ESTRO 2025 - Abstract Book

S2406

Interdisciplinary – Other

ESTRO 2025

deformable registration and calculation of the total equivalent dose in 2 Gy fractions (EqD2). The assessment of the total EqD2 was performed using Raystation (v.12A) planning system and the workflow (Figure 1) has been set within the context of institutional guidelines.

Results

A total of 62 patients were included: 11 (18 %) patients with breast cancer, 11 (18%) with head and neck recurrence, 8 (12%) with brain malignancies, 16 (26%) with prostate cancer, 12 (19%) with pelvic recurrence from different primary tumors (anal canal, rectal and gynecological cancers), 3 (5%) with abdominal recurrence (pancreatic adenocarcinoma, liposarcoma, epatocarcinoma) and 1 (2%) patient re-irradiated for oligoprogressive renal cancer’s bone metastases. DICOM files were available for 38 pts (61%). Among the 23 remaining pts, the lack of DICOM files were due to: 2D treatments in 6 pts (26 %), Intraoperative treatment in 2 pts (9%), brachytherapy treatment in 5 pts (22%) other causes in the remaining patients. When DICOM files were available, deformable registration with EqD 2 was the most frequent (24pts, 63%) approach ( Figure 2 shows an example of summed dose in EqD2). The main reason that did not allow to use method 4 was the modified anatomy between the treatments. The worst-case scenario and qualitative slice-by-slice evaluation was used for 26 (42%) and 12 (19%) patients, respectively. The isodose line transfer method was not used. Conclusion When DICOM images of the previous treatment plans were available, deformable registration and total dose in EqD 2 assessment could be performed in more than two-third of patients ensuring a high-quality assurance in the reRT workflow.

Keywords: re-irradiation, proton therapy, summed dopses