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Fixed- versus Variable-RBE Computations for Intensity Modulated Proton Therapy.

Pablo Yepes1,2, Antony Adair1,2, Steven J Frank3

  • 1Physics and Astronomy Department, Rice University, Houston, Texas.

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Summary
This summary is machine-generated.

Variable relative biological effectiveness (RBE) models in intensity modulated proton therapy (IMPT) show increased doses to organs at risk (OARs), unlike fixed RBE calculations. Further research is needed to minimize potential toxicity from high linear energy transfer in critical structures.

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Area of Science:

  • Radiation Oncology
  • Medical Physics

Background:

  • Intensity modulated proton therapy (IMPT) is an advanced radiation technique.
  • Current IMPT practice often uses a fixed relative biological effectiveness (RBE) of 1.1.
  • Variable RBE models offer a more nuanced approach to biological dose calculation.

Purpose of the Study:

  • To compare dosimetric differences between fixed and variable RBE models in IMPT treatment plans.
  • To evaluate the impact of different RBE models on target volumes and organs at risk (OARs).

Main Methods:

  • Retrospective analysis of IMPT plans for brain, head-and-neck, thoracic, and prostate cancers.
  • Dose recalculations using a fixed RBE (1.1) and three variable RBE models (McNamara, Wedenberg, repair-misrepair-fixation).
  • Comparison of dosimetric indices (D02, D50, D98, mean dose) between fixed and variable RBE calculations.

Main Results:

  • No variable RBE model predicted an RBE < 1.05 for target volumes across all patient cohorts.
  • Linear energy transfer-based models (McNamara, Wedenberg) systematically predicted RBE > 1.1 for most OARs.
  • Significant mean dose increases in OARs were predicted by variable RBE models, reaching up to 1.4 for brain and 1.3 for head-and-neck cancers.

Conclusions:

  • Variable RBE models indicate potential for increased OAR doses in IMPT.
  • Strategies to mitigate high linear energy transfer in critical structures are necessary.
  • Further investigation into variable RBE models is crucial for optimizing IMPT safety and efficacy.