ESTRO 2025 - Abstract Book

S1519

Clinical – Mixed sites & palliation

ESTRO 2025

Material/Methods: Patients with bone metastases are eligible for inclusion. Single fraction as well as fractionated RT is allowed (8Gy/1fx or 20Gy/4fx). Target delineation and treatment planning is carried out on an existing diagnostic CT scan, before the patient arrives at the hospital. RT is delivered on a standard Elekta C-arm linac (Infinity, Versa HD or Harmony Pro). The CBCT image acquired for patient localization is exported to RayStation (version 11B) for online plan adaptation, to account for differences in patient positioning and other anatomical changes. While the patient remains on the treatment couch, target structures are propagated to a corrected CBCT (Figure 1) suitable for treatment planning, and the plan is adapted to the present anatomy. After plan approval and independent quality assurance according to our department protocols, the first fraction is delivered. Subsequent fractions for fractionated treatment are delivered without any further adaptation.

Results: One pilot and the first two protocol patients have successfully been treated, with treatment times from entry to exit of the bunker between 46 and 52 minutes (Figure 2). Online plan adaptation was performed in 22 minutes or less. With more experience and planned software upgrades, we expect to be able to complete treatment within 40 minutes on a linac not initially designed for oART. Patient satisfaction was high, with none of the patients finding it troublesome to lie on the treatment couch during treatment preparation. The participating staff were satisfied with the workflow as well.