Streamlining Liver SABR: Validation and Initial Experience of Bulk Density Override Based Single-Session, Simulation-Free Adaptive Workflow
In brief
A one-visit liver radiation workflow matched CT dose calculations in five patients
A simulation-free, single-session MRI-guided liver radiation workflow produced dose calculations close to CT-based plans: in its first five patients, target coverage differed by no more than 1.5%, and key doses to nearby organs differed by less than 0.5 Gy. Retrospective testing in 17 prior treatment plans also showed close agreement, but the approach needs evaluation in more patients.
- Journal
- Practical radiation oncology (Q1)
- Published
- 22 October 2026
- Study design
- Non-randomized / quasi-experimental trial
- Evidence level
- Level 2, Moderate (CEBM 2b)
- Authors
- Yu Gao, Eric Hsu, Daniel Pham, Lawrie Skinner, Cynthia Chuang, Lianli Liu, et al.
- PMID
- 42913914
- DOI
- 10.1016/j.prro.2026.10.006
Why clinicians should know about it
- Picked for Medical Physics (paper of the day, 24 October 2026): Validates MR-guided liver SABR dose calculation and workflow
Abstract
PURPOSE: Conventional liver stereotactic ablative radiotherapy (SABR) typically requires a CT simulation visit followed by multiple treatment fractions, which can increase patient burden and limit access. We propose an approach that consolidates imaging, planning, adaptation, and delivery into one session, utilizing an MR-guided adaptive workflow. We report here the workflow and dosimetric validation of a streamlined bulk density override (BDO) strategy and the initial clinical implementation of this simulation-free approach. METHODS AND MATERIALS: A single-institution phase II trial was designed to deliver liver SABR (30-40 Gy in 1 fraction) in a single-session using an MR-guided Linac for patients with liver cancers using BDO strategy. To validate dosimetric accuracy, 17 previously treated single-fraction liver SABR plans were recalculated retrospectively using (1) CT-based electron density and (2) BDO-based density. DVH endpoints and 3D gamma analysis (1%/1mm) were compared. Early clinical experience from the first five trial patients is reported, including dose comparisons between BDO-based calculations and diagnostic CT-based calculations. RESULTS: For the retrospective analysis, BDO-based calculation closely matched the CT-based calculation. For the PTV and GTV, the median percent differences were close to zero for all evaluated metrics and the maximum percent differences were all within 2%. For organ-at-risk (OAR) endpoints (chest wall, bowel, liver minus GTV, spinal cord), mean and maximum dose differences were within 0.1 Gy and 0.6 Gy, respectively. The average 3D gamma pass rate was 99.2%. For the first 5 patients treated on trial, BDO- and diagnostic CT-based reference plan metrics agreed within 1.5% for PTV coverage and within 0.5 Gy for key OAR endpoints. The mean gamma pass rate was 98.8%. CONCLUSIONS: The BDO strategy provides dosimetric agreement comparable to CT-based calculation and supports an efficient and patient-centric single-visit delivery model. Our results support further investigation of simulation-free, single-session MR-guided adaptive liver SABR.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.