Online CBCT-based adaptive radiation with reduced PTV margins for prostate cancer: Does reference plan comparison tell the whole story?
Bibliographic record
Abstract
Background: Online adaptive radiation (ART) is a novel treatment approach that allows for a new daily treatment plan based on cone beam CT (CBCT) imaging. This daily adaptation facilitates precise tumor and organ-at-risk (OAR) localization and minimizes the impact of interfractional motion, allowing for planning target volume (PTV) margin reduction. Isotropic PTV margins for localized non-stereotactic adaptive prostate radiation performed on an ETHOS linear accelerator with HyperSight have been reduced from standard 7 mm to 5 mm. This study assesses the impact of margin reduction by evaluating the dose metrics of patient reference plans, as well as daily treated plans, for 7 mm vs 5 mm PTV margins. Methods: Patients with prostate cancer receiving moderately hypofractionated adaptive radiation were initially treated with a 7 mm PTV margin (n = 10). This retrospective study generated 5 mm PTV margin treatment plans (n = 10) for these patients for comparison. In addition, a full adaptive 20 fraction treatment course was simulated with margin reduction to identify differences not recognized with reference plan comparison alone. Results: Bladder V40.8 and V48.6 but not V60 were significantly reduced in 5 mm treatment plans compared to 7 mm treatment plans. However, when daily treated plan data was examined bladder V60 was lower for the 5 mm PTV case. Similarly, rectum doses V24.6-V57 but not V60 were significantly reduced in 5 mm PTV margin treatment plans. Further differences were identified when looking at the daily treated plan data as opposed to simply comparing reference plans. Significance: In the era of online ART, with significant data available, such as daily treated plan dosimetry, analysis of reference plans alone may not be sufficient. PTV margin reduction, made possible due to the use of online ART, reduced the volume of bladder and rectum receiving <60 Gy, which may reduce toxicity and secondary malignancy risk.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".