ESTRO 2023 - Abstract Book

S1727

Digital Posters

ESTRO 2023

PO-1963 Arc proton therapy for esophageal cancer: feasibility and first plan comparison with IMPT

M. Chocan 1 , H. Ozan 1 , A.C. Wera 1 , S. Wuyckens 1 , E. Engwall 2 , V. Wase 3 , O. Marthin 2 , J. Sundström 3 , A. Barragan 1 , J.A. Lee 1 , E. Sterpin 1 1 UCLouvain, MIRO, Brussels, Belgium; 2 RaySearch Laboratories , Research and Development, Stockholm, Sweden; 3 RaySearch Laboratories, Research and Development, Stockholm, Sweden Purpose or Objective Arc proton therapy (ArcPT) appears as an alternative to IMPT due to its capability to improve dose conformality, while reducing both the treatment time and the probability of normal tissue complications (NTCP) for several tumor locations, such as lungs, breast, brain, head and neck, and prostate. This work aims to study the feasibility and performance of ArcPT against IMPT in esophageal cancer, for which no results have been reported yet, and to analyze potential benefits and pitfalls of ArcPT for this tumor location. Materials and Methods Dynamic ArcPT plans were created for a database of 20 patients with a dedicated optimization algorithm (1) in a research version of RayStation 12A, following the clinical goals established in the PROTECT clinical trial (prescription of 50.4Gy). A beamset of 2 entangled arcs in opposing rotation, 1 revolution each, and 2° angular spacing was used. The arc range was set to 80-200° (Fig 1a). Robust optimization was performed simulating 7 mm setup and ±2.6% range error. In total, 28 scenarios were later evaluated. Conventional IMPT plans were also generated for each patient, using 2 posterior oblique beams (Fig 1b). All IMPT plans were clinically approved by an experienced physician. ArcPT and IMPT plans were compared in terms of clinically relevant dose-volume metrics, in both the nominal and worst-case scenarios, for the target volume and main organs at risk (OARs). Body integral dose and NTCP for lung toxicity (2) were also assessed.

Figure 1. Beam configuration: (a) arcPT (b) IMPT

Results