Dosimetric impact of CBCT-guided online adaptive stereotactic body radiotherapy for prostate cancer: a 250-fraction retrospective analysis
In brief
Adaptive prostate radiation avoided 20% target-coverage drops seen in 3.6% of fractions
In a retrospective analysis of 250 treatment fractions, daily adaptive plans had better target coverage and none showed the large drops seen in 3.6% of scheduled-plan fractions. Yet scheduled plans stayed near prescription in most fractions, and cumulative dose was about 5% lower in only one patient; the main benefit appears to be protection from occasional shortfalls, not routine improvement.
- Journal
- Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology (Q1)
- Published
- 1 November 2026
- Study design
- Cohort / observational study
- Evidence level
- Level 4, Very Low (CEBM 4)
- Authors
- Ahmed Eldib, Andy T Clark, Joseph Panetta, Robab Hashemi, Lili Chen, Robert Price, et al.
- PMID
- 42967541
- DOI
- 10.1016/j.radonc.2026.111857
Why clinicians should know about it
- Picked for Medical Physics (top studies of the week, 8 November 2026): Quantifies adaptive SBRT dosimetry across 250 treatment fractions
Abstract
PURPOSE: To quantitatively evaluate the dosimetric benefit of CBCT-guided online adaptive radiotherapy (ART) for prostate SBRT compared with non-adaptive treatment planning, with emphasis on target coverage preservation and organ-at-risk (OAR) sparing. METHODS AND MATERIALS: Fifty prostate patients treated on the Varian Ethos platform were retrospectively analyzed. For each fraction, scheduled plans (reference plan recalculated on daily anatomy) were compared with adapted plans (daily reoptimized plans). Target coverage was assessed using PTV D95% while bladder and rectal metrics were evaluated using institutional constraints. Fraction-level paired comparisons used the Wilcoxon signed-rank test. Fractions with substantial scheduled-plan under-coverage (PTV D95% ≤80%) underwent cumulative dose reconstruction. RESULTS: Adaptive plans achieved higher target coverage than scheduled plans (p < 0.001), although scheduled plans remained within ∼3% of prescription in 83% of fractions. Scheduled plans demonstrated a 20% reduction in PTV D95% in 3.6% of fractions and >5% coverage reduction in 11%, whereas no adaptive fractions showed similarly large deviations. Cumulative scheduled-only dose remained near prescription for most affected patients, with only one patient demonstrating a cumulative D95% reduction of ∼5%. OAR differences were small overall, with ART planning mainly reducing occasional constraint violations. Strict application of planning objectives resulted in 234 adaptive fractions meeting goals versus 62 scheduled fractions, improving to 135 with offline renormalization. CONCLUSIONS: CBCT-guided ART for prostate SBRT primarily improves robustness against infrequent but clinically significant dosimetric deviations rather than providing consistent superiority across most fractions.
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.