Clinical indicators for dose re-optimization in magnetic resonance-guided online adaptive radiotherapy for prostate cancer
In brief
Dose re-optimization applied in 60% of fractions rescues coverage below 95%
In a review of 150 treatment fractions for five-fraction prostate SBRT, online dose re-optimization was needed in 60% of sessions, especially later ones, to counteract a median 3.7% drop in PTV V100% and prevent the 95% coverage threshold from being missed. The technique preserved target dose while keeping bladder and rectum doses within limits, highlighting a practical trigger for adaptive planning.
- Journal
- Physics and imaging in radiation oncology (Q1)
- Published
- 5 August 2026
- Study design
- Cohort / observational study
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Masato Nishitani, Hiroyuki Okamoto, Weishan Chang, Junichi Kuwahara, Takahito Chiba, Tatsuya Sakasai, et al.
- PMID
- 42668485
- DOI
- 10.1016/j.phro.2026.101060
Why clinicians should know about it
- Picked for Medical Physics (top studies of the week, 6 September 2026): Target volume expansion triggers need for online dose re‑optimization
Abstract
BACKGROUND AND PURPOSE: This study aimed to identify dose-volume parameters and anatomical features associated with the implementation of online dose re-optimization in magnetic resonance-guided adaptive radiotherapy (ART) for prostate cancer and to evaluate its impact on target coverage and organs-at-risk dose-volume parameters. MATERIALS AND METHODS: Treatment plans from 150 fractions (with and without dose re-optimization) in 30 patients receiving five-fraction stereotactic body radiotherapy were retrospectively analyzed. Evaluated parameters included planning target volume (PTV) V 100%, bladder and rectum dose-volume parameters, volumetric changes, and relationship between changes in target coverage. RESULTS: Online dose re-optimization was performed in 60% of fractions and became more frequent in later fractions (p = 0.02). Compared with reference plans, non-ART plans showed a 3.7% lower median PTV V 100% (p < 0.01), and 65.3% of fractions failed to achieve the 95% coverage threshold. The target volume increased significantly after the third fraction (p < 0.05). Target volume expansion was associated with reductions in PTV V 100% in non-ART plans, while this relationship was substantially weakened after dose re-optimization. Although bladder and rectum dose-volume parameters increased significantly in non-ART plans, all median values remained within predefined dose constraints. CONCLUSIONS: Progressive target-volume expansion appears to be the primary anatomical factor associated with deterioration in target coverage. A reduction in PTV V 100%, particularly below 95%, represented a clinically meaningful indicator for online dose re-optimization. These findings suggested that online dose re-optimization remained important for maintaining target coverage and limiting gradual deterioration of organs-at-risk dose-volume parameters, even when predicted plans satisfied clinical constraints.
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.