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Prescription dose in permanent (131)Cs seed prostate implants
Ning Yue1, Dwight E Heron, Krishna Komanduri
1Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15232, USA.
Medical Physics
|October 1, 2005
Summary
New cesium-131 (131Cs) seeds for prostate cancer require different radiation doses than older isotopes. This study determined appropriate prescription doses for 131Cs prostate implants using a radiobiological model, finding values around 121-127 Gy.
Area of Science:
- Medical Physics
- Radiation Oncology
- Nuclear Medicine
Background:
- Cesium-131 (131Cs) seeds are a novel option for permanent prostate brachytherapy.
- 131Cs seeds possess distinct physical and radiobiological properties compared to Iodine-125 (125I) and Palladium-103 (103Pd).
Purpose of the Study:
- To determine an appropriate dose prescription for 131Cs permanent seed prostate implants.
- To evaluate the impact of tumor characteristics and prostate edema on dose prescription.
Main Methods:
- Utilized a linear-quadratic radiobiological model.
- Incorporated prostate edema into calculations.
- Simulated various tumor doubling times and radiobiological parameters.
Main Results:
- Derived prescription doses for 131Cs implants are tumor- and edema-dependent.
- For slow-growing prostate cancers (doubling time ~40 days), recommended doses are 127(+5)(-12) Gy (based on 125I experience) and 121(+0)(-3) Gy (based on 103Pd experience).
Conclusions:
- The unique dosimetry of 131Cs necessitates distinct prescription doses compared to 125I and 103Pd.
- Radiobiological modeling provides a framework for establishing safe and effective 131Cs prostate implant protocols.