In Silico Evaluation of Direct-to-Unit, Single-Visit Celiac Plexus Pain Ablation Using Computed Tomography Guided Adaptive Radiation Therapy.

Purpose: Celiac plexus stereotactic body radiation therapy (CP-SBRT) using 25 Gy in a single fraction is an effective method of palliative pain relief for patients suffering from celiac axis tumor invasion. Standard complex stereotactic body radiation therapy workflows for simulation and planning result in delays in pain relief during end-of-life care. We propose a simulation-free, direct-to-unit (DTU) adaptive radiation therapy (ART) approach, using a diagnostic computed tomography (CT) preplan and online adaptation for final plan construction to enable the same-day radiation oncology consult and CP-SBRT. We aimed to demonstrate that this advanced imaging has increased electron density accuracy which enables the test of this DTU, adaptive CP-SBRT workflow in silico.

Methods and materials: Ten patients with abdominal malignancies were imaged on a HyperSight Cone Beam Computed Tomography (CBCT) solution on a C-arm linear accelerator as part of a prospective imaging clinical trial (NCT05975619). These patients' existing diagnostic CT scans were used to generate CP-SBRT preplans. To simulate a simulation-free, DTU workflow, HyperSight CBCT images were injected into a CT guided ART treatment planning system environment as the primary data set, with target contours propagated from the registered diagnostic CT. Contours were updated as needed to reflect the treatment anatomy and positioning. A standard online ART workflow was used for the predicted and final adaptive plan calculation. Dose-volume values for each clinical goal were compared between predicted and final plans. Timing and measured quality assurance data were also collected.

Results: DTU adaptive CP-SBRT plans were successfully created for all 10 patients and met all clinical goals. Without adaptation, predicted plans were infeasible for clinical use; 9 of 10 patients had nondeliverable predicted plans. The average time to complete ART contouring was 6 minutes. The average gamma passing rate for 3%/2 mm was 92.6%.

Conclusion: DTU ART for CP-SBRT is dosimetrically feasible. Adaptation is a critical component for DTU CP-SBRT to achieve deliverable plans. This approach could reduce treatment delay for cancer-related celiac pain.