ESTRO 2021 Abstract Book

S1276

ESTRO 2021

2).

Conclusion Iso-WEPLs were comparable to isodoses re-calculated in the rCTs. The proposed strategy could detect target dose degradations occurring in the rCTs, and could be an alternative to a full dose re-calculation to detect anatomical variations severely influencing proton range. PO-1552 Fraction ∆NTCP calculation using automatic 4D accumulated dose in IMPT for thoracic indications A.C. Hengeveld 1 , C.O. Ribeiro 1 , A. Meijers 1 , C.T. Muijs 1 , A. Crijns 1 , A. Niezink 1 , R. Wijsman 1 , J.A. Langendijk 1 , S. Both 1 , G. Guterres Marmitt 1 1 UMCG, Radiotherapy, Groningen, The Netherlands Purpose or Objective In the Netherlands, patient selection for proton treatment is performed according to the model based approach (MBA) via Normal Tissue Complication Probability (NTCP) models that quantify the potential proton