ESTRO 2025 - Abstract Book

S1482

Clinical – Mixed sites & palliation

ESTRO 2025

Cancer consensus recommendation. Lancet Oncol. 2020 Jan;21(1):e18-e28. doi: 10.1016/S1470-2045(19)30718-1. PMID: 31908301

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Mini-Oral Diagnostic Imaging for VERTebral metastases (DIVERT) – Results of a prospective patient study Madeleine L Van de Kleut 1 , Kelly Linden 2 , Elsayed Ali 1 , Lesley Buckley 1 , Gordon Locke 3 , Marc Gaudet 3 , Kristopher Dennis 3 1 Medical Physics, The Ottawa Hospital, Ottawa, Canada. 2 Radiation Medicine Program, The Ottawa Hospital, Ottawa, Canada. 3 Radiation Oncology, The Ottawa Hospital, Ottawa, Canada Purpose/Objective: The primary objective of this study is to assess the feasibility of using diagnostic (dCT) scans for palliative VMAT treatment to vertebral metastases. The secondary objectives are: to quantify the time required to set up patients using their dCT scan setup; to assess the ease of setting up patients without localization tattoos at the treatment unit; and to assess the degree of anatomic change observed between dCT scan acquisition and simulation treatment planning CT (TPCT), to potentially identify an upper limit on the utility of dCT planning. Material/Methods: This is an REB-approved single-center non-randomized prospective cohort study with sample size n=30 patients, following a preliminary evaluation of the dosimetric impact of planning with dCTs. Patients with an existing dCT covering the extent of vertebral pathology at the time of study enrolment were included. The dCT was contoured and treatment plan created in the local TPS. A separate TPCT was acquired, mimicking the dCT setup, with patients positioned on a curved Styrofoam couch-top. The TPCT was also contoured, and plan created and delivered to the patient, following CBCT and alignment correction with a 6-DoF treatment couch. The dCT and TPCT scan sets were registered at the level of the target, and the dCT plan recalculated on the TPCT geometry. DVH metrics of interest were recorded for the recalculated plan. Target contours between dCT and TPCT scan sets were compared using standard overlap metrics. Qualitative assessments (binary, Likert-scale, open comments) were evaluated through electronic questionnaire distributed to the involved staff. Results: Results for n=11 (n=4 lumbosacral, n=3 lumbar or thoracolumbar, n=4 thoracic) cases to date are presented (Tables 1, 2). The mean duration between dCT and TPCT was 45 days (range 5-94 days). There was no correlation between clinical target volume difference (%) and time between dCT and TPCT (R 2 =0.02). Feedback from the qualitative questionnaire highlights ‘good’ or ‘acceptable’ agreement between dCT and TPCT reproducibility. Localization tattoos were not used for patient setup, and a 6-DoF treatment couch appropriately corrected patient alignment. Booking time was appropriate and did not take more time than conventional setup and delivery.