ESTRO 2023 - Abstract Book

S1731

Digital Posters

ESTRO 2023

OAR doses, which is even more pronounced when estimating the equivalent dose in 30 fractions. The gain can instead be seen in the delivery time, which is substantially reduced in the beam-partitioned plans.

Conclusion Beam-partitioned arc plans can provide improved plan quality compared to IMPT, while reducing delivery times compared to full arc plans. This technique could pave the way for introduction of proton arc delivery at the clinics with existing delivery machines.

PO-1966 Isotoxic dose escalation with proton beam therapy for distal oesophageal cancer

M. Esien 1 , A. Abbas 2 , C. Rose 3 , S. Gwynne 4 , O. Nicholas 4 , R. Hugtenburg 2,3

1 Swansea University, School of Medicine , Swansea, United Kingdom; 2 Swansea University, School of Medicine, Swansea, United Kingdom; 3 Swansea Bay University Health Board, Medical Physics and Clinical Engineering, Swansea, United Kingdom; 4 South West Wales Cancer Centre, Oncology, Swansea, United Kingdom Purpose or Objective Dose escalation in oesophageal cancer (OEC) has potential to improve TCP and overall survival, but so far clinical trials have been negative, possibly due to increased dose to critical OARs. SCOPE 2, a current photon RCT limits dose escalation of GTV to 60Gy. Proton beam therapy (PBT) offers the possibility of dose escalation to GTV with same or reduced dose to OAR because of its physical properties. This work investigates the feasibility of Isotoxic dose escalation of GTV to 70Gy using PBT for distal OEC. Materials and Methods Proton treatment plans were created using Eclipse™ v13.7 TPS from on anonymised patient 4DCT scans obtained from RTQA database (NeoScope). Isotoxic dose escalation from nominal plan of 50Gy to 55Gy, 60Gy, 65Gy and 70Gy was done, while maintaining 50Gy to ITV. Multi-beam plans were robustly optimised and evaluated for 12 uncertainty scenarios using SCOPE 2 protocol OAR constraints. Results were reported for the second-worst scenario. All plans were deemed clinically acceptable by a clinical oncologist.

Results