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Published on: May 26, 2019
(Radio)biological optimization of external-beam radiotherapy
1Physics Department, Clatterbridge Cancer Centre, Bebington CH63 4JY, UK. alan.nahum@clatterbridgecc.nhs.uk
Computational and Mathematical Methods in Medicine
|December 20, 2012
Summary
Biological optimization (BIOP) tailors radiation therapy using tumor control and normal tissue complication probabilities. Four BIOP levels offer increasingly sophisticated treatment planning, from dose adjustments to incorporating advanced imaging for improved outcomes.
Area of Science:
- Radiation Oncology
- Medical Physics
- Biophysics
Background:
- Biological optimization (BIOP) integrates radiobiological models, such as tumor control probability (TCP) and normal-tissue complication probability (NTCP), into treatment planning.
- Traditional treatment planning often relies on standardized protocols rather than individual patient radiobiology.
Purpose of the Study:
- To delineate and describe four distinct levels of biological optimization (BIOP) in radiation therapy planning.
- To illustrate the application and potential benefits of each BIOP level using specific examples and software.
Main Methods:
- Level I BIOP: Isotoxic individualization of prescription dose (D(presc)) at a fixed fraction number, adjusting D(presc) to maintain constant organ-at-risk (OAR) NTCP.
- Level II BIOP: Individualized isotoxic combination of D(presc) and fractionation, suitable for parallel OARs (e.g., lung, parotids), exemplified by hypofractionated stereotactic ablative radiotherapy (SABR) for NSCLC.
- Level III BIOP: Integration of radiobiological functions into inverse planning for intensity-modulated radiation therapy (IMRT), optimizing target dose distribution while respecting OAR NTCP constraints.
- Level IV BIOP: Incorporates functional imaging data (e.g., hypoxia, clonogen location) into Level III planning, demonstrated by prostate dose painting protocols.
Main Results:
- Level I BIOP shows potential for improved local control in non-small-cell lung tumors.
- Level II BIOP, including hypofractionated SABR, is effective for early-stage NSCLC and suitable for parallel OARs.
- Level III BIOP enables non-uniform target doses by utilizing NTCP model parameters to guide inverse planning, particularly for quasi-serial OARs.
- Level IV BIOP allows for advanced "dose painting" strategies in treatments like prostate cancer.
Conclusions:
- BIOP offers a framework for progressively sophisticated radiation therapy planning, moving beyond fixed fractionation and dose prescriptions.
- The four identified levels of BIOP provide a structured approach to incorporate radiobiological principles, enhancing treatment efficacy and safety.
- While BIOP models offer significant potential, their inherent limitations and uncertainties must be acknowledged and addressed in clinical practice.
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