integrated Boost (SIB) technique that, without fine tuning, had similar or better target coverage and OAR sparing compared to the clinically used Intensity Modulated Radiotherapy (IMRT) plans. Material and Methods An Autoplan treatment technique was designed, based on the clinical protocol. For patients with malignancies on both sides a dual arc of 178-182 degrees was selected. For patients with a tumour on one side a 350-150 or 220- 10 degree dual arc was used, depending on the location of the tumour. Treatment goals were added to improve plan quality. The radiation oncologists approved the developed treatment plans, based on coverage, conformality, OAR sparing and overall quality. Finally, the Sun Nuclear ArcCHECK system was used to investigate deliverability. Next, the Autoplan treatment technique was tested on a patient group of 9 patients and compared to the clinically used manual IMRT plans. Dose parameters and DVH curves of both plans were used for quantitative and qualitative comparison. Results For Autoplan 40 iterations were used, as this was found to be sufficient and time efficient. For the advanced settings a tuning balance of 10% and a dose fall-off margin of 1.5 cm were selected, the cold spot ROIs was switched on and the hot-spot maximum was set to 107%. A treatment time of 90 s per beam was selected. The automatically generated VMAT plans resulted in a comparable or lower dose to the OARs compared to the IMRT plans. The distributions of the mean dose to OARs are shown in Figure 1.

A standardized Autoplan treatment technique can offer a one-click solution for all patients in the study, at least competitive to the manual IMRT plans. ArcCheck measurements passed using our criteria. Conclusion A class-solution for H&N patients was developed with Pinnacle Autoplan. This resulted in more consistent treatment plans with better OAR sparing while using much less planner time. The study has led to clinical implementation of VMAT using Autoplan. EP-1884 Automated treatment planning of volumetric arc therapy for patient with prostate cancer M. Olminska 1 , A. Skrobala 1,2 , B. Pawalowski 1 , T. Piotrowski 1,2 1 Greater Poland Cancer Centre, Department of Medical Physics, Poznan, Poland 2 Poznan University of Medical Sciences, Department of Electroradiology, Poznan, Poland Purpose or Objective The study aimed to evaluate whether plans optimized manually (MO plans) by planners were comparable to RapidPlan based plans (RP plans) created by a single optimization in volumetric modulated arc therapy (VMAT) for patients with prostate cancer. Material and Methods The prostate model was trained using 35 prostate patients previously treated with 74 Gy in 37 fractions. Plans were created using 2 arcs volumetric modulated arc therapy. The final model was validated on a set of 10 patients. RP plans were created by a single optimization without planner intervention during optimization. Differences between RP plans and manual optimization plans created by planners for the same patients were analyzed in terms of D 95% , and D 2% to planning target volume (PTV), mean dose to rectum, bladder, intestine and femoral heads and V 40Gy to rectum and bladder, number of monitor units. Results RP and MO values for PTV D 95% were significantly similar (p<0.05 for all); for D 2% RP plans were better than MO plans (values were lower). RP plans mean dose to rectum, bladder, intestine and femoral heads were comparable to MO values; RP plans V 40Gy to rectum and bladder were lower than in MO plans (p<0.05). MU values