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Cluster models of dose-volume effects.
Howard D Thames1, Ming Zhang, Susan L Tucker
1Department of Biostatistics, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA. hdt@odin.mdacc.tmc.edu
Summary
Cluster models improve normal tissue complication probability predictions by considering the spatial arrangement of radiation-sterilized cells. These models are particularly useful for predicting complications from intensity-modulated radiotherapy
Area of Science:
- Radiation Oncology
- Medical Physics
- Biophysics
Background:
- Traditional normal tissue complication probability (NTCP) models often overlook the spatial distribution of radiation effects.
- Understanding the impact of dose inhomogeneity is crucial for optimizing radiotherapy treatment plans.
Purpose of the Study:
- To introduce and describe cluster models for predicting normal tissue complications in radiotherapy.
- To evaluate the role of both the number and spatial location of radiation-sterilized functional subunits in complication probability.
Main Methods:
- Computer simulations were employed to determine the maximum cluster size of sterilized subunits for given dose distributions.
- Complication probability was associated with the presence and size of these clusters.
Main Results:
- Cluster models demonstrate a volume effect, where larger volumes or higher doses increase complication probability.
- For uniform irradiation, cluster models align with existing NTCP models.
- Inhomogeneous dose distributions predicted different complication probabilities based on spatial 'hot spot' arrangements; contiguous hot spots yielded higher probabilities than dispersed ones, even with identical dose-volume histograms.
Conclusions:
- Cluster models provide a novel framework for quantifying complication probability, especially in scenarios with diverse hot-spot distributions.
- These models offer a consistent method for predicting complications arising from inhomogeneous dose distributions common in intensity-modulated radiotherapy.