Journal
PHYSICS IN MEDICINE AND BIOLOGY
Volume 56, Issue 15, Pages 4631-4647Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0031-9155/56/15/001
Keywords
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Funding
- Canadian Breast Cancer Research Alliance (CBCRA) [019374]
- Canadian Institute for Health Research (CIHR)
- Terry Fox Foundation
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Canadian Institute of Health Research
- US Army Department of Defense Breast Cancer Research [W81XWH-08-1-0519, P00002]
- University of Toronto
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Gold nanoparticle (AuNP) radiosensitization represents a novel approach to enhance the effectiveness of ionizing radiation. Its efficiency varies widely with photon source energy and AuNP size, concentration, and intracellular localization. In this Monte Carlo study we explored the effects of those parameters to define the optimal clinical use of AuNPs. Photon sources included Pd-103 and I-125 brachytherapy seeds; Yb-169, Ir-192 high dose rate sources, and external beam sources 300 kVp and 6 MV. AuNP sizes were 1.9, 5, 30, and 100 nm. We observed a 10(3) increase in the rate of photoelectric absorption using I-125 compared to 6 MV. For a I-125 source, to double the dose requires concentrations of 5.33-6.26 mg g(-1) of Au or 7.10 x 10(4) 30 nm AuNPs per tumor cell. For 6MV, concentrations of 1560-1760 mg g(-1) or 2.17 x 10(7) 30 nm AuNPs per cell are needed, which is not clinically achievable. Examining the proportion of energy transferred to escaping particles or internally absorbed in the nanoparticle suggests two clinical strategies: the first uses photon energies below the k-edge and takes advantage of the extremely localized Auger cascade. It requires small AuNPs conjugated to tumor targeted moieties and nuclear localizing sequences. The second, using photon sources above the k-edge, requires a higher gold concentration in the tumor region. In this approach, energy deposited by photoelectrons is the main contribution to radiosensitization; AuNP size and cellular localization are less relevant.
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