P.N. Lebedev Physical Institute, 119991 Moscow, Russia.
Int J Mol Sci. 2024 Sep 2;25(17):9525. doi: 10.3390/ijms25179525.
Conventional X-ray therapy (XRT) is commonly applied to suppress cancerous tumors; however, it often inflicts collateral damage to nearby healthy tissue. In order to provide a better conformity of the dose distribution in the irradiated tumor, proton therapy (PT) is increasingly being used to treat solid tumors. Furthermore, radiosensitization with gold nanoparticles (GNPs) has been extensively studied to increase the therapeutic ratio. The mechanism of radiosensitization is assumed to be connected to an enhancement of the absorbed dose due to huge photoelectric cross-sections with gold. Nevertheless, numerous theoretical studies, mostly based on Monte Carlo (MC) simulations, did not provide a consistent and thorough picture of dose enhancement and, therefore, the radiosensitization effect. Radiosensitization by nanoparticles in PT is even less studied than in XRT. Therefore, we investigate the physics picture of GNP-enhanced RT using an MC simulation with Geant4 equipped with the most recent physics models, taking into account a wide range of physics processes relevant for realistic PT and XRT. Namely, we measured dose enhancement factors in the vicinity of GNP, with diameters ranging from 10 nm to 80 nm. The dose enhancement in the vicinity of GNP reaches high values for XRT, while it is very modest for PT. The macroscopic dose enhancement factors for realistic therapeutic GNP concentrations are rather low for all RT scenarios; therefore, other physico-chemical and biological mechanisms should be additionally invoked for an explanation of the radiosensitization effect observed in many experiments.
传统的 X 射线治疗（XRT）常用于抑制癌性肿瘤，但它经常对附近的健康组织造成附带损伤。为了在受照射的肿瘤中提供更好的剂量分布一致性，质子治疗（PT）越来越多地用于治疗实体瘤。此外，金纳米粒子（GNPs）的放射增敏作用已被广泛研究，以提高治疗比率。放射增敏作用的机制被认为与金的巨大光电截面导致吸收剂量的增加有关。然而，许多理论研究，主要基于蒙特卡罗（MC）模拟，并没有提供一致和全面的剂量增强图，因此也没有提供放射增敏作用的效果。与 XRT 相比，PT 中的纳米粒子放射增敏作用的研究甚至更少。因此，我们使用配备了最新物理模型的 Geant4 的 MC 模拟来研究 GNP 增强 RT 的物理图像，考虑到与现实的 PT 和 XRT 相关的广泛物理过程。具体来说，我们测量了 GNP 附近的剂量增强因子，GNP 的直径范围从 10nm 到 80nm。GNP 附近的剂量增强在 XRT 中达到很高的值，而在 PT 中则非常适中。对于所有 RT 情况，实际治疗用 GNP 浓度的宏观剂量增强因子都相当低；因此，应该额外调用其他物理化学和生物学机制来解释许多实验中观察到的放射增敏作用。
