ESTRO 2023 - Abstract Book

S1732

Digital Posters

ESTRO 2023

Table 1: Dose escalation statistics showing a sample result for robustly optimised dose escalations at 55Gy, 60Gy, 65Gy, and 70Gy. The result is given for the second worst-case scenario. For each dose escalation scenario, the prescribed dose to ITV was maintained at 50Gy.

Escalating dose to GTV increased dose to OAR, but constraints were met with acceptable GTV coverage. Adding extra beams improved the dose distribution conformity to the GTV, limiting dose to OAR. Conclusion The results show that dose escalation to GTV to 70Gy may be achieved with a multi-beam configuration, without significant increased risk to OARs. Effective management of dose gradient between ITV and GTV is critical for successful dose escalation. Isotoxic dose escalation to GTV in distal OEC appears feasible with PBT, however further work is required in a larger sample, taking into consideration additional uncertainties such as motion and variable RBE.

PO-1967 Inter-fraction robustness and organ sparing potential of post-operative cervical cancer IMPT

E. Gort 1 , J.C. Beukema 1 , H. Hoekstra 1 , A. Sibma 1 , M.J. Spijkerman-Bergsma 1 , M.L. de Vries-de Groot 1 , S. Both 1 , J.A. Langendijk 1 , W.P. Matysiak 1 , C.L. Brouwer 1

1 University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands

Purpose or Objective Volumetric Modulated Arc Therapy (VMAT) is the current post-operative radiotherapy modality for cervical cancer patients. However, with the increasing availability of Intensity Modulated Proton Therapy (IMPT) and robust treatment planning techniques, protons may have significant advantages for this patient category to reduce bowel and bone marrow toxicity. In this study, IMPT and VMAT were compared, examining target coverage and organs at risk (OARs) doses, taking inter fraction variability into account.