ESTRO 2020 Abstract book

S838 ESTRO 2020

based on the benchmark dose calculated by the integrated Feasiblity module from PlanIQ, Sun Nuclear. The clinical Auto-Planning template was used as starting point for personalized planning, where we set the dose volume histogram (DVH) parameters for rectal wall, anal wall based on feasibility-value (F-value) of 0 and for the bladder an F-value of 0.1. A stop-watch was used to measure the total planning time. Results We compared the plan quality for 10 prostate plan cases using our current automated planning and personalized automated planning. All plans met the clinical criteria. The planning time is reduced from 30 min to about 10 min for each case using personalised planning including some warm restarts for PTV coverage. Figure 1 shows an example of the current and new dose distribution and the DVH results.

Table 1: Differences in mean dose, percentages for 30 Gy and 60 Gy volumes for rectal wall, anal wall and bladder and monitor units (MUs). Positive values indicate that these dose metric values were improved compared to the clinical plan. The average mean dose to the rectal wall was decreased with 0.9 Gy and for the anal wall increased with 0.6 Gy. The average V60 for the rectal wall was increased with 0.3% and the average V30 for the anal was increased with 0.7%. The other dose metrics were not significantly different. The MUs for the personalized plans are slightly higher and on average 729 MUs. A warm restart was ran to steer for an optimal PTV coverage and maximum dose. Dosimetry QA results were good. Conclusion Plan quality is in general the same when using automated personalized planning.The planning efficiency improved from 30 min to 10 min. It is feasible to implement this new treatment planning module in our clinic for prostate radiotherapy. PO-1471 Dosimetric comparison of neoadjuvant proton beam therapy vs VMAT in distal oesophageal cancer O. Nicholas 1 , A. Selby 2 , J. Lambert 3 , R. Hugtenburg 4 , S.H. Gwynne 5 1 Swansea University, Swansea University Medical School, Swansea, United Kingdom ; 2 Swansea Bay University Health Board, Department of Physics- South West Wales Cancer Centre, Swansea, United Kingdom ; 3 Rutherford Cancer Centres, Department of Physics, Newport, United Kingdom ; 4 Swansea University, Department of Medical Physics, Swansea, United Kingdom ; 5 Swansea Bay University Health Board, South West Wales Cancer Centre, Swansea, United Kingdom Purpose or Objective Despite established survival benefit, use of neoadjuvant chemoradiotherapy (NACRT) for oesophageal cancer remains low in the UK due in part to concerns of post- operative pulmonary and cardiac toxicities. Pencil beam scanning proton beam therapy (PBS) has the potential to reduce dose to lung and heart, therefore reduce these toxicities. NeoSCOPE is a UK phase II randomized control trial of two NACRT regimens in oesophageal cancer that undertook a rigorous RTTQA programme. We undertook a

Figure 1 shows the axial dose distribution and DVHs between current auto-planning (solid line) and new personalized automated planning (dashed lines) approach. The plan quality between clinical plans and the personalized plans are comparable in general. Table 1 shows the differences for all cases for each OAR.