SU-E-T-616: Efficacy of Biological Dose Painting for Head and Neck Cancer
Bibliographic record
Abstract
PURPOSE: Study the feasibility and planning robustness of a novel biological dose painting approach prescribing biological effect instead of dose. METHODS: Prescribed'effect maps' were generated using models relating FMISO-PET tracer uptake to hypoxia reduction factors (HRF). HRFs decrease the LQ-model radio response parameters a and β and therefore the delivered biological effect. The model is driven by four parameters (m, K, p50, Imax), whose values have been determined through a comprehensive literature search. A planning study on ten previously treated patients with oropharyngeal cancer was conducted. Dose-painted plans were generated with the KonRad inverse planning system (DKFZ, Heidelberg). Simulated FMISO-PET images were generated by defining clinically relevant hypoxic sub-volumes within the GTV. Tracer uptake values were derived from various PET imaging studies for head and neck cancer. Each treatment plan was developed in four steps: 1) Simulate hypoxia tracer distribution in GTV. 2) Prescribe biological effect. 3) Optimize dose-painted plan under the same normal tissue constraints of the nominal clinical plan. 4) Conduct robustness analysis by evaluation of the dose-painted plan for 27 parameters combinations of K, m, p50 (mean ± 1SD). RESULTS: The predicted biological effect of clinical plans under normoxic conditions overestimates the delivered effect due to decreased radio-sensitivity in hypoxic tumours. Biological dose painting compensates for hypoxia by delivering a higher dose to hypoxic sub-volumes while still maintaining all critical structure dose limits. Model parameter uncertainties clearly affect robustness. The high uncertainty on p50 (pO2 for which tracer concentration is half of maximum uptake) was found to cause the largest variations in the delivered biological effect. CONCLUSIONS: Clinically acceptable dose-painted plans can be generated without sacrificing the normal tissue constraints. Planning robustness suffers from the high uncertainty on the p50 value. Improved methods to determine the model parameters would be desirable. Financial support provided by Ryerson University, Toronto, Ontario, Canada.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".