This is a prospective, single-arm, pilot feasibility clinical trial designed to evaluate the feasibility and safety of a simulation-free adaptive radiotherapy workflow to enable single-session celiac plexus SBRT planning and delivery. In this trial, the treatment itself is non-investigational (standard-of-care celiac plexus SBRT) but the treatment workflow (simulation-free, using adaptive radiotherapy to compress treatment planning and delivery into a single session) is novel. Investigators hypothesize the successful completion of the simulation-free ART workflow through treatment delivery in the first on-table treatment attempt for at least 80% of patients.