Monte Carlo study shows no significant difference in second cancer risk between 6-and 18-MV intensity-modulated radiation therapy
Monte Carlo study shows no significant difference in second cancer risk between 6-and 18-MV intensity-modulated radiation therapy
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DOI：
10.1016/j.radonc.2008.11.020
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发表时间：
2009-04-01
影响因子：
5.7
通讯作者：
Followill, David
中科院分区：
文献类型：
--
作者：
Kry, Stephen F.;Salehpour, Mohammad;Followill, David
目的：用蒙特卡罗模型评价6 MV和18 MV调强放射治疗(IMRT)的光子和中子场外剂量当量，并探讨两者差异对诱发二次恶性肿瘤相关风险的影响。方法和材料：利用MCNPX建立的蒙特卡罗模型计算6 MV和18 MV束流能量下模拟前列腺调强放射治疗的场外光子剂量和中子剂量当量。计算了拟人体模敏感器官的场外剂量当量。基于这些剂量，根据器官、性别和年龄特定的风险系数计算了一名50岁男性继发恶性肿瘤的风险。结果：蒙特卡罗模型预测的中子剂量当量比之前确定的要低得多。进一步的分析表明，中子剂量当量存在很大的不确定性，需要更好地确定该值，这在估计继发性恶性肿瘤的风险方面发挥了很大作用。蒙特卡罗计算发现，与先前的发现相反，高能调强放射治疗与低能量调强放射治疗在继发恶性肿瘤风险方面的差异很小且不显著。结论：与高能放射治疗相关的继发恶性肿瘤风险可能没有以前报道的那么大，可能不会阻止高能射线的使用。然而，患者体内特定位置的中子剂量当量的巨大不确定性值得进一步研究，以便能够更准确地估计继发性癌症的风险。(C)2008爱思唯尔爱尔兰有限公司。保留所有权利。放射治疗与肿瘤学91(2009)132-137
Purpose: To evaluate the photon and neutron out-of-field dose equivalents from 6- and 18-MV intensity-modulated radiation therapy (IMRT) and to investigate the impact of the differences on the associated risk of induced second malignancy using a Monte Carlo model.Methods and materials: A Monte Carlo model created with MCNPX was used to calculate the out-of-field photon dose and neutron dose equivalent from simulated IMRT of the prostate conducted at beam energies of 6 and 18 MV. The out-of-field dose equivalent was calculated at the locations of sensitive organs in an anthropomorphic phantom. Based on these doses, the risk of secondary malignancy was calculated based on organ-, gender-, and age-specific risk coefficients for a 50-year-old man.Results: The Monte Carlo model predicted much lower neutron dose equivalents than had been determined previously. Further analysis illuminated the large uncertainties in the neutron dose equivalent and demonstrated the need for better determination of this value, which plays a large role in estimating the risk of secondary malignancies. The Monte Carlo calculations found that the differences in the risk of secondary malignancies conferred by high-energy IMRT versus low-energy IMRT are minimal and insignificant, contrary to prior findings.Conclusions: The risk of secondary malignancy associated with high-energy radiation therapy may not be as large as previously reported, and likely should not deter the use of high-energy beams. However, the large uncertainties in neutron dose equivalents at specific locations within the patient warrant further study so that the risk of secondary cancers can be estimated with greater accuracy. (C) 2008 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 91 (2009) 132-137