Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain.
Radiother Oncol. 2013 May;107(2):234-41. doi: 10.1016/j.radonc.2013.03.011. Epub 2013 Apr 16.
Second cancer, as a consequence of a curative intent radiotherapy (RT), represents a growing concern nowadays. The unwanted neutron exposure is an important contributor to this risk in patients irradiated with high energy photon beams. The design and development by our group of a neutron digital detector, together with the methodology to estimate, from the detector readings, the neutron equivalent dose in organs, made possible the unprecedented clinical implementation of an online and systematic neutron dosimetry system. The aim of this study was to systematically estimate neutron equivalent dose in organs of a large patient group treated in different installations.
Neutron dosimetry was carried out in 1377 adult patients at more than 30 different institutions using the new neutron digital detector located inside the RT room. Second cancer risk estimates were performed applying ICRP risk coefficients.
Averaged equivalent dose in organs ranges between 0.5 mSv and 129 mSv depending on the type of treatment (dose and beam-on time), the distance to isocenter and the linac model. The mean value of the second cancer risk for our patient group is 1.2%. Reference values are proposed for an overall estimation of the risks in 15 linac models (from 2.8 × 10(-5) to 62.7 × 10(-5)%/MU).
The therapeutic benefit of RT must outweigh the second cancer risk. Thus, these results should be taken into account when taking clinical decisions regarding treatment strategy choice during RT planning.
如今，作为治愈意图放射治疗（RT）的后果，第二癌症是一个日益令人关注的问题。在接受高能光子束照射的患者中，不必要的中子暴露是增加这种风险的一个重要因素。我们小组设计和开发了一种中子数字探测器，以及一种从探测器读数估算器官中中子等效剂量的方法，这使得在临床上首次实现了在线和系统的中子剂量测量系统。本研究的目的是系统地估算在 30 多个不同机构治疗的大量患者群体中器官的中子等效剂量。
在 30 多个不同的机构中，使用位于 RT 室内的新型中子数字探测器对 1377 名成年患者进行了中子剂量测量。应用 ICRP 风险系数对第二癌症风险进行了估计。
根据治疗类型（剂量和束流时间）、与等中心点的距离和直线加速器模型，器官的平均等效剂量在 0.5 毫西弗至 129 毫西弗之间。我们患者群体的第二癌症风险平均值为 1.2%。针对 15 种直线加速器模型（从 2.8×10（-5）至 62.7×10（-5）%/MU），提出了参考值，以便对风险进行全面估计。
RT 的治疗益处必须超过第二癌症风险。因此，在 RT 计划期间，当根据治疗策略选择做出临床决策时，应该考虑这些结果。
