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A simulation study to assess the potential impact of developing normal tissue complication probability models with
Molly M McCulloch1,2,3, Daniel G Muenz4, Matthew J Schipper2,4
1Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan.
Advances in Radiation Oncology
|October 30, 2018
Summary
This study shows that using accumulated doses, not planned doses, in normal tissue complication probability (NTCP) models more accurately predicts toxicity risk in liver cancer patients. Further clinical trials are needed to confirm these findings for radiation therapy planning.
Area of Science:
- Radiation Oncology
- Medical Physics
- Clinical Oncology
Background:
- Accurate prediction of normal tissue complication probability (NTCP) is crucial for optimizing radiation therapy.
- Differences between planned and delivered radiation doses can impact treatment outcomes.
- Normal tissue complication probability (NTCP) models are essential tools in radiation oncology for predicting treatment toxicity.
Purpose of the Study:
- To analyze the clinical impact of discrepancies between planned and accumulated radiation doses on NTCP model development and application.
- To evaluate how using accumulated doses versus planned doses affects the accuracy of NTCP models for liver cancer patients treated with stereotactic body radiation therapy (SBRT).
Main Methods:
- Retrospective analysis of 30 liver cancer patients treated with SBRT.
- Calculation of linear quadratic equivalent dose and generalized equivalent uniform dose for both planned and accumulated doses.
- Development of stomach and duodenal Lyman-Kutcher-Burman NTCP models using planned and accumulated doses.
- Assessment of differences between models and evaluation of toxicity prediction errors.
Main Results:
- Standard NTCP models based on planned doses can overestimate or underestimate toxicity risk depending on the dose level.
- Using accumulated doses in NTCP models altered predicted toxicity risk by up to 16% for duodenal and 6% for stomach toxicity.
- A 10% iso-toxicity risk to the duodenum required different maximum dose constraints (15.7 Gy vs. 17.6 Gy) depending on whether planned or accumulated doses were used.
Conclusions:
- Accumulated dose may be a more accurate reflection of the true delivered dose than planned dose in SBRT.
- This simulation study highlights the potential clinical significance of using accumulated doses for NTCP model development.
- Prospective clinical trials are warranted to validate the impact of building NTCP models based on accumulated doses.
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